1 // SPDX-License-Identifier: GPL-2.0-only
5 * Core kernel scheduler code and related syscalls
7 * Copyright (C) 1991-2002 Linus Torvalds
9 #include <linux/highmem.h>
10 #include <linux/hrtimer_api.h>
11 #include <linux/ktime_api.h>
12 #include <linux/sched/signal.h>
13 #include <linux/syscalls_api.h>
14 #include <linux/debug_locks.h>
15 #include <linux/prefetch.h>
16 #include <linux/capability.h>
17 #include <linux/pgtable_api.h>
18 #include <linux/wait_bit.h>
19 #include <linux/jiffies.h>
20 #include <linux/spinlock_api.h>
21 #include <linux/cpumask_api.h>
22 #include <linux/lockdep_api.h>
23 #include <linux/hardirq.h>
24 #include <linux/softirq.h>
25 #include <linux/refcount_api.h>
26 #include <linux/topology.h>
27 #include <linux/sched/clock.h>
28 #include <linux/sched/cond_resched.h>
29 #include <linux/sched/cputime.h>
30 #include <linux/sched/debug.h>
31 #include <linux/sched/hotplug.h>
32 #include <linux/sched/init.h>
33 #include <linux/sched/isolation.h>
34 #include <linux/sched/loadavg.h>
35 #include <linux/sched/mm.h>
36 #include <linux/sched/nohz.h>
37 #include <linux/sched/rseq_api.h>
38 #include <linux/sched/rt.h>
40 #include <linux/blkdev.h>
41 #include <linux/context_tracking.h>
42 #include <linux/cpuset.h>
43 #include <linux/delayacct.h>
44 #include <linux/init_task.h>
45 #include <linux/interrupt.h>
46 #include <linux/ioprio.h>
47 #include <linux/kallsyms.h>
48 #include <linux/kcov.h>
49 #include <linux/kprobes.h>
50 #include <linux/llist_api.h>
51 #include <linux/mmu_context.h>
52 #include <linux/mmzone.h>
53 #include <linux/mutex_api.h>
54 #include <linux/nmi.h>
55 #include <linux/nospec.h>
56 #include <linux/perf_event_api.h>
57 #include <linux/profile.h>
58 #include <linux/psi.h>
59 #include <linux/rcuwait_api.h>
60 #include <linux/sched/wake_q.h>
61 #include <linux/scs.h>
62 #include <linux/slab.h>
63 #include <linux/syscalls.h>
64 #include <linux/vtime.h>
65 #include <linux/wait_api.h>
66 #include <linux/workqueue_api.h>
68 #ifdef CONFIG_PREEMPT_DYNAMIC
69 # ifdef CONFIG_GENERIC_ENTRY
70 # include <linux/entry-common.h>
74 #include <uapi/linux/sched/types.h>
76 #include <asm/irq_regs.h>
77 #include <asm/switch_to.h>
80 #define CREATE_TRACE_POINTS
81 #include <linux/sched/rseq_api.h>
82 #include <trace/events/sched.h>
83 #include <trace/events/ipi.h>
84 #undef CREATE_TRACE_POINTS
88 #include "autogroup.h"
90 #include "autogroup.h"
95 #include "../workqueue_internal.h"
96 #include "../../io_uring/io-wq.h"
97 #include "../smpboot.h"
99 EXPORT_TRACEPOINT_SYMBOL_GPL(ipi_send_cpu);
100 EXPORT_TRACEPOINT_SYMBOL_GPL(ipi_send_cpumask);
103 * Export tracepoints that act as a bare tracehook (ie: have no trace event
104 * associated with them) to allow external modules to probe them.
106 EXPORT_TRACEPOINT_SYMBOL_GPL(pelt_cfs_tp);
107 EXPORT_TRACEPOINT_SYMBOL_GPL(pelt_rt_tp);
108 EXPORT_TRACEPOINT_SYMBOL_GPL(pelt_dl_tp);
109 EXPORT_TRACEPOINT_SYMBOL_GPL(pelt_irq_tp);
110 EXPORT_TRACEPOINT_SYMBOL_GPL(pelt_se_tp);
111 EXPORT_TRACEPOINT_SYMBOL_GPL(pelt_thermal_tp);
112 EXPORT_TRACEPOINT_SYMBOL_GPL(sched_cpu_capacity_tp);
113 EXPORT_TRACEPOINT_SYMBOL_GPL(sched_overutilized_tp);
114 EXPORT_TRACEPOINT_SYMBOL_GPL(sched_util_est_cfs_tp);
115 EXPORT_TRACEPOINT_SYMBOL_GPL(sched_util_est_se_tp);
116 EXPORT_TRACEPOINT_SYMBOL_GPL(sched_update_nr_running_tp);
118 DEFINE_PER_CPU_SHARED_ALIGNED(struct rq, runqueues);
120 #ifdef CONFIG_SCHED_DEBUG
122 * Debugging: various feature bits
124 * If SCHED_DEBUG is disabled, each compilation unit has its own copy of
125 * sysctl_sched_features, defined in sched.h, to allow constants propagation
126 * at compile time and compiler optimization based on features default.
128 #define SCHED_FEAT(name, enabled) \
129 (1UL << __SCHED_FEAT_##name) * enabled |
130 const_debug unsigned int sysctl_sched_features =
131 #include "features.h"
136 * Print a warning if need_resched is set for the given duration (if
137 * LATENCY_WARN is enabled).
139 * If sysctl_resched_latency_warn_once is set, only one warning will be shown
142 __read_mostly int sysctl_resched_latency_warn_ms = 100;
143 __read_mostly int sysctl_resched_latency_warn_once = 1;
144 #endif /* CONFIG_SCHED_DEBUG */
147 * Number of tasks to iterate in a single balance run.
148 * Limited because this is done with IRQs disabled.
150 const_debug unsigned int sysctl_sched_nr_migrate = SCHED_NR_MIGRATE_BREAK;
152 __read_mostly int scheduler_running;
154 #ifdef CONFIG_SCHED_CORE
156 DEFINE_STATIC_KEY_FALSE(__sched_core_enabled);
158 /* kernel prio, less is more */
159 static inline int __task_prio(const struct task_struct *p)
161 if (p->sched_class == &stop_sched_class) /* trumps deadline */
164 if (rt_prio(p->prio)) /* includes deadline */
165 return p->prio; /* [-1, 99] */
167 if (p->sched_class == &idle_sched_class)
168 return MAX_RT_PRIO + NICE_WIDTH; /* 140 */
170 return MAX_RT_PRIO + MAX_NICE; /* 120, squash fair */
180 /* real prio, less is less */
181 static inline bool prio_less(const struct task_struct *a,
182 const struct task_struct *b, bool in_fi)
185 int pa = __task_prio(a), pb = __task_prio(b);
193 if (pa == -1) /* dl_prio() doesn't work because of stop_class above */
194 return !dl_time_before(a->dl.deadline, b->dl.deadline);
196 if (pa == MAX_RT_PRIO + MAX_NICE) /* fair */
197 return cfs_prio_less(a, b, in_fi);
202 static inline bool __sched_core_less(const struct task_struct *a,
203 const struct task_struct *b)
205 if (a->core_cookie < b->core_cookie)
208 if (a->core_cookie > b->core_cookie)
211 /* flip prio, so high prio is leftmost */
212 if (prio_less(b, a, !!task_rq(a)->core->core_forceidle_count))
218 #define __node_2_sc(node) rb_entry((node), struct task_struct, core_node)
220 static inline bool rb_sched_core_less(struct rb_node *a, const struct rb_node *b)
222 return __sched_core_less(__node_2_sc(a), __node_2_sc(b));
225 static inline int rb_sched_core_cmp(const void *key, const struct rb_node *node)
227 const struct task_struct *p = __node_2_sc(node);
228 unsigned long cookie = (unsigned long)key;
230 if (cookie < p->core_cookie)
233 if (cookie > p->core_cookie)
239 void sched_core_enqueue(struct rq *rq, struct task_struct *p)
241 rq->core->core_task_seq++;
246 rb_add(&p->core_node, &rq->core_tree, rb_sched_core_less);
249 void sched_core_dequeue(struct rq *rq, struct task_struct *p, int flags)
251 rq->core->core_task_seq++;
253 if (sched_core_enqueued(p)) {
254 rb_erase(&p->core_node, &rq->core_tree);
255 RB_CLEAR_NODE(&p->core_node);
259 * Migrating the last task off the cpu, with the cpu in forced idle
260 * state. Reschedule to create an accounting edge for forced idle,
261 * and re-examine whether the core is still in forced idle state.
263 if (!(flags & DEQUEUE_SAVE) && rq->nr_running == 1 &&
264 rq->core->core_forceidle_count && rq->curr == rq->idle)
268 static int sched_task_is_throttled(struct task_struct *p, int cpu)
270 if (p->sched_class->task_is_throttled)
271 return p->sched_class->task_is_throttled(p, cpu);
276 static struct task_struct *sched_core_next(struct task_struct *p, unsigned long cookie)
278 struct rb_node *node = &p->core_node;
279 int cpu = task_cpu(p);
282 node = rb_next(node);
286 p = __node_2_sc(node);
287 if (p->core_cookie != cookie)
290 } while (sched_task_is_throttled(p, cpu));
296 * Find left-most (aka, highest priority) and unthrottled task matching @cookie.
297 * If no suitable task is found, NULL will be returned.
299 static struct task_struct *sched_core_find(struct rq *rq, unsigned long cookie)
301 struct task_struct *p;
302 struct rb_node *node;
304 node = rb_find_first((void *)cookie, &rq->core_tree, rb_sched_core_cmp);
308 p = __node_2_sc(node);
309 if (!sched_task_is_throttled(p, rq->cpu))
312 return sched_core_next(p, cookie);
316 * Magic required such that:
318 * raw_spin_rq_lock(rq);
320 * raw_spin_rq_unlock(rq);
322 * ends up locking and unlocking the _same_ lock, and all CPUs
323 * always agree on what rq has what lock.
325 * XXX entirely possible to selectively enable cores, don't bother for now.
328 static DEFINE_MUTEX(sched_core_mutex);
329 static atomic_t sched_core_count;
330 static struct cpumask sched_core_mask;
332 static void sched_core_lock(int cpu, unsigned long *flags)
334 const struct cpumask *smt_mask = cpu_smt_mask(cpu);
337 local_irq_save(*flags);
338 for_each_cpu(t, smt_mask)
339 raw_spin_lock_nested(&cpu_rq(t)->__lock, i++);
342 static void sched_core_unlock(int cpu, unsigned long *flags)
344 const struct cpumask *smt_mask = cpu_smt_mask(cpu);
347 for_each_cpu(t, smt_mask)
348 raw_spin_unlock(&cpu_rq(t)->__lock);
349 local_irq_restore(*flags);
352 static void __sched_core_flip(bool enabled)
360 * Toggle the online cores, one by one.
362 cpumask_copy(&sched_core_mask, cpu_online_mask);
363 for_each_cpu(cpu, &sched_core_mask) {
364 const struct cpumask *smt_mask = cpu_smt_mask(cpu);
366 sched_core_lock(cpu, &flags);
368 for_each_cpu(t, smt_mask)
369 cpu_rq(t)->core_enabled = enabled;
371 cpu_rq(cpu)->core->core_forceidle_start = 0;
373 sched_core_unlock(cpu, &flags);
375 cpumask_andnot(&sched_core_mask, &sched_core_mask, smt_mask);
379 * Toggle the offline CPUs.
381 for_each_cpu_andnot(cpu, cpu_possible_mask, cpu_online_mask)
382 cpu_rq(cpu)->core_enabled = enabled;
387 static void sched_core_assert_empty(void)
391 for_each_possible_cpu(cpu)
392 WARN_ON_ONCE(!RB_EMPTY_ROOT(&cpu_rq(cpu)->core_tree));
395 static void __sched_core_enable(void)
397 static_branch_enable(&__sched_core_enabled);
399 * Ensure all previous instances of raw_spin_rq_*lock() have finished
400 * and future ones will observe !sched_core_disabled().
403 __sched_core_flip(true);
404 sched_core_assert_empty();
407 static void __sched_core_disable(void)
409 sched_core_assert_empty();
410 __sched_core_flip(false);
411 static_branch_disable(&__sched_core_enabled);
414 void sched_core_get(void)
416 if (atomic_inc_not_zero(&sched_core_count))
419 mutex_lock(&sched_core_mutex);
420 if (!atomic_read(&sched_core_count))
421 __sched_core_enable();
423 smp_mb__before_atomic();
424 atomic_inc(&sched_core_count);
425 mutex_unlock(&sched_core_mutex);
428 static void __sched_core_put(struct work_struct *work)
430 if (atomic_dec_and_mutex_lock(&sched_core_count, &sched_core_mutex)) {
431 __sched_core_disable();
432 mutex_unlock(&sched_core_mutex);
436 void sched_core_put(void)
438 static DECLARE_WORK(_work, __sched_core_put);
441 * "There can be only one"
443 * Either this is the last one, or we don't actually need to do any
444 * 'work'. If it is the last *again*, we rely on
445 * WORK_STRUCT_PENDING_BIT.
447 if (!atomic_add_unless(&sched_core_count, -1, 1))
448 schedule_work(&_work);
451 #else /* !CONFIG_SCHED_CORE */
453 static inline void sched_core_enqueue(struct rq *rq, struct task_struct *p) { }
455 sched_core_dequeue(struct rq *rq, struct task_struct *p, int flags) { }
457 #endif /* CONFIG_SCHED_CORE */
460 * Serialization rules:
466 * hrtimer_cpu_base->lock (hrtimer_start() for bandwidth controls)
469 * rq2->lock where: rq1 < rq2
473 * Normal scheduling state is serialized by rq->lock. __schedule() takes the
474 * local CPU's rq->lock, it optionally removes the task from the runqueue and
475 * always looks at the local rq data structures to find the most eligible task
478 * Task enqueue is also under rq->lock, possibly taken from another CPU.
479 * Wakeups from another LLC domain might use an IPI to transfer the enqueue to
480 * the local CPU to avoid bouncing the runqueue state around [ see
481 * ttwu_queue_wakelist() ]
483 * Task wakeup, specifically wakeups that involve migration, are horribly
484 * complicated to avoid having to take two rq->locks.
488 * System-calls and anything external will use task_rq_lock() which acquires
489 * both p->pi_lock and rq->lock. As a consequence the state they change is
490 * stable while holding either lock:
492 * - sched_setaffinity()/
493 * set_cpus_allowed_ptr(): p->cpus_ptr, p->nr_cpus_allowed
494 * - set_user_nice(): p->se.load, p->*prio
495 * - __sched_setscheduler(): p->sched_class, p->policy, p->*prio,
496 * p->se.load, p->rt_priority,
497 * p->dl.dl_{runtime, deadline, period, flags, bw, density}
498 * - sched_setnuma(): p->numa_preferred_nid
499 * - sched_move_task(): p->sched_task_group
500 * - uclamp_update_active() p->uclamp*
502 * p->state <- TASK_*:
504 * is changed locklessly using set_current_state(), __set_current_state() or
505 * set_special_state(), see their respective comments, or by
506 * try_to_wake_up(). This latter uses p->pi_lock to serialize against
509 * p->on_rq <- { 0, 1 = TASK_ON_RQ_QUEUED, 2 = TASK_ON_RQ_MIGRATING }:
511 * is set by activate_task() and cleared by deactivate_task(), under
512 * rq->lock. Non-zero indicates the task is runnable, the special
513 * ON_RQ_MIGRATING state is used for migration without holding both
514 * rq->locks. It indicates task_cpu() is not stable, see task_rq_lock().
516 * p->on_cpu <- { 0, 1 }:
518 * is set by prepare_task() and cleared by finish_task() such that it will be
519 * set before p is scheduled-in and cleared after p is scheduled-out, both
520 * under rq->lock. Non-zero indicates the task is running on its CPU.
522 * [ The astute reader will observe that it is possible for two tasks on one
523 * CPU to have ->on_cpu = 1 at the same time. ]
525 * task_cpu(p): is changed by set_task_cpu(), the rules are:
527 * - Don't call set_task_cpu() on a blocked task:
529 * We don't care what CPU we're not running on, this simplifies hotplug,
530 * the CPU assignment of blocked tasks isn't required to be valid.
532 * - for try_to_wake_up(), called under p->pi_lock:
534 * This allows try_to_wake_up() to only take one rq->lock, see its comment.
536 * - for migration called under rq->lock:
537 * [ see task_on_rq_migrating() in task_rq_lock() ]
539 * o move_queued_task()
542 * - for migration called under double_rq_lock():
544 * o __migrate_swap_task()
545 * o push_rt_task() / pull_rt_task()
546 * o push_dl_task() / pull_dl_task()
547 * o dl_task_offline_migration()
551 void raw_spin_rq_lock_nested(struct rq *rq, int subclass)
553 raw_spinlock_t *lock;
555 /* Matches synchronize_rcu() in __sched_core_enable() */
557 if (sched_core_disabled()) {
558 raw_spin_lock_nested(&rq->__lock, subclass);
559 /* preempt_count *MUST* be > 1 */
560 preempt_enable_no_resched();
565 lock = __rq_lockp(rq);
566 raw_spin_lock_nested(lock, subclass);
567 if (likely(lock == __rq_lockp(rq))) {
568 /* preempt_count *MUST* be > 1 */
569 preempt_enable_no_resched();
572 raw_spin_unlock(lock);
576 bool raw_spin_rq_trylock(struct rq *rq)
578 raw_spinlock_t *lock;
581 /* Matches synchronize_rcu() in __sched_core_enable() */
583 if (sched_core_disabled()) {
584 ret = raw_spin_trylock(&rq->__lock);
590 lock = __rq_lockp(rq);
591 ret = raw_spin_trylock(lock);
592 if (!ret || (likely(lock == __rq_lockp(rq)))) {
596 raw_spin_unlock(lock);
600 void raw_spin_rq_unlock(struct rq *rq)
602 raw_spin_unlock(rq_lockp(rq));
607 * double_rq_lock - safely lock two runqueues
609 void double_rq_lock(struct rq *rq1, struct rq *rq2)
611 lockdep_assert_irqs_disabled();
613 if (rq_order_less(rq2, rq1))
616 raw_spin_rq_lock(rq1);
617 if (__rq_lockp(rq1) != __rq_lockp(rq2))
618 raw_spin_rq_lock_nested(rq2, SINGLE_DEPTH_NESTING);
620 double_rq_clock_clear_update(rq1, rq2);
625 * __task_rq_lock - lock the rq @p resides on.
627 struct rq *__task_rq_lock(struct task_struct *p, struct rq_flags *rf)
632 lockdep_assert_held(&p->pi_lock);
636 raw_spin_rq_lock(rq);
637 if (likely(rq == task_rq(p) && !task_on_rq_migrating(p))) {
641 raw_spin_rq_unlock(rq);
643 while (unlikely(task_on_rq_migrating(p)))
649 * task_rq_lock - lock p->pi_lock and lock the rq @p resides on.
651 struct rq *task_rq_lock(struct task_struct *p, struct rq_flags *rf)
652 __acquires(p->pi_lock)
658 raw_spin_lock_irqsave(&p->pi_lock, rf->flags);
660 raw_spin_rq_lock(rq);
662 * move_queued_task() task_rq_lock()
665 * [S] ->on_rq = MIGRATING [L] rq = task_rq()
666 * WMB (__set_task_cpu()) ACQUIRE (rq->lock);
667 * [S] ->cpu = new_cpu [L] task_rq()
671 * If we observe the old CPU in task_rq_lock(), the acquire of
672 * the old rq->lock will fully serialize against the stores.
674 * If we observe the new CPU in task_rq_lock(), the address
675 * dependency headed by '[L] rq = task_rq()' and the acquire
676 * will pair with the WMB to ensure we then also see migrating.
678 if (likely(rq == task_rq(p) && !task_on_rq_migrating(p))) {
682 raw_spin_rq_unlock(rq);
683 raw_spin_unlock_irqrestore(&p->pi_lock, rf->flags);
685 while (unlikely(task_on_rq_migrating(p)))
691 * RQ-clock updating methods:
694 static void update_rq_clock_task(struct rq *rq, s64 delta)
697 * In theory, the compile should just see 0 here, and optimize out the call
698 * to sched_rt_avg_update. But I don't trust it...
700 s64 __maybe_unused steal = 0, irq_delta = 0;
702 #ifdef CONFIG_IRQ_TIME_ACCOUNTING
703 irq_delta = irq_time_read(cpu_of(rq)) - rq->prev_irq_time;
706 * Since irq_time is only updated on {soft,}irq_exit, we might run into
707 * this case when a previous update_rq_clock() happened inside a
710 * When this happens, we stop ->clock_task and only update the
711 * prev_irq_time stamp to account for the part that fit, so that a next
712 * update will consume the rest. This ensures ->clock_task is
715 * It does however cause some slight miss-attribution of {soft,}irq
716 * time, a more accurate solution would be to update the irq_time using
717 * the current rq->clock timestamp, except that would require using
720 if (irq_delta > delta)
723 rq->prev_irq_time += irq_delta;
725 psi_account_irqtime(rq->curr, irq_delta);
726 delayacct_irq(rq->curr, irq_delta);
728 #ifdef CONFIG_PARAVIRT_TIME_ACCOUNTING
729 if (static_key_false((¶virt_steal_rq_enabled))) {
730 steal = paravirt_steal_clock(cpu_of(rq));
731 steal -= rq->prev_steal_time_rq;
733 if (unlikely(steal > delta))
736 rq->prev_steal_time_rq += steal;
741 rq->clock_task += delta;
743 #ifdef CONFIG_HAVE_SCHED_AVG_IRQ
744 if ((irq_delta + steal) && sched_feat(NONTASK_CAPACITY))
745 update_irq_load_avg(rq, irq_delta + steal);
747 update_rq_clock_pelt(rq, delta);
750 void update_rq_clock(struct rq *rq)
754 lockdep_assert_rq_held(rq);
756 if (rq->clock_update_flags & RQCF_ACT_SKIP)
759 #ifdef CONFIG_SCHED_DEBUG
760 if (sched_feat(WARN_DOUBLE_CLOCK))
761 SCHED_WARN_ON(rq->clock_update_flags & RQCF_UPDATED);
762 rq->clock_update_flags |= RQCF_UPDATED;
765 delta = sched_clock_cpu(cpu_of(rq)) - rq->clock;
769 update_rq_clock_task(rq, delta);
772 #ifdef CONFIG_SCHED_HRTICK
774 * Use HR-timers to deliver accurate preemption points.
777 static void hrtick_clear(struct rq *rq)
779 if (hrtimer_active(&rq->hrtick_timer))
780 hrtimer_cancel(&rq->hrtick_timer);
784 * High-resolution timer tick.
785 * Runs from hardirq context with interrupts disabled.
787 static enum hrtimer_restart hrtick(struct hrtimer *timer)
789 struct rq *rq = container_of(timer, struct rq, hrtick_timer);
792 WARN_ON_ONCE(cpu_of(rq) != smp_processor_id());
796 rq->curr->sched_class->task_tick(rq, rq->curr, 1);
799 return HRTIMER_NORESTART;
804 static void __hrtick_restart(struct rq *rq)
806 struct hrtimer *timer = &rq->hrtick_timer;
807 ktime_t time = rq->hrtick_time;
809 hrtimer_start(timer, time, HRTIMER_MODE_ABS_PINNED_HARD);
813 * called from hardirq (IPI) context
815 static void __hrtick_start(void *arg)
821 __hrtick_restart(rq);
826 * Called to set the hrtick timer state.
828 * called with rq->lock held and irqs disabled
830 void hrtick_start(struct rq *rq, u64 delay)
832 struct hrtimer *timer = &rq->hrtick_timer;
836 * Don't schedule slices shorter than 10000ns, that just
837 * doesn't make sense and can cause timer DoS.
839 delta = max_t(s64, delay, 10000LL);
840 rq->hrtick_time = ktime_add_ns(timer->base->get_time(), delta);
843 __hrtick_restart(rq);
845 smp_call_function_single_async(cpu_of(rq), &rq->hrtick_csd);
850 * Called to set the hrtick timer state.
852 * called with rq->lock held and irqs disabled
854 void hrtick_start(struct rq *rq, u64 delay)
857 * Don't schedule slices shorter than 10000ns, that just
858 * doesn't make sense. Rely on vruntime for fairness.
860 delay = max_t(u64, delay, 10000LL);
861 hrtimer_start(&rq->hrtick_timer, ns_to_ktime(delay),
862 HRTIMER_MODE_REL_PINNED_HARD);
865 #endif /* CONFIG_SMP */
867 static void hrtick_rq_init(struct rq *rq)
870 INIT_CSD(&rq->hrtick_csd, __hrtick_start, rq);
872 hrtimer_init(&rq->hrtick_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL_HARD);
873 rq->hrtick_timer.function = hrtick;
875 #else /* CONFIG_SCHED_HRTICK */
876 static inline void hrtick_clear(struct rq *rq)
880 static inline void hrtick_rq_init(struct rq *rq)
883 #endif /* CONFIG_SCHED_HRTICK */
886 * cmpxchg based fetch_or, macro so it works for different integer types
888 #define fetch_or(ptr, mask) \
890 typeof(ptr) _ptr = (ptr); \
891 typeof(mask) _mask = (mask); \
892 typeof(*_ptr) _val = *_ptr; \
895 } while (!try_cmpxchg(_ptr, &_val, _val | _mask)); \
899 #if defined(CONFIG_SMP) && defined(TIF_POLLING_NRFLAG)
901 * Atomically set TIF_NEED_RESCHED and test for TIF_POLLING_NRFLAG,
902 * this avoids any races wrt polling state changes and thereby avoids
905 static inline bool set_nr_and_not_polling(struct task_struct *p)
907 struct thread_info *ti = task_thread_info(p);
908 return !(fetch_or(&ti->flags, _TIF_NEED_RESCHED) & _TIF_POLLING_NRFLAG);
912 * Atomically set TIF_NEED_RESCHED if TIF_POLLING_NRFLAG is set.
914 * If this returns true, then the idle task promises to call
915 * sched_ttwu_pending() and reschedule soon.
917 static bool set_nr_if_polling(struct task_struct *p)
919 struct thread_info *ti = task_thread_info(p);
920 typeof(ti->flags) val = READ_ONCE(ti->flags);
923 if (!(val & _TIF_POLLING_NRFLAG))
925 if (val & _TIF_NEED_RESCHED)
927 if (try_cmpxchg(&ti->flags, &val, val | _TIF_NEED_RESCHED))
934 static inline bool set_nr_and_not_polling(struct task_struct *p)
936 set_tsk_need_resched(p);
941 static inline bool set_nr_if_polling(struct task_struct *p)
948 static bool __wake_q_add(struct wake_q_head *head, struct task_struct *task)
950 struct wake_q_node *node = &task->wake_q;
953 * Atomically grab the task, if ->wake_q is !nil already it means
954 * it's already queued (either by us or someone else) and will get the
955 * wakeup due to that.
957 * In order to ensure that a pending wakeup will observe our pending
958 * state, even in the failed case, an explicit smp_mb() must be used.
960 smp_mb__before_atomic();
961 if (unlikely(cmpxchg_relaxed(&node->next, NULL, WAKE_Q_TAIL)))
965 * The head is context local, there can be no concurrency.
968 head->lastp = &node->next;
973 * wake_q_add() - queue a wakeup for 'later' waking.
974 * @head: the wake_q_head to add @task to
975 * @task: the task to queue for 'later' wakeup
977 * Queue a task for later wakeup, most likely by the wake_up_q() call in the
978 * same context, _HOWEVER_ this is not guaranteed, the wakeup can come
981 * This function must be used as-if it were wake_up_process(); IOW the task
982 * must be ready to be woken at this location.
984 void wake_q_add(struct wake_q_head *head, struct task_struct *task)
986 if (__wake_q_add(head, task))
987 get_task_struct(task);
991 * wake_q_add_safe() - safely queue a wakeup for 'later' waking.
992 * @head: the wake_q_head to add @task to
993 * @task: the task to queue for 'later' wakeup
995 * Queue a task for later wakeup, most likely by the wake_up_q() call in the
996 * same context, _HOWEVER_ this is not guaranteed, the wakeup can come
999 * This function must be used as-if it were wake_up_process(); IOW the task
1000 * must be ready to be woken at this location.
1002 * This function is essentially a task-safe equivalent to wake_q_add(). Callers
1003 * that already hold reference to @task can call the 'safe' version and trust
1004 * wake_q to do the right thing depending whether or not the @task is already
1005 * queued for wakeup.
1007 void wake_q_add_safe(struct wake_q_head *head, struct task_struct *task)
1009 if (!__wake_q_add(head, task))
1010 put_task_struct(task);
1013 void wake_up_q(struct wake_q_head *head)
1015 struct wake_q_node *node = head->first;
1017 while (node != WAKE_Q_TAIL) {
1018 struct task_struct *task;
1020 task = container_of(node, struct task_struct, wake_q);
1021 /* Task can safely be re-inserted now: */
1023 task->wake_q.next = NULL;
1026 * wake_up_process() executes a full barrier, which pairs with
1027 * the queueing in wake_q_add() so as not to miss wakeups.
1029 wake_up_process(task);
1030 put_task_struct(task);
1035 * resched_curr - mark rq's current task 'to be rescheduled now'.
1037 * On UP this means the setting of the need_resched flag, on SMP it
1038 * might also involve a cross-CPU call to trigger the scheduler on
1041 void resched_curr(struct rq *rq)
1043 struct task_struct *curr = rq->curr;
1046 lockdep_assert_rq_held(rq);
1048 if (test_tsk_need_resched(curr))
1053 if (cpu == smp_processor_id()) {
1054 set_tsk_need_resched(curr);
1055 set_preempt_need_resched();
1059 if (set_nr_and_not_polling(curr))
1060 smp_send_reschedule(cpu);
1062 trace_sched_wake_idle_without_ipi(cpu);
1065 void resched_cpu(int cpu)
1067 struct rq *rq = cpu_rq(cpu);
1068 unsigned long flags;
1070 raw_spin_rq_lock_irqsave(rq, flags);
1071 if (cpu_online(cpu) || cpu == smp_processor_id())
1073 raw_spin_rq_unlock_irqrestore(rq, flags);
1077 #ifdef CONFIG_NO_HZ_COMMON
1079 * In the semi idle case, use the nearest busy CPU for migrating timers
1080 * from an idle CPU. This is good for power-savings.
1082 * We don't do similar optimization for completely idle system, as
1083 * selecting an idle CPU will add more delays to the timers than intended
1084 * (as that CPU's timer base may not be uptodate wrt jiffies etc).
1086 int get_nohz_timer_target(void)
1088 int i, cpu = smp_processor_id(), default_cpu = -1;
1089 struct sched_domain *sd;
1090 const struct cpumask *hk_mask;
1092 if (housekeeping_cpu(cpu, HK_TYPE_TIMER)) {
1098 hk_mask = housekeeping_cpumask(HK_TYPE_TIMER);
1102 for_each_domain(cpu, sd) {
1103 for_each_cpu_and(i, sched_domain_span(sd), hk_mask) {
1112 if (default_cpu == -1)
1113 default_cpu = housekeeping_any_cpu(HK_TYPE_TIMER);
1119 * When add_timer_on() enqueues a timer into the timer wheel of an
1120 * idle CPU then this timer might expire before the next timer event
1121 * which is scheduled to wake up that CPU. In case of a completely
1122 * idle system the next event might even be infinite time into the
1123 * future. wake_up_idle_cpu() ensures that the CPU is woken up and
1124 * leaves the inner idle loop so the newly added timer is taken into
1125 * account when the CPU goes back to idle and evaluates the timer
1126 * wheel for the next timer event.
1128 static void wake_up_idle_cpu(int cpu)
1130 struct rq *rq = cpu_rq(cpu);
1132 if (cpu == smp_processor_id())
1135 if (set_nr_and_not_polling(rq->idle))
1136 smp_send_reschedule(cpu);
1138 trace_sched_wake_idle_without_ipi(cpu);
1141 static bool wake_up_full_nohz_cpu(int cpu)
1144 * We just need the target to call irq_exit() and re-evaluate
1145 * the next tick. The nohz full kick at least implies that.
1146 * If needed we can still optimize that later with an
1149 if (cpu_is_offline(cpu))
1150 return true; /* Don't try to wake offline CPUs. */
1151 if (tick_nohz_full_cpu(cpu)) {
1152 if (cpu != smp_processor_id() ||
1153 tick_nohz_tick_stopped())
1154 tick_nohz_full_kick_cpu(cpu);
1162 * Wake up the specified CPU. If the CPU is going offline, it is the
1163 * caller's responsibility to deal with the lost wakeup, for example,
1164 * by hooking into the CPU_DEAD notifier like timers and hrtimers do.
1166 void wake_up_nohz_cpu(int cpu)
1168 if (!wake_up_full_nohz_cpu(cpu))
1169 wake_up_idle_cpu(cpu);
1172 static void nohz_csd_func(void *info)
1174 struct rq *rq = info;
1175 int cpu = cpu_of(rq);
1179 * Release the rq::nohz_csd.
1181 flags = atomic_fetch_andnot(NOHZ_KICK_MASK | NOHZ_NEWILB_KICK, nohz_flags(cpu));
1182 WARN_ON(!(flags & NOHZ_KICK_MASK));
1184 rq->idle_balance = idle_cpu(cpu);
1185 if (rq->idle_balance && !need_resched()) {
1186 rq->nohz_idle_balance = flags;
1187 raise_softirq_irqoff(SCHED_SOFTIRQ);
1191 #endif /* CONFIG_NO_HZ_COMMON */
1193 #ifdef CONFIG_NO_HZ_FULL
1194 static inline bool __need_bw_check(struct rq *rq, struct task_struct *p)
1196 if (rq->nr_running != 1)
1199 if (p->sched_class != &fair_sched_class)
1202 if (!task_on_rq_queued(p))
1208 bool sched_can_stop_tick(struct rq *rq)
1210 int fifo_nr_running;
1212 /* Deadline tasks, even if single, need the tick */
1213 if (rq->dl.dl_nr_running)
1217 * If there are more than one RR tasks, we need the tick to affect the
1218 * actual RR behaviour.
1220 if (rq->rt.rr_nr_running) {
1221 if (rq->rt.rr_nr_running == 1)
1228 * If there's no RR tasks, but FIFO tasks, we can skip the tick, no
1229 * forced preemption between FIFO tasks.
1231 fifo_nr_running = rq->rt.rt_nr_running - rq->rt.rr_nr_running;
1232 if (fifo_nr_running)
1236 * If there are no DL,RR/FIFO tasks, there must only be CFS tasks left;
1237 * if there's more than one we need the tick for involuntary
1240 if (rq->nr_running > 1)
1244 * If there is one task and it has CFS runtime bandwidth constraints
1245 * and it's on the cpu now we don't want to stop the tick.
1246 * This check prevents clearing the bit if a newly enqueued task here is
1247 * dequeued by migrating while the constrained task continues to run.
1248 * E.g. going from 2->1 without going through pick_next_task().
1250 if (sched_feat(HZ_BW) && __need_bw_check(rq, rq->curr)) {
1251 if (cfs_task_bw_constrained(rq->curr))
1257 #endif /* CONFIG_NO_HZ_FULL */
1258 #endif /* CONFIG_SMP */
1260 #if defined(CONFIG_RT_GROUP_SCHED) || (defined(CONFIG_FAIR_GROUP_SCHED) && \
1261 (defined(CONFIG_SMP) || defined(CONFIG_CFS_BANDWIDTH)))
1263 * Iterate task_group tree rooted at *from, calling @down when first entering a
1264 * node and @up when leaving it for the final time.
1266 * Caller must hold rcu_lock or sufficient equivalent.
1268 int walk_tg_tree_from(struct task_group *from,
1269 tg_visitor down, tg_visitor up, void *data)
1271 struct task_group *parent, *child;
1277 ret = (*down)(parent, data);
1280 list_for_each_entry_rcu(child, &parent->children, siblings) {
1287 ret = (*up)(parent, data);
1288 if (ret || parent == from)
1292 parent = parent->parent;
1299 int tg_nop(struct task_group *tg, void *data)
1305 static void set_load_weight(struct task_struct *p, bool update_load)
1307 int prio = p->static_prio - MAX_RT_PRIO;
1308 struct load_weight *load = &p->se.load;
1311 * SCHED_IDLE tasks get minimal weight:
1313 if (task_has_idle_policy(p)) {
1314 load->weight = scale_load(WEIGHT_IDLEPRIO);
1315 load->inv_weight = WMULT_IDLEPRIO;
1320 * SCHED_OTHER tasks have to update their load when changing their
1323 if (update_load && p->sched_class == &fair_sched_class) {
1324 reweight_task(p, prio);
1326 load->weight = scale_load(sched_prio_to_weight[prio]);
1327 load->inv_weight = sched_prio_to_wmult[prio];
1331 #ifdef CONFIG_UCLAMP_TASK
1333 * Serializes updates of utilization clamp values
1335 * The (slow-path) user-space triggers utilization clamp value updates which
1336 * can require updates on (fast-path) scheduler's data structures used to
1337 * support enqueue/dequeue operations.
1338 * While the per-CPU rq lock protects fast-path update operations, user-space
1339 * requests are serialized using a mutex to reduce the risk of conflicting
1340 * updates or API abuses.
1342 static DEFINE_MUTEX(uclamp_mutex);
1344 /* Max allowed minimum utilization */
1345 static unsigned int __maybe_unused sysctl_sched_uclamp_util_min = SCHED_CAPACITY_SCALE;
1347 /* Max allowed maximum utilization */
1348 static unsigned int __maybe_unused sysctl_sched_uclamp_util_max = SCHED_CAPACITY_SCALE;
1351 * By default RT tasks run at the maximum performance point/capacity of the
1352 * system. Uclamp enforces this by always setting UCLAMP_MIN of RT tasks to
1353 * SCHED_CAPACITY_SCALE.
1355 * This knob allows admins to change the default behavior when uclamp is being
1356 * used. In battery powered devices, particularly, running at the maximum
1357 * capacity and frequency will increase energy consumption and shorten the
1360 * This knob only affects RT tasks that their uclamp_se->user_defined == false.
1362 * This knob will not override the system default sched_util_clamp_min defined
1365 static unsigned int sysctl_sched_uclamp_util_min_rt_default = SCHED_CAPACITY_SCALE;
1367 /* All clamps are required to be less or equal than these values */
1368 static struct uclamp_se uclamp_default[UCLAMP_CNT];
1371 * This static key is used to reduce the uclamp overhead in the fast path. It
1372 * primarily disables the call to uclamp_rq_{inc, dec}() in
1373 * enqueue/dequeue_task().
1375 * This allows users to continue to enable uclamp in their kernel config with
1376 * minimum uclamp overhead in the fast path.
1378 * As soon as userspace modifies any of the uclamp knobs, the static key is
1379 * enabled, since we have an actual users that make use of uclamp
1382 * The knobs that would enable this static key are:
1384 * * A task modifying its uclamp value with sched_setattr().
1385 * * An admin modifying the sysctl_sched_uclamp_{min, max} via procfs.
1386 * * An admin modifying the cgroup cpu.uclamp.{min, max}
1388 DEFINE_STATIC_KEY_FALSE(sched_uclamp_used);
1390 /* Integer rounded range for each bucket */
1391 #define UCLAMP_BUCKET_DELTA DIV_ROUND_CLOSEST(SCHED_CAPACITY_SCALE, UCLAMP_BUCKETS)
1393 #define for_each_clamp_id(clamp_id) \
1394 for ((clamp_id) = 0; (clamp_id) < UCLAMP_CNT; (clamp_id)++)
1396 static inline unsigned int uclamp_bucket_id(unsigned int clamp_value)
1398 return min_t(unsigned int, clamp_value / UCLAMP_BUCKET_DELTA, UCLAMP_BUCKETS - 1);
1401 static inline unsigned int uclamp_none(enum uclamp_id clamp_id)
1403 if (clamp_id == UCLAMP_MIN)
1405 return SCHED_CAPACITY_SCALE;
1408 static inline void uclamp_se_set(struct uclamp_se *uc_se,
1409 unsigned int value, bool user_defined)
1411 uc_se->value = value;
1412 uc_se->bucket_id = uclamp_bucket_id(value);
1413 uc_se->user_defined = user_defined;
1416 static inline unsigned int
1417 uclamp_idle_value(struct rq *rq, enum uclamp_id clamp_id,
1418 unsigned int clamp_value)
1421 * Avoid blocked utilization pushing up the frequency when we go
1422 * idle (which drops the max-clamp) by retaining the last known
1425 if (clamp_id == UCLAMP_MAX) {
1426 rq->uclamp_flags |= UCLAMP_FLAG_IDLE;
1430 return uclamp_none(UCLAMP_MIN);
1433 static inline void uclamp_idle_reset(struct rq *rq, enum uclamp_id clamp_id,
1434 unsigned int clamp_value)
1436 /* Reset max-clamp retention only on idle exit */
1437 if (!(rq->uclamp_flags & UCLAMP_FLAG_IDLE))
1440 uclamp_rq_set(rq, clamp_id, clamp_value);
1444 unsigned int uclamp_rq_max_value(struct rq *rq, enum uclamp_id clamp_id,
1445 unsigned int clamp_value)
1447 struct uclamp_bucket *bucket = rq->uclamp[clamp_id].bucket;
1448 int bucket_id = UCLAMP_BUCKETS - 1;
1451 * Since both min and max clamps are max aggregated, find the
1452 * top most bucket with tasks in.
1454 for ( ; bucket_id >= 0; bucket_id--) {
1455 if (!bucket[bucket_id].tasks)
1457 return bucket[bucket_id].value;
1460 /* No tasks -- default clamp values */
1461 return uclamp_idle_value(rq, clamp_id, clamp_value);
1464 static void __uclamp_update_util_min_rt_default(struct task_struct *p)
1466 unsigned int default_util_min;
1467 struct uclamp_se *uc_se;
1469 lockdep_assert_held(&p->pi_lock);
1471 uc_se = &p->uclamp_req[UCLAMP_MIN];
1473 /* Only sync if user didn't override the default */
1474 if (uc_se->user_defined)
1477 default_util_min = sysctl_sched_uclamp_util_min_rt_default;
1478 uclamp_se_set(uc_se, default_util_min, false);
1481 static void uclamp_update_util_min_rt_default(struct task_struct *p)
1489 /* Protect updates to p->uclamp_* */
1490 rq = task_rq_lock(p, &rf);
1491 __uclamp_update_util_min_rt_default(p);
1492 task_rq_unlock(rq, p, &rf);
1495 static inline struct uclamp_se
1496 uclamp_tg_restrict(struct task_struct *p, enum uclamp_id clamp_id)
1498 /* Copy by value as we could modify it */
1499 struct uclamp_se uc_req = p->uclamp_req[clamp_id];
1500 #ifdef CONFIG_UCLAMP_TASK_GROUP
1501 unsigned int tg_min, tg_max, value;
1504 * Tasks in autogroups or root task group will be
1505 * restricted by system defaults.
1507 if (task_group_is_autogroup(task_group(p)))
1509 if (task_group(p) == &root_task_group)
1512 tg_min = task_group(p)->uclamp[UCLAMP_MIN].value;
1513 tg_max = task_group(p)->uclamp[UCLAMP_MAX].value;
1514 value = uc_req.value;
1515 value = clamp(value, tg_min, tg_max);
1516 uclamp_se_set(&uc_req, value, false);
1523 * The effective clamp bucket index of a task depends on, by increasing
1525 * - the task specific clamp value, when explicitly requested from userspace
1526 * - the task group effective clamp value, for tasks not either in the root
1527 * group or in an autogroup
1528 * - the system default clamp value, defined by the sysadmin
1530 static inline struct uclamp_se
1531 uclamp_eff_get(struct task_struct *p, enum uclamp_id clamp_id)
1533 struct uclamp_se uc_req = uclamp_tg_restrict(p, clamp_id);
1534 struct uclamp_se uc_max = uclamp_default[clamp_id];
1536 /* System default restrictions always apply */
1537 if (unlikely(uc_req.value > uc_max.value))
1543 unsigned long uclamp_eff_value(struct task_struct *p, enum uclamp_id clamp_id)
1545 struct uclamp_se uc_eff;
1547 /* Task currently refcounted: use back-annotated (effective) value */
1548 if (p->uclamp[clamp_id].active)
1549 return (unsigned long)p->uclamp[clamp_id].value;
1551 uc_eff = uclamp_eff_get(p, clamp_id);
1553 return (unsigned long)uc_eff.value;
1557 * When a task is enqueued on a rq, the clamp bucket currently defined by the
1558 * task's uclamp::bucket_id is refcounted on that rq. This also immediately
1559 * updates the rq's clamp value if required.
1561 * Tasks can have a task-specific value requested from user-space, track
1562 * within each bucket the maximum value for tasks refcounted in it.
1563 * This "local max aggregation" allows to track the exact "requested" value
1564 * for each bucket when all its RUNNABLE tasks require the same clamp.
1566 static inline void uclamp_rq_inc_id(struct rq *rq, struct task_struct *p,
1567 enum uclamp_id clamp_id)
1569 struct uclamp_rq *uc_rq = &rq->uclamp[clamp_id];
1570 struct uclamp_se *uc_se = &p->uclamp[clamp_id];
1571 struct uclamp_bucket *bucket;
1573 lockdep_assert_rq_held(rq);
1575 /* Update task effective clamp */
1576 p->uclamp[clamp_id] = uclamp_eff_get(p, clamp_id);
1578 bucket = &uc_rq->bucket[uc_se->bucket_id];
1580 uc_se->active = true;
1582 uclamp_idle_reset(rq, clamp_id, uc_se->value);
1585 * Local max aggregation: rq buckets always track the max
1586 * "requested" clamp value of its RUNNABLE tasks.
1588 if (bucket->tasks == 1 || uc_se->value > bucket->value)
1589 bucket->value = uc_se->value;
1591 if (uc_se->value > uclamp_rq_get(rq, clamp_id))
1592 uclamp_rq_set(rq, clamp_id, uc_se->value);
1596 * When a task is dequeued from a rq, the clamp bucket refcounted by the task
1597 * is released. If this is the last task reference counting the rq's max
1598 * active clamp value, then the rq's clamp value is updated.
1600 * Both refcounted tasks and rq's cached clamp values are expected to be
1601 * always valid. If it's detected they are not, as defensive programming,
1602 * enforce the expected state and warn.
1604 static inline void uclamp_rq_dec_id(struct rq *rq, struct task_struct *p,
1605 enum uclamp_id clamp_id)
1607 struct uclamp_rq *uc_rq = &rq->uclamp[clamp_id];
1608 struct uclamp_se *uc_se = &p->uclamp[clamp_id];
1609 struct uclamp_bucket *bucket;
1610 unsigned int bkt_clamp;
1611 unsigned int rq_clamp;
1613 lockdep_assert_rq_held(rq);
1616 * If sched_uclamp_used was enabled after task @p was enqueued,
1617 * we could end up with unbalanced call to uclamp_rq_dec_id().
1619 * In this case the uc_se->active flag should be false since no uclamp
1620 * accounting was performed at enqueue time and we can just return
1623 * Need to be careful of the following enqueue/dequeue ordering
1627 * // sched_uclamp_used gets enabled
1630 * // Must not decrement bucket->tasks here
1633 * where we could end up with stale data in uc_se and
1634 * bucket[uc_se->bucket_id].
1636 * The following check here eliminates the possibility of such race.
1638 if (unlikely(!uc_se->active))
1641 bucket = &uc_rq->bucket[uc_se->bucket_id];
1643 SCHED_WARN_ON(!bucket->tasks);
1644 if (likely(bucket->tasks))
1647 uc_se->active = false;
1650 * Keep "local max aggregation" simple and accept to (possibly)
1651 * overboost some RUNNABLE tasks in the same bucket.
1652 * The rq clamp bucket value is reset to its base value whenever
1653 * there are no more RUNNABLE tasks refcounting it.
1655 if (likely(bucket->tasks))
1658 rq_clamp = uclamp_rq_get(rq, clamp_id);
1660 * Defensive programming: this should never happen. If it happens,
1661 * e.g. due to future modification, warn and fixup the expected value.
1663 SCHED_WARN_ON(bucket->value > rq_clamp);
1664 if (bucket->value >= rq_clamp) {
1665 bkt_clamp = uclamp_rq_max_value(rq, clamp_id, uc_se->value);
1666 uclamp_rq_set(rq, clamp_id, bkt_clamp);
1670 static inline void uclamp_rq_inc(struct rq *rq, struct task_struct *p)
1672 enum uclamp_id clamp_id;
1675 * Avoid any overhead until uclamp is actually used by the userspace.
1677 * The condition is constructed such that a NOP is generated when
1678 * sched_uclamp_used is disabled.
1680 if (!static_branch_unlikely(&sched_uclamp_used))
1683 if (unlikely(!p->sched_class->uclamp_enabled))
1686 for_each_clamp_id(clamp_id)
1687 uclamp_rq_inc_id(rq, p, clamp_id);
1689 /* Reset clamp idle holding when there is one RUNNABLE task */
1690 if (rq->uclamp_flags & UCLAMP_FLAG_IDLE)
1691 rq->uclamp_flags &= ~UCLAMP_FLAG_IDLE;
1694 static inline void uclamp_rq_dec(struct rq *rq, struct task_struct *p)
1696 enum uclamp_id clamp_id;
1699 * Avoid any overhead until uclamp is actually used by the userspace.
1701 * The condition is constructed such that a NOP is generated when
1702 * sched_uclamp_used is disabled.
1704 if (!static_branch_unlikely(&sched_uclamp_used))
1707 if (unlikely(!p->sched_class->uclamp_enabled))
1710 for_each_clamp_id(clamp_id)
1711 uclamp_rq_dec_id(rq, p, clamp_id);
1714 static inline void uclamp_rq_reinc_id(struct rq *rq, struct task_struct *p,
1715 enum uclamp_id clamp_id)
1717 if (!p->uclamp[clamp_id].active)
1720 uclamp_rq_dec_id(rq, p, clamp_id);
1721 uclamp_rq_inc_id(rq, p, clamp_id);
1724 * Make sure to clear the idle flag if we've transiently reached 0
1725 * active tasks on rq.
1727 if (clamp_id == UCLAMP_MAX && (rq->uclamp_flags & UCLAMP_FLAG_IDLE))
1728 rq->uclamp_flags &= ~UCLAMP_FLAG_IDLE;
1732 uclamp_update_active(struct task_struct *p)
1734 enum uclamp_id clamp_id;
1739 * Lock the task and the rq where the task is (or was) queued.
1741 * We might lock the (previous) rq of a !RUNNABLE task, but that's the
1742 * price to pay to safely serialize util_{min,max} updates with
1743 * enqueues, dequeues and migration operations.
1744 * This is the same locking schema used by __set_cpus_allowed_ptr().
1746 rq = task_rq_lock(p, &rf);
1749 * Setting the clamp bucket is serialized by task_rq_lock().
1750 * If the task is not yet RUNNABLE and its task_struct is not
1751 * affecting a valid clamp bucket, the next time it's enqueued,
1752 * it will already see the updated clamp bucket value.
1754 for_each_clamp_id(clamp_id)
1755 uclamp_rq_reinc_id(rq, p, clamp_id);
1757 task_rq_unlock(rq, p, &rf);
1760 #ifdef CONFIG_UCLAMP_TASK_GROUP
1762 uclamp_update_active_tasks(struct cgroup_subsys_state *css)
1764 struct css_task_iter it;
1765 struct task_struct *p;
1767 css_task_iter_start(css, 0, &it);
1768 while ((p = css_task_iter_next(&it)))
1769 uclamp_update_active(p);
1770 css_task_iter_end(&it);
1773 static void cpu_util_update_eff(struct cgroup_subsys_state *css);
1776 #ifdef CONFIG_SYSCTL
1777 #ifdef CONFIG_UCLAMP_TASK
1778 #ifdef CONFIG_UCLAMP_TASK_GROUP
1779 static void uclamp_update_root_tg(void)
1781 struct task_group *tg = &root_task_group;
1783 uclamp_se_set(&tg->uclamp_req[UCLAMP_MIN],
1784 sysctl_sched_uclamp_util_min, false);
1785 uclamp_se_set(&tg->uclamp_req[UCLAMP_MAX],
1786 sysctl_sched_uclamp_util_max, false);
1789 cpu_util_update_eff(&root_task_group.css);
1793 static void uclamp_update_root_tg(void) { }
1796 static void uclamp_sync_util_min_rt_default(void)
1798 struct task_struct *g, *p;
1801 * copy_process() sysctl_uclamp
1802 * uclamp_min_rt = X;
1803 * write_lock(&tasklist_lock) read_lock(&tasklist_lock)
1804 * // link thread smp_mb__after_spinlock()
1805 * write_unlock(&tasklist_lock) read_unlock(&tasklist_lock);
1806 * sched_post_fork() for_each_process_thread()
1807 * __uclamp_sync_rt() __uclamp_sync_rt()
1809 * Ensures that either sched_post_fork() will observe the new
1810 * uclamp_min_rt or for_each_process_thread() will observe the new
1813 read_lock(&tasklist_lock);
1814 smp_mb__after_spinlock();
1815 read_unlock(&tasklist_lock);
1818 for_each_process_thread(g, p)
1819 uclamp_update_util_min_rt_default(p);
1823 static int sysctl_sched_uclamp_handler(struct ctl_table *table, int write,
1824 void *buffer, size_t *lenp, loff_t *ppos)
1826 bool update_root_tg = false;
1827 int old_min, old_max, old_min_rt;
1830 guard(mutex)(&uclamp_mutex);
1832 old_min = sysctl_sched_uclamp_util_min;
1833 old_max = sysctl_sched_uclamp_util_max;
1834 old_min_rt = sysctl_sched_uclamp_util_min_rt_default;
1836 result = proc_dointvec(table, write, buffer, lenp, ppos);
1842 if (sysctl_sched_uclamp_util_min > sysctl_sched_uclamp_util_max ||
1843 sysctl_sched_uclamp_util_max > SCHED_CAPACITY_SCALE ||
1844 sysctl_sched_uclamp_util_min_rt_default > SCHED_CAPACITY_SCALE) {
1850 if (old_min != sysctl_sched_uclamp_util_min) {
1851 uclamp_se_set(&uclamp_default[UCLAMP_MIN],
1852 sysctl_sched_uclamp_util_min, false);
1853 update_root_tg = true;
1855 if (old_max != sysctl_sched_uclamp_util_max) {
1856 uclamp_se_set(&uclamp_default[UCLAMP_MAX],
1857 sysctl_sched_uclamp_util_max, false);
1858 update_root_tg = true;
1861 if (update_root_tg) {
1862 static_branch_enable(&sched_uclamp_used);
1863 uclamp_update_root_tg();
1866 if (old_min_rt != sysctl_sched_uclamp_util_min_rt_default) {
1867 static_branch_enable(&sched_uclamp_used);
1868 uclamp_sync_util_min_rt_default();
1872 * We update all RUNNABLE tasks only when task groups are in use.
1873 * Otherwise, keep it simple and do just a lazy update at each next
1874 * task enqueue time.
1879 sysctl_sched_uclamp_util_min = old_min;
1880 sysctl_sched_uclamp_util_max = old_max;
1881 sysctl_sched_uclamp_util_min_rt_default = old_min_rt;
1887 static int uclamp_validate(struct task_struct *p,
1888 const struct sched_attr *attr)
1890 int util_min = p->uclamp_req[UCLAMP_MIN].value;
1891 int util_max = p->uclamp_req[UCLAMP_MAX].value;
1893 if (attr->sched_flags & SCHED_FLAG_UTIL_CLAMP_MIN) {
1894 util_min = attr->sched_util_min;
1896 if (util_min + 1 > SCHED_CAPACITY_SCALE + 1)
1900 if (attr->sched_flags & SCHED_FLAG_UTIL_CLAMP_MAX) {
1901 util_max = attr->sched_util_max;
1903 if (util_max + 1 > SCHED_CAPACITY_SCALE + 1)
1907 if (util_min != -1 && util_max != -1 && util_min > util_max)
1911 * We have valid uclamp attributes; make sure uclamp is enabled.
1913 * We need to do that here, because enabling static branches is a
1914 * blocking operation which obviously cannot be done while holding
1917 static_branch_enable(&sched_uclamp_used);
1922 static bool uclamp_reset(const struct sched_attr *attr,
1923 enum uclamp_id clamp_id,
1924 struct uclamp_se *uc_se)
1926 /* Reset on sched class change for a non user-defined clamp value. */
1927 if (likely(!(attr->sched_flags & SCHED_FLAG_UTIL_CLAMP)) &&
1928 !uc_se->user_defined)
1931 /* Reset on sched_util_{min,max} == -1. */
1932 if (clamp_id == UCLAMP_MIN &&
1933 attr->sched_flags & SCHED_FLAG_UTIL_CLAMP_MIN &&
1934 attr->sched_util_min == -1) {
1938 if (clamp_id == UCLAMP_MAX &&
1939 attr->sched_flags & SCHED_FLAG_UTIL_CLAMP_MAX &&
1940 attr->sched_util_max == -1) {
1947 static void __setscheduler_uclamp(struct task_struct *p,
1948 const struct sched_attr *attr)
1950 enum uclamp_id clamp_id;
1952 for_each_clamp_id(clamp_id) {
1953 struct uclamp_se *uc_se = &p->uclamp_req[clamp_id];
1956 if (!uclamp_reset(attr, clamp_id, uc_se))
1960 * RT by default have a 100% boost value that could be modified
1963 if (unlikely(rt_task(p) && clamp_id == UCLAMP_MIN))
1964 value = sysctl_sched_uclamp_util_min_rt_default;
1966 value = uclamp_none(clamp_id);
1968 uclamp_se_set(uc_se, value, false);
1972 if (likely(!(attr->sched_flags & SCHED_FLAG_UTIL_CLAMP)))
1975 if (attr->sched_flags & SCHED_FLAG_UTIL_CLAMP_MIN &&
1976 attr->sched_util_min != -1) {
1977 uclamp_se_set(&p->uclamp_req[UCLAMP_MIN],
1978 attr->sched_util_min, true);
1981 if (attr->sched_flags & SCHED_FLAG_UTIL_CLAMP_MAX &&
1982 attr->sched_util_max != -1) {
1983 uclamp_se_set(&p->uclamp_req[UCLAMP_MAX],
1984 attr->sched_util_max, true);
1988 static void uclamp_fork(struct task_struct *p)
1990 enum uclamp_id clamp_id;
1993 * We don't need to hold task_rq_lock() when updating p->uclamp_* here
1994 * as the task is still at its early fork stages.
1996 for_each_clamp_id(clamp_id)
1997 p->uclamp[clamp_id].active = false;
1999 if (likely(!p->sched_reset_on_fork))
2002 for_each_clamp_id(clamp_id) {
2003 uclamp_se_set(&p->uclamp_req[clamp_id],
2004 uclamp_none(clamp_id), false);
2008 static void uclamp_post_fork(struct task_struct *p)
2010 uclamp_update_util_min_rt_default(p);
2013 static void __init init_uclamp_rq(struct rq *rq)
2015 enum uclamp_id clamp_id;
2016 struct uclamp_rq *uc_rq = rq->uclamp;
2018 for_each_clamp_id(clamp_id) {
2019 uc_rq[clamp_id] = (struct uclamp_rq) {
2020 .value = uclamp_none(clamp_id)
2024 rq->uclamp_flags = UCLAMP_FLAG_IDLE;
2027 static void __init init_uclamp(void)
2029 struct uclamp_se uc_max = {};
2030 enum uclamp_id clamp_id;
2033 for_each_possible_cpu(cpu)
2034 init_uclamp_rq(cpu_rq(cpu));
2036 for_each_clamp_id(clamp_id) {
2037 uclamp_se_set(&init_task.uclamp_req[clamp_id],
2038 uclamp_none(clamp_id), false);
2041 /* System defaults allow max clamp values for both indexes */
2042 uclamp_se_set(&uc_max, uclamp_none(UCLAMP_MAX), false);
2043 for_each_clamp_id(clamp_id) {
2044 uclamp_default[clamp_id] = uc_max;
2045 #ifdef CONFIG_UCLAMP_TASK_GROUP
2046 root_task_group.uclamp_req[clamp_id] = uc_max;
2047 root_task_group.uclamp[clamp_id] = uc_max;
2052 #else /* CONFIG_UCLAMP_TASK */
2053 static inline void uclamp_rq_inc(struct rq *rq, struct task_struct *p) { }
2054 static inline void uclamp_rq_dec(struct rq *rq, struct task_struct *p) { }
2055 static inline int uclamp_validate(struct task_struct *p,
2056 const struct sched_attr *attr)
2060 static void __setscheduler_uclamp(struct task_struct *p,
2061 const struct sched_attr *attr) { }
2062 static inline void uclamp_fork(struct task_struct *p) { }
2063 static inline void uclamp_post_fork(struct task_struct *p) { }
2064 static inline void init_uclamp(void) { }
2065 #endif /* CONFIG_UCLAMP_TASK */
2067 bool sched_task_on_rq(struct task_struct *p)
2069 return task_on_rq_queued(p);
2072 unsigned long get_wchan(struct task_struct *p)
2074 unsigned long ip = 0;
2077 if (!p || p == current)
2080 /* Only get wchan if task is blocked and we can keep it that way. */
2081 raw_spin_lock_irq(&p->pi_lock);
2082 state = READ_ONCE(p->__state);
2083 smp_rmb(); /* see try_to_wake_up() */
2084 if (state != TASK_RUNNING && state != TASK_WAKING && !p->on_rq)
2085 ip = __get_wchan(p);
2086 raw_spin_unlock_irq(&p->pi_lock);
2091 static inline void enqueue_task(struct rq *rq, struct task_struct *p, int flags)
2093 if (!(flags & ENQUEUE_NOCLOCK))
2094 update_rq_clock(rq);
2096 if (!(flags & ENQUEUE_RESTORE)) {
2097 sched_info_enqueue(rq, p);
2098 psi_enqueue(p, (flags & ENQUEUE_WAKEUP) && !(flags & ENQUEUE_MIGRATED));
2101 uclamp_rq_inc(rq, p);
2102 p->sched_class->enqueue_task(rq, p, flags);
2104 if (sched_core_enabled(rq))
2105 sched_core_enqueue(rq, p);
2108 static inline void dequeue_task(struct rq *rq, struct task_struct *p, int flags)
2110 if (sched_core_enabled(rq))
2111 sched_core_dequeue(rq, p, flags);
2113 if (!(flags & DEQUEUE_NOCLOCK))
2114 update_rq_clock(rq);
2116 if (!(flags & DEQUEUE_SAVE)) {
2117 sched_info_dequeue(rq, p);
2118 psi_dequeue(p, flags & DEQUEUE_SLEEP);
2121 uclamp_rq_dec(rq, p);
2122 p->sched_class->dequeue_task(rq, p, flags);
2125 void activate_task(struct rq *rq, struct task_struct *p, int flags)
2127 if (task_on_rq_migrating(p))
2128 flags |= ENQUEUE_MIGRATED;
2129 if (flags & ENQUEUE_MIGRATED)
2130 sched_mm_cid_migrate_to(rq, p);
2132 enqueue_task(rq, p, flags);
2134 p->on_rq = TASK_ON_RQ_QUEUED;
2137 void deactivate_task(struct rq *rq, struct task_struct *p, int flags)
2139 p->on_rq = (flags & DEQUEUE_SLEEP) ? 0 : TASK_ON_RQ_MIGRATING;
2141 dequeue_task(rq, p, flags);
2144 static inline int __normal_prio(int policy, int rt_prio, int nice)
2148 if (dl_policy(policy))
2149 prio = MAX_DL_PRIO - 1;
2150 else if (rt_policy(policy))
2151 prio = MAX_RT_PRIO - 1 - rt_prio;
2153 prio = NICE_TO_PRIO(nice);
2159 * Calculate the expected normal priority: i.e. priority
2160 * without taking RT-inheritance into account. Might be
2161 * boosted by interactivity modifiers. Changes upon fork,
2162 * setprio syscalls, and whenever the interactivity
2163 * estimator recalculates.
2165 static inline int normal_prio(struct task_struct *p)
2167 return __normal_prio(p->policy, p->rt_priority, PRIO_TO_NICE(p->static_prio));
2171 * Calculate the current priority, i.e. the priority
2172 * taken into account by the scheduler. This value might
2173 * be boosted by RT tasks, or might be boosted by
2174 * interactivity modifiers. Will be RT if the task got
2175 * RT-boosted. If not then it returns p->normal_prio.
2177 static int effective_prio(struct task_struct *p)
2179 p->normal_prio = normal_prio(p);
2181 * If we are RT tasks or we were boosted to RT priority,
2182 * keep the priority unchanged. Otherwise, update priority
2183 * to the normal priority:
2185 if (!rt_prio(p->prio))
2186 return p->normal_prio;
2191 * task_curr - is this task currently executing on a CPU?
2192 * @p: the task in question.
2194 * Return: 1 if the task is currently executing. 0 otherwise.
2196 inline int task_curr(const struct task_struct *p)
2198 return cpu_curr(task_cpu(p)) == p;
2202 * switched_from, switched_to and prio_changed must _NOT_ drop rq->lock,
2203 * use the balance_callback list if you want balancing.
2205 * this means any call to check_class_changed() must be followed by a call to
2206 * balance_callback().
2208 static inline void check_class_changed(struct rq *rq, struct task_struct *p,
2209 const struct sched_class *prev_class,
2212 if (prev_class != p->sched_class) {
2213 if (prev_class->switched_from)
2214 prev_class->switched_from(rq, p);
2216 p->sched_class->switched_to(rq, p);
2217 } else if (oldprio != p->prio || dl_task(p))
2218 p->sched_class->prio_changed(rq, p, oldprio);
2221 void check_preempt_curr(struct rq *rq, struct task_struct *p, int flags)
2223 if (p->sched_class == rq->curr->sched_class)
2224 rq->curr->sched_class->check_preempt_curr(rq, p, flags);
2225 else if (sched_class_above(p->sched_class, rq->curr->sched_class))
2229 * A queue event has occurred, and we're going to schedule. In
2230 * this case, we can save a useless back to back clock update.
2232 if (task_on_rq_queued(rq->curr) && test_tsk_need_resched(rq->curr))
2233 rq_clock_skip_update(rq);
2236 static __always_inline
2237 int __task_state_match(struct task_struct *p, unsigned int state)
2239 if (READ_ONCE(p->__state) & state)
2242 #ifdef CONFIG_PREEMPT_RT
2243 if (READ_ONCE(p->saved_state) & state)
2249 static __always_inline
2250 int task_state_match(struct task_struct *p, unsigned int state)
2252 #ifdef CONFIG_PREEMPT_RT
2256 * Serialize against current_save_and_set_rtlock_wait_state() and
2257 * current_restore_rtlock_saved_state().
2259 raw_spin_lock_irq(&p->pi_lock);
2260 match = __task_state_match(p, state);
2261 raw_spin_unlock_irq(&p->pi_lock);
2265 return __task_state_match(p, state);
2270 * wait_task_inactive - wait for a thread to unschedule.
2272 * Wait for the thread to block in any of the states set in @match_state.
2273 * If it changes, i.e. @p might have woken up, then return zero. When we
2274 * succeed in waiting for @p to be off its CPU, we return a positive number
2275 * (its total switch count). If a second call a short while later returns the
2276 * same number, the caller can be sure that @p has remained unscheduled the
2279 * The caller must ensure that the task *will* unschedule sometime soon,
2280 * else this function might spin for a *long* time. This function can't
2281 * be called with interrupts off, or it may introduce deadlock with
2282 * smp_call_function() if an IPI is sent by the same process we are
2283 * waiting to become inactive.
2285 unsigned long wait_task_inactive(struct task_struct *p, unsigned int match_state)
2287 int running, queued, match;
2294 * We do the initial early heuristics without holding
2295 * any task-queue locks at all. We'll only try to get
2296 * the runqueue lock when things look like they will
2302 * If the task is actively running on another CPU
2303 * still, just relax and busy-wait without holding
2306 * NOTE! Since we don't hold any locks, it's not
2307 * even sure that "rq" stays as the right runqueue!
2308 * But we don't care, since "task_on_cpu()" will
2309 * return false if the runqueue has changed and p
2310 * is actually now running somewhere else!
2312 while (task_on_cpu(rq, p)) {
2313 if (!task_state_match(p, match_state))
2319 * Ok, time to look more closely! We need the rq
2320 * lock now, to be *sure*. If we're wrong, we'll
2321 * just go back and repeat.
2323 rq = task_rq_lock(p, &rf);
2324 trace_sched_wait_task(p);
2325 running = task_on_cpu(rq, p);
2326 queued = task_on_rq_queued(p);
2328 if ((match = __task_state_match(p, match_state))) {
2330 * When matching on p->saved_state, consider this task
2331 * still queued so it will wait.
2335 ncsw = p->nvcsw | LONG_MIN; /* sets MSB */
2337 task_rq_unlock(rq, p, &rf);
2340 * If it changed from the expected state, bail out now.
2342 if (unlikely(!ncsw))
2346 * Was it really running after all now that we
2347 * checked with the proper locks actually held?
2349 * Oops. Go back and try again..
2351 if (unlikely(running)) {
2357 * It's not enough that it's not actively running,
2358 * it must be off the runqueue _entirely_, and not
2361 * So if it was still runnable (but just not actively
2362 * running right now), it's preempted, and we should
2363 * yield - it could be a while.
2365 if (unlikely(queued)) {
2366 ktime_t to = NSEC_PER_SEC / HZ;
2368 set_current_state(TASK_UNINTERRUPTIBLE);
2369 schedule_hrtimeout(&to, HRTIMER_MODE_REL_HARD);
2374 * Ahh, all good. It wasn't running, and it wasn't
2375 * runnable, which means that it will never become
2376 * running in the future either. We're all done!
2387 __do_set_cpus_allowed(struct task_struct *p, struct affinity_context *ctx);
2389 static int __set_cpus_allowed_ptr(struct task_struct *p,
2390 struct affinity_context *ctx);
2392 static void migrate_disable_switch(struct rq *rq, struct task_struct *p)
2394 struct affinity_context ac = {
2395 .new_mask = cpumask_of(rq->cpu),
2396 .flags = SCA_MIGRATE_DISABLE,
2399 if (likely(!p->migration_disabled))
2402 if (p->cpus_ptr != &p->cpus_mask)
2406 * Violates locking rules! see comment in __do_set_cpus_allowed().
2408 __do_set_cpus_allowed(p, &ac);
2411 void migrate_disable(void)
2413 struct task_struct *p = current;
2415 if (p->migration_disabled) {
2416 p->migration_disabled++;
2421 this_rq()->nr_pinned++;
2422 p->migration_disabled = 1;
2425 EXPORT_SYMBOL_GPL(migrate_disable);
2427 void migrate_enable(void)
2429 struct task_struct *p = current;
2430 struct affinity_context ac = {
2431 .new_mask = &p->cpus_mask,
2432 .flags = SCA_MIGRATE_ENABLE,
2435 if (p->migration_disabled > 1) {
2436 p->migration_disabled--;
2440 if (WARN_ON_ONCE(!p->migration_disabled))
2444 * Ensure stop_task runs either before or after this, and that
2445 * __set_cpus_allowed_ptr(SCA_MIGRATE_ENABLE) doesn't schedule().
2448 if (p->cpus_ptr != &p->cpus_mask)
2449 __set_cpus_allowed_ptr(p, &ac);
2451 * Mustn't clear migration_disabled() until cpus_ptr points back at the
2452 * regular cpus_mask, otherwise things that race (eg.
2453 * select_fallback_rq) get confused.
2456 p->migration_disabled = 0;
2457 this_rq()->nr_pinned--;
2460 EXPORT_SYMBOL_GPL(migrate_enable);
2462 static inline bool rq_has_pinned_tasks(struct rq *rq)
2464 return rq->nr_pinned;
2468 * Per-CPU kthreads are allowed to run on !active && online CPUs, see
2469 * __set_cpus_allowed_ptr() and select_fallback_rq().
2471 static inline bool is_cpu_allowed(struct task_struct *p, int cpu)
2473 /* When not in the task's cpumask, no point in looking further. */
2474 if (!cpumask_test_cpu(cpu, p->cpus_ptr))
2477 /* migrate_disabled() must be allowed to finish. */
2478 if (is_migration_disabled(p))
2479 return cpu_online(cpu);
2481 /* Non kernel threads are not allowed during either online or offline. */
2482 if (!(p->flags & PF_KTHREAD))
2483 return cpu_active(cpu) && task_cpu_possible(cpu, p);
2485 /* KTHREAD_IS_PER_CPU is always allowed. */
2486 if (kthread_is_per_cpu(p))
2487 return cpu_online(cpu);
2489 /* Regular kernel threads don't get to stay during offline. */
2493 /* But are allowed during online. */
2494 return cpu_online(cpu);
2498 * This is how migration works:
2500 * 1) we invoke migration_cpu_stop() on the target CPU using
2502 * 2) stopper starts to run (implicitly forcing the migrated thread
2504 * 3) it checks whether the migrated task is still in the wrong runqueue.
2505 * 4) if it's in the wrong runqueue then the migration thread removes
2506 * it and puts it into the right queue.
2507 * 5) stopper completes and stop_one_cpu() returns and the migration
2512 * move_queued_task - move a queued task to new rq.
2514 * Returns (locked) new rq. Old rq's lock is released.
2516 static struct rq *move_queued_task(struct rq *rq, struct rq_flags *rf,
2517 struct task_struct *p, int new_cpu)
2519 lockdep_assert_rq_held(rq);
2521 deactivate_task(rq, p, DEQUEUE_NOCLOCK);
2522 set_task_cpu(p, new_cpu);
2525 rq = cpu_rq(new_cpu);
2528 WARN_ON_ONCE(task_cpu(p) != new_cpu);
2529 activate_task(rq, p, 0);
2530 check_preempt_curr(rq, p, 0);
2535 struct migration_arg {
2536 struct task_struct *task;
2538 struct set_affinity_pending *pending;
2542 * @refs: number of wait_for_completion()
2543 * @stop_pending: is @stop_work in use
2545 struct set_affinity_pending {
2547 unsigned int stop_pending;
2548 struct completion done;
2549 struct cpu_stop_work stop_work;
2550 struct migration_arg arg;
2554 * Move (not current) task off this CPU, onto the destination CPU. We're doing
2555 * this because either it can't run here any more (set_cpus_allowed()
2556 * away from this CPU, or CPU going down), or because we're
2557 * attempting to rebalance this task on exec (sched_exec).
2559 * So we race with normal scheduler movements, but that's OK, as long
2560 * as the task is no longer on this CPU.
2562 static struct rq *__migrate_task(struct rq *rq, struct rq_flags *rf,
2563 struct task_struct *p, int dest_cpu)
2565 /* Affinity changed (again). */
2566 if (!is_cpu_allowed(p, dest_cpu))
2569 rq = move_queued_task(rq, rf, p, dest_cpu);
2575 * migration_cpu_stop - this will be executed by a highprio stopper thread
2576 * and performs thread migration by bumping thread off CPU then
2577 * 'pushing' onto another runqueue.
2579 static int migration_cpu_stop(void *data)
2581 struct migration_arg *arg = data;
2582 struct set_affinity_pending *pending = arg->pending;
2583 struct task_struct *p = arg->task;
2584 struct rq *rq = this_rq();
2585 bool complete = false;
2589 * The original target CPU might have gone down and we might
2590 * be on another CPU but it doesn't matter.
2592 local_irq_save(rf.flags);
2594 * We need to explicitly wake pending tasks before running
2595 * __migrate_task() such that we will not miss enforcing cpus_ptr
2596 * during wakeups, see set_cpus_allowed_ptr()'s TASK_WAKING test.
2598 flush_smp_call_function_queue();
2600 raw_spin_lock(&p->pi_lock);
2604 * If we were passed a pending, then ->stop_pending was set, thus
2605 * p->migration_pending must have remained stable.
2607 WARN_ON_ONCE(pending && pending != p->migration_pending);
2610 * If task_rq(p) != rq, it cannot be migrated here, because we're
2611 * holding rq->lock, if p->on_rq == 0 it cannot get enqueued because
2612 * we're holding p->pi_lock.
2614 if (task_rq(p) == rq) {
2615 if (is_migration_disabled(p))
2619 p->migration_pending = NULL;
2622 if (cpumask_test_cpu(task_cpu(p), &p->cpus_mask))
2626 if (task_on_rq_queued(p)) {
2627 update_rq_clock(rq);
2628 rq = __migrate_task(rq, &rf, p, arg->dest_cpu);
2630 p->wake_cpu = arg->dest_cpu;
2634 * XXX __migrate_task() can fail, at which point we might end
2635 * up running on a dodgy CPU, AFAICT this can only happen
2636 * during CPU hotplug, at which point we'll get pushed out
2637 * anyway, so it's probably not a big deal.
2640 } else if (pending) {
2642 * This happens when we get migrated between migrate_enable()'s
2643 * preempt_enable() and scheduling the stopper task. At that
2644 * point we're a regular task again and not current anymore.
2646 * A !PREEMPT kernel has a giant hole here, which makes it far
2651 * The task moved before the stopper got to run. We're holding
2652 * ->pi_lock, so the allowed mask is stable - if it got
2653 * somewhere allowed, we're done.
2655 if (cpumask_test_cpu(task_cpu(p), p->cpus_ptr)) {
2656 p->migration_pending = NULL;
2662 * When migrate_enable() hits a rq mis-match we can't reliably
2663 * determine is_migration_disabled() and so have to chase after
2666 WARN_ON_ONCE(!pending->stop_pending);
2668 task_rq_unlock(rq, p, &rf);
2669 stop_one_cpu_nowait(task_cpu(p), migration_cpu_stop,
2670 &pending->arg, &pending->stop_work);
2676 pending->stop_pending = false;
2677 task_rq_unlock(rq, p, &rf);
2680 complete_all(&pending->done);
2685 int push_cpu_stop(void *arg)
2687 struct rq *lowest_rq = NULL, *rq = this_rq();
2688 struct task_struct *p = arg;
2690 raw_spin_lock_irq(&p->pi_lock);
2691 raw_spin_rq_lock(rq);
2693 if (task_rq(p) != rq)
2696 if (is_migration_disabled(p)) {
2697 p->migration_flags |= MDF_PUSH;
2701 p->migration_flags &= ~MDF_PUSH;
2703 if (p->sched_class->find_lock_rq)
2704 lowest_rq = p->sched_class->find_lock_rq(p, rq);
2709 // XXX validate p is still the highest prio task
2710 if (task_rq(p) == rq) {
2711 deactivate_task(rq, p, 0);
2712 set_task_cpu(p, lowest_rq->cpu);
2713 activate_task(lowest_rq, p, 0);
2714 resched_curr(lowest_rq);
2717 double_unlock_balance(rq, lowest_rq);
2720 rq->push_busy = false;
2721 raw_spin_rq_unlock(rq);
2722 raw_spin_unlock_irq(&p->pi_lock);
2729 * sched_class::set_cpus_allowed must do the below, but is not required to
2730 * actually call this function.
2732 void set_cpus_allowed_common(struct task_struct *p, struct affinity_context *ctx)
2734 if (ctx->flags & (SCA_MIGRATE_ENABLE | SCA_MIGRATE_DISABLE)) {
2735 p->cpus_ptr = ctx->new_mask;
2739 cpumask_copy(&p->cpus_mask, ctx->new_mask);
2740 p->nr_cpus_allowed = cpumask_weight(ctx->new_mask);
2743 * Swap in a new user_cpus_ptr if SCA_USER flag set
2745 if (ctx->flags & SCA_USER)
2746 swap(p->user_cpus_ptr, ctx->user_mask);
2750 __do_set_cpus_allowed(struct task_struct *p, struct affinity_context *ctx)
2752 struct rq *rq = task_rq(p);
2753 bool queued, running;
2756 * This here violates the locking rules for affinity, since we're only
2757 * supposed to change these variables while holding both rq->lock and
2760 * HOWEVER, it magically works, because ttwu() is the only code that
2761 * accesses these variables under p->pi_lock and only does so after
2762 * smp_cond_load_acquire(&p->on_cpu, !VAL), and we're in __schedule()
2763 * before finish_task().
2765 * XXX do further audits, this smells like something putrid.
2767 if (ctx->flags & SCA_MIGRATE_DISABLE)
2768 SCHED_WARN_ON(!p->on_cpu);
2770 lockdep_assert_held(&p->pi_lock);
2772 queued = task_on_rq_queued(p);
2773 running = task_current(rq, p);
2777 * Because __kthread_bind() calls this on blocked tasks without
2780 lockdep_assert_rq_held(rq);
2781 dequeue_task(rq, p, DEQUEUE_SAVE | DEQUEUE_NOCLOCK);
2784 put_prev_task(rq, p);
2786 p->sched_class->set_cpus_allowed(p, ctx);
2789 enqueue_task(rq, p, ENQUEUE_RESTORE | ENQUEUE_NOCLOCK);
2791 set_next_task(rq, p);
2795 * Used for kthread_bind() and select_fallback_rq(), in both cases the user
2796 * affinity (if any) should be destroyed too.
2798 void do_set_cpus_allowed(struct task_struct *p, const struct cpumask *new_mask)
2800 struct affinity_context ac = {
2801 .new_mask = new_mask,
2803 .flags = SCA_USER, /* clear the user requested mask */
2805 union cpumask_rcuhead {
2807 struct rcu_head rcu;
2810 __do_set_cpus_allowed(p, &ac);
2813 * Because this is called with p->pi_lock held, it is not possible
2814 * to use kfree() here (when PREEMPT_RT=y), therefore punt to using
2817 kfree_rcu((union cpumask_rcuhead *)ac.user_mask, rcu);
2820 static cpumask_t *alloc_user_cpus_ptr(int node)
2823 * See do_set_cpus_allowed() above for the rcu_head usage.
2825 int size = max_t(int, cpumask_size(), sizeof(struct rcu_head));
2827 return kmalloc_node(size, GFP_KERNEL, node);
2830 int dup_user_cpus_ptr(struct task_struct *dst, struct task_struct *src,
2833 cpumask_t *user_mask;
2834 unsigned long flags;
2837 * Always clear dst->user_cpus_ptr first as their user_cpus_ptr's
2838 * may differ by now due to racing.
2840 dst->user_cpus_ptr = NULL;
2843 * This check is racy and losing the race is a valid situation.
2844 * It is not worth the extra overhead of taking the pi_lock on
2847 if (data_race(!src->user_cpus_ptr))
2850 user_mask = alloc_user_cpus_ptr(node);
2855 * Use pi_lock to protect content of user_cpus_ptr
2857 * Though unlikely, user_cpus_ptr can be reset to NULL by a concurrent
2858 * do_set_cpus_allowed().
2860 raw_spin_lock_irqsave(&src->pi_lock, flags);
2861 if (src->user_cpus_ptr) {
2862 swap(dst->user_cpus_ptr, user_mask);
2863 cpumask_copy(dst->user_cpus_ptr, src->user_cpus_ptr);
2865 raw_spin_unlock_irqrestore(&src->pi_lock, flags);
2867 if (unlikely(user_mask))
2873 static inline struct cpumask *clear_user_cpus_ptr(struct task_struct *p)
2875 struct cpumask *user_mask = NULL;
2877 swap(p->user_cpus_ptr, user_mask);
2882 void release_user_cpus_ptr(struct task_struct *p)
2884 kfree(clear_user_cpus_ptr(p));
2888 * This function is wildly self concurrent; here be dragons.
2891 * When given a valid mask, __set_cpus_allowed_ptr() must block until the
2892 * designated task is enqueued on an allowed CPU. If that task is currently
2893 * running, we have to kick it out using the CPU stopper.
2895 * Migrate-Disable comes along and tramples all over our nice sandcastle.
2898 * Initial conditions: P0->cpus_mask = [0, 1]
2902 * migrate_disable();
2904 * set_cpus_allowed_ptr(P0, [1]);
2906 * P1 *cannot* return from this set_cpus_allowed_ptr() call until P0 executes
2907 * its outermost migrate_enable() (i.e. it exits its Migrate-Disable region).
2908 * This means we need the following scheme:
2912 * migrate_disable();
2914 * set_cpus_allowed_ptr(P0, [1]);
2918 * __set_cpus_allowed_ptr();
2919 * <wakes local stopper>
2920 * `--> <woken on migration completion>
2922 * Now the fun stuff: there may be several P1-like tasks, i.e. multiple
2923 * concurrent set_cpus_allowed_ptr(P0, [*]) calls. CPU affinity changes of any
2924 * task p are serialized by p->pi_lock, which we can leverage: the one that
2925 * should come into effect at the end of the Migrate-Disable region is the last
2926 * one. This means we only need to track a single cpumask (i.e. p->cpus_mask),
2927 * but we still need to properly signal those waiting tasks at the appropriate
2930 * This is implemented using struct set_affinity_pending. The first
2931 * __set_cpus_allowed_ptr() caller within a given Migrate-Disable region will
2932 * setup an instance of that struct and install it on the targeted task_struct.
2933 * Any and all further callers will reuse that instance. Those then wait for
2934 * a completion signaled at the tail of the CPU stopper callback (1), triggered
2935 * on the end of the Migrate-Disable region (i.e. outermost migrate_enable()).
2938 * (1) In the cases covered above. There is one more where the completion is
2939 * signaled within affine_move_task() itself: when a subsequent affinity request
2940 * occurs after the stopper bailed out due to the targeted task still being
2941 * Migrate-Disable. Consider:
2943 * Initial conditions: P0->cpus_mask = [0, 1]
2947 * migrate_disable();
2949 * set_cpus_allowed_ptr(P0, [1]);
2952 * migration_cpu_stop()
2953 * is_migration_disabled()
2955 * set_cpus_allowed_ptr(P0, [0, 1]);
2956 * <signal completion>
2959 * Note that the above is safe vs a concurrent migrate_enable(), as any
2960 * pending affinity completion is preceded by an uninstallation of
2961 * p->migration_pending done with p->pi_lock held.
2963 static int affine_move_task(struct rq *rq, struct task_struct *p, struct rq_flags *rf,
2964 int dest_cpu, unsigned int flags)
2965 __releases(rq->lock)
2966 __releases(p->pi_lock)
2968 struct set_affinity_pending my_pending = { }, *pending = NULL;
2969 bool stop_pending, complete = false;
2971 /* Can the task run on the task's current CPU? If so, we're done */
2972 if (cpumask_test_cpu(task_cpu(p), &p->cpus_mask)) {
2973 struct task_struct *push_task = NULL;
2975 if ((flags & SCA_MIGRATE_ENABLE) &&
2976 (p->migration_flags & MDF_PUSH) && !rq->push_busy) {
2977 rq->push_busy = true;
2978 push_task = get_task_struct(p);
2982 * If there are pending waiters, but no pending stop_work,
2983 * then complete now.
2985 pending = p->migration_pending;
2986 if (pending && !pending->stop_pending) {
2987 p->migration_pending = NULL;
2992 task_rq_unlock(rq, p, rf);
2994 stop_one_cpu_nowait(rq->cpu, push_cpu_stop,
3000 complete_all(&pending->done);
3005 if (!(flags & SCA_MIGRATE_ENABLE)) {
3006 /* serialized by p->pi_lock */
3007 if (!p->migration_pending) {
3008 /* Install the request */
3009 refcount_set(&my_pending.refs, 1);
3010 init_completion(&my_pending.done);
3011 my_pending.arg = (struct migration_arg) {
3013 .dest_cpu = dest_cpu,
3014 .pending = &my_pending,
3017 p->migration_pending = &my_pending;
3019 pending = p->migration_pending;
3020 refcount_inc(&pending->refs);
3022 * Affinity has changed, but we've already installed a
3023 * pending. migration_cpu_stop() *must* see this, else
3024 * we risk a completion of the pending despite having a
3025 * task on a disallowed CPU.
3027 * Serialized by p->pi_lock, so this is safe.
3029 pending->arg.dest_cpu = dest_cpu;
3032 pending = p->migration_pending;
3034 * - !MIGRATE_ENABLE:
3035 * we'll have installed a pending if there wasn't one already.
3038 * we're here because the current CPU isn't matching anymore,
3039 * the only way that can happen is because of a concurrent
3040 * set_cpus_allowed_ptr() call, which should then still be
3041 * pending completion.
3043 * Either way, we really should have a @pending here.
3045 if (WARN_ON_ONCE(!pending)) {
3046 task_rq_unlock(rq, p, rf);
3050 if (task_on_cpu(rq, p) || READ_ONCE(p->__state) == TASK_WAKING) {
3052 * MIGRATE_ENABLE gets here because 'p == current', but for
3053 * anything else we cannot do is_migration_disabled(), punt
3054 * and have the stopper function handle it all race-free.
3056 stop_pending = pending->stop_pending;
3058 pending->stop_pending = true;
3060 if (flags & SCA_MIGRATE_ENABLE)
3061 p->migration_flags &= ~MDF_PUSH;
3064 task_rq_unlock(rq, p, rf);
3065 if (!stop_pending) {
3066 stop_one_cpu_nowait(cpu_of(rq), migration_cpu_stop,
3067 &pending->arg, &pending->stop_work);
3071 if (flags & SCA_MIGRATE_ENABLE)
3075 if (!is_migration_disabled(p)) {
3076 if (task_on_rq_queued(p))
3077 rq = move_queued_task(rq, rf, p, dest_cpu);
3079 if (!pending->stop_pending) {
3080 p->migration_pending = NULL;
3084 task_rq_unlock(rq, p, rf);
3087 complete_all(&pending->done);
3090 wait_for_completion(&pending->done);
3092 if (refcount_dec_and_test(&pending->refs))
3093 wake_up_var(&pending->refs); /* No UaF, just an address */
3096 * Block the original owner of &pending until all subsequent callers
3097 * have seen the completion and decremented the refcount
3099 wait_var_event(&my_pending.refs, !refcount_read(&my_pending.refs));
3102 WARN_ON_ONCE(my_pending.stop_pending);
3108 * Called with both p->pi_lock and rq->lock held; drops both before returning.
3110 static int __set_cpus_allowed_ptr_locked(struct task_struct *p,
3111 struct affinity_context *ctx,
3113 struct rq_flags *rf)
3114 __releases(rq->lock)
3115 __releases(p->pi_lock)
3117 const struct cpumask *cpu_allowed_mask = task_cpu_possible_mask(p);
3118 const struct cpumask *cpu_valid_mask = cpu_active_mask;
3119 bool kthread = p->flags & PF_KTHREAD;
3120 unsigned int dest_cpu;
3123 update_rq_clock(rq);
3125 if (kthread || is_migration_disabled(p)) {
3127 * Kernel threads are allowed on online && !active CPUs,
3128 * however, during cpu-hot-unplug, even these might get pushed
3129 * away if not KTHREAD_IS_PER_CPU.
3131 * Specifically, migration_disabled() tasks must not fail the
3132 * cpumask_any_and_distribute() pick below, esp. so on
3133 * SCA_MIGRATE_ENABLE, otherwise we'll not call
3134 * set_cpus_allowed_common() and actually reset p->cpus_ptr.
3136 cpu_valid_mask = cpu_online_mask;
3139 if (!kthread && !cpumask_subset(ctx->new_mask, cpu_allowed_mask)) {
3145 * Must re-check here, to close a race against __kthread_bind(),
3146 * sched_setaffinity() is not guaranteed to observe the flag.
3148 if ((ctx->flags & SCA_CHECK) && (p->flags & PF_NO_SETAFFINITY)) {
3153 if (!(ctx->flags & SCA_MIGRATE_ENABLE)) {
3154 if (cpumask_equal(&p->cpus_mask, ctx->new_mask)) {
3155 if (ctx->flags & SCA_USER)
3156 swap(p->user_cpus_ptr, ctx->user_mask);
3160 if (WARN_ON_ONCE(p == current &&
3161 is_migration_disabled(p) &&
3162 !cpumask_test_cpu(task_cpu(p), ctx->new_mask))) {
3169 * Picking a ~random cpu helps in cases where we are changing affinity
3170 * for groups of tasks (ie. cpuset), so that load balancing is not
3171 * immediately required to distribute the tasks within their new mask.
3173 dest_cpu = cpumask_any_and_distribute(cpu_valid_mask, ctx->new_mask);
3174 if (dest_cpu >= nr_cpu_ids) {
3179 __do_set_cpus_allowed(p, ctx);
3181 return affine_move_task(rq, p, rf, dest_cpu, ctx->flags);
3184 task_rq_unlock(rq, p, rf);
3190 * Change a given task's CPU affinity. Migrate the thread to a
3191 * proper CPU and schedule it away if the CPU it's executing on
3192 * is removed from the allowed bitmask.
3194 * NOTE: the caller must have a valid reference to the task, the
3195 * task must not exit() & deallocate itself prematurely. The
3196 * call is not atomic; no spinlocks may be held.
3198 static int __set_cpus_allowed_ptr(struct task_struct *p,
3199 struct affinity_context *ctx)
3204 rq = task_rq_lock(p, &rf);
3206 * Masking should be skipped if SCA_USER or any of the SCA_MIGRATE_*
3209 if (p->user_cpus_ptr &&
3210 !(ctx->flags & (SCA_USER | SCA_MIGRATE_ENABLE | SCA_MIGRATE_DISABLE)) &&
3211 cpumask_and(rq->scratch_mask, ctx->new_mask, p->user_cpus_ptr))
3212 ctx->new_mask = rq->scratch_mask;
3214 return __set_cpus_allowed_ptr_locked(p, ctx, rq, &rf);
3217 int set_cpus_allowed_ptr(struct task_struct *p, const struct cpumask *new_mask)
3219 struct affinity_context ac = {
3220 .new_mask = new_mask,
3224 return __set_cpus_allowed_ptr(p, &ac);
3226 EXPORT_SYMBOL_GPL(set_cpus_allowed_ptr);
3229 * Change a given task's CPU affinity to the intersection of its current
3230 * affinity mask and @subset_mask, writing the resulting mask to @new_mask.
3231 * If user_cpus_ptr is defined, use it as the basis for restricting CPU
3232 * affinity or use cpu_online_mask instead.
3234 * If the resulting mask is empty, leave the affinity unchanged and return
3237 static int restrict_cpus_allowed_ptr(struct task_struct *p,
3238 struct cpumask *new_mask,
3239 const struct cpumask *subset_mask)
3241 struct affinity_context ac = {
3242 .new_mask = new_mask,
3249 rq = task_rq_lock(p, &rf);
3252 * Forcefully restricting the affinity of a deadline task is
3253 * likely to cause problems, so fail and noisily override the
3256 if (task_has_dl_policy(p) && dl_bandwidth_enabled()) {
3261 if (!cpumask_and(new_mask, task_user_cpus(p), subset_mask)) {
3266 return __set_cpus_allowed_ptr_locked(p, &ac, rq, &rf);
3269 task_rq_unlock(rq, p, &rf);
3274 * Restrict the CPU affinity of task @p so that it is a subset of
3275 * task_cpu_possible_mask() and point @p->user_cpus_ptr to a copy of the
3276 * old affinity mask. If the resulting mask is empty, we warn and walk
3277 * up the cpuset hierarchy until we find a suitable mask.
3279 void force_compatible_cpus_allowed_ptr(struct task_struct *p)
3281 cpumask_var_t new_mask;
3282 const struct cpumask *override_mask = task_cpu_possible_mask(p);
3284 alloc_cpumask_var(&new_mask, GFP_KERNEL);
3287 * __migrate_task() can fail silently in the face of concurrent
3288 * offlining of the chosen destination CPU, so take the hotplug
3289 * lock to ensure that the migration succeeds.
3292 if (!cpumask_available(new_mask))
3295 if (!restrict_cpus_allowed_ptr(p, new_mask, override_mask))
3299 * We failed to find a valid subset of the affinity mask for the
3300 * task, so override it based on its cpuset hierarchy.
3302 cpuset_cpus_allowed(p, new_mask);
3303 override_mask = new_mask;
3306 if (printk_ratelimit()) {
3307 printk_deferred("Overriding affinity for process %d (%s) to CPUs %*pbl\n",
3308 task_pid_nr(p), p->comm,
3309 cpumask_pr_args(override_mask));
3312 WARN_ON(set_cpus_allowed_ptr(p, override_mask));
3315 free_cpumask_var(new_mask);
3319 __sched_setaffinity(struct task_struct *p, struct affinity_context *ctx);
3322 * Restore the affinity of a task @p which was previously restricted by a
3323 * call to force_compatible_cpus_allowed_ptr().
3325 * It is the caller's responsibility to serialise this with any calls to
3326 * force_compatible_cpus_allowed_ptr(@p).
3328 void relax_compatible_cpus_allowed_ptr(struct task_struct *p)
3330 struct affinity_context ac = {
3331 .new_mask = task_user_cpus(p),
3337 * Try to restore the old affinity mask with __sched_setaffinity().
3338 * Cpuset masking will be done there too.
3340 ret = __sched_setaffinity(p, &ac);
3344 void set_task_cpu(struct task_struct *p, unsigned int new_cpu)
3346 #ifdef CONFIG_SCHED_DEBUG
3347 unsigned int state = READ_ONCE(p->__state);
3350 * We should never call set_task_cpu() on a blocked task,
3351 * ttwu() will sort out the placement.
3353 WARN_ON_ONCE(state != TASK_RUNNING && state != TASK_WAKING && !p->on_rq);
3356 * Migrating fair class task must have p->on_rq = TASK_ON_RQ_MIGRATING,
3357 * because schedstat_wait_{start,end} rebase migrating task's wait_start
3358 * time relying on p->on_rq.
3360 WARN_ON_ONCE(state == TASK_RUNNING &&
3361 p->sched_class == &fair_sched_class &&
3362 (p->on_rq && !task_on_rq_migrating(p)));
3364 #ifdef CONFIG_LOCKDEP
3366 * The caller should hold either p->pi_lock or rq->lock, when changing
3367 * a task's CPU. ->pi_lock for waking tasks, rq->lock for runnable tasks.
3369 * sched_move_task() holds both and thus holding either pins the cgroup,
3372 * Furthermore, all task_rq users should acquire both locks, see
3375 WARN_ON_ONCE(debug_locks && !(lockdep_is_held(&p->pi_lock) ||
3376 lockdep_is_held(__rq_lockp(task_rq(p)))));
3379 * Clearly, migrating tasks to offline CPUs is a fairly daft thing.
3381 WARN_ON_ONCE(!cpu_online(new_cpu));
3383 WARN_ON_ONCE(is_migration_disabled(p));
3386 trace_sched_migrate_task(p, new_cpu);
3388 if (task_cpu(p) != new_cpu) {
3389 if (p->sched_class->migrate_task_rq)
3390 p->sched_class->migrate_task_rq(p, new_cpu);
3391 p->se.nr_migrations++;
3393 sched_mm_cid_migrate_from(p);
3394 perf_event_task_migrate(p);
3397 __set_task_cpu(p, new_cpu);
3400 #ifdef CONFIG_NUMA_BALANCING
3401 static void __migrate_swap_task(struct task_struct *p, int cpu)
3403 if (task_on_rq_queued(p)) {
3404 struct rq *src_rq, *dst_rq;
3405 struct rq_flags srf, drf;
3407 src_rq = task_rq(p);
3408 dst_rq = cpu_rq(cpu);
3410 rq_pin_lock(src_rq, &srf);
3411 rq_pin_lock(dst_rq, &drf);
3413 deactivate_task(src_rq, p, 0);
3414 set_task_cpu(p, cpu);
3415 activate_task(dst_rq, p, 0);
3416 check_preempt_curr(dst_rq, p, 0);
3418 rq_unpin_lock(dst_rq, &drf);
3419 rq_unpin_lock(src_rq, &srf);
3423 * Task isn't running anymore; make it appear like we migrated
3424 * it before it went to sleep. This means on wakeup we make the
3425 * previous CPU our target instead of where it really is.
3431 struct migration_swap_arg {
3432 struct task_struct *src_task, *dst_task;
3433 int src_cpu, dst_cpu;
3436 static int migrate_swap_stop(void *data)
3438 struct migration_swap_arg *arg = data;
3439 struct rq *src_rq, *dst_rq;
3441 if (!cpu_active(arg->src_cpu) || !cpu_active(arg->dst_cpu))
3444 src_rq = cpu_rq(arg->src_cpu);
3445 dst_rq = cpu_rq(arg->dst_cpu);
3447 guard(double_raw_spinlock)(&arg->src_task->pi_lock, &arg->dst_task->pi_lock);
3448 guard(double_rq_lock)(src_rq, dst_rq);
3450 if (task_cpu(arg->dst_task) != arg->dst_cpu)
3453 if (task_cpu(arg->src_task) != arg->src_cpu)
3456 if (!cpumask_test_cpu(arg->dst_cpu, arg->src_task->cpus_ptr))
3459 if (!cpumask_test_cpu(arg->src_cpu, arg->dst_task->cpus_ptr))
3462 __migrate_swap_task(arg->src_task, arg->dst_cpu);
3463 __migrate_swap_task(arg->dst_task, arg->src_cpu);
3469 * Cross migrate two tasks
3471 int migrate_swap(struct task_struct *cur, struct task_struct *p,
3472 int target_cpu, int curr_cpu)
3474 struct migration_swap_arg arg;
3477 arg = (struct migration_swap_arg){
3479 .src_cpu = curr_cpu,
3481 .dst_cpu = target_cpu,
3484 if (arg.src_cpu == arg.dst_cpu)
3488 * These three tests are all lockless; this is OK since all of them
3489 * will be re-checked with proper locks held further down the line.
3491 if (!cpu_active(arg.src_cpu) || !cpu_active(arg.dst_cpu))
3494 if (!cpumask_test_cpu(arg.dst_cpu, arg.src_task->cpus_ptr))
3497 if (!cpumask_test_cpu(arg.src_cpu, arg.dst_task->cpus_ptr))
3500 trace_sched_swap_numa(cur, arg.src_cpu, p, arg.dst_cpu);
3501 ret = stop_two_cpus(arg.dst_cpu, arg.src_cpu, migrate_swap_stop, &arg);
3506 #endif /* CONFIG_NUMA_BALANCING */
3509 * kick_process - kick a running thread to enter/exit the kernel
3510 * @p: the to-be-kicked thread
3512 * Cause a process which is running on another CPU to enter
3513 * kernel-mode, without any delay. (to get signals handled.)
3515 * NOTE: this function doesn't have to take the runqueue lock,
3516 * because all it wants to ensure is that the remote task enters
3517 * the kernel. If the IPI races and the task has been migrated
3518 * to another CPU then no harm is done and the purpose has been
3521 void kick_process(struct task_struct *p)
3527 if ((cpu != smp_processor_id()) && task_curr(p))
3528 smp_send_reschedule(cpu);
3531 EXPORT_SYMBOL_GPL(kick_process);
3534 * ->cpus_ptr is protected by both rq->lock and p->pi_lock
3536 * A few notes on cpu_active vs cpu_online:
3538 * - cpu_active must be a subset of cpu_online
3540 * - on CPU-up we allow per-CPU kthreads on the online && !active CPU,
3541 * see __set_cpus_allowed_ptr(). At this point the newly online
3542 * CPU isn't yet part of the sched domains, and balancing will not
3545 * - on CPU-down we clear cpu_active() to mask the sched domains and
3546 * avoid the load balancer to place new tasks on the to be removed
3547 * CPU. Existing tasks will remain running there and will be taken
3550 * This means that fallback selection must not select !active CPUs.
3551 * And can assume that any active CPU must be online. Conversely
3552 * select_task_rq() below may allow selection of !active CPUs in order
3553 * to satisfy the above rules.
3555 static int select_fallback_rq(int cpu, struct task_struct *p)
3557 int nid = cpu_to_node(cpu);
3558 const struct cpumask *nodemask = NULL;
3559 enum { cpuset, possible, fail } state = cpuset;
3563 * If the node that the CPU is on has been offlined, cpu_to_node()
3564 * will return -1. There is no CPU on the node, and we should
3565 * select the CPU on the other node.
3568 nodemask = cpumask_of_node(nid);
3570 /* Look for allowed, online CPU in same node. */
3571 for_each_cpu(dest_cpu, nodemask) {
3572 if (is_cpu_allowed(p, dest_cpu))
3578 /* Any allowed, online CPU? */
3579 for_each_cpu(dest_cpu, p->cpus_ptr) {
3580 if (!is_cpu_allowed(p, dest_cpu))
3586 /* No more Mr. Nice Guy. */
3589 if (cpuset_cpus_allowed_fallback(p)) {
3596 * XXX When called from select_task_rq() we only
3597 * hold p->pi_lock and again violate locking order.
3599 * More yuck to audit.
3601 do_set_cpus_allowed(p, task_cpu_possible_mask(p));
3611 if (state != cpuset) {
3613 * Don't tell them about moving exiting tasks or
3614 * kernel threads (both mm NULL), since they never
3617 if (p->mm && printk_ratelimit()) {
3618 printk_deferred("process %d (%s) no longer affine to cpu%d\n",
3619 task_pid_nr(p), p->comm, cpu);
3627 * The caller (fork, wakeup) owns p->pi_lock, ->cpus_ptr is stable.
3630 int select_task_rq(struct task_struct *p, int cpu, int wake_flags)
3632 lockdep_assert_held(&p->pi_lock);
3634 if (p->nr_cpus_allowed > 1 && !is_migration_disabled(p))
3635 cpu = p->sched_class->select_task_rq(p, cpu, wake_flags);
3637 cpu = cpumask_any(p->cpus_ptr);
3640 * In order not to call set_task_cpu() on a blocking task we need
3641 * to rely on ttwu() to place the task on a valid ->cpus_ptr
3644 * Since this is common to all placement strategies, this lives here.
3646 * [ this allows ->select_task() to simply return task_cpu(p) and
3647 * not worry about this generic constraint ]
3649 if (unlikely(!is_cpu_allowed(p, cpu)))
3650 cpu = select_fallback_rq(task_cpu(p), p);
3655 void sched_set_stop_task(int cpu, struct task_struct *stop)
3657 static struct lock_class_key stop_pi_lock;
3658 struct sched_param param = { .sched_priority = MAX_RT_PRIO - 1 };
3659 struct task_struct *old_stop = cpu_rq(cpu)->stop;
3663 * Make it appear like a SCHED_FIFO task, its something
3664 * userspace knows about and won't get confused about.
3666 * Also, it will make PI more or less work without too
3667 * much confusion -- but then, stop work should not
3668 * rely on PI working anyway.
3670 sched_setscheduler_nocheck(stop, SCHED_FIFO, ¶m);
3672 stop->sched_class = &stop_sched_class;
3675 * The PI code calls rt_mutex_setprio() with ->pi_lock held to
3676 * adjust the effective priority of a task. As a result,
3677 * rt_mutex_setprio() can trigger (RT) balancing operations,
3678 * which can then trigger wakeups of the stop thread to push
3679 * around the current task.
3681 * The stop task itself will never be part of the PI-chain, it
3682 * never blocks, therefore that ->pi_lock recursion is safe.
3683 * Tell lockdep about this by placing the stop->pi_lock in its
3686 lockdep_set_class(&stop->pi_lock, &stop_pi_lock);
3689 cpu_rq(cpu)->stop = stop;
3693 * Reset it back to a normal scheduling class so that
3694 * it can die in pieces.
3696 old_stop->sched_class = &rt_sched_class;
3700 #else /* CONFIG_SMP */
3702 static inline int __set_cpus_allowed_ptr(struct task_struct *p,
3703 struct affinity_context *ctx)
3705 return set_cpus_allowed_ptr(p, ctx->new_mask);
3708 static inline void migrate_disable_switch(struct rq *rq, struct task_struct *p) { }
3710 static inline bool rq_has_pinned_tasks(struct rq *rq)
3715 static inline cpumask_t *alloc_user_cpus_ptr(int node)
3720 #endif /* !CONFIG_SMP */
3723 ttwu_stat(struct task_struct *p, int cpu, int wake_flags)
3727 if (!schedstat_enabled())
3733 if (cpu == rq->cpu) {
3734 __schedstat_inc(rq->ttwu_local);
3735 __schedstat_inc(p->stats.nr_wakeups_local);
3737 struct sched_domain *sd;
3739 __schedstat_inc(p->stats.nr_wakeups_remote);
3742 for_each_domain(rq->cpu, sd) {
3743 if (cpumask_test_cpu(cpu, sched_domain_span(sd))) {
3744 __schedstat_inc(sd->ttwu_wake_remote);
3750 if (wake_flags & WF_MIGRATED)
3751 __schedstat_inc(p->stats.nr_wakeups_migrate);
3752 #endif /* CONFIG_SMP */
3754 __schedstat_inc(rq->ttwu_count);
3755 __schedstat_inc(p->stats.nr_wakeups);
3757 if (wake_flags & WF_SYNC)
3758 __schedstat_inc(p->stats.nr_wakeups_sync);
3762 * Mark the task runnable.
3764 static inline void ttwu_do_wakeup(struct task_struct *p)
3766 WRITE_ONCE(p->__state, TASK_RUNNING);
3767 trace_sched_wakeup(p);
3771 ttwu_do_activate(struct rq *rq, struct task_struct *p, int wake_flags,
3772 struct rq_flags *rf)
3774 int en_flags = ENQUEUE_WAKEUP | ENQUEUE_NOCLOCK;
3776 lockdep_assert_rq_held(rq);
3778 if (p->sched_contributes_to_load)
3779 rq->nr_uninterruptible--;
3782 if (wake_flags & WF_MIGRATED)
3783 en_flags |= ENQUEUE_MIGRATED;
3787 delayacct_blkio_end(p);
3788 atomic_dec(&task_rq(p)->nr_iowait);
3791 activate_task(rq, p, en_flags);
3792 check_preempt_curr(rq, p, wake_flags);
3797 if (p->sched_class->task_woken) {
3799 * Our task @p is fully woken up and running; so it's safe to
3800 * drop the rq->lock, hereafter rq is only used for statistics.
3802 rq_unpin_lock(rq, rf);
3803 p->sched_class->task_woken(rq, p);
3804 rq_repin_lock(rq, rf);
3807 if (rq->idle_stamp) {
3808 u64 delta = rq_clock(rq) - rq->idle_stamp;
3809 u64 max = 2*rq->max_idle_balance_cost;
3811 update_avg(&rq->avg_idle, delta);
3813 if (rq->avg_idle > max)
3816 rq->wake_stamp = jiffies;
3817 rq->wake_avg_idle = rq->avg_idle / 2;
3825 * Consider @p being inside a wait loop:
3828 * set_current_state(TASK_UNINTERRUPTIBLE);
3835 * __set_current_state(TASK_RUNNING);
3837 * between set_current_state() and schedule(). In this case @p is still
3838 * runnable, so all that needs doing is change p->state back to TASK_RUNNING in
3841 * By taking task_rq(p)->lock we serialize against schedule(), if @p->on_rq
3842 * then schedule() must still happen and p->state can be changed to
3843 * TASK_RUNNING. Otherwise we lost the race, schedule() has happened, and we
3844 * need to do a full wakeup with enqueue.
3846 * Returns: %true when the wakeup is done,
3849 static int ttwu_runnable(struct task_struct *p, int wake_flags)
3855 rq = __task_rq_lock(p, &rf);
3856 if (task_on_rq_queued(p)) {
3857 if (!task_on_cpu(rq, p)) {
3859 * When on_rq && !on_cpu the task is preempted, see if
3860 * it should preempt the task that is current now.
3862 update_rq_clock(rq);
3863 check_preempt_curr(rq, p, wake_flags);
3868 __task_rq_unlock(rq, &rf);
3874 void sched_ttwu_pending(void *arg)
3876 struct llist_node *llist = arg;
3877 struct rq *rq = this_rq();
3878 struct task_struct *p, *t;
3884 rq_lock_irqsave(rq, &rf);
3885 update_rq_clock(rq);
3887 llist_for_each_entry_safe(p, t, llist, wake_entry.llist) {
3888 if (WARN_ON_ONCE(p->on_cpu))
3889 smp_cond_load_acquire(&p->on_cpu, !VAL);
3891 if (WARN_ON_ONCE(task_cpu(p) != cpu_of(rq)))
3892 set_task_cpu(p, cpu_of(rq));
3894 ttwu_do_activate(rq, p, p->sched_remote_wakeup ? WF_MIGRATED : 0, &rf);
3898 * Must be after enqueueing at least once task such that
3899 * idle_cpu() does not observe a false-negative -- if it does,
3900 * it is possible for select_idle_siblings() to stack a number
3901 * of tasks on this CPU during that window.
3903 * It is ok to clear ttwu_pending when another task pending.
3904 * We will receive IPI after local irq enabled and then enqueue it.
3905 * Since now nr_running > 0, idle_cpu() will always get correct result.
3907 WRITE_ONCE(rq->ttwu_pending, 0);
3908 rq_unlock_irqrestore(rq, &rf);
3912 * Prepare the scene for sending an IPI for a remote smp_call
3914 * Returns true if the caller can proceed with sending the IPI.
3915 * Returns false otherwise.
3917 bool call_function_single_prep_ipi(int cpu)
3919 if (set_nr_if_polling(cpu_rq(cpu)->idle)) {
3920 trace_sched_wake_idle_without_ipi(cpu);
3928 * Queue a task on the target CPUs wake_list and wake the CPU via IPI if
3929 * necessary. The wakee CPU on receipt of the IPI will queue the task
3930 * via sched_ttwu_wakeup() for activation so the wakee incurs the cost
3931 * of the wakeup instead of the waker.
3933 static void __ttwu_queue_wakelist(struct task_struct *p, int cpu, int wake_flags)
3935 struct rq *rq = cpu_rq(cpu);
3937 p->sched_remote_wakeup = !!(wake_flags & WF_MIGRATED);
3939 WRITE_ONCE(rq->ttwu_pending, 1);
3940 __smp_call_single_queue(cpu, &p->wake_entry.llist);
3943 void wake_up_if_idle(int cpu)
3945 struct rq *rq = cpu_rq(cpu);
3948 if (is_idle_task(rcu_dereference(rq->curr))) {
3949 guard(rq_lock_irqsave)(rq);
3950 if (is_idle_task(rq->curr))
3955 bool cpus_share_cache(int this_cpu, int that_cpu)
3957 if (this_cpu == that_cpu)
3960 return per_cpu(sd_llc_id, this_cpu) == per_cpu(sd_llc_id, that_cpu);
3963 static inline bool ttwu_queue_cond(struct task_struct *p, int cpu)
3966 * Do not complicate things with the async wake_list while the CPU is
3969 if (!cpu_active(cpu))
3972 /* Ensure the task will still be allowed to run on the CPU. */
3973 if (!cpumask_test_cpu(cpu, p->cpus_ptr))
3977 * If the CPU does not share cache, then queue the task on the
3978 * remote rqs wakelist to avoid accessing remote data.
3980 if (!cpus_share_cache(smp_processor_id(), cpu))
3983 if (cpu == smp_processor_id())
3987 * If the wakee cpu is idle, or the task is descheduling and the
3988 * only running task on the CPU, then use the wakelist to offload
3989 * the task activation to the idle (or soon-to-be-idle) CPU as
3990 * the current CPU is likely busy. nr_running is checked to
3991 * avoid unnecessary task stacking.
3993 * Note that we can only get here with (wakee) p->on_rq=0,
3994 * p->on_cpu can be whatever, we've done the dequeue, so
3995 * the wakee has been accounted out of ->nr_running.
3997 if (!cpu_rq(cpu)->nr_running)
4003 static bool ttwu_queue_wakelist(struct task_struct *p, int cpu, int wake_flags)
4005 if (sched_feat(TTWU_QUEUE) && ttwu_queue_cond(p, cpu)) {
4006 sched_clock_cpu(cpu); /* Sync clocks across CPUs */
4007 __ttwu_queue_wakelist(p, cpu, wake_flags);
4014 #else /* !CONFIG_SMP */
4016 static inline bool ttwu_queue_wakelist(struct task_struct *p, int cpu, int wake_flags)
4021 #endif /* CONFIG_SMP */
4023 static void ttwu_queue(struct task_struct *p, int cpu, int wake_flags)
4025 struct rq *rq = cpu_rq(cpu);
4028 if (ttwu_queue_wakelist(p, cpu, wake_flags))
4032 update_rq_clock(rq);
4033 ttwu_do_activate(rq, p, wake_flags, &rf);
4038 * Invoked from try_to_wake_up() to check whether the task can be woken up.
4040 * The caller holds p::pi_lock if p != current or has preemption
4041 * disabled when p == current.
4043 * The rules of PREEMPT_RT saved_state:
4045 * The related locking code always holds p::pi_lock when updating
4046 * p::saved_state, which means the code is fully serialized in both cases.
4048 * The lock wait and lock wakeups happen via TASK_RTLOCK_WAIT. No other
4049 * bits set. This allows to distinguish all wakeup scenarios.
4051 static __always_inline
4052 bool ttwu_state_match(struct task_struct *p, unsigned int state, int *success)
4056 if (IS_ENABLED(CONFIG_DEBUG_PREEMPT)) {
4057 WARN_ON_ONCE((state & TASK_RTLOCK_WAIT) &&
4058 state != TASK_RTLOCK_WAIT);
4061 *success = !!(match = __task_state_match(p, state));
4063 #ifdef CONFIG_PREEMPT_RT
4065 * Saved state preserves the task state across blocking on
4066 * an RT lock. If the state matches, set p::saved_state to
4067 * TASK_RUNNING, but do not wake the task because it waits
4068 * for a lock wakeup. Also indicate success because from
4069 * the regular waker's point of view this has succeeded.
4071 * After acquiring the lock the task will restore p::__state
4072 * from p::saved_state which ensures that the regular
4073 * wakeup is not lost. The restore will also set
4074 * p::saved_state to TASK_RUNNING so any further tests will
4075 * not result in false positives vs. @success
4078 p->saved_state = TASK_RUNNING;
4084 * Notes on Program-Order guarantees on SMP systems.
4088 * The basic program-order guarantee on SMP systems is that when a task [t]
4089 * migrates, all its activity on its old CPU [c0] happens-before any subsequent
4090 * execution on its new CPU [c1].
4092 * For migration (of runnable tasks) this is provided by the following means:
4094 * A) UNLOCK of the rq(c0)->lock scheduling out task t
4095 * B) migration for t is required to synchronize *both* rq(c0)->lock and
4096 * rq(c1)->lock (if not at the same time, then in that order).
4097 * C) LOCK of the rq(c1)->lock scheduling in task
4099 * Release/acquire chaining guarantees that B happens after A and C after B.
4100 * Note: the CPU doing B need not be c0 or c1
4109 * UNLOCK rq(0)->lock
4111 * LOCK rq(0)->lock // orders against CPU0
4113 * UNLOCK rq(0)->lock
4117 * UNLOCK rq(1)->lock
4119 * LOCK rq(1)->lock // orders against CPU2
4122 * UNLOCK rq(1)->lock
4125 * BLOCKING -- aka. SLEEP + WAKEUP
4127 * For blocking we (obviously) need to provide the same guarantee as for
4128 * migration. However the means are completely different as there is no lock
4129 * chain to provide order. Instead we do:
4131 * 1) smp_store_release(X->on_cpu, 0) -- finish_task()
4132 * 2) smp_cond_load_acquire(!X->on_cpu) -- try_to_wake_up()
4136 * CPU0 (schedule) CPU1 (try_to_wake_up) CPU2 (schedule)
4138 * LOCK rq(0)->lock LOCK X->pi_lock
4141 * smp_store_release(X->on_cpu, 0);
4143 * smp_cond_load_acquire(&X->on_cpu, !VAL);
4149 * X->state = RUNNING
4150 * UNLOCK rq(2)->lock
4152 * LOCK rq(2)->lock // orders against CPU1
4155 * UNLOCK rq(2)->lock
4158 * UNLOCK rq(0)->lock
4161 * However, for wakeups there is a second guarantee we must provide, namely we
4162 * must ensure that CONDITION=1 done by the caller can not be reordered with
4163 * accesses to the task state; see try_to_wake_up() and set_current_state().
4167 * try_to_wake_up - wake up a thread
4168 * @p: the thread to be awakened
4169 * @state: the mask of task states that can be woken
4170 * @wake_flags: wake modifier flags (WF_*)
4172 * Conceptually does:
4174 * If (@state & @p->state) @p->state = TASK_RUNNING.
4176 * If the task was not queued/runnable, also place it back on a runqueue.
4178 * This function is atomic against schedule() which would dequeue the task.
4180 * It issues a full memory barrier before accessing @p->state, see the comment
4181 * with set_current_state().
4183 * Uses p->pi_lock to serialize against concurrent wake-ups.
4185 * Relies on p->pi_lock stabilizing:
4188 * - p->sched_task_group
4189 * in order to do migration, see its use of select_task_rq()/set_task_cpu().
4191 * Tries really hard to only take one task_rq(p)->lock for performance.
4192 * Takes rq->lock in:
4193 * - ttwu_runnable() -- old rq, unavoidable, see comment there;
4194 * - ttwu_queue() -- new rq, for enqueue of the task;
4195 * - psi_ttwu_dequeue() -- much sadness :-( accounting will kill us.
4197 * As a consequence we race really badly with just about everything. See the
4198 * many memory barriers and their comments for details.
4200 * Return: %true if @p->state changes (an actual wakeup was done),
4203 int try_to_wake_up(struct task_struct *p, unsigned int state, int wake_flags)
4206 int cpu, success = 0;
4210 * We're waking current, this means 'p->on_rq' and 'task_cpu(p)
4211 * == smp_processor_id()'. Together this means we can special
4212 * case the whole 'p->on_rq && ttwu_runnable()' case below
4213 * without taking any locks.
4216 * - we rely on Program-Order guarantees for all the ordering,
4217 * - we're serialized against set_special_state() by virtue of
4218 * it disabling IRQs (this allows not taking ->pi_lock).
4220 if (!ttwu_state_match(p, state, &success))
4223 trace_sched_waking(p);
4229 * If we are going to wake up a thread waiting for CONDITION we
4230 * need to ensure that CONDITION=1 done by the caller can not be
4231 * reordered with p->state check below. This pairs with smp_store_mb()
4232 * in set_current_state() that the waiting thread does.
4234 scoped_guard (raw_spinlock_irqsave, &p->pi_lock) {
4235 smp_mb__after_spinlock();
4236 if (!ttwu_state_match(p, state, &success))
4239 trace_sched_waking(p);
4242 * Ensure we load p->on_rq _after_ p->state, otherwise it would
4243 * be possible to, falsely, observe p->on_rq == 0 and get stuck
4244 * in smp_cond_load_acquire() below.
4246 * sched_ttwu_pending() try_to_wake_up()
4247 * STORE p->on_rq = 1 LOAD p->state
4250 * __schedule() (switch to task 'p')
4251 * LOCK rq->lock smp_rmb();
4252 * smp_mb__after_spinlock();
4256 * STORE p->state = UNINTERRUPTIBLE LOAD p->on_rq
4258 * Pairs with the LOCK+smp_mb__after_spinlock() on rq->lock in
4259 * __schedule(). See the comment for smp_mb__after_spinlock().
4261 * A similar smb_rmb() lives in try_invoke_on_locked_down_task().
4264 if (READ_ONCE(p->on_rq) && ttwu_runnable(p, wake_flags))
4269 * Ensure we load p->on_cpu _after_ p->on_rq, otherwise it would be
4270 * possible to, falsely, observe p->on_cpu == 0.
4272 * One must be running (->on_cpu == 1) in order to remove oneself
4273 * from the runqueue.
4275 * __schedule() (switch to task 'p') try_to_wake_up()
4276 * STORE p->on_cpu = 1 LOAD p->on_rq
4279 * __schedule() (put 'p' to sleep)
4280 * LOCK rq->lock smp_rmb();
4281 * smp_mb__after_spinlock();
4282 * STORE p->on_rq = 0 LOAD p->on_cpu
4284 * Pairs with the LOCK+smp_mb__after_spinlock() on rq->lock in
4285 * __schedule(). See the comment for smp_mb__after_spinlock().
4287 * Form a control-dep-acquire with p->on_rq == 0 above, to ensure
4288 * schedule()'s deactivate_task() has 'happened' and p will no longer
4289 * care about it's own p->state. See the comment in __schedule().
4291 smp_acquire__after_ctrl_dep();
4294 * We're doing the wakeup (@success == 1), they did a dequeue (p->on_rq
4295 * == 0), which means we need to do an enqueue, change p->state to
4296 * TASK_WAKING such that we can unlock p->pi_lock before doing the
4297 * enqueue, such as ttwu_queue_wakelist().
4299 WRITE_ONCE(p->__state, TASK_WAKING);
4302 * If the owning (remote) CPU is still in the middle of schedule() with
4303 * this task as prev, considering queueing p on the remote CPUs wake_list
4304 * which potentially sends an IPI instead of spinning on p->on_cpu to
4305 * let the waker make forward progress. This is safe because IRQs are
4306 * disabled and the IPI will deliver after on_cpu is cleared.
4308 * Ensure we load task_cpu(p) after p->on_cpu:
4310 * set_task_cpu(p, cpu);
4311 * STORE p->cpu = @cpu
4312 * __schedule() (switch to task 'p')
4314 * smp_mb__after_spin_lock() smp_cond_load_acquire(&p->on_cpu)
4315 * STORE p->on_cpu = 1 LOAD p->cpu
4317 * to ensure we observe the correct CPU on which the task is currently
4320 if (smp_load_acquire(&p->on_cpu) &&
4321 ttwu_queue_wakelist(p, task_cpu(p), wake_flags))
4325 * If the owning (remote) CPU is still in the middle of schedule() with
4326 * this task as prev, wait until it's done referencing the task.
4328 * Pairs with the smp_store_release() in finish_task().
4330 * This ensures that tasks getting woken will be fully ordered against
4331 * their previous state and preserve Program Order.
4333 smp_cond_load_acquire(&p->on_cpu, !VAL);
4335 cpu = select_task_rq(p, p->wake_cpu, wake_flags | WF_TTWU);
4336 if (task_cpu(p) != cpu) {
4338 delayacct_blkio_end(p);
4339 atomic_dec(&task_rq(p)->nr_iowait);
4342 wake_flags |= WF_MIGRATED;
4343 psi_ttwu_dequeue(p);
4344 set_task_cpu(p, cpu);
4348 #endif /* CONFIG_SMP */
4350 ttwu_queue(p, cpu, wake_flags);
4354 ttwu_stat(p, task_cpu(p), wake_flags);
4359 static bool __task_needs_rq_lock(struct task_struct *p)
4361 unsigned int state = READ_ONCE(p->__state);
4364 * Since pi->lock blocks try_to_wake_up(), we don't need rq->lock when
4365 * the task is blocked. Make sure to check @state since ttwu() can drop
4366 * locks at the end, see ttwu_queue_wakelist().
4368 if (state == TASK_RUNNING || state == TASK_WAKING)
4372 * Ensure we load p->on_rq after p->__state, otherwise it would be
4373 * possible to, falsely, observe p->on_rq == 0.
4375 * See try_to_wake_up() for a longer comment.
4383 * Ensure the task has finished __schedule() and will not be referenced
4384 * anymore. Again, see try_to_wake_up() for a longer comment.
4387 smp_cond_load_acquire(&p->on_cpu, !VAL);
4394 * task_call_func - Invoke a function on task in fixed state
4395 * @p: Process for which the function is to be invoked, can be @current.
4396 * @func: Function to invoke.
4397 * @arg: Argument to function.
4399 * Fix the task in it's current state by avoiding wakeups and or rq operations
4400 * and call @func(@arg) on it. This function can use ->on_rq and task_curr()
4401 * to work out what the state is, if required. Given that @func can be invoked
4402 * with a runqueue lock held, it had better be quite lightweight.
4405 * Whatever @func returns
4407 int task_call_func(struct task_struct *p, task_call_f func, void *arg)
4409 struct rq *rq = NULL;
4413 raw_spin_lock_irqsave(&p->pi_lock, rf.flags);
4415 if (__task_needs_rq_lock(p))
4416 rq = __task_rq_lock(p, &rf);
4419 * At this point the task is pinned; either:
4420 * - blocked and we're holding off wakeups (pi->lock)
4421 * - woken, and we're holding off enqueue (rq->lock)
4422 * - queued, and we're holding off schedule (rq->lock)
4423 * - running, and we're holding off de-schedule (rq->lock)
4425 * The called function (@func) can use: task_curr(), p->on_rq and
4426 * p->__state to differentiate between these states.
4433 raw_spin_unlock_irqrestore(&p->pi_lock, rf.flags);
4438 * cpu_curr_snapshot - Return a snapshot of the currently running task
4439 * @cpu: The CPU on which to snapshot the task.
4441 * Returns the task_struct pointer of the task "currently" running on
4442 * the specified CPU. If the same task is running on that CPU throughout,
4443 * the return value will be a pointer to that task's task_struct structure.
4444 * If the CPU did any context switches even vaguely concurrently with the
4445 * execution of this function, the return value will be a pointer to the
4446 * task_struct structure of a randomly chosen task that was running on
4447 * that CPU somewhere around the time that this function was executing.
4449 * If the specified CPU was offline, the return value is whatever it
4450 * is, perhaps a pointer to the task_struct structure of that CPU's idle
4451 * task, but there is no guarantee. Callers wishing a useful return
4452 * value must take some action to ensure that the specified CPU remains
4453 * online throughout.
4455 * This function executes full memory barriers before and after fetching
4456 * the pointer, which permits the caller to confine this function's fetch
4457 * with respect to the caller's accesses to other shared variables.
4459 struct task_struct *cpu_curr_snapshot(int cpu)
4461 struct task_struct *t;
4463 smp_mb(); /* Pairing determined by caller's synchronization design. */
4464 t = rcu_dereference(cpu_curr(cpu));
4465 smp_mb(); /* Pairing determined by caller's synchronization design. */
4470 * wake_up_process - Wake up a specific process
4471 * @p: The process to be woken up.
4473 * Attempt to wake up the nominated process and move it to the set of runnable
4476 * Return: 1 if the process was woken up, 0 if it was already running.
4478 * This function executes a full memory barrier before accessing the task state.
4480 int wake_up_process(struct task_struct *p)
4482 return try_to_wake_up(p, TASK_NORMAL, 0);
4484 EXPORT_SYMBOL(wake_up_process);
4486 int wake_up_state(struct task_struct *p, unsigned int state)
4488 return try_to_wake_up(p, state, 0);
4492 * Perform scheduler related setup for a newly forked process p.
4493 * p is forked by current.
4495 * __sched_fork() is basic setup used by init_idle() too:
4497 static void __sched_fork(unsigned long clone_flags, struct task_struct *p)
4502 p->se.exec_start = 0;
4503 p->se.sum_exec_runtime = 0;
4504 p->se.prev_sum_exec_runtime = 0;
4505 p->se.nr_migrations = 0;
4508 p->se.slice = sysctl_sched_base_slice;
4509 INIT_LIST_HEAD(&p->se.group_node);
4511 #ifdef CONFIG_FAIR_GROUP_SCHED
4512 p->se.cfs_rq = NULL;
4515 #ifdef CONFIG_SCHEDSTATS
4516 /* Even if schedstat is disabled, there should not be garbage */
4517 memset(&p->stats, 0, sizeof(p->stats));
4520 RB_CLEAR_NODE(&p->dl.rb_node);
4521 init_dl_task_timer(&p->dl);
4522 init_dl_inactive_task_timer(&p->dl);
4523 __dl_clear_params(p);
4525 INIT_LIST_HEAD(&p->rt.run_list);
4527 p->rt.time_slice = sched_rr_timeslice;
4531 #ifdef CONFIG_PREEMPT_NOTIFIERS
4532 INIT_HLIST_HEAD(&p->preempt_notifiers);
4535 #ifdef CONFIG_COMPACTION
4536 p->capture_control = NULL;
4538 init_numa_balancing(clone_flags, p);
4540 p->wake_entry.u_flags = CSD_TYPE_TTWU;
4541 p->migration_pending = NULL;
4543 init_sched_mm_cid(p);
4546 DEFINE_STATIC_KEY_FALSE(sched_numa_balancing);
4548 #ifdef CONFIG_NUMA_BALANCING
4550 int sysctl_numa_balancing_mode;
4552 static void __set_numabalancing_state(bool enabled)
4555 static_branch_enable(&sched_numa_balancing);
4557 static_branch_disable(&sched_numa_balancing);
4560 void set_numabalancing_state(bool enabled)
4563 sysctl_numa_balancing_mode = NUMA_BALANCING_NORMAL;
4565 sysctl_numa_balancing_mode = NUMA_BALANCING_DISABLED;
4566 __set_numabalancing_state(enabled);
4569 #ifdef CONFIG_PROC_SYSCTL
4570 static void reset_memory_tiering(void)
4572 struct pglist_data *pgdat;
4574 for_each_online_pgdat(pgdat) {
4575 pgdat->nbp_threshold = 0;
4576 pgdat->nbp_th_nr_cand = node_page_state(pgdat, PGPROMOTE_CANDIDATE);
4577 pgdat->nbp_th_start = jiffies_to_msecs(jiffies);
4581 static int sysctl_numa_balancing(struct ctl_table *table, int write,
4582 void *buffer, size_t *lenp, loff_t *ppos)
4586 int state = sysctl_numa_balancing_mode;
4588 if (write && !capable(CAP_SYS_ADMIN))
4593 err = proc_dointvec_minmax(&t, write, buffer, lenp, ppos);
4597 if (!(sysctl_numa_balancing_mode & NUMA_BALANCING_MEMORY_TIERING) &&
4598 (state & NUMA_BALANCING_MEMORY_TIERING))
4599 reset_memory_tiering();
4600 sysctl_numa_balancing_mode = state;
4601 __set_numabalancing_state(state);
4608 #ifdef CONFIG_SCHEDSTATS
4610 DEFINE_STATIC_KEY_FALSE(sched_schedstats);
4612 static void set_schedstats(bool enabled)
4615 static_branch_enable(&sched_schedstats);
4617 static_branch_disable(&sched_schedstats);
4620 void force_schedstat_enabled(void)
4622 if (!schedstat_enabled()) {
4623 pr_info("kernel profiling enabled schedstats, disable via kernel.sched_schedstats.\n");
4624 static_branch_enable(&sched_schedstats);
4628 static int __init setup_schedstats(char *str)
4634 if (!strcmp(str, "enable")) {
4635 set_schedstats(true);
4637 } else if (!strcmp(str, "disable")) {
4638 set_schedstats(false);
4643 pr_warn("Unable to parse schedstats=\n");
4647 __setup("schedstats=", setup_schedstats);
4649 #ifdef CONFIG_PROC_SYSCTL
4650 static int sysctl_schedstats(struct ctl_table *table, int write, void *buffer,
4651 size_t *lenp, loff_t *ppos)
4655 int state = static_branch_likely(&sched_schedstats);
4657 if (write && !capable(CAP_SYS_ADMIN))
4662 err = proc_dointvec_minmax(&t, write, buffer, lenp, ppos);
4666 set_schedstats(state);
4669 #endif /* CONFIG_PROC_SYSCTL */
4670 #endif /* CONFIG_SCHEDSTATS */
4672 #ifdef CONFIG_SYSCTL
4673 static struct ctl_table sched_core_sysctls[] = {
4674 #ifdef CONFIG_SCHEDSTATS
4676 .procname = "sched_schedstats",
4678 .maxlen = sizeof(unsigned int),
4680 .proc_handler = sysctl_schedstats,
4681 .extra1 = SYSCTL_ZERO,
4682 .extra2 = SYSCTL_ONE,
4684 #endif /* CONFIG_SCHEDSTATS */
4685 #ifdef CONFIG_UCLAMP_TASK
4687 .procname = "sched_util_clamp_min",
4688 .data = &sysctl_sched_uclamp_util_min,
4689 .maxlen = sizeof(unsigned int),
4691 .proc_handler = sysctl_sched_uclamp_handler,
4694 .procname = "sched_util_clamp_max",
4695 .data = &sysctl_sched_uclamp_util_max,
4696 .maxlen = sizeof(unsigned int),
4698 .proc_handler = sysctl_sched_uclamp_handler,
4701 .procname = "sched_util_clamp_min_rt_default",
4702 .data = &sysctl_sched_uclamp_util_min_rt_default,
4703 .maxlen = sizeof(unsigned int),
4705 .proc_handler = sysctl_sched_uclamp_handler,
4707 #endif /* CONFIG_UCLAMP_TASK */
4708 #ifdef CONFIG_NUMA_BALANCING
4710 .procname = "numa_balancing",
4711 .data = NULL, /* filled in by handler */
4712 .maxlen = sizeof(unsigned int),
4714 .proc_handler = sysctl_numa_balancing,
4715 .extra1 = SYSCTL_ZERO,
4716 .extra2 = SYSCTL_FOUR,
4718 #endif /* CONFIG_NUMA_BALANCING */
4721 static int __init sched_core_sysctl_init(void)
4723 register_sysctl_init("kernel", sched_core_sysctls);
4726 late_initcall(sched_core_sysctl_init);
4727 #endif /* CONFIG_SYSCTL */
4730 * fork()/clone()-time setup:
4732 int sched_fork(unsigned long clone_flags, struct task_struct *p)
4734 __sched_fork(clone_flags, p);
4736 * We mark the process as NEW here. This guarantees that
4737 * nobody will actually run it, and a signal or other external
4738 * event cannot wake it up and insert it on the runqueue either.
4740 p->__state = TASK_NEW;
4743 * Make sure we do not leak PI boosting priority to the child.
4745 p->prio = current->normal_prio;
4750 * Revert to default priority/policy on fork if requested.
4752 if (unlikely(p->sched_reset_on_fork)) {
4753 if (task_has_dl_policy(p) || task_has_rt_policy(p)) {
4754 p->policy = SCHED_NORMAL;
4755 p->static_prio = NICE_TO_PRIO(0);
4757 } else if (PRIO_TO_NICE(p->static_prio) < 0)
4758 p->static_prio = NICE_TO_PRIO(0);
4760 p->prio = p->normal_prio = p->static_prio;
4761 set_load_weight(p, false);
4764 * We don't need the reset flag anymore after the fork. It has
4765 * fulfilled its duty:
4767 p->sched_reset_on_fork = 0;
4770 if (dl_prio(p->prio))
4772 else if (rt_prio(p->prio))
4773 p->sched_class = &rt_sched_class;
4775 p->sched_class = &fair_sched_class;
4777 init_entity_runnable_average(&p->se);
4780 #ifdef CONFIG_SCHED_INFO
4781 if (likely(sched_info_on()))
4782 memset(&p->sched_info, 0, sizeof(p->sched_info));
4784 #if defined(CONFIG_SMP)
4787 init_task_preempt_count(p);
4789 plist_node_init(&p->pushable_tasks, MAX_PRIO);
4790 RB_CLEAR_NODE(&p->pushable_dl_tasks);
4795 void sched_cgroup_fork(struct task_struct *p, struct kernel_clone_args *kargs)
4797 unsigned long flags;
4800 * Because we're not yet on the pid-hash, p->pi_lock isn't strictly
4801 * required yet, but lockdep gets upset if rules are violated.
4803 raw_spin_lock_irqsave(&p->pi_lock, flags);
4804 #ifdef CONFIG_CGROUP_SCHED
4806 struct task_group *tg;
4807 tg = container_of(kargs->cset->subsys[cpu_cgrp_id],
4808 struct task_group, css);
4809 tg = autogroup_task_group(p, tg);
4810 p->sched_task_group = tg;
4815 * We're setting the CPU for the first time, we don't migrate,
4816 * so use __set_task_cpu().
4818 __set_task_cpu(p, smp_processor_id());
4819 if (p->sched_class->task_fork)
4820 p->sched_class->task_fork(p);
4821 raw_spin_unlock_irqrestore(&p->pi_lock, flags);
4824 void sched_post_fork(struct task_struct *p)
4826 uclamp_post_fork(p);
4829 unsigned long to_ratio(u64 period, u64 runtime)
4831 if (runtime == RUNTIME_INF)
4835 * Doing this here saves a lot of checks in all
4836 * the calling paths, and returning zero seems
4837 * safe for them anyway.
4842 return div64_u64(runtime << BW_SHIFT, period);
4846 * wake_up_new_task - wake up a newly created task for the first time.
4848 * This function will do some initial scheduler statistics housekeeping
4849 * that must be done for every newly created context, then puts the task
4850 * on the runqueue and wakes it.
4852 void wake_up_new_task(struct task_struct *p)
4857 raw_spin_lock_irqsave(&p->pi_lock, rf.flags);
4858 WRITE_ONCE(p->__state, TASK_RUNNING);
4861 * Fork balancing, do it here and not earlier because:
4862 * - cpus_ptr can change in the fork path
4863 * - any previously selected CPU might disappear through hotplug
4865 * Use __set_task_cpu() to avoid calling sched_class::migrate_task_rq,
4866 * as we're not fully set-up yet.
4868 p->recent_used_cpu = task_cpu(p);
4870 __set_task_cpu(p, select_task_rq(p, task_cpu(p), WF_FORK));
4872 rq = __task_rq_lock(p, &rf);
4873 update_rq_clock(rq);
4874 post_init_entity_util_avg(p);
4876 activate_task(rq, p, ENQUEUE_NOCLOCK);
4877 trace_sched_wakeup_new(p);
4878 check_preempt_curr(rq, p, WF_FORK);
4880 if (p->sched_class->task_woken) {
4882 * Nothing relies on rq->lock after this, so it's fine to
4885 rq_unpin_lock(rq, &rf);
4886 p->sched_class->task_woken(rq, p);
4887 rq_repin_lock(rq, &rf);
4890 task_rq_unlock(rq, p, &rf);
4893 #ifdef CONFIG_PREEMPT_NOTIFIERS
4895 static DEFINE_STATIC_KEY_FALSE(preempt_notifier_key);
4897 void preempt_notifier_inc(void)
4899 static_branch_inc(&preempt_notifier_key);
4901 EXPORT_SYMBOL_GPL(preempt_notifier_inc);
4903 void preempt_notifier_dec(void)
4905 static_branch_dec(&preempt_notifier_key);
4907 EXPORT_SYMBOL_GPL(preempt_notifier_dec);
4910 * preempt_notifier_register - tell me when current is being preempted & rescheduled
4911 * @notifier: notifier struct to register
4913 void preempt_notifier_register(struct preempt_notifier *notifier)
4915 if (!static_branch_unlikely(&preempt_notifier_key))
4916 WARN(1, "registering preempt_notifier while notifiers disabled\n");
4918 hlist_add_head(¬ifier->link, ¤t->preempt_notifiers);
4920 EXPORT_SYMBOL_GPL(preempt_notifier_register);
4923 * preempt_notifier_unregister - no longer interested in preemption notifications
4924 * @notifier: notifier struct to unregister
4926 * This is *not* safe to call from within a preemption notifier.
4928 void preempt_notifier_unregister(struct preempt_notifier *notifier)
4930 hlist_del(¬ifier->link);
4932 EXPORT_SYMBOL_GPL(preempt_notifier_unregister);
4934 static void __fire_sched_in_preempt_notifiers(struct task_struct *curr)
4936 struct preempt_notifier *notifier;
4938 hlist_for_each_entry(notifier, &curr->preempt_notifiers, link)
4939 notifier->ops->sched_in(notifier, raw_smp_processor_id());
4942 static __always_inline void fire_sched_in_preempt_notifiers(struct task_struct *curr)
4944 if (static_branch_unlikely(&preempt_notifier_key))
4945 __fire_sched_in_preempt_notifiers(curr);
4949 __fire_sched_out_preempt_notifiers(struct task_struct *curr,
4950 struct task_struct *next)
4952 struct preempt_notifier *notifier;
4954 hlist_for_each_entry(notifier, &curr->preempt_notifiers, link)
4955 notifier->ops->sched_out(notifier, next);
4958 static __always_inline void
4959 fire_sched_out_preempt_notifiers(struct task_struct *curr,
4960 struct task_struct *next)
4962 if (static_branch_unlikely(&preempt_notifier_key))
4963 __fire_sched_out_preempt_notifiers(curr, next);
4966 #else /* !CONFIG_PREEMPT_NOTIFIERS */
4968 static inline void fire_sched_in_preempt_notifiers(struct task_struct *curr)
4973 fire_sched_out_preempt_notifiers(struct task_struct *curr,
4974 struct task_struct *next)
4978 #endif /* CONFIG_PREEMPT_NOTIFIERS */
4980 static inline void prepare_task(struct task_struct *next)
4984 * Claim the task as running, we do this before switching to it
4985 * such that any running task will have this set.
4987 * See the smp_load_acquire(&p->on_cpu) case in ttwu() and
4988 * its ordering comment.
4990 WRITE_ONCE(next->on_cpu, 1);
4994 static inline void finish_task(struct task_struct *prev)
4998 * This must be the very last reference to @prev from this CPU. After
4999 * p->on_cpu is cleared, the task can be moved to a different CPU. We
5000 * must ensure this doesn't happen until the switch is completely
5003 * In particular, the load of prev->state in finish_task_switch() must
5004 * happen before this.
5006 * Pairs with the smp_cond_load_acquire() in try_to_wake_up().
5008 smp_store_release(&prev->on_cpu, 0);
5014 static void do_balance_callbacks(struct rq *rq, struct balance_callback *head)
5016 void (*func)(struct rq *rq);
5017 struct balance_callback *next;
5019 lockdep_assert_rq_held(rq);
5022 func = (void (*)(struct rq *))head->func;
5031 static void balance_push(struct rq *rq);
5034 * balance_push_callback is a right abuse of the callback interface and plays
5035 * by significantly different rules.
5037 * Where the normal balance_callback's purpose is to be ran in the same context
5038 * that queued it (only later, when it's safe to drop rq->lock again),
5039 * balance_push_callback is specifically targeted at __schedule().
5041 * This abuse is tolerated because it places all the unlikely/odd cases behind
5042 * a single test, namely: rq->balance_callback == NULL.
5044 struct balance_callback balance_push_callback = {
5046 .func = balance_push,
5049 static inline struct balance_callback *
5050 __splice_balance_callbacks(struct rq *rq, bool split)
5052 struct balance_callback *head = rq->balance_callback;
5057 lockdep_assert_rq_held(rq);
5059 * Must not take balance_push_callback off the list when
5060 * splice_balance_callbacks() and balance_callbacks() are not
5061 * in the same rq->lock section.
5063 * In that case it would be possible for __schedule() to interleave
5064 * and observe the list empty.
5066 if (split && head == &balance_push_callback)
5069 rq->balance_callback = NULL;
5074 static inline struct balance_callback *splice_balance_callbacks(struct rq *rq)
5076 return __splice_balance_callbacks(rq, true);
5079 static void __balance_callbacks(struct rq *rq)
5081 do_balance_callbacks(rq, __splice_balance_callbacks(rq, false));
5084 static inline void balance_callbacks(struct rq *rq, struct balance_callback *head)
5086 unsigned long flags;
5088 if (unlikely(head)) {
5089 raw_spin_rq_lock_irqsave(rq, flags);
5090 do_balance_callbacks(rq, head);
5091 raw_spin_rq_unlock_irqrestore(rq, flags);
5097 static inline void __balance_callbacks(struct rq *rq)
5101 static inline struct balance_callback *splice_balance_callbacks(struct rq *rq)
5106 static inline void balance_callbacks(struct rq *rq, struct balance_callback *head)
5113 prepare_lock_switch(struct rq *rq, struct task_struct *next, struct rq_flags *rf)
5116 * Since the runqueue lock will be released by the next
5117 * task (which is an invalid locking op but in the case
5118 * of the scheduler it's an obvious special-case), so we
5119 * do an early lockdep release here:
5121 rq_unpin_lock(rq, rf);
5122 spin_release(&__rq_lockp(rq)->dep_map, _THIS_IP_);
5123 #ifdef CONFIG_DEBUG_SPINLOCK
5124 /* this is a valid case when another task releases the spinlock */
5125 rq_lockp(rq)->owner = next;
5129 static inline void finish_lock_switch(struct rq *rq)
5132 * If we are tracking spinlock dependencies then we have to
5133 * fix up the runqueue lock - which gets 'carried over' from
5134 * prev into current:
5136 spin_acquire(&__rq_lockp(rq)->dep_map, 0, 0, _THIS_IP_);
5137 __balance_callbacks(rq);
5138 raw_spin_rq_unlock_irq(rq);
5142 * NOP if the arch has not defined these:
5145 #ifndef prepare_arch_switch
5146 # define prepare_arch_switch(next) do { } while (0)
5149 #ifndef finish_arch_post_lock_switch
5150 # define finish_arch_post_lock_switch() do { } while (0)
5153 static inline void kmap_local_sched_out(void)
5155 #ifdef CONFIG_KMAP_LOCAL
5156 if (unlikely(current->kmap_ctrl.idx))
5157 __kmap_local_sched_out();
5161 static inline void kmap_local_sched_in(void)
5163 #ifdef CONFIG_KMAP_LOCAL
5164 if (unlikely(current->kmap_ctrl.idx))
5165 __kmap_local_sched_in();
5170 * prepare_task_switch - prepare to switch tasks
5171 * @rq: the runqueue preparing to switch
5172 * @prev: the current task that is being switched out
5173 * @next: the task we are going to switch to.
5175 * This is called with the rq lock held and interrupts off. It must
5176 * be paired with a subsequent finish_task_switch after the context
5179 * prepare_task_switch sets up locking and calls architecture specific
5183 prepare_task_switch(struct rq *rq, struct task_struct *prev,
5184 struct task_struct *next)
5186 kcov_prepare_switch(prev);
5187 sched_info_switch(rq, prev, next);
5188 perf_event_task_sched_out(prev, next);
5190 fire_sched_out_preempt_notifiers(prev, next);
5191 kmap_local_sched_out();
5193 prepare_arch_switch(next);
5197 * finish_task_switch - clean up after a task-switch
5198 * @prev: the thread we just switched away from.
5200 * finish_task_switch must be called after the context switch, paired
5201 * with a prepare_task_switch call before the context switch.
5202 * finish_task_switch will reconcile locking set up by prepare_task_switch,
5203 * and do any other architecture-specific cleanup actions.
5205 * Note that we may have delayed dropping an mm in context_switch(). If
5206 * so, we finish that here outside of the runqueue lock. (Doing it
5207 * with the lock held can cause deadlocks; see schedule() for
5210 * The context switch have flipped the stack from under us and restored the
5211 * local variables which were saved when this task called schedule() in the
5212 * past. prev == current is still correct but we need to recalculate this_rq
5213 * because prev may have moved to another CPU.
5215 static struct rq *finish_task_switch(struct task_struct *prev)
5216 __releases(rq->lock)
5218 struct rq *rq = this_rq();
5219 struct mm_struct *mm = rq->prev_mm;
5220 unsigned int prev_state;
5223 * The previous task will have left us with a preempt_count of 2
5224 * because it left us after:
5227 * preempt_disable(); // 1
5229 * raw_spin_lock_irq(&rq->lock) // 2
5231 * Also, see FORK_PREEMPT_COUNT.
5233 if (WARN_ONCE(preempt_count() != 2*PREEMPT_DISABLE_OFFSET,
5234 "corrupted preempt_count: %s/%d/0x%x\n",
5235 current->comm, current->pid, preempt_count()))
5236 preempt_count_set(FORK_PREEMPT_COUNT);
5241 * A task struct has one reference for the use as "current".
5242 * If a task dies, then it sets TASK_DEAD in tsk->state and calls
5243 * schedule one last time. The schedule call will never return, and
5244 * the scheduled task must drop that reference.
5246 * We must observe prev->state before clearing prev->on_cpu (in
5247 * finish_task), otherwise a concurrent wakeup can get prev
5248 * running on another CPU and we could rave with its RUNNING -> DEAD
5249 * transition, resulting in a double drop.
5251 prev_state = READ_ONCE(prev->__state);
5252 vtime_task_switch(prev);
5253 perf_event_task_sched_in(prev, current);
5255 tick_nohz_task_switch();
5256 finish_lock_switch(rq);
5257 finish_arch_post_lock_switch();
5258 kcov_finish_switch(current);
5260 * kmap_local_sched_out() is invoked with rq::lock held and
5261 * interrupts disabled. There is no requirement for that, but the
5262 * sched out code does not have an interrupt enabled section.
5263 * Restoring the maps on sched in does not require interrupts being
5266 kmap_local_sched_in();
5268 fire_sched_in_preempt_notifiers(current);
5270 * When switching through a kernel thread, the loop in
5271 * membarrier_{private,global}_expedited() may have observed that
5272 * kernel thread and not issued an IPI. It is therefore possible to
5273 * schedule between user->kernel->user threads without passing though
5274 * switch_mm(). Membarrier requires a barrier after storing to
5275 * rq->curr, before returning to userspace, so provide them here:
5277 * - a full memory barrier for {PRIVATE,GLOBAL}_EXPEDITED, implicitly
5278 * provided by mmdrop_lazy_tlb(),
5279 * - a sync_core for SYNC_CORE.
5282 membarrier_mm_sync_core_before_usermode(mm);
5283 mmdrop_lazy_tlb_sched(mm);
5286 if (unlikely(prev_state == TASK_DEAD)) {
5287 if (prev->sched_class->task_dead)
5288 prev->sched_class->task_dead(prev);
5290 /* Task is done with its stack. */
5291 put_task_stack(prev);
5293 put_task_struct_rcu_user(prev);
5300 * schedule_tail - first thing a freshly forked thread must call.
5301 * @prev: the thread we just switched away from.
5303 asmlinkage __visible void schedule_tail(struct task_struct *prev)
5304 __releases(rq->lock)
5307 * New tasks start with FORK_PREEMPT_COUNT, see there and
5308 * finish_task_switch() for details.
5310 * finish_task_switch() will drop rq->lock() and lower preempt_count
5311 * and the preempt_enable() will end up enabling preemption (on
5312 * PREEMPT_COUNT kernels).
5315 finish_task_switch(prev);
5318 if (current->set_child_tid)
5319 put_user(task_pid_vnr(current), current->set_child_tid);
5321 calculate_sigpending();
5325 * context_switch - switch to the new MM and the new thread's register state.
5327 static __always_inline struct rq *
5328 context_switch(struct rq *rq, struct task_struct *prev,
5329 struct task_struct *next, struct rq_flags *rf)
5331 prepare_task_switch(rq, prev, next);
5334 * For paravirt, this is coupled with an exit in switch_to to
5335 * combine the page table reload and the switch backend into
5338 arch_start_context_switch(prev);
5341 * kernel -> kernel lazy + transfer active
5342 * user -> kernel lazy + mmgrab_lazy_tlb() active
5344 * kernel -> user switch + mmdrop_lazy_tlb() active
5345 * user -> user switch
5347 * switch_mm_cid() needs to be updated if the barriers provided
5348 * by context_switch() are modified.
5350 if (!next->mm) { // to kernel
5351 enter_lazy_tlb(prev->active_mm, next);
5353 next->active_mm = prev->active_mm;
5354 if (prev->mm) // from user
5355 mmgrab_lazy_tlb(prev->active_mm);
5357 prev->active_mm = NULL;
5359 membarrier_switch_mm(rq, prev->active_mm, next->mm);
5361 * sys_membarrier() requires an smp_mb() between setting
5362 * rq->curr / membarrier_switch_mm() and returning to userspace.
5364 * The below provides this either through switch_mm(), or in
5365 * case 'prev->active_mm == next->mm' through
5366 * finish_task_switch()'s mmdrop().
5368 switch_mm_irqs_off(prev->active_mm, next->mm, next);
5369 lru_gen_use_mm(next->mm);
5371 if (!prev->mm) { // from kernel
5372 /* will mmdrop_lazy_tlb() in finish_task_switch(). */
5373 rq->prev_mm = prev->active_mm;
5374 prev->active_mm = NULL;
5378 /* switch_mm_cid() requires the memory barriers above. */
5379 switch_mm_cid(rq, prev, next);
5381 prepare_lock_switch(rq, next, rf);
5383 /* Here we just switch the register state and the stack. */
5384 switch_to(prev, next, prev);
5387 return finish_task_switch(prev);
5391 * nr_running and nr_context_switches:
5393 * externally visible scheduler statistics: current number of runnable
5394 * threads, total number of context switches performed since bootup.
5396 unsigned int nr_running(void)
5398 unsigned int i, sum = 0;
5400 for_each_online_cpu(i)
5401 sum += cpu_rq(i)->nr_running;
5407 * Check if only the current task is running on the CPU.
5409 * Caution: this function does not check that the caller has disabled
5410 * preemption, thus the result might have a time-of-check-to-time-of-use
5411 * race. The caller is responsible to use it correctly, for example:
5413 * - from a non-preemptible section (of course)
5415 * - from a thread that is bound to a single CPU
5417 * - in a loop with very short iterations (e.g. a polling loop)
5419 bool single_task_running(void)
5421 return raw_rq()->nr_running == 1;
5423 EXPORT_SYMBOL(single_task_running);
5425 unsigned long long nr_context_switches_cpu(int cpu)
5427 return cpu_rq(cpu)->nr_switches;
5430 unsigned long long nr_context_switches(void)
5433 unsigned long long sum = 0;
5435 for_each_possible_cpu(i)
5436 sum += cpu_rq(i)->nr_switches;
5442 * Consumers of these two interfaces, like for example the cpuidle menu
5443 * governor, are using nonsensical data. Preferring shallow idle state selection
5444 * for a CPU that has IO-wait which might not even end up running the task when
5445 * it does become runnable.
5448 unsigned int nr_iowait_cpu(int cpu)
5450 return atomic_read(&cpu_rq(cpu)->nr_iowait);
5454 * IO-wait accounting, and how it's mostly bollocks (on SMP).
5456 * The idea behind IO-wait account is to account the idle time that we could
5457 * have spend running if it were not for IO. That is, if we were to improve the
5458 * storage performance, we'd have a proportional reduction in IO-wait time.
5460 * This all works nicely on UP, where, when a task blocks on IO, we account
5461 * idle time as IO-wait, because if the storage were faster, it could've been
5462 * running and we'd not be idle.
5464 * This has been extended to SMP, by doing the same for each CPU. This however
5467 * Imagine for instance the case where two tasks block on one CPU, only the one
5468 * CPU will have IO-wait accounted, while the other has regular idle. Even
5469 * though, if the storage were faster, both could've ran at the same time,
5470 * utilising both CPUs.
5472 * This means, that when looking globally, the current IO-wait accounting on
5473 * SMP is a lower bound, by reason of under accounting.
5475 * Worse, since the numbers are provided per CPU, they are sometimes
5476 * interpreted per CPU, and that is nonsensical. A blocked task isn't strictly
5477 * associated with any one particular CPU, it can wake to another CPU than it
5478 * blocked on. This means the per CPU IO-wait number is meaningless.
5480 * Task CPU affinities can make all that even more 'interesting'.
5483 unsigned int nr_iowait(void)
5485 unsigned int i, sum = 0;
5487 for_each_possible_cpu(i)
5488 sum += nr_iowait_cpu(i);
5496 * sched_exec - execve() is a valuable balancing opportunity, because at
5497 * this point the task has the smallest effective memory and cache footprint.
5499 void sched_exec(void)
5501 struct task_struct *p = current;
5502 struct migration_arg arg;
5505 scoped_guard (raw_spinlock_irqsave, &p->pi_lock) {
5506 dest_cpu = p->sched_class->select_task_rq(p, task_cpu(p), WF_EXEC);
5507 if (dest_cpu == smp_processor_id())
5510 if (unlikely(!cpu_active(dest_cpu)))
5513 arg = (struct migration_arg){ p, dest_cpu };
5515 stop_one_cpu(task_cpu(p), migration_cpu_stop, &arg);
5520 DEFINE_PER_CPU(struct kernel_stat, kstat);
5521 DEFINE_PER_CPU(struct kernel_cpustat, kernel_cpustat);
5523 EXPORT_PER_CPU_SYMBOL(kstat);
5524 EXPORT_PER_CPU_SYMBOL(kernel_cpustat);
5527 * The function fair_sched_class.update_curr accesses the struct curr
5528 * and its field curr->exec_start; when called from task_sched_runtime(),
5529 * we observe a high rate of cache misses in practice.
5530 * Prefetching this data results in improved performance.
5532 static inline void prefetch_curr_exec_start(struct task_struct *p)
5534 #ifdef CONFIG_FAIR_GROUP_SCHED
5535 struct sched_entity *curr = (&p->se)->cfs_rq->curr;
5537 struct sched_entity *curr = (&task_rq(p)->cfs)->curr;
5540 prefetch(&curr->exec_start);
5544 * Return accounted runtime for the task.
5545 * In case the task is currently running, return the runtime plus current's
5546 * pending runtime that have not been accounted yet.
5548 unsigned long long task_sched_runtime(struct task_struct *p)
5554 #if defined(CONFIG_64BIT) && defined(CONFIG_SMP)
5556 * 64-bit doesn't need locks to atomically read a 64-bit value.
5557 * So we have a optimization chance when the task's delta_exec is 0.
5558 * Reading ->on_cpu is racy, but this is ok.
5560 * If we race with it leaving CPU, we'll take a lock. So we're correct.
5561 * If we race with it entering CPU, unaccounted time is 0. This is
5562 * indistinguishable from the read occurring a few cycles earlier.
5563 * If we see ->on_cpu without ->on_rq, the task is leaving, and has
5564 * been accounted, so we're correct here as well.
5566 if (!p->on_cpu || !task_on_rq_queued(p))
5567 return p->se.sum_exec_runtime;
5570 rq = task_rq_lock(p, &rf);
5572 * Must be ->curr _and_ ->on_rq. If dequeued, we would
5573 * project cycles that may never be accounted to this
5574 * thread, breaking clock_gettime().
5576 if (task_current(rq, p) && task_on_rq_queued(p)) {
5577 prefetch_curr_exec_start(p);
5578 update_rq_clock(rq);
5579 p->sched_class->update_curr(rq);
5581 ns = p->se.sum_exec_runtime;
5582 task_rq_unlock(rq, p, &rf);
5587 #ifdef CONFIG_SCHED_DEBUG
5588 static u64 cpu_resched_latency(struct rq *rq)
5590 int latency_warn_ms = READ_ONCE(sysctl_resched_latency_warn_ms);
5591 u64 resched_latency, now = rq_clock(rq);
5592 static bool warned_once;
5594 if (sysctl_resched_latency_warn_once && warned_once)
5597 if (!need_resched() || !latency_warn_ms)
5600 if (system_state == SYSTEM_BOOTING)
5603 if (!rq->last_seen_need_resched_ns) {
5604 rq->last_seen_need_resched_ns = now;
5605 rq->ticks_without_resched = 0;
5609 rq->ticks_without_resched++;
5610 resched_latency = now - rq->last_seen_need_resched_ns;
5611 if (resched_latency <= latency_warn_ms * NSEC_PER_MSEC)
5616 return resched_latency;
5619 static int __init setup_resched_latency_warn_ms(char *str)
5623 if ((kstrtol(str, 0, &val))) {
5624 pr_warn("Unable to set resched_latency_warn_ms\n");
5628 sysctl_resched_latency_warn_ms = val;
5631 __setup("resched_latency_warn_ms=", setup_resched_latency_warn_ms);
5633 static inline u64 cpu_resched_latency(struct rq *rq) { return 0; }
5634 #endif /* CONFIG_SCHED_DEBUG */
5637 * This function gets called by the timer code, with HZ frequency.
5638 * We call it with interrupts disabled.
5640 void scheduler_tick(void)
5642 int cpu = smp_processor_id();
5643 struct rq *rq = cpu_rq(cpu);
5644 struct task_struct *curr = rq->curr;
5646 unsigned long thermal_pressure;
5647 u64 resched_latency;
5649 if (housekeeping_cpu(cpu, HK_TYPE_TICK))
5650 arch_scale_freq_tick();
5656 update_rq_clock(rq);
5657 thermal_pressure = arch_scale_thermal_pressure(cpu_of(rq));
5658 update_thermal_load_avg(rq_clock_thermal(rq), rq, thermal_pressure);
5659 curr->sched_class->task_tick(rq, curr, 0);
5660 if (sched_feat(LATENCY_WARN))
5661 resched_latency = cpu_resched_latency(rq);
5662 calc_global_load_tick(rq);
5663 sched_core_tick(rq);
5664 task_tick_mm_cid(rq, curr);
5668 if (sched_feat(LATENCY_WARN) && resched_latency)
5669 resched_latency_warn(cpu, resched_latency);
5671 perf_event_task_tick();
5673 if (curr->flags & PF_WQ_WORKER)
5674 wq_worker_tick(curr);
5677 rq->idle_balance = idle_cpu(cpu);
5678 trigger_load_balance(rq);
5682 #ifdef CONFIG_NO_HZ_FULL
5687 struct delayed_work work;
5689 /* Values for ->state, see diagram below. */
5690 #define TICK_SCHED_REMOTE_OFFLINE 0
5691 #define TICK_SCHED_REMOTE_OFFLINING 1
5692 #define TICK_SCHED_REMOTE_RUNNING 2
5695 * State diagram for ->state:
5698 * TICK_SCHED_REMOTE_OFFLINE
5701 * | | sched_tick_remote()
5704 * +--TICK_SCHED_REMOTE_OFFLINING
5707 * sched_tick_start() | | sched_tick_stop()
5710 * TICK_SCHED_REMOTE_RUNNING
5713 * Other transitions get WARN_ON_ONCE(), except that sched_tick_remote()
5714 * and sched_tick_start() are happy to leave the state in RUNNING.
5717 static struct tick_work __percpu *tick_work_cpu;
5719 static void sched_tick_remote(struct work_struct *work)
5721 struct delayed_work *dwork = to_delayed_work(work);
5722 struct tick_work *twork = container_of(dwork, struct tick_work, work);
5723 int cpu = twork->cpu;
5724 struct rq *rq = cpu_rq(cpu);
5728 * Handle the tick only if it appears the remote CPU is running in full
5729 * dynticks mode. The check is racy by nature, but missing a tick or
5730 * having one too much is no big deal because the scheduler tick updates
5731 * statistics and checks timeslices in a time-independent way, regardless
5732 * of when exactly it is running.
5734 if (tick_nohz_tick_stopped_cpu(cpu)) {
5735 guard(rq_lock_irq)(rq);
5736 struct task_struct *curr = rq->curr;
5738 if (cpu_online(cpu)) {
5739 update_rq_clock(rq);
5741 if (!is_idle_task(curr)) {
5743 * Make sure the next tick runs within a
5744 * reasonable amount of time.
5746 u64 delta = rq_clock_task(rq) - curr->se.exec_start;
5747 WARN_ON_ONCE(delta > (u64)NSEC_PER_SEC * 3);
5749 curr->sched_class->task_tick(rq, curr, 0);
5751 calc_load_nohz_remote(rq);
5756 * Run the remote tick once per second (1Hz). This arbitrary
5757 * frequency is large enough to avoid overload but short enough
5758 * to keep scheduler internal stats reasonably up to date. But
5759 * first update state to reflect hotplug activity if required.
5761 os = atomic_fetch_add_unless(&twork->state, -1, TICK_SCHED_REMOTE_RUNNING);
5762 WARN_ON_ONCE(os == TICK_SCHED_REMOTE_OFFLINE);
5763 if (os == TICK_SCHED_REMOTE_RUNNING)
5764 queue_delayed_work(system_unbound_wq, dwork, HZ);
5767 static void sched_tick_start(int cpu)
5770 struct tick_work *twork;
5772 if (housekeeping_cpu(cpu, HK_TYPE_TICK))
5775 WARN_ON_ONCE(!tick_work_cpu);
5777 twork = per_cpu_ptr(tick_work_cpu, cpu);
5778 os = atomic_xchg(&twork->state, TICK_SCHED_REMOTE_RUNNING);
5779 WARN_ON_ONCE(os == TICK_SCHED_REMOTE_RUNNING);
5780 if (os == TICK_SCHED_REMOTE_OFFLINE) {
5782 INIT_DELAYED_WORK(&twork->work, sched_tick_remote);
5783 queue_delayed_work(system_unbound_wq, &twork->work, HZ);
5787 #ifdef CONFIG_HOTPLUG_CPU
5788 static void sched_tick_stop(int cpu)
5790 struct tick_work *twork;
5793 if (housekeeping_cpu(cpu, HK_TYPE_TICK))
5796 WARN_ON_ONCE(!tick_work_cpu);
5798 twork = per_cpu_ptr(tick_work_cpu, cpu);
5799 /* There cannot be competing actions, but don't rely on stop-machine. */
5800 os = atomic_xchg(&twork->state, TICK_SCHED_REMOTE_OFFLINING);
5801 WARN_ON_ONCE(os != TICK_SCHED_REMOTE_RUNNING);
5802 /* Don't cancel, as this would mess up the state machine. */
5804 #endif /* CONFIG_HOTPLUG_CPU */
5806 int __init sched_tick_offload_init(void)
5808 tick_work_cpu = alloc_percpu(struct tick_work);
5809 BUG_ON(!tick_work_cpu);
5813 #else /* !CONFIG_NO_HZ_FULL */
5814 static inline void sched_tick_start(int cpu) { }
5815 static inline void sched_tick_stop(int cpu) { }
5818 #if defined(CONFIG_PREEMPTION) && (defined(CONFIG_DEBUG_PREEMPT) || \
5819 defined(CONFIG_TRACE_PREEMPT_TOGGLE))
5821 * If the value passed in is equal to the current preempt count
5822 * then we just disabled preemption. Start timing the latency.
5824 static inline void preempt_latency_start(int val)
5826 if (preempt_count() == val) {
5827 unsigned long ip = get_lock_parent_ip();
5828 #ifdef CONFIG_DEBUG_PREEMPT
5829 current->preempt_disable_ip = ip;
5831 trace_preempt_off(CALLER_ADDR0, ip);
5835 void preempt_count_add(int val)
5837 #ifdef CONFIG_DEBUG_PREEMPT
5841 if (DEBUG_LOCKS_WARN_ON((preempt_count() < 0)))
5844 __preempt_count_add(val);
5845 #ifdef CONFIG_DEBUG_PREEMPT
5847 * Spinlock count overflowing soon?
5849 DEBUG_LOCKS_WARN_ON((preempt_count() & PREEMPT_MASK) >=
5852 preempt_latency_start(val);
5854 EXPORT_SYMBOL(preempt_count_add);
5855 NOKPROBE_SYMBOL(preempt_count_add);
5858 * If the value passed in equals to the current preempt count
5859 * then we just enabled preemption. Stop timing the latency.
5861 static inline void preempt_latency_stop(int val)
5863 if (preempt_count() == val)
5864 trace_preempt_on(CALLER_ADDR0, get_lock_parent_ip());
5867 void preempt_count_sub(int val)
5869 #ifdef CONFIG_DEBUG_PREEMPT
5873 if (DEBUG_LOCKS_WARN_ON(val > preempt_count()))
5876 * Is the spinlock portion underflowing?
5878 if (DEBUG_LOCKS_WARN_ON((val < PREEMPT_MASK) &&
5879 !(preempt_count() & PREEMPT_MASK)))
5883 preempt_latency_stop(val);
5884 __preempt_count_sub(val);
5886 EXPORT_SYMBOL(preempt_count_sub);
5887 NOKPROBE_SYMBOL(preempt_count_sub);
5890 static inline void preempt_latency_start(int val) { }
5891 static inline void preempt_latency_stop(int val) { }
5894 static inline unsigned long get_preempt_disable_ip(struct task_struct *p)
5896 #ifdef CONFIG_DEBUG_PREEMPT
5897 return p->preempt_disable_ip;
5904 * Print scheduling while atomic bug:
5906 static noinline void __schedule_bug(struct task_struct *prev)
5908 /* Save this before calling printk(), since that will clobber it */
5909 unsigned long preempt_disable_ip = get_preempt_disable_ip(current);
5911 if (oops_in_progress)
5914 printk(KERN_ERR "BUG: scheduling while atomic: %s/%d/0x%08x\n",
5915 prev->comm, prev->pid, preempt_count());
5917 debug_show_held_locks(prev);
5919 if (irqs_disabled())
5920 print_irqtrace_events(prev);
5921 if (IS_ENABLED(CONFIG_DEBUG_PREEMPT)
5922 && in_atomic_preempt_off()) {
5923 pr_err("Preemption disabled at:");
5924 print_ip_sym(KERN_ERR, preempt_disable_ip);
5926 check_panic_on_warn("scheduling while atomic");
5929 add_taint(TAINT_WARN, LOCKDEP_STILL_OK);
5933 * Various schedule()-time debugging checks and statistics:
5935 static inline void schedule_debug(struct task_struct *prev, bool preempt)
5937 #ifdef CONFIG_SCHED_STACK_END_CHECK
5938 if (task_stack_end_corrupted(prev))
5939 panic("corrupted stack end detected inside scheduler\n");
5941 if (task_scs_end_corrupted(prev))
5942 panic("corrupted shadow stack detected inside scheduler\n");
5945 #ifdef CONFIG_DEBUG_ATOMIC_SLEEP
5946 if (!preempt && READ_ONCE(prev->__state) && prev->non_block_count) {
5947 printk(KERN_ERR "BUG: scheduling in a non-blocking section: %s/%d/%i\n",
5948 prev->comm, prev->pid, prev->non_block_count);
5950 add_taint(TAINT_WARN, LOCKDEP_STILL_OK);
5954 if (unlikely(in_atomic_preempt_off())) {
5955 __schedule_bug(prev);
5956 preempt_count_set(PREEMPT_DISABLED);
5959 SCHED_WARN_ON(ct_state() == CONTEXT_USER);
5961 profile_hit(SCHED_PROFILING, __builtin_return_address(0));
5963 schedstat_inc(this_rq()->sched_count);
5966 static void put_prev_task_balance(struct rq *rq, struct task_struct *prev,
5967 struct rq_flags *rf)
5970 const struct sched_class *class;
5972 * We must do the balancing pass before put_prev_task(), such
5973 * that when we release the rq->lock the task is in the same
5974 * state as before we took rq->lock.
5976 * We can terminate the balance pass as soon as we know there is
5977 * a runnable task of @class priority or higher.
5979 for_class_range(class, prev->sched_class, &idle_sched_class) {
5980 if (class->balance(rq, prev, rf))
5985 put_prev_task(rq, prev);
5989 * Pick up the highest-prio task:
5991 static inline struct task_struct *
5992 __pick_next_task(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
5994 const struct sched_class *class;
5995 struct task_struct *p;
5998 * Optimization: we know that if all tasks are in the fair class we can
5999 * call that function directly, but only if the @prev task wasn't of a
6000 * higher scheduling class, because otherwise those lose the
6001 * opportunity to pull in more work from other CPUs.
6003 if (likely(!sched_class_above(prev->sched_class, &fair_sched_class) &&
6004 rq->nr_running == rq->cfs.h_nr_running)) {
6006 p = pick_next_task_fair(rq, prev, rf);
6007 if (unlikely(p == RETRY_TASK))
6010 /* Assume the next prioritized class is idle_sched_class */
6012 put_prev_task(rq, prev);
6013 p = pick_next_task_idle(rq);
6020 put_prev_task_balance(rq, prev, rf);
6022 for_each_class(class) {
6023 p = class->pick_next_task(rq);
6028 BUG(); /* The idle class should always have a runnable task. */
6031 #ifdef CONFIG_SCHED_CORE
6032 static inline bool is_task_rq_idle(struct task_struct *t)
6034 return (task_rq(t)->idle == t);
6037 static inline bool cookie_equals(struct task_struct *a, unsigned long cookie)
6039 return is_task_rq_idle(a) || (a->core_cookie == cookie);
6042 static inline bool cookie_match(struct task_struct *a, struct task_struct *b)
6044 if (is_task_rq_idle(a) || is_task_rq_idle(b))
6047 return a->core_cookie == b->core_cookie;
6050 static inline struct task_struct *pick_task(struct rq *rq)
6052 const struct sched_class *class;
6053 struct task_struct *p;
6055 for_each_class(class) {
6056 p = class->pick_task(rq);
6061 BUG(); /* The idle class should always have a runnable task. */
6064 extern void task_vruntime_update(struct rq *rq, struct task_struct *p, bool in_fi);
6066 static void queue_core_balance(struct rq *rq);
6068 static struct task_struct *
6069 pick_next_task(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
6071 struct task_struct *next, *p, *max = NULL;
6072 const struct cpumask *smt_mask;
6073 bool fi_before = false;
6074 bool core_clock_updated = (rq == rq->core);
6075 unsigned long cookie;
6076 int i, cpu, occ = 0;
6080 if (!sched_core_enabled(rq))
6081 return __pick_next_task(rq, prev, rf);
6085 /* Stopper task is switching into idle, no need core-wide selection. */
6086 if (cpu_is_offline(cpu)) {
6088 * Reset core_pick so that we don't enter the fastpath when
6089 * coming online. core_pick would already be migrated to
6090 * another cpu during offline.
6092 rq->core_pick = NULL;
6093 return __pick_next_task(rq, prev, rf);
6097 * If there were no {en,de}queues since we picked (IOW, the task
6098 * pointers are all still valid), and we haven't scheduled the last
6099 * pick yet, do so now.
6101 * rq->core_pick can be NULL if no selection was made for a CPU because
6102 * it was either offline or went offline during a sibling's core-wide
6103 * selection. In this case, do a core-wide selection.
6105 if (rq->core->core_pick_seq == rq->core->core_task_seq &&
6106 rq->core->core_pick_seq != rq->core_sched_seq &&
6108 WRITE_ONCE(rq->core_sched_seq, rq->core->core_pick_seq);
6110 next = rq->core_pick;
6112 put_prev_task(rq, prev);
6113 set_next_task(rq, next);
6116 rq->core_pick = NULL;
6120 put_prev_task_balance(rq, prev, rf);
6122 smt_mask = cpu_smt_mask(cpu);
6123 need_sync = !!rq->core->core_cookie;
6126 rq->core->core_cookie = 0UL;
6127 if (rq->core->core_forceidle_count) {
6128 if (!core_clock_updated) {
6129 update_rq_clock(rq->core);
6130 core_clock_updated = true;
6132 sched_core_account_forceidle(rq);
6133 /* reset after accounting force idle */
6134 rq->core->core_forceidle_start = 0;
6135 rq->core->core_forceidle_count = 0;
6136 rq->core->core_forceidle_occupation = 0;
6142 * core->core_task_seq, core->core_pick_seq, rq->core_sched_seq
6144 * @task_seq guards the task state ({en,de}queues)
6145 * @pick_seq is the @task_seq we did a selection on
6146 * @sched_seq is the @pick_seq we scheduled
6148 * However, preemptions can cause multiple picks on the same task set.
6149 * 'Fix' this by also increasing @task_seq for every pick.
6151 rq->core->core_task_seq++;
6154 * Optimize for common case where this CPU has no cookies
6155 * and there are no cookied tasks running on siblings.
6158 next = pick_task(rq);
6159 if (!next->core_cookie) {
6160 rq->core_pick = NULL;
6162 * For robustness, update the min_vruntime_fi for
6163 * unconstrained picks as well.
6165 WARN_ON_ONCE(fi_before);
6166 task_vruntime_update(rq, next, false);
6172 * For each thread: do the regular task pick and find the max prio task
6175 * Tie-break prio towards the current CPU
6177 for_each_cpu_wrap(i, smt_mask, cpu) {
6181 * Current cpu always has its clock updated on entrance to
6182 * pick_next_task(). If the current cpu is not the core,
6183 * the core may also have been updated above.
6185 if (i != cpu && (rq_i != rq->core || !core_clock_updated))
6186 update_rq_clock(rq_i);
6188 p = rq_i->core_pick = pick_task(rq_i);
6189 if (!max || prio_less(max, p, fi_before))
6193 cookie = rq->core->core_cookie = max->core_cookie;
6196 * For each thread: try and find a runnable task that matches @max or
6199 for_each_cpu(i, smt_mask) {
6201 p = rq_i->core_pick;
6203 if (!cookie_equals(p, cookie)) {
6206 p = sched_core_find(rq_i, cookie);
6208 p = idle_sched_class.pick_task(rq_i);
6211 rq_i->core_pick = p;
6213 if (p == rq_i->idle) {
6214 if (rq_i->nr_running) {
6215 rq->core->core_forceidle_count++;
6217 rq->core->core_forceidle_seq++;
6224 if (schedstat_enabled() && rq->core->core_forceidle_count) {
6225 rq->core->core_forceidle_start = rq_clock(rq->core);
6226 rq->core->core_forceidle_occupation = occ;
6229 rq->core->core_pick_seq = rq->core->core_task_seq;
6230 next = rq->core_pick;
6231 rq->core_sched_seq = rq->core->core_pick_seq;
6233 /* Something should have been selected for current CPU */
6234 WARN_ON_ONCE(!next);
6237 * Reschedule siblings
6239 * NOTE: L1TF -- at this point we're no longer running the old task and
6240 * sending an IPI (below) ensures the sibling will no longer be running
6241 * their task. This ensures there is no inter-sibling overlap between
6242 * non-matching user state.
6244 for_each_cpu(i, smt_mask) {
6248 * An online sibling might have gone offline before a task
6249 * could be picked for it, or it might be offline but later
6250 * happen to come online, but its too late and nothing was
6251 * picked for it. That's Ok - it will pick tasks for itself,
6254 if (!rq_i->core_pick)
6258 * Update for new !FI->FI transitions, or if continuing to be in !FI:
6259 * fi_before fi update?
6265 if (!(fi_before && rq->core->core_forceidle_count))
6266 task_vruntime_update(rq_i, rq_i->core_pick, !!rq->core->core_forceidle_count);
6268 rq_i->core_pick->core_occupation = occ;
6271 rq_i->core_pick = NULL;
6275 /* Did we break L1TF mitigation requirements? */
6276 WARN_ON_ONCE(!cookie_match(next, rq_i->core_pick));
6278 if (rq_i->curr == rq_i->core_pick) {
6279 rq_i->core_pick = NULL;
6287 set_next_task(rq, next);
6289 if (rq->core->core_forceidle_count && next == rq->idle)
6290 queue_core_balance(rq);
6295 static bool try_steal_cookie(int this, int that)
6297 struct rq *dst = cpu_rq(this), *src = cpu_rq(that);
6298 struct task_struct *p;
6299 unsigned long cookie;
6300 bool success = false;
6303 guard(double_rq_lock)(dst, src);
6305 cookie = dst->core->core_cookie;
6309 if (dst->curr != dst->idle)
6312 p = sched_core_find(src, cookie);
6317 if (p == src->core_pick || p == src->curr)
6320 if (!is_cpu_allowed(p, this))
6323 if (p->core_occupation > dst->idle->core_occupation)
6326 * sched_core_find() and sched_core_next() will ensure
6327 * that task @p is not throttled now, we also need to
6328 * check whether the runqueue of the destination CPU is
6331 if (sched_task_is_throttled(p, this))
6334 deactivate_task(src, p, 0);
6335 set_task_cpu(p, this);
6336 activate_task(dst, p, 0);
6344 p = sched_core_next(p, cookie);
6350 static bool steal_cookie_task(int cpu, struct sched_domain *sd)
6354 for_each_cpu_wrap(i, sched_domain_span(sd), cpu + 1) {
6361 if (try_steal_cookie(cpu, i))
6368 static void sched_core_balance(struct rq *rq)
6370 struct sched_domain *sd;
6371 int cpu = cpu_of(rq);
6375 raw_spin_rq_unlock_irq(rq);
6376 for_each_domain(cpu, sd) {
6380 if (steal_cookie_task(cpu, sd))
6383 raw_spin_rq_lock_irq(rq);
6388 static DEFINE_PER_CPU(struct balance_callback, core_balance_head);
6390 static void queue_core_balance(struct rq *rq)
6392 if (!sched_core_enabled(rq))
6395 if (!rq->core->core_cookie)
6398 if (!rq->nr_running) /* not forced idle */
6401 queue_balance_callback(rq, &per_cpu(core_balance_head, rq->cpu), sched_core_balance);
6404 DEFINE_LOCK_GUARD_1(core_lock, int,
6405 sched_core_lock(*_T->lock, &_T->flags),
6406 sched_core_unlock(*_T->lock, &_T->flags),
6407 unsigned long flags)
6409 static void sched_core_cpu_starting(unsigned int cpu)
6411 const struct cpumask *smt_mask = cpu_smt_mask(cpu);
6412 struct rq *rq = cpu_rq(cpu), *core_rq = NULL;
6415 guard(core_lock)(&cpu);
6417 WARN_ON_ONCE(rq->core != rq);
6419 /* if we're the first, we'll be our own leader */
6420 if (cpumask_weight(smt_mask) == 1)
6423 /* find the leader */
6424 for_each_cpu(t, smt_mask) {
6428 if (rq->core == rq) {
6434 if (WARN_ON_ONCE(!core_rq)) /* whoopsie */
6437 /* install and validate core_rq */
6438 for_each_cpu(t, smt_mask) {
6444 WARN_ON_ONCE(rq->core != core_rq);
6448 static void sched_core_cpu_deactivate(unsigned int cpu)
6450 const struct cpumask *smt_mask = cpu_smt_mask(cpu);
6451 struct rq *rq = cpu_rq(cpu), *core_rq = NULL;
6454 guard(core_lock)(&cpu);
6456 /* if we're the last man standing, nothing to do */
6457 if (cpumask_weight(smt_mask) == 1) {
6458 WARN_ON_ONCE(rq->core != rq);
6462 /* if we're not the leader, nothing to do */
6466 /* find a new leader */
6467 for_each_cpu(t, smt_mask) {
6470 core_rq = cpu_rq(t);
6474 if (WARN_ON_ONCE(!core_rq)) /* impossible */
6477 /* copy the shared state to the new leader */
6478 core_rq->core_task_seq = rq->core_task_seq;
6479 core_rq->core_pick_seq = rq->core_pick_seq;
6480 core_rq->core_cookie = rq->core_cookie;
6481 core_rq->core_forceidle_count = rq->core_forceidle_count;
6482 core_rq->core_forceidle_seq = rq->core_forceidle_seq;
6483 core_rq->core_forceidle_occupation = rq->core_forceidle_occupation;
6486 * Accounting edge for forced idle is handled in pick_next_task().
6487 * Don't need another one here, since the hotplug thread shouldn't
6490 core_rq->core_forceidle_start = 0;
6492 /* install new leader */
6493 for_each_cpu(t, smt_mask) {
6499 static inline void sched_core_cpu_dying(unsigned int cpu)
6501 struct rq *rq = cpu_rq(cpu);
6507 #else /* !CONFIG_SCHED_CORE */
6509 static inline void sched_core_cpu_starting(unsigned int cpu) {}
6510 static inline void sched_core_cpu_deactivate(unsigned int cpu) {}
6511 static inline void sched_core_cpu_dying(unsigned int cpu) {}
6513 static struct task_struct *
6514 pick_next_task(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
6516 return __pick_next_task(rq, prev, rf);
6519 #endif /* CONFIG_SCHED_CORE */
6522 * Constants for the sched_mode argument of __schedule().
6524 * The mode argument allows RT enabled kernels to differentiate a
6525 * preemption from blocking on an 'sleeping' spin/rwlock. Note that
6526 * SM_MASK_PREEMPT for !RT has all bits set, which allows the compiler to
6527 * optimize the AND operation out and just check for zero.
6530 #define SM_PREEMPT 0x1
6531 #define SM_RTLOCK_WAIT 0x2
6533 #ifndef CONFIG_PREEMPT_RT
6534 # define SM_MASK_PREEMPT (~0U)
6536 # define SM_MASK_PREEMPT SM_PREEMPT
6540 * __schedule() is the main scheduler function.
6542 * The main means of driving the scheduler and thus entering this function are:
6544 * 1. Explicit blocking: mutex, semaphore, waitqueue, etc.
6546 * 2. TIF_NEED_RESCHED flag is checked on interrupt and userspace return
6547 * paths. For example, see arch/x86/entry_64.S.
6549 * To drive preemption between tasks, the scheduler sets the flag in timer
6550 * interrupt handler scheduler_tick().
6552 * 3. Wakeups don't really cause entry into schedule(). They add a
6553 * task to the run-queue and that's it.
6555 * Now, if the new task added to the run-queue preempts the current
6556 * task, then the wakeup sets TIF_NEED_RESCHED and schedule() gets
6557 * called on the nearest possible occasion:
6559 * - If the kernel is preemptible (CONFIG_PREEMPTION=y):
6561 * - in syscall or exception context, at the next outmost
6562 * preempt_enable(). (this might be as soon as the wake_up()'s
6565 * - in IRQ context, return from interrupt-handler to
6566 * preemptible context
6568 * - If the kernel is not preemptible (CONFIG_PREEMPTION is not set)
6571 * - cond_resched() call
6572 * - explicit schedule() call
6573 * - return from syscall or exception to user-space
6574 * - return from interrupt-handler to user-space
6576 * WARNING: must be called with preemption disabled!
6578 static void __sched notrace __schedule(unsigned int sched_mode)
6580 struct task_struct *prev, *next;
6581 unsigned long *switch_count;
6582 unsigned long prev_state;
6587 cpu = smp_processor_id();
6591 schedule_debug(prev, !!sched_mode);
6593 if (sched_feat(HRTICK) || sched_feat(HRTICK_DL))
6596 local_irq_disable();
6597 rcu_note_context_switch(!!sched_mode);
6600 * Make sure that signal_pending_state()->signal_pending() below
6601 * can't be reordered with __set_current_state(TASK_INTERRUPTIBLE)
6602 * done by the caller to avoid the race with signal_wake_up():
6604 * __set_current_state(@state) signal_wake_up()
6605 * schedule() set_tsk_thread_flag(p, TIF_SIGPENDING)
6606 * wake_up_state(p, state)
6607 * LOCK rq->lock LOCK p->pi_state
6608 * smp_mb__after_spinlock() smp_mb__after_spinlock()
6609 * if (signal_pending_state()) if (p->state & @state)
6611 * Also, the membarrier system call requires a full memory barrier
6612 * after coming from user-space, before storing to rq->curr.
6615 smp_mb__after_spinlock();
6617 /* Promote REQ to ACT */
6618 rq->clock_update_flags <<= 1;
6619 update_rq_clock(rq);
6620 rq->clock_update_flags = RQCF_UPDATED;
6622 switch_count = &prev->nivcsw;
6625 * We must load prev->state once (task_struct::state is volatile), such
6626 * that we form a control dependency vs deactivate_task() below.
6628 prev_state = READ_ONCE(prev->__state);
6629 if (!(sched_mode & SM_MASK_PREEMPT) && prev_state) {
6630 if (signal_pending_state(prev_state, prev)) {
6631 WRITE_ONCE(prev->__state, TASK_RUNNING);
6633 prev->sched_contributes_to_load =
6634 (prev_state & TASK_UNINTERRUPTIBLE) &&
6635 !(prev_state & TASK_NOLOAD) &&
6636 !(prev_state & TASK_FROZEN);
6638 if (prev->sched_contributes_to_load)
6639 rq->nr_uninterruptible++;
6642 * __schedule() ttwu()
6643 * prev_state = prev->state; if (p->on_rq && ...)
6644 * if (prev_state) goto out;
6645 * p->on_rq = 0; smp_acquire__after_ctrl_dep();
6646 * p->state = TASK_WAKING
6648 * Where __schedule() and ttwu() have matching control dependencies.
6650 * After this, schedule() must not care about p->state any more.
6652 deactivate_task(rq, prev, DEQUEUE_SLEEP | DEQUEUE_NOCLOCK);
6654 if (prev->in_iowait) {
6655 atomic_inc(&rq->nr_iowait);
6656 delayacct_blkio_start();
6659 switch_count = &prev->nvcsw;
6662 next = pick_next_task(rq, prev, &rf);
6663 clear_tsk_need_resched(prev);
6664 clear_preempt_need_resched();
6665 #ifdef CONFIG_SCHED_DEBUG
6666 rq->last_seen_need_resched_ns = 0;
6669 if (likely(prev != next)) {
6672 * RCU users of rcu_dereference(rq->curr) may not see
6673 * changes to task_struct made by pick_next_task().
6675 RCU_INIT_POINTER(rq->curr, next);
6677 * The membarrier system call requires each architecture
6678 * to have a full memory barrier after updating
6679 * rq->curr, before returning to user-space.
6681 * Here are the schemes providing that barrier on the
6682 * various architectures:
6683 * - mm ? switch_mm() : mmdrop() for x86, s390, sparc, PowerPC.
6684 * switch_mm() rely on membarrier_arch_switch_mm() on PowerPC.
6685 * - finish_lock_switch() for weakly-ordered
6686 * architectures where spin_unlock is a full barrier,
6687 * - switch_to() for arm64 (weakly-ordered, spin_unlock
6688 * is a RELEASE barrier),
6692 migrate_disable_switch(rq, prev);
6693 psi_sched_switch(prev, next, !task_on_rq_queued(prev));
6695 trace_sched_switch(sched_mode & SM_MASK_PREEMPT, prev, next, prev_state);
6697 /* Also unlocks the rq: */
6698 rq = context_switch(rq, prev, next, &rf);
6700 rq_unpin_lock(rq, &rf);
6701 __balance_callbacks(rq);
6702 raw_spin_rq_unlock_irq(rq);
6706 void __noreturn do_task_dead(void)
6708 /* Causes final put_task_struct in finish_task_switch(): */
6709 set_special_state(TASK_DEAD);
6711 /* Tell freezer to ignore us: */
6712 current->flags |= PF_NOFREEZE;
6714 __schedule(SM_NONE);
6717 /* Avoid "noreturn function does return" - but don't continue if BUG() is a NOP: */
6722 static inline void sched_submit_work(struct task_struct *tsk)
6724 unsigned int task_flags;
6726 if (task_is_running(tsk))
6729 task_flags = tsk->flags;
6731 * If a worker goes to sleep, notify and ask workqueue whether it
6732 * wants to wake up a task to maintain concurrency.
6734 if (task_flags & (PF_WQ_WORKER | PF_IO_WORKER)) {
6735 if (task_flags & PF_WQ_WORKER)
6736 wq_worker_sleeping(tsk);
6738 io_wq_worker_sleeping(tsk);
6742 * spinlock and rwlock must not flush block requests. This will
6743 * deadlock if the callback attempts to acquire a lock which is
6746 SCHED_WARN_ON(current->__state & TASK_RTLOCK_WAIT);
6749 * If we are going to sleep and we have plugged IO queued,
6750 * make sure to submit it to avoid deadlocks.
6752 blk_flush_plug(tsk->plug, true);
6755 static void sched_update_worker(struct task_struct *tsk)
6757 if (tsk->flags & (PF_WQ_WORKER | PF_IO_WORKER)) {
6758 if (tsk->flags & PF_WQ_WORKER)
6759 wq_worker_running(tsk);
6761 io_wq_worker_running(tsk);
6765 asmlinkage __visible void __sched schedule(void)
6767 struct task_struct *tsk = current;
6769 sched_submit_work(tsk);
6772 __schedule(SM_NONE);
6773 sched_preempt_enable_no_resched();
6774 } while (need_resched());
6775 sched_update_worker(tsk);
6777 EXPORT_SYMBOL(schedule);
6780 * synchronize_rcu_tasks() makes sure that no task is stuck in preempted
6781 * state (have scheduled out non-voluntarily) by making sure that all
6782 * tasks have either left the run queue or have gone into user space.
6783 * As idle tasks do not do either, they must not ever be preempted
6784 * (schedule out non-voluntarily).
6786 * schedule_idle() is similar to schedule_preempt_disable() except that it
6787 * never enables preemption because it does not call sched_submit_work().
6789 void __sched schedule_idle(void)
6792 * As this skips calling sched_submit_work(), which the idle task does
6793 * regardless because that function is a nop when the task is in a
6794 * TASK_RUNNING state, make sure this isn't used someplace that the
6795 * current task can be in any other state. Note, idle is always in the
6796 * TASK_RUNNING state.
6798 WARN_ON_ONCE(current->__state);
6800 __schedule(SM_NONE);
6801 } while (need_resched());
6804 #if defined(CONFIG_CONTEXT_TRACKING_USER) && !defined(CONFIG_HAVE_CONTEXT_TRACKING_USER_OFFSTACK)
6805 asmlinkage __visible void __sched schedule_user(void)
6808 * If we come here after a random call to set_need_resched(),
6809 * or we have been woken up remotely but the IPI has not yet arrived,
6810 * we haven't yet exited the RCU idle mode. Do it here manually until
6811 * we find a better solution.
6813 * NB: There are buggy callers of this function. Ideally we
6814 * should warn if prev_state != CONTEXT_USER, but that will trigger
6815 * too frequently to make sense yet.
6817 enum ctx_state prev_state = exception_enter();
6819 exception_exit(prev_state);
6824 * schedule_preempt_disabled - called with preemption disabled
6826 * Returns with preemption disabled. Note: preempt_count must be 1
6828 void __sched schedule_preempt_disabled(void)
6830 sched_preempt_enable_no_resched();
6835 #ifdef CONFIG_PREEMPT_RT
6836 void __sched notrace schedule_rtlock(void)
6840 __schedule(SM_RTLOCK_WAIT);
6841 sched_preempt_enable_no_resched();
6842 } while (need_resched());
6844 NOKPROBE_SYMBOL(schedule_rtlock);
6847 static void __sched notrace preempt_schedule_common(void)
6851 * Because the function tracer can trace preempt_count_sub()
6852 * and it also uses preempt_enable/disable_notrace(), if
6853 * NEED_RESCHED is set, the preempt_enable_notrace() called
6854 * by the function tracer will call this function again and
6855 * cause infinite recursion.
6857 * Preemption must be disabled here before the function
6858 * tracer can trace. Break up preempt_disable() into two
6859 * calls. One to disable preemption without fear of being
6860 * traced. The other to still record the preemption latency,
6861 * which can also be traced by the function tracer.
6863 preempt_disable_notrace();
6864 preempt_latency_start(1);
6865 __schedule(SM_PREEMPT);
6866 preempt_latency_stop(1);
6867 preempt_enable_no_resched_notrace();
6870 * Check again in case we missed a preemption opportunity
6871 * between schedule and now.
6873 } while (need_resched());
6876 #ifdef CONFIG_PREEMPTION
6878 * This is the entry point to schedule() from in-kernel preemption
6879 * off of preempt_enable.
6881 asmlinkage __visible void __sched notrace preempt_schedule(void)
6884 * If there is a non-zero preempt_count or interrupts are disabled,
6885 * we do not want to preempt the current task. Just return..
6887 if (likely(!preemptible()))
6889 preempt_schedule_common();
6891 NOKPROBE_SYMBOL(preempt_schedule);
6892 EXPORT_SYMBOL(preempt_schedule);
6894 #ifdef CONFIG_PREEMPT_DYNAMIC
6895 #if defined(CONFIG_HAVE_PREEMPT_DYNAMIC_CALL)
6896 #ifndef preempt_schedule_dynamic_enabled
6897 #define preempt_schedule_dynamic_enabled preempt_schedule
6898 #define preempt_schedule_dynamic_disabled NULL
6900 DEFINE_STATIC_CALL(preempt_schedule, preempt_schedule_dynamic_enabled);
6901 EXPORT_STATIC_CALL_TRAMP(preempt_schedule);
6902 #elif defined(CONFIG_HAVE_PREEMPT_DYNAMIC_KEY)
6903 static DEFINE_STATIC_KEY_TRUE(sk_dynamic_preempt_schedule);
6904 void __sched notrace dynamic_preempt_schedule(void)
6906 if (!static_branch_unlikely(&sk_dynamic_preempt_schedule))
6910 NOKPROBE_SYMBOL(dynamic_preempt_schedule);
6911 EXPORT_SYMBOL(dynamic_preempt_schedule);
6916 * preempt_schedule_notrace - preempt_schedule called by tracing
6918 * The tracing infrastructure uses preempt_enable_notrace to prevent
6919 * recursion and tracing preempt enabling caused by the tracing
6920 * infrastructure itself. But as tracing can happen in areas coming
6921 * from userspace or just about to enter userspace, a preempt enable
6922 * can occur before user_exit() is called. This will cause the scheduler
6923 * to be called when the system is still in usermode.
6925 * To prevent this, the preempt_enable_notrace will use this function
6926 * instead of preempt_schedule() to exit user context if needed before
6927 * calling the scheduler.
6929 asmlinkage __visible void __sched notrace preempt_schedule_notrace(void)
6931 enum ctx_state prev_ctx;
6933 if (likely(!preemptible()))
6938 * Because the function tracer can trace preempt_count_sub()
6939 * and it also uses preempt_enable/disable_notrace(), if
6940 * NEED_RESCHED is set, the preempt_enable_notrace() called
6941 * by the function tracer will call this function again and
6942 * cause infinite recursion.
6944 * Preemption must be disabled here before the function
6945 * tracer can trace. Break up preempt_disable() into two
6946 * calls. One to disable preemption without fear of being
6947 * traced. The other to still record the preemption latency,
6948 * which can also be traced by the function tracer.
6950 preempt_disable_notrace();
6951 preempt_latency_start(1);
6953 * Needs preempt disabled in case user_exit() is traced
6954 * and the tracer calls preempt_enable_notrace() causing
6955 * an infinite recursion.
6957 prev_ctx = exception_enter();
6958 __schedule(SM_PREEMPT);
6959 exception_exit(prev_ctx);
6961 preempt_latency_stop(1);
6962 preempt_enable_no_resched_notrace();
6963 } while (need_resched());
6965 EXPORT_SYMBOL_GPL(preempt_schedule_notrace);
6967 #ifdef CONFIG_PREEMPT_DYNAMIC
6968 #if defined(CONFIG_HAVE_PREEMPT_DYNAMIC_CALL)
6969 #ifndef preempt_schedule_notrace_dynamic_enabled
6970 #define preempt_schedule_notrace_dynamic_enabled preempt_schedule_notrace
6971 #define preempt_schedule_notrace_dynamic_disabled NULL
6973 DEFINE_STATIC_CALL(preempt_schedule_notrace, preempt_schedule_notrace_dynamic_enabled);
6974 EXPORT_STATIC_CALL_TRAMP(preempt_schedule_notrace);
6975 #elif defined(CONFIG_HAVE_PREEMPT_DYNAMIC_KEY)
6976 static DEFINE_STATIC_KEY_TRUE(sk_dynamic_preempt_schedule_notrace);
6977 void __sched notrace dynamic_preempt_schedule_notrace(void)
6979 if (!static_branch_unlikely(&sk_dynamic_preempt_schedule_notrace))
6981 preempt_schedule_notrace();
6983 NOKPROBE_SYMBOL(dynamic_preempt_schedule_notrace);
6984 EXPORT_SYMBOL(dynamic_preempt_schedule_notrace);
6988 #endif /* CONFIG_PREEMPTION */
6991 * This is the entry point to schedule() from kernel preemption
6992 * off of irq context.
6993 * Note, that this is called and return with irqs disabled. This will
6994 * protect us against recursive calling from irq.
6996 asmlinkage __visible void __sched preempt_schedule_irq(void)
6998 enum ctx_state prev_state;
7000 /* Catch callers which need to be fixed */
7001 BUG_ON(preempt_count() || !irqs_disabled());
7003 prev_state = exception_enter();
7008 __schedule(SM_PREEMPT);
7009 local_irq_disable();
7010 sched_preempt_enable_no_resched();
7011 } while (need_resched());
7013 exception_exit(prev_state);
7016 int default_wake_function(wait_queue_entry_t *curr, unsigned mode, int wake_flags,
7019 WARN_ON_ONCE(IS_ENABLED(CONFIG_SCHED_DEBUG) && wake_flags & ~(WF_SYNC|WF_CURRENT_CPU));
7020 return try_to_wake_up(curr->private, mode, wake_flags);
7022 EXPORT_SYMBOL(default_wake_function);
7024 static void __setscheduler_prio(struct task_struct *p, int prio)
7027 p->sched_class = &dl_sched_class;
7028 else if (rt_prio(prio))
7029 p->sched_class = &rt_sched_class;
7031 p->sched_class = &fair_sched_class;
7036 #ifdef CONFIG_RT_MUTEXES
7038 static inline int __rt_effective_prio(struct task_struct *pi_task, int prio)
7041 prio = min(prio, pi_task->prio);
7046 static inline int rt_effective_prio(struct task_struct *p, int prio)
7048 struct task_struct *pi_task = rt_mutex_get_top_task(p);
7050 return __rt_effective_prio(pi_task, prio);
7054 * rt_mutex_setprio - set the current priority of a task
7056 * @pi_task: donor task
7058 * This function changes the 'effective' priority of a task. It does
7059 * not touch ->normal_prio like __setscheduler().
7061 * Used by the rt_mutex code to implement priority inheritance
7062 * logic. Call site only calls if the priority of the task changed.
7064 void rt_mutex_setprio(struct task_struct *p, struct task_struct *pi_task)
7066 int prio, oldprio, queued, running, queue_flag =
7067 DEQUEUE_SAVE | DEQUEUE_MOVE | DEQUEUE_NOCLOCK;
7068 const struct sched_class *prev_class;
7072 /* XXX used to be waiter->prio, not waiter->task->prio */
7073 prio = __rt_effective_prio(pi_task, p->normal_prio);
7076 * If nothing changed; bail early.
7078 if (p->pi_top_task == pi_task && prio == p->prio && !dl_prio(prio))
7081 rq = __task_rq_lock(p, &rf);
7082 update_rq_clock(rq);
7084 * Set under pi_lock && rq->lock, such that the value can be used under
7087 * Note that there is loads of tricky to make this pointer cache work
7088 * right. rt_mutex_slowunlock()+rt_mutex_postunlock() work together to
7089 * ensure a task is de-boosted (pi_task is set to NULL) before the
7090 * task is allowed to run again (and can exit). This ensures the pointer
7091 * points to a blocked task -- which guarantees the task is present.
7093 p->pi_top_task = pi_task;
7096 * For FIFO/RR we only need to set prio, if that matches we're done.
7098 if (prio == p->prio && !dl_prio(prio))
7102 * Idle task boosting is a nono in general. There is one
7103 * exception, when PREEMPT_RT and NOHZ is active:
7105 * The idle task calls get_next_timer_interrupt() and holds
7106 * the timer wheel base->lock on the CPU and another CPU wants
7107 * to access the timer (probably to cancel it). We can safely
7108 * ignore the boosting request, as the idle CPU runs this code
7109 * with interrupts disabled and will complete the lock
7110 * protected section without being interrupted. So there is no
7111 * real need to boost.
7113 if (unlikely(p == rq->idle)) {
7114 WARN_ON(p != rq->curr);
7115 WARN_ON(p->pi_blocked_on);
7119 trace_sched_pi_setprio(p, pi_task);
7122 if (oldprio == prio)
7123 queue_flag &= ~DEQUEUE_MOVE;
7125 prev_class = p->sched_class;
7126 queued = task_on_rq_queued(p);
7127 running = task_current(rq, p);
7129 dequeue_task(rq, p, queue_flag);
7131 put_prev_task(rq, p);
7134 * Boosting condition are:
7135 * 1. -rt task is running and holds mutex A
7136 * --> -dl task blocks on mutex A
7138 * 2. -dl task is running and holds mutex A
7139 * --> -dl task blocks on mutex A and could preempt the
7142 if (dl_prio(prio)) {
7143 if (!dl_prio(p->normal_prio) ||
7144 (pi_task && dl_prio(pi_task->prio) &&
7145 dl_entity_preempt(&pi_task->dl, &p->dl))) {
7146 p->dl.pi_se = pi_task->dl.pi_se;
7147 queue_flag |= ENQUEUE_REPLENISH;
7149 p->dl.pi_se = &p->dl;
7151 } else if (rt_prio(prio)) {
7152 if (dl_prio(oldprio))
7153 p->dl.pi_se = &p->dl;
7155 queue_flag |= ENQUEUE_HEAD;
7157 if (dl_prio(oldprio))
7158 p->dl.pi_se = &p->dl;
7159 if (rt_prio(oldprio))
7163 __setscheduler_prio(p, prio);
7166 enqueue_task(rq, p, queue_flag);
7168 set_next_task(rq, p);
7170 check_class_changed(rq, p, prev_class, oldprio);
7172 /* Avoid rq from going away on us: */
7175 rq_unpin_lock(rq, &rf);
7176 __balance_callbacks(rq);
7177 raw_spin_rq_unlock(rq);
7182 static inline int rt_effective_prio(struct task_struct *p, int prio)
7188 void set_user_nice(struct task_struct *p, long nice)
7190 bool queued, running;
7195 if (task_nice(p) == nice || nice < MIN_NICE || nice > MAX_NICE)
7198 * We have to be careful, if called from sys_setpriority(),
7199 * the task might be in the middle of scheduling on another CPU.
7201 rq = task_rq_lock(p, &rf);
7202 update_rq_clock(rq);
7205 * The RT priorities are set via sched_setscheduler(), but we still
7206 * allow the 'normal' nice value to be set - but as expected
7207 * it won't have any effect on scheduling until the task is
7208 * SCHED_DEADLINE, SCHED_FIFO or SCHED_RR:
7210 if (task_has_dl_policy(p) || task_has_rt_policy(p)) {
7211 p->static_prio = NICE_TO_PRIO(nice);
7214 queued = task_on_rq_queued(p);
7215 running = task_current(rq, p);
7217 dequeue_task(rq, p, DEQUEUE_SAVE | DEQUEUE_NOCLOCK);
7219 put_prev_task(rq, p);
7221 p->static_prio = NICE_TO_PRIO(nice);
7222 set_load_weight(p, true);
7224 p->prio = effective_prio(p);
7227 enqueue_task(rq, p, ENQUEUE_RESTORE | ENQUEUE_NOCLOCK);
7229 set_next_task(rq, p);
7232 * If the task increased its priority or is running and
7233 * lowered its priority, then reschedule its CPU:
7235 p->sched_class->prio_changed(rq, p, old_prio);
7238 task_rq_unlock(rq, p, &rf);
7240 EXPORT_SYMBOL(set_user_nice);
7243 * is_nice_reduction - check if nice value is an actual reduction
7245 * Similar to can_nice() but does not perform a capability check.
7250 static bool is_nice_reduction(const struct task_struct *p, const int nice)
7252 /* Convert nice value [19,-20] to rlimit style value [1,40]: */
7253 int nice_rlim = nice_to_rlimit(nice);
7255 return (nice_rlim <= task_rlimit(p, RLIMIT_NICE));
7259 * can_nice - check if a task can reduce its nice value
7263 int can_nice(const struct task_struct *p, const int nice)
7265 return is_nice_reduction(p, nice) || capable(CAP_SYS_NICE);
7268 #ifdef __ARCH_WANT_SYS_NICE
7271 * sys_nice - change the priority of the current process.
7272 * @increment: priority increment
7274 * sys_setpriority is a more generic, but much slower function that
7275 * does similar things.
7277 SYSCALL_DEFINE1(nice, int, increment)
7282 * Setpriority might change our priority at the same moment.
7283 * We don't have to worry. Conceptually one call occurs first
7284 * and we have a single winner.
7286 increment = clamp(increment, -NICE_WIDTH, NICE_WIDTH);
7287 nice = task_nice(current) + increment;
7289 nice = clamp_val(nice, MIN_NICE, MAX_NICE);
7290 if (increment < 0 && !can_nice(current, nice))
7293 retval = security_task_setnice(current, nice);
7297 set_user_nice(current, nice);
7304 * task_prio - return the priority value of a given task.
7305 * @p: the task in question.
7307 * Return: The priority value as seen by users in /proc.
7309 * sched policy return value kernel prio user prio/nice
7311 * normal, batch, idle [0 ... 39] [100 ... 139] 0/[-20 ... 19]
7312 * fifo, rr [-2 ... -100] [98 ... 0] [1 ... 99]
7313 * deadline -101 -1 0
7315 int task_prio(const struct task_struct *p)
7317 return p->prio - MAX_RT_PRIO;
7321 * idle_cpu - is a given CPU idle currently?
7322 * @cpu: the processor in question.
7324 * Return: 1 if the CPU is currently idle. 0 otherwise.
7326 int idle_cpu(int cpu)
7328 struct rq *rq = cpu_rq(cpu);
7330 if (rq->curr != rq->idle)
7337 if (rq->ttwu_pending)
7345 * available_idle_cpu - is a given CPU idle for enqueuing work.
7346 * @cpu: the CPU in question.
7348 * Return: 1 if the CPU is currently idle. 0 otherwise.
7350 int available_idle_cpu(int cpu)
7355 if (vcpu_is_preempted(cpu))
7362 * idle_task - return the idle task for a given CPU.
7363 * @cpu: the processor in question.
7365 * Return: The idle task for the CPU @cpu.
7367 struct task_struct *idle_task(int cpu)
7369 return cpu_rq(cpu)->idle;
7372 #ifdef CONFIG_SCHED_CORE
7373 int sched_core_idle_cpu(int cpu)
7375 struct rq *rq = cpu_rq(cpu);
7377 if (sched_core_enabled(rq) && rq->curr == rq->idle)
7380 return idle_cpu(cpu);
7387 * This function computes an effective utilization for the given CPU, to be
7388 * used for frequency selection given the linear relation: f = u * f_max.
7390 * The scheduler tracks the following metrics:
7392 * cpu_util_{cfs,rt,dl,irq}()
7395 * Where the cfs,rt and dl util numbers are tracked with the same metric and
7396 * synchronized windows and are thus directly comparable.
7398 * The cfs,rt,dl utilization are the running times measured with rq->clock_task
7399 * which excludes things like IRQ and steal-time. These latter are then accrued
7400 * in the irq utilization.
7402 * The DL bandwidth number otoh is not a measured metric but a value computed
7403 * based on the task model parameters and gives the minimal utilization
7404 * required to meet deadlines.
7406 unsigned long effective_cpu_util(int cpu, unsigned long util_cfs,
7407 enum cpu_util_type type,
7408 struct task_struct *p)
7410 unsigned long dl_util, util, irq, max;
7411 struct rq *rq = cpu_rq(cpu);
7413 max = arch_scale_cpu_capacity(cpu);
7415 if (!uclamp_is_used() &&
7416 type == FREQUENCY_UTIL && rt_rq_is_runnable(&rq->rt)) {
7421 * Early check to see if IRQ/steal time saturates the CPU, can be
7422 * because of inaccuracies in how we track these -- see
7423 * update_irq_load_avg().
7425 irq = cpu_util_irq(rq);
7426 if (unlikely(irq >= max))
7430 * Because the time spend on RT/DL tasks is visible as 'lost' time to
7431 * CFS tasks and we use the same metric to track the effective
7432 * utilization (PELT windows are synchronized) we can directly add them
7433 * to obtain the CPU's actual utilization.
7435 * CFS and RT utilization can be boosted or capped, depending on
7436 * utilization clamp constraints requested by currently RUNNABLE
7438 * When there are no CFS RUNNABLE tasks, clamps are released and
7439 * frequency will be gracefully reduced with the utilization decay.
7441 util = util_cfs + cpu_util_rt(rq);
7442 if (type == FREQUENCY_UTIL)
7443 util = uclamp_rq_util_with(rq, util, p);
7445 dl_util = cpu_util_dl(rq);
7448 * For frequency selection we do not make cpu_util_dl() a permanent part
7449 * of this sum because we want to use cpu_bw_dl() later on, but we need
7450 * to check if the CFS+RT+DL sum is saturated (ie. no idle time) such
7451 * that we select f_max when there is no idle time.
7453 * NOTE: numerical errors or stop class might cause us to not quite hit
7454 * saturation when we should -- something for later.
7456 if (util + dl_util >= max)
7460 * OTOH, for energy computation we need the estimated running time, so
7461 * include util_dl and ignore dl_bw.
7463 if (type == ENERGY_UTIL)
7467 * There is still idle time; further improve the number by using the
7468 * irq metric. Because IRQ/steal time is hidden from the task clock we
7469 * need to scale the task numbers:
7472 * U' = irq + --------- * U
7475 util = scale_irq_capacity(util, irq, max);
7479 * Bandwidth required by DEADLINE must always be granted while, for
7480 * FAIR and RT, we use blocked utilization of IDLE CPUs as a mechanism
7481 * to gracefully reduce the frequency when no tasks show up for longer
7484 * Ideally we would like to set bw_dl as min/guaranteed freq and util +
7485 * bw_dl as requested freq. However, cpufreq is not yet ready for such
7486 * an interface. So, we only do the latter for now.
7488 if (type == FREQUENCY_UTIL)
7489 util += cpu_bw_dl(rq);
7491 return min(max, util);
7494 unsigned long sched_cpu_util(int cpu)
7496 return effective_cpu_util(cpu, cpu_util_cfs(cpu), ENERGY_UTIL, NULL);
7498 #endif /* CONFIG_SMP */
7501 * find_process_by_pid - find a process with a matching PID value.
7502 * @pid: the pid in question.
7504 * The task of @pid, if found. %NULL otherwise.
7506 static struct task_struct *find_process_by_pid(pid_t pid)
7508 return pid ? find_task_by_vpid(pid) : current;
7512 * sched_setparam() passes in -1 for its policy, to let the functions
7513 * it calls know not to change it.
7515 #define SETPARAM_POLICY -1
7517 static void __setscheduler_params(struct task_struct *p,
7518 const struct sched_attr *attr)
7520 int policy = attr->sched_policy;
7522 if (policy == SETPARAM_POLICY)
7527 if (dl_policy(policy))
7528 __setparam_dl(p, attr);
7529 else if (fair_policy(policy))
7530 p->static_prio = NICE_TO_PRIO(attr->sched_nice);
7533 * __sched_setscheduler() ensures attr->sched_priority == 0 when
7534 * !rt_policy. Always setting this ensures that things like
7535 * getparam()/getattr() don't report silly values for !rt tasks.
7537 p->rt_priority = attr->sched_priority;
7538 p->normal_prio = normal_prio(p);
7539 set_load_weight(p, true);
7543 * Check the target process has a UID that matches the current process's:
7545 static bool check_same_owner(struct task_struct *p)
7547 const struct cred *cred = current_cred(), *pcred;
7551 pcred = __task_cred(p);
7552 match = (uid_eq(cred->euid, pcred->euid) ||
7553 uid_eq(cred->euid, pcred->uid));
7559 * Allow unprivileged RT tasks to decrease priority.
7560 * Only issue a capable test if needed and only once to avoid an audit
7561 * event on permitted non-privileged operations:
7563 static int user_check_sched_setscheduler(struct task_struct *p,
7564 const struct sched_attr *attr,
7565 int policy, int reset_on_fork)
7567 if (fair_policy(policy)) {
7568 if (attr->sched_nice < task_nice(p) &&
7569 !is_nice_reduction(p, attr->sched_nice))
7573 if (rt_policy(policy)) {
7574 unsigned long rlim_rtprio = task_rlimit(p, RLIMIT_RTPRIO);
7576 /* Can't set/change the rt policy: */
7577 if (policy != p->policy && !rlim_rtprio)
7580 /* Can't increase priority: */
7581 if (attr->sched_priority > p->rt_priority &&
7582 attr->sched_priority > rlim_rtprio)
7587 * Can't set/change SCHED_DEADLINE policy at all for now
7588 * (safest behavior); in the future we would like to allow
7589 * unprivileged DL tasks to increase their relative deadline
7590 * or reduce their runtime (both ways reducing utilization)
7592 if (dl_policy(policy))
7596 * Treat SCHED_IDLE as nice 20. Only allow a switch to
7597 * SCHED_NORMAL if the RLIMIT_NICE would normally permit it.
7599 if (task_has_idle_policy(p) && !idle_policy(policy)) {
7600 if (!is_nice_reduction(p, task_nice(p)))
7604 /* Can't change other user's priorities: */
7605 if (!check_same_owner(p))
7608 /* Normal users shall not reset the sched_reset_on_fork flag: */
7609 if (p->sched_reset_on_fork && !reset_on_fork)
7615 if (!capable(CAP_SYS_NICE))
7621 static int __sched_setscheduler(struct task_struct *p,
7622 const struct sched_attr *attr,
7625 int oldpolicy = -1, policy = attr->sched_policy;
7626 int retval, oldprio, newprio, queued, running;
7627 const struct sched_class *prev_class;
7628 struct balance_callback *head;
7631 int queue_flags = DEQUEUE_SAVE | DEQUEUE_MOVE | DEQUEUE_NOCLOCK;
7633 bool cpuset_locked = false;
7635 /* The pi code expects interrupts enabled */
7636 BUG_ON(pi && in_interrupt());
7638 /* Double check policy once rq lock held: */
7640 reset_on_fork = p->sched_reset_on_fork;
7641 policy = oldpolicy = p->policy;
7643 reset_on_fork = !!(attr->sched_flags & SCHED_FLAG_RESET_ON_FORK);
7645 if (!valid_policy(policy))
7649 if (attr->sched_flags & ~(SCHED_FLAG_ALL | SCHED_FLAG_SUGOV))
7653 * Valid priorities for SCHED_FIFO and SCHED_RR are
7654 * 1..MAX_RT_PRIO-1, valid priority for SCHED_NORMAL,
7655 * SCHED_BATCH and SCHED_IDLE is 0.
7657 if (attr->sched_priority > MAX_RT_PRIO-1)
7659 if ((dl_policy(policy) && !__checkparam_dl(attr)) ||
7660 (rt_policy(policy) != (attr->sched_priority != 0)))
7664 retval = user_check_sched_setscheduler(p, attr, policy, reset_on_fork);
7668 if (attr->sched_flags & SCHED_FLAG_SUGOV)
7671 retval = security_task_setscheduler(p);
7676 /* Update task specific "requested" clamps */
7677 if (attr->sched_flags & SCHED_FLAG_UTIL_CLAMP) {
7678 retval = uclamp_validate(p, attr);
7684 * SCHED_DEADLINE bandwidth accounting relies on stable cpusets
7687 if (dl_policy(policy) || dl_policy(p->policy)) {
7688 cpuset_locked = true;
7693 * Make sure no PI-waiters arrive (or leave) while we are
7694 * changing the priority of the task:
7696 * To be able to change p->policy safely, the appropriate
7697 * runqueue lock must be held.
7699 rq = task_rq_lock(p, &rf);
7700 update_rq_clock(rq);
7703 * Changing the policy of the stop threads its a very bad idea:
7705 if (p == rq->stop) {
7711 * If not changing anything there's no need to proceed further,
7712 * but store a possible modification of reset_on_fork.
7714 if (unlikely(policy == p->policy)) {
7715 if (fair_policy(policy) && attr->sched_nice != task_nice(p))
7717 if (rt_policy(policy) && attr->sched_priority != p->rt_priority)
7719 if (dl_policy(policy) && dl_param_changed(p, attr))
7721 if (attr->sched_flags & SCHED_FLAG_UTIL_CLAMP)
7724 p->sched_reset_on_fork = reset_on_fork;
7731 #ifdef CONFIG_RT_GROUP_SCHED
7733 * Do not allow realtime tasks into groups that have no runtime
7736 if (rt_bandwidth_enabled() && rt_policy(policy) &&
7737 task_group(p)->rt_bandwidth.rt_runtime == 0 &&
7738 !task_group_is_autogroup(task_group(p))) {
7744 if (dl_bandwidth_enabled() && dl_policy(policy) &&
7745 !(attr->sched_flags & SCHED_FLAG_SUGOV)) {
7746 cpumask_t *span = rq->rd->span;
7749 * Don't allow tasks with an affinity mask smaller than
7750 * the entire root_domain to become SCHED_DEADLINE. We
7751 * will also fail if there's no bandwidth available.
7753 if (!cpumask_subset(span, p->cpus_ptr) ||
7754 rq->rd->dl_bw.bw == 0) {
7762 /* Re-check policy now with rq lock held: */
7763 if (unlikely(oldpolicy != -1 && oldpolicy != p->policy)) {
7764 policy = oldpolicy = -1;
7765 task_rq_unlock(rq, p, &rf);
7772 * If setscheduling to SCHED_DEADLINE (or changing the parameters
7773 * of a SCHED_DEADLINE task) we need to check if enough bandwidth
7776 if ((dl_policy(policy) || dl_task(p)) && sched_dl_overflow(p, policy, attr)) {
7781 p->sched_reset_on_fork = reset_on_fork;
7784 newprio = __normal_prio(policy, attr->sched_priority, attr->sched_nice);
7787 * Take priority boosted tasks into account. If the new
7788 * effective priority is unchanged, we just store the new
7789 * normal parameters and do not touch the scheduler class and
7790 * the runqueue. This will be done when the task deboost
7793 newprio = rt_effective_prio(p, newprio);
7794 if (newprio == oldprio)
7795 queue_flags &= ~DEQUEUE_MOVE;
7798 queued = task_on_rq_queued(p);
7799 running = task_current(rq, p);
7801 dequeue_task(rq, p, queue_flags);
7803 put_prev_task(rq, p);
7805 prev_class = p->sched_class;
7807 if (!(attr->sched_flags & SCHED_FLAG_KEEP_PARAMS)) {
7808 __setscheduler_params(p, attr);
7809 __setscheduler_prio(p, newprio);
7811 __setscheduler_uclamp(p, attr);
7815 * We enqueue to tail when the priority of a task is
7816 * increased (user space view).
7818 if (oldprio < p->prio)
7819 queue_flags |= ENQUEUE_HEAD;
7821 enqueue_task(rq, p, queue_flags);
7824 set_next_task(rq, p);
7826 check_class_changed(rq, p, prev_class, oldprio);
7828 /* Avoid rq from going away on us: */
7830 head = splice_balance_callbacks(rq);
7831 task_rq_unlock(rq, p, &rf);
7836 rt_mutex_adjust_pi(p);
7839 /* Run balance callbacks after we've adjusted the PI chain: */
7840 balance_callbacks(rq, head);
7846 task_rq_unlock(rq, p, &rf);
7852 static int _sched_setscheduler(struct task_struct *p, int policy,
7853 const struct sched_param *param, bool check)
7855 struct sched_attr attr = {
7856 .sched_policy = policy,
7857 .sched_priority = param->sched_priority,
7858 .sched_nice = PRIO_TO_NICE(p->static_prio),
7861 /* Fixup the legacy SCHED_RESET_ON_FORK hack. */
7862 if ((policy != SETPARAM_POLICY) && (policy & SCHED_RESET_ON_FORK)) {
7863 attr.sched_flags |= SCHED_FLAG_RESET_ON_FORK;
7864 policy &= ~SCHED_RESET_ON_FORK;
7865 attr.sched_policy = policy;
7868 return __sched_setscheduler(p, &attr, check, true);
7871 * sched_setscheduler - change the scheduling policy and/or RT priority of a thread.
7872 * @p: the task in question.
7873 * @policy: new policy.
7874 * @param: structure containing the new RT priority.
7876 * Use sched_set_fifo(), read its comment.
7878 * Return: 0 on success. An error code otherwise.
7880 * NOTE that the task may be already dead.
7882 int sched_setscheduler(struct task_struct *p, int policy,
7883 const struct sched_param *param)
7885 return _sched_setscheduler(p, policy, param, true);
7888 int sched_setattr(struct task_struct *p, const struct sched_attr *attr)
7890 return __sched_setscheduler(p, attr, true, true);
7893 int sched_setattr_nocheck(struct task_struct *p, const struct sched_attr *attr)
7895 return __sched_setscheduler(p, attr, false, true);
7897 EXPORT_SYMBOL_GPL(sched_setattr_nocheck);
7900 * sched_setscheduler_nocheck - change the scheduling policy and/or RT priority of a thread from kernelspace.
7901 * @p: the task in question.
7902 * @policy: new policy.
7903 * @param: structure containing the new RT priority.
7905 * Just like sched_setscheduler, only don't bother checking if the
7906 * current context has permission. For example, this is needed in
7907 * stop_machine(): we create temporary high priority worker threads,
7908 * but our caller might not have that capability.
7910 * Return: 0 on success. An error code otherwise.
7912 int sched_setscheduler_nocheck(struct task_struct *p, int policy,
7913 const struct sched_param *param)
7915 return _sched_setscheduler(p, policy, param, false);
7919 * SCHED_FIFO is a broken scheduler model; that is, it is fundamentally
7920 * incapable of resource management, which is the one thing an OS really should
7923 * This is of course the reason it is limited to privileged users only.
7925 * Worse still; it is fundamentally impossible to compose static priority
7926 * workloads. You cannot take two correctly working static prio workloads
7927 * and smash them together and still expect them to work.
7929 * For this reason 'all' FIFO tasks the kernel creates are basically at:
7933 * The administrator _MUST_ configure the system, the kernel simply doesn't
7934 * know enough information to make a sensible choice.
7936 void sched_set_fifo(struct task_struct *p)
7938 struct sched_param sp = { .sched_priority = MAX_RT_PRIO / 2 };
7939 WARN_ON_ONCE(sched_setscheduler_nocheck(p, SCHED_FIFO, &sp) != 0);
7941 EXPORT_SYMBOL_GPL(sched_set_fifo);
7944 * For when you don't much care about FIFO, but want to be above SCHED_NORMAL.
7946 void sched_set_fifo_low(struct task_struct *p)
7948 struct sched_param sp = { .sched_priority = 1 };
7949 WARN_ON_ONCE(sched_setscheduler_nocheck(p, SCHED_FIFO, &sp) != 0);
7951 EXPORT_SYMBOL_GPL(sched_set_fifo_low);
7953 void sched_set_normal(struct task_struct *p, int nice)
7955 struct sched_attr attr = {
7956 .sched_policy = SCHED_NORMAL,
7959 WARN_ON_ONCE(sched_setattr_nocheck(p, &attr) != 0);
7961 EXPORT_SYMBOL_GPL(sched_set_normal);
7964 do_sched_setscheduler(pid_t pid, int policy, struct sched_param __user *param)
7966 struct sched_param lparam;
7967 struct task_struct *p;
7970 if (!param || pid < 0)
7972 if (copy_from_user(&lparam, param, sizeof(struct sched_param)))
7977 p = find_process_by_pid(pid);
7983 retval = sched_setscheduler(p, policy, &lparam);
7991 * Mimics kernel/events/core.c perf_copy_attr().
7993 static int sched_copy_attr(struct sched_attr __user *uattr, struct sched_attr *attr)
7998 /* Zero the full structure, so that a short copy will be nice: */
7999 memset(attr, 0, sizeof(*attr));
8001 ret = get_user(size, &uattr->size);
8005 /* ABI compatibility quirk: */
8007 size = SCHED_ATTR_SIZE_VER0;
8008 if (size < SCHED_ATTR_SIZE_VER0 || size > PAGE_SIZE)
8011 ret = copy_struct_from_user(attr, sizeof(*attr), uattr, size);
8018 if ((attr->sched_flags & SCHED_FLAG_UTIL_CLAMP) &&
8019 size < SCHED_ATTR_SIZE_VER1)
8023 * XXX: Do we want to be lenient like existing syscalls; or do we want
8024 * to be strict and return an error on out-of-bounds values?
8026 attr->sched_nice = clamp(attr->sched_nice, MIN_NICE, MAX_NICE);
8031 put_user(sizeof(*attr), &uattr->size);
8035 static void get_params(struct task_struct *p, struct sched_attr *attr)
8037 if (task_has_dl_policy(p))
8038 __getparam_dl(p, attr);
8039 else if (task_has_rt_policy(p))
8040 attr->sched_priority = p->rt_priority;
8042 attr->sched_nice = task_nice(p);
8046 * sys_sched_setscheduler - set/change the scheduler policy and RT priority
8047 * @pid: the pid in question.
8048 * @policy: new policy.
8049 * @param: structure containing the new RT priority.
8051 * Return: 0 on success. An error code otherwise.
8053 SYSCALL_DEFINE3(sched_setscheduler, pid_t, pid, int, policy, struct sched_param __user *, param)
8058 return do_sched_setscheduler(pid, policy, param);
8062 * sys_sched_setparam - set/change the RT priority of a thread
8063 * @pid: the pid in question.
8064 * @param: structure containing the new RT priority.
8066 * Return: 0 on success. An error code otherwise.
8068 SYSCALL_DEFINE2(sched_setparam, pid_t, pid, struct sched_param __user *, param)
8070 return do_sched_setscheduler(pid, SETPARAM_POLICY, param);
8074 * sys_sched_setattr - same as above, but with extended sched_attr
8075 * @pid: the pid in question.
8076 * @uattr: structure containing the extended parameters.
8077 * @flags: for future extension.
8079 SYSCALL_DEFINE3(sched_setattr, pid_t, pid, struct sched_attr __user *, uattr,
8080 unsigned int, flags)
8082 struct sched_attr attr;
8083 struct task_struct *p;
8086 if (!uattr || pid < 0 || flags)
8089 retval = sched_copy_attr(uattr, &attr);
8093 if ((int)attr.sched_policy < 0)
8095 if (attr.sched_flags & SCHED_FLAG_KEEP_POLICY)
8096 attr.sched_policy = SETPARAM_POLICY;
8100 p = find_process_by_pid(pid);
8106 if (attr.sched_flags & SCHED_FLAG_KEEP_PARAMS)
8107 get_params(p, &attr);
8108 retval = sched_setattr(p, &attr);
8116 * sys_sched_getscheduler - get the policy (scheduling class) of a thread
8117 * @pid: the pid in question.
8119 * Return: On success, the policy of the thread. Otherwise, a negative error
8122 SYSCALL_DEFINE1(sched_getscheduler, pid_t, pid)
8124 struct task_struct *p;
8132 p = find_process_by_pid(pid);
8134 retval = security_task_getscheduler(p);
8137 | (p->sched_reset_on_fork ? SCHED_RESET_ON_FORK : 0);
8144 * sys_sched_getparam - get the RT priority of a thread
8145 * @pid: the pid in question.
8146 * @param: structure containing the RT priority.
8148 * Return: On success, 0 and the RT priority is in @param. Otherwise, an error
8151 SYSCALL_DEFINE2(sched_getparam, pid_t, pid, struct sched_param __user *, param)
8153 struct sched_param lp = { .sched_priority = 0 };
8154 struct task_struct *p;
8157 if (!param || pid < 0)
8161 p = find_process_by_pid(pid);
8166 retval = security_task_getscheduler(p);
8170 if (task_has_rt_policy(p))
8171 lp.sched_priority = p->rt_priority;
8175 * This one might sleep, we cannot do it with a spinlock held ...
8177 retval = copy_to_user(param, &lp, sizeof(*param)) ? -EFAULT : 0;
8187 * Copy the kernel size attribute structure (which might be larger
8188 * than what user-space knows about) to user-space.
8190 * Note that all cases are valid: user-space buffer can be larger or
8191 * smaller than the kernel-space buffer. The usual case is that both
8192 * have the same size.
8195 sched_attr_copy_to_user(struct sched_attr __user *uattr,
8196 struct sched_attr *kattr,
8199 unsigned int ksize = sizeof(*kattr);
8201 if (!access_ok(uattr, usize))
8205 * sched_getattr() ABI forwards and backwards compatibility:
8207 * If usize == ksize then we just copy everything to user-space and all is good.
8209 * If usize < ksize then we only copy as much as user-space has space for,
8210 * this keeps ABI compatibility as well. We skip the rest.
8212 * If usize > ksize then user-space is using a newer version of the ABI,
8213 * which part the kernel doesn't know about. Just ignore it - tooling can
8214 * detect the kernel's knowledge of attributes from the attr->size value
8215 * which is set to ksize in this case.
8217 kattr->size = min(usize, ksize);
8219 if (copy_to_user(uattr, kattr, kattr->size))
8226 * sys_sched_getattr - similar to sched_getparam, but with sched_attr
8227 * @pid: the pid in question.
8228 * @uattr: structure containing the extended parameters.
8229 * @usize: sizeof(attr) for fwd/bwd comp.
8230 * @flags: for future extension.
8232 SYSCALL_DEFINE4(sched_getattr, pid_t, pid, struct sched_attr __user *, uattr,
8233 unsigned int, usize, unsigned int, flags)
8235 struct sched_attr kattr = { };
8236 struct task_struct *p;
8239 if (!uattr || pid < 0 || usize > PAGE_SIZE ||
8240 usize < SCHED_ATTR_SIZE_VER0 || flags)
8244 p = find_process_by_pid(pid);
8249 retval = security_task_getscheduler(p);
8253 kattr.sched_policy = p->policy;
8254 if (p->sched_reset_on_fork)
8255 kattr.sched_flags |= SCHED_FLAG_RESET_ON_FORK;
8256 get_params(p, &kattr);
8257 kattr.sched_flags &= SCHED_FLAG_ALL;
8259 #ifdef CONFIG_UCLAMP_TASK
8261 * This could race with another potential updater, but this is fine
8262 * because it'll correctly read the old or the new value. We don't need
8263 * to guarantee who wins the race as long as it doesn't return garbage.
8265 kattr.sched_util_min = p->uclamp_req[UCLAMP_MIN].value;
8266 kattr.sched_util_max = p->uclamp_req[UCLAMP_MAX].value;
8271 return sched_attr_copy_to_user(uattr, &kattr, usize);
8279 int dl_task_check_affinity(struct task_struct *p, const struct cpumask *mask)
8284 * If the task isn't a deadline task or admission control is
8285 * disabled then we don't care about affinity changes.
8287 if (!task_has_dl_policy(p) || !dl_bandwidth_enabled())
8291 * Since bandwidth control happens on root_domain basis,
8292 * if admission test is enabled, we only admit -deadline
8293 * tasks allowed to run on all the CPUs in the task's
8297 if (!cpumask_subset(task_rq(p)->rd->span, mask))
8305 __sched_setaffinity(struct task_struct *p, struct affinity_context *ctx)
8308 cpumask_var_t cpus_allowed, new_mask;
8310 if (!alloc_cpumask_var(&cpus_allowed, GFP_KERNEL))
8313 if (!alloc_cpumask_var(&new_mask, GFP_KERNEL)) {
8315 goto out_free_cpus_allowed;
8318 cpuset_cpus_allowed(p, cpus_allowed);
8319 cpumask_and(new_mask, ctx->new_mask, cpus_allowed);
8321 ctx->new_mask = new_mask;
8322 ctx->flags |= SCA_CHECK;
8324 retval = dl_task_check_affinity(p, new_mask);
8326 goto out_free_new_mask;
8328 retval = __set_cpus_allowed_ptr(p, ctx);
8330 goto out_free_new_mask;
8332 cpuset_cpus_allowed(p, cpus_allowed);
8333 if (!cpumask_subset(new_mask, cpus_allowed)) {
8335 * We must have raced with a concurrent cpuset update.
8336 * Just reset the cpumask to the cpuset's cpus_allowed.
8338 cpumask_copy(new_mask, cpus_allowed);
8341 * If SCA_USER is set, a 2nd call to __set_cpus_allowed_ptr()
8342 * will restore the previous user_cpus_ptr value.
8344 * In the unlikely event a previous user_cpus_ptr exists,
8345 * we need to further restrict the mask to what is allowed
8346 * by that old user_cpus_ptr.
8348 if (unlikely((ctx->flags & SCA_USER) && ctx->user_mask)) {
8349 bool empty = !cpumask_and(new_mask, new_mask,
8352 if (WARN_ON_ONCE(empty))
8353 cpumask_copy(new_mask, cpus_allowed);
8355 __set_cpus_allowed_ptr(p, ctx);
8360 free_cpumask_var(new_mask);
8361 out_free_cpus_allowed:
8362 free_cpumask_var(cpus_allowed);
8366 long sched_setaffinity(pid_t pid, const struct cpumask *in_mask)
8368 struct affinity_context ac;
8369 struct cpumask *user_mask;
8370 struct task_struct *p;
8375 p = find_process_by_pid(pid);
8381 /* Prevent p going away */
8385 if (p->flags & PF_NO_SETAFFINITY) {
8390 if (!check_same_owner(p)) {
8392 if (!ns_capable(__task_cred(p)->user_ns, CAP_SYS_NICE)) {
8400 retval = security_task_setscheduler(p);
8405 * With non-SMP configs, user_cpus_ptr/user_mask isn't used and
8406 * alloc_user_cpus_ptr() returns NULL.
8408 user_mask = alloc_user_cpus_ptr(NUMA_NO_NODE);
8410 cpumask_copy(user_mask, in_mask);
8411 } else if (IS_ENABLED(CONFIG_SMP)) {
8416 ac = (struct affinity_context){
8417 .new_mask = in_mask,
8418 .user_mask = user_mask,
8422 retval = __sched_setaffinity(p, &ac);
8423 kfree(ac.user_mask);
8430 static int get_user_cpu_mask(unsigned long __user *user_mask_ptr, unsigned len,
8431 struct cpumask *new_mask)
8433 if (len < cpumask_size())
8434 cpumask_clear(new_mask);
8435 else if (len > cpumask_size())
8436 len = cpumask_size();
8438 return copy_from_user(new_mask, user_mask_ptr, len) ? -EFAULT : 0;
8442 * sys_sched_setaffinity - set the CPU affinity of a process
8443 * @pid: pid of the process
8444 * @len: length in bytes of the bitmask pointed to by user_mask_ptr
8445 * @user_mask_ptr: user-space pointer to the new CPU mask
8447 * Return: 0 on success. An error code otherwise.
8449 SYSCALL_DEFINE3(sched_setaffinity, pid_t, pid, unsigned int, len,
8450 unsigned long __user *, user_mask_ptr)
8452 cpumask_var_t new_mask;
8455 if (!alloc_cpumask_var(&new_mask, GFP_KERNEL))
8458 retval = get_user_cpu_mask(user_mask_ptr, len, new_mask);
8460 retval = sched_setaffinity(pid, new_mask);
8461 free_cpumask_var(new_mask);
8465 long sched_getaffinity(pid_t pid, struct cpumask *mask)
8467 struct task_struct *p;
8468 unsigned long flags;
8474 p = find_process_by_pid(pid);
8478 retval = security_task_getscheduler(p);
8482 raw_spin_lock_irqsave(&p->pi_lock, flags);
8483 cpumask_and(mask, &p->cpus_mask, cpu_active_mask);
8484 raw_spin_unlock_irqrestore(&p->pi_lock, flags);
8493 * sys_sched_getaffinity - get the CPU affinity of a process
8494 * @pid: pid of the process
8495 * @len: length in bytes of the bitmask pointed to by user_mask_ptr
8496 * @user_mask_ptr: user-space pointer to hold the current CPU mask
8498 * Return: size of CPU mask copied to user_mask_ptr on success. An
8499 * error code otherwise.
8501 SYSCALL_DEFINE3(sched_getaffinity, pid_t, pid, unsigned int, len,
8502 unsigned long __user *, user_mask_ptr)
8507 if ((len * BITS_PER_BYTE) < nr_cpu_ids)
8509 if (len & (sizeof(unsigned long)-1))
8512 if (!zalloc_cpumask_var(&mask, GFP_KERNEL))
8515 ret = sched_getaffinity(pid, mask);
8517 unsigned int retlen = min(len, cpumask_size());
8519 if (copy_to_user(user_mask_ptr, cpumask_bits(mask), retlen))
8524 free_cpumask_var(mask);
8529 static void do_sched_yield(void)
8534 rq = this_rq_lock_irq(&rf);
8536 schedstat_inc(rq->yld_count);
8537 current->sched_class->yield_task(rq);
8540 rq_unlock_irq(rq, &rf);
8541 sched_preempt_enable_no_resched();
8547 * sys_sched_yield - yield the current processor to other threads.
8549 * This function yields the current CPU to other tasks. If there are no
8550 * other threads running on this CPU then this function will return.
8554 SYSCALL_DEFINE0(sched_yield)
8560 #if !defined(CONFIG_PREEMPTION) || defined(CONFIG_PREEMPT_DYNAMIC)
8561 int __sched __cond_resched(void)
8563 if (should_resched(0)) {
8564 preempt_schedule_common();
8568 * In preemptible kernels, ->rcu_read_lock_nesting tells the tick
8569 * whether the current CPU is in an RCU read-side critical section,
8570 * so the tick can report quiescent states even for CPUs looping
8571 * in kernel context. In contrast, in non-preemptible kernels,
8572 * RCU readers leave no in-memory hints, which means that CPU-bound
8573 * processes executing in kernel context might never report an
8574 * RCU quiescent state. Therefore, the following code causes
8575 * cond_resched() to report a quiescent state, but only when RCU
8576 * is in urgent need of one.
8578 #ifndef CONFIG_PREEMPT_RCU
8583 EXPORT_SYMBOL(__cond_resched);
8586 #ifdef CONFIG_PREEMPT_DYNAMIC
8587 #if defined(CONFIG_HAVE_PREEMPT_DYNAMIC_CALL)
8588 #define cond_resched_dynamic_enabled __cond_resched
8589 #define cond_resched_dynamic_disabled ((void *)&__static_call_return0)
8590 DEFINE_STATIC_CALL_RET0(cond_resched, __cond_resched);
8591 EXPORT_STATIC_CALL_TRAMP(cond_resched);
8593 #define might_resched_dynamic_enabled __cond_resched
8594 #define might_resched_dynamic_disabled ((void *)&__static_call_return0)
8595 DEFINE_STATIC_CALL_RET0(might_resched, __cond_resched);
8596 EXPORT_STATIC_CALL_TRAMP(might_resched);
8597 #elif defined(CONFIG_HAVE_PREEMPT_DYNAMIC_KEY)
8598 static DEFINE_STATIC_KEY_FALSE(sk_dynamic_cond_resched);
8599 int __sched dynamic_cond_resched(void)
8601 klp_sched_try_switch();
8602 if (!static_branch_unlikely(&sk_dynamic_cond_resched))
8604 return __cond_resched();
8606 EXPORT_SYMBOL(dynamic_cond_resched);
8608 static DEFINE_STATIC_KEY_FALSE(sk_dynamic_might_resched);
8609 int __sched dynamic_might_resched(void)
8611 if (!static_branch_unlikely(&sk_dynamic_might_resched))
8613 return __cond_resched();
8615 EXPORT_SYMBOL(dynamic_might_resched);
8620 * __cond_resched_lock() - if a reschedule is pending, drop the given lock,
8621 * call schedule, and on return reacquire the lock.
8623 * This works OK both with and without CONFIG_PREEMPTION. We do strange low-level
8624 * operations here to prevent schedule() from being called twice (once via
8625 * spin_unlock(), once by hand).
8627 int __cond_resched_lock(spinlock_t *lock)
8629 int resched = should_resched(PREEMPT_LOCK_OFFSET);
8632 lockdep_assert_held(lock);
8634 if (spin_needbreak(lock) || resched) {
8636 if (!_cond_resched())
8643 EXPORT_SYMBOL(__cond_resched_lock);
8645 int __cond_resched_rwlock_read(rwlock_t *lock)
8647 int resched = should_resched(PREEMPT_LOCK_OFFSET);
8650 lockdep_assert_held_read(lock);
8652 if (rwlock_needbreak(lock) || resched) {
8654 if (!_cond_resched())
8661 EXPORT_SYMBOL(__cond_resched_rwlock_read);
8663 int __cond_resched_rwlock_write(rwlock_t *lock)
8665 int resched = should_resched(PREEMPT_LOCK_OFFSET);
8668 lockdep_assert_held_write(lock);
8670 if (rwlock_needbreak(lock) || resched) {
8672 if (!_cond_resched())
8679 EXPORT_SYMBOL(__cond_resched_rwlock_write);
8681 #ifdef CONFIG_PREEMPT_DYNAMIC
8683 #ifdef CONFIG_GENERIC_ENTRY
8684 #include <linux/entry-common.h>
8690 * SC:preempt_schedule
8691 * SC:preempt_schedule_notrace
8692 * SC:irqentry_exit_cond_resched
8696 * cond_resched <- __cond_resched
8697 * might_resched <- RET0
8698 * preempt_schedule <- NOP
8699 * preempt_schedule_notrace <- NOP
8700 * irqentry_exit_cond_resched <- NOP
8703 * cond_resched <- __cond_resched
8704 * might_resched <- __cond_resched
8705 * preempt_schedule <- NOP
8706 * preempt_schedule_notrace <- NOP
8707 * irqentry_exit_cond_resched <- NOP
8710 * cond_resched <- RET0
8711 * might_resched <- RET0
8712 * preempt_schedule <- preempt_schedule
8713 * preempt_schedule_notrace <- preempt_schedule_notrace
8714 * irqentry_exit_cond_resched <- irqentry_exit_cond_resched
8718 preempt_dynamic_undefined = -1,
8719 preempt_dynamic_none,
8720 preempt_dynamic_voluntary,
8721 preempt_dynamic_full,
8724 int preempt_dynamic_mode = preempt_dynamic_undefined;
8726 int sched_dynamic_mode(const char *str)
8728 if (!strcmp(str, "none"))
8729 return preempt_dynamic_none;
8731 if (!strcmp(str, "voluntary"))
8732 return preempt_dynamic_voluntary;
8734 if (!strcmp(str, "full"))
8735 return preempt_dynamic_full;
8740 #if defined(CONFIG_HAVE_PREEMPT_DYNAMIC_CALL)
8741 #define preempt_dynamic_enable(f) static_call_update(f, f##_dynamic_enabled)
8742 #define preempt_dynamic_disable(f) static_call_update(f, f##_dynamic_disabled)
8743 #elif defined(CONFIG_HAVE_PREEMPT_DYNAMIC_KEY)
8744 #define preempt_dynamic_enable(f) static_key_enable(&sk_dynamic_##f.key)
8745 #define preempt_dynamic_disable(f) static_key_disable(&sk_dynamic_##f.key)
8747 #error "Unsupported PREEMPT_DYNAMIC mechanism"
8750 static DEFINE_MUTEX(sched_dynamic_mutex);
8751 static bool klp_override;
8753 static void __sched_dynamic_update(int mode)
8756 * Avoid {NONE,VOLUNTARY} -> FULL transitions from ever ending up in
8757 * the ZERO state, which is invalid.
8760 preempt_dynamic_enable(cond_resched);
8761 preempt_dynamic_enable(might_resched);
8762 preempt_dynamic_enable(preempt_schedule);
8763 preempt_dynamic_enable(preempt_schedule_notrace);
8764 preempt_dynamic_enable(irqentry_exit_cond_resched);
8767 case preempt_dynamic_none:
8769 preempt_dynamic_enable(cond_resched);
8770 preempt_dynamic_disable(might_resched);
8771 preempt_dynamic_disable(preempt_schedule);
8772 preempt_dynamic_disable(preempt_schedule_notrace);
8773 preempt_dynamic_disable(irqentry_exit_cond_resched);
8774 if (mode != preempt_dynamic_mode)
8775 pr_info("Dynamic Preempt: none\n");
8778 case preempt_dynamic_voluntary:
8780 preempt_dynamic_enable(cond_resched);
8781 preempt_dynamic_enable(might_resched);
8782 preempt_dynamic_disable(preempt_schedule);
8783 preempt_dynamic_disable(preempt_schedule_notrace);
8784 preempt_dynamic_disable(irqentry_exit_cond_resched);
8785 if (mode != preempt_dynamic_mode)
8786 pr_info("Dynamic Preempt: voluntary\n");
8789 case preempt_dynamic_full:
8791 preempt_dynamic_disable(cond_resched);
8792 preempt_dynamic_disable(might_resched);
8793 preempt_dynamic_enable(preempt_schedule);
8794 preempt_dynamic_enable(preempt_schedule_notrace);
8795 preempt_dynamic_enable(irqentry_exit_cond_resched);
8796 if (mode != preempt_dynamic_mode)
8797 pr_info("Dynamic Preempt: full\n");
8801 preempt_dynamic_mode = mode;
8804 void sched_dynamic_update(int mode)
8806 mutex_lock(&sched_dynamic_mutex);
8807 __sched_dynamic_update(mode);
8808 mutex_unlock(&sched_dynamic_mutex);
8811 #ifdef CONFIG_HAVE_PREEMPT_DYNAMIC_CALL
8813 static int klp_cond_resched(void)
8815 __klp_sched_try_switch();
8816 return __cond_resched();
8819 void sched_dynamic_klp_enable(void)
8821 mutex_lock(&sched_dynamic_mutex);
8823 klp_override = true;
8824 static_call_update(cond_resched, klp_cond_resched);
8826 mutex_unlock(&sched_dynamic_mutex);
8829 void sched_dynamic_klp_disable(void)
8831 mutex_lock(&sched_dynamic_mutex);
8833 klp_override = false;
8834 __sched_dynamic_update(preempt_dynamic_mode);
8836 mutex_unlock(&sched_dynamic_mutex);
8839 #endif /* CONFIG_HAVE_PREEMPT_DYNAMIC_CALL */
8841 static int __init setup_preempt_mode(char *str)
8843 int mode = sched_dynamic_mode(str);
8845 pr_warn("Dynamic Preempt: unsupported mode: %s\n", str);
8849 sched_dynamic_update(mode);
8852 __setup("preempt=", setup_preempt_mode);
8854 static void __init preempt_dynamic_init(void)
8856 if (preempt_dynamic_mode == preempt_dynamic_undefined) {
8857 if (IS_ENABLED(CONFIG_PREEMPT_NONE)) {
8858 sched_dynamic_update(preempt_dynamic_none);
8859 } else if (IS_ENABLED(CONFIG_PREEMPT_VOLUNTARY)) {
8860 sched_dynamic_update(preempt_dynamic_voluntary);
8862 /* Default static call setting, nothing to do */
8863 WARN_ON_ONCE(!IS_ENABLED(CONFIG_PREEMPT));
8864 preempt_dynamic_mode = preempt_dynamic_full;
8865 pr_info("Dynamic Preempt: full\n");
8870 #define PREEMPT_MODEL_ACCESSOR(mode) \
8871 bool preempt_model_##mode(void) \
8873 WARN_ON_ONCE(preempt_dynamic_mode == preempt_dynamic_undefined); \
8874 return preempt_dynamic_mode == preempt_dynamic_##mode; \
8876 EXPORT_SYMBOL_GPL(preempt_model_##mode)
8878 PREEMPT_MODEL_ACCESSOR(none);
8879 PREEMPT_MODEL_ACCESSOR(voluntary);
8880 PREEMPT_MODEL_ACCESSOR(full);
8882 #else /* !CONFIG_PREEMPT_DYNAMIC */
8884 static inline void preempt_dynamic_init(void) { }
8886 #endif /* #ifdef CONFIG_PREEMPT_DYNAMIC */
8889 * yield - yield the current processor to other threads.
8891 * Do not ever use this function, there's a 99% chance you're doing it wrong.
8893 * The scheduler is at all times free to pick the calling task as the most
8894 * eligible task to run, if removing the yield() call from your code breaks
8895 * it, it's already broken.
8897 * Typical broken usage is:
8902 * where one assumes that yield() will let 'the other' process run that will
8903 * make event true. If the current task is a SCHED_FIFO task that will never
8904 * happen. Never use yield() as a progress guarantee!!
8906 * If you want to use yield() to wait for something, use wait_event().
8907 * If you want to use yield() to be 'nice' for others, use cond_resched().
8908 * If you still want to use yield(), do not!
8910 void __sched yield(void)
8912 set_current_state(TASK_RUNNING);
8915 EXPORT_SYMBOL(yield);
8918 * yield_to - yield the current processor to another thread in
8919 * your thread group, or accelerate that thread toward the
8920 * processor it's on.
8922 * @preempt: whether task preemption is allowed or not
8924 * It's the caller's job to ensure that the target task struct
8925 * can't go away on us before we can do any checks.
8928 * true (>0) if we indeed boosted the target task.
8929 * false (0) if we failed to boost the target.
8930 * -ESRCH if there's no task to yield to.
8932 int __sched yield_to(struct task_struct *p, bool preempt)
8934 struct task_struct *curr = current;
8935 struct rq *rq, *p_rq;
8936 unsigned long flags;
8939 local_irq_save(flags);
8945 * If we're the only runnable task on the rq and target rq also
8946 * has only one task, there's absolutely no point in yielding.
8948 if (rq->nr_running == 1 && p_rq->nr_running == 1) {
8953 double_rq_lock(rq, p_rq);
8954 if (task_rq(p) != p_rq) {
8955 double_rq_unlock(rq, p_rq);
8959 if (!curr->sched_class->yield_to_task)
8962 if (curr->sched_class != p->sched_class)
8965 if (task_on_cpu(p_rq, p) || !task_is_running(p))
8968 yielded = curr->sched_class->yield_to_task(rq, p);
8970 schedstat_inc(rq->yld_count);
8972 * Make p's CPU reschedule; pick_next_entity takes care of
8975 if (preempt && rq != p_rq)
8980 double_rq_unlock(rq, p_rq);
8982 local_irq_restore(flags);
8989 EXPORT_SYMBOL_GPL(yield_to);
8991 int io_schedule_prepare(void)
8993 int old_iowait = current->in_iowait;
8995 current->in_iowait = 1;
8996 blk_flush_plug(current->plug, true);
9000 void io_schedule_finish(int token)
9002 current->in_iowait = token;
9006 * This task is about to go to sleep on IO. Increment rq->nr_iowait so
9007 * that process accounting knows that this is a task in IO wait state.
9009 long __sched io_schedule_timeout(long timeout)
9014 token = io_schedule_prepare();
9015 ret = schedule_timeout(timeout);
9016 io_schedule_finish(token);
9020 EXPORT_SYMBOL(io_schedule_timeout);
9022 void __sched io_schedule(void)
9026 token = io_schedule_prepare();
9028 io_schedule_finish(token);
9030 EXPORT_SYMBOL(io_schedule);
9033 * sys_sched_get_priority_max - return maximum RT priority.
9034 * @policy: scheduling class.
9036 * Return: On success, this syscall returns the maximum
9037 * rt_priority that can be used by a given scheduling class.
9038 * On failure, a negative error code is returned.
9040 SYSCALL_DEFINE1(sched_get_priority_max, int, policy)
9047 ret = MAX_RT_PRIO-1;
9049 case SCHED_DEADLINE:
9060 * sys_sched_get_priority_min - return minimum RT priority.
9061 * @policy: scheduling class.
9063 * Return: On success, this syscall returns the minimum
9064 * rt_priority that can be used by a given scheduling class.
9065 * On failure, a negative error code is returned.
9067 SYSCALL_DEFINE1(sched_get_priority_min, int, policy)
9076 case SCHED_DEADLINE:
9085 static int sched_rr_get_interval(pid_t pid, struct timespec64 *t)
9087 struct task_struct *p;
9088 unsigned int time_slice;
9098 p = find_process_by_pid(pid);
9102 retval = security_task_getscheduler(p);
9106 rq = task_rq_lock(p, &rf);
9108 if (p->sched_class->get_rr_interval)
9109 time_slice = p->sched_class->get_rr_interval(rq, p);
9110 task_rq_unlock(rq, p, &rf);
9113 jiffies_to_timespec64(time_slice, t);
9122 * sys_sched_rr_get_interval - return the default timeslice of a process.
9123 * @pid: pid of the process.
9124 * @interval: userspace pointer to the timeslice value.
9126 * this syscall writes the default timeslice value of a given process
9127 * into the user-space timespec buffer. A value of '0' means infinity.
9129 * Return: On success, 0 and the timeslice is in @interval. Otherwise,
9132 SYSCALL_DEFINE2(sched_rr_get_interval, pid_t, pid,
9133 struct __kernel_timespec __user *, interval)
9135 struct timespec64 t;
9136 int retval = sched_rr_get_interval(pid, &t);
9139 retval = put_timespec64(&t, interval);
9144 #ifdef CONFIG_COMPAT_32BIT_TIME
9145 SYSCALL_DEFINE2(sched_rr_get_interval_time32, pid_t, pid,
9146 struct old_timespec32 __user *, interval)
9148 struct timespec64 t;
9149 int retval = sched_rr_get_interval(pid, &t);
9152 retval = put_old_timespec32(&t, interval);
9157 void sched_show_task(struct task_struct *p)
9159 unsigned long free = 0;
9162 if (!try_get_task_stack(p))
9165 pr_info("task:%-15.15s state:%c", p->comm, task_state_to_char(p));
9167 if (task_is_running(p))
9168 pr_cont(" running task ");
9169 #ifdef CONFIG_DEBUG_STACK_USAGE
9170 free = stack_not_used(p);
9175 ppid = task_pid_nr(rcu_dereference(p->real_parent));
9177 pr_cont(" stack:%-5lu pid:%-5d ppid:%-6d flags:0x%08lx\n",
9178 free, task_pid_nr(p), ppid,
9179 read_task_thread_flags(p));
9181 print_worker_info(KERN_INFO, p);
9182 print_stop_info(KERN_INFO, p);
9183 show_stack(p, NULL, KERN_INFO);
9186 EXPORT_SYMBOL_GPL(sched_show_task);
9189 state_filter_match(unsigned long state_filter, struct task_struct *p)
9191 unsigned int state = READ_ONCE(p->__state);
9193 /* no filter, everything matches */
9197 /* filter, but doesn't match */
9198 if (!(state & state_filter))
9202 * When looking for TASK_UNINTERRUPTIBLE skip TASK_IDLE (allows
9205 if (state_filter == TASK_UNINTERRUPTIBLE && (state & TASK_NOLOAD))
9212 void show_state_filter(unsigned int state_filter)
9214 struct task_struct *g, *p;
9217 for_each_process_thread(g, p) {
9219 * reset the NMI-timeout, listing all files on a slow
9220 * console might take a lot of time:
9221 * Also, reset softlockup watchdogs on all CPUs, because
9222 * another CPU might be blocked waiting for us to process
9225 touch_nmi_watchdog();
9226 touch_all_softlockup_watchdogs();
9227 if (state_filter_match(state_filter, p))
9231 #ifdef CONFIG_SCHED_DEBUG
9233 sysrq_sched_debug_show();
9237 * Only show locks if all tasks are dumped:
9240 debug_show_all_locks();
9244 * init_idle - set up an idle thread for a given CPU
9245 * @idle: task in question
9246 * @cpu: CPU the idle task belongs to
9248 * NOTE: this function does not set the idle thread's NEED_RESCHED
9249 * flag, to make booting more robust.
9251 void __init init_idle(struct task_struct *idle, int cpu)
9254 struct affinity_context ac = (struct affinity_context) {
9255 .new_mask = cpumask_of(cpu),
9259 struct rq *rq = cpu_rq(cpu);
9260 unsigned long flags;
9262 __sched_fork(0, idle);
9264 raw_spin_lock_irqsave(&idle->pi_lock, flags);
9265 raw_spin_rq_lock(rq);
9267 idle->__state = TASK_RUNNING;
9268 idle->se.exec_start = sched_clock();
9270 * PF_KTHREAD should already be set at this point; regardless, make it
9271 * look like a proper per-CPU kthread.
9273 idle->flags |= PF_KTHREAD | PF_NO_SETAFFINITY;
9274 kthread_set_per_cpu(idle, cpu);
9278 * It's possible that init_idle() gets called multiple times on a task,
9279 * in that case do_set_cpus_allowed() will not do the right thing.
9281 * And since this is boot we can forgo the serialization.
9283 set_cpus_allowed_common(idle, &ac);
9286 * We're having a chicken and egg problem, even though we are
9287 * holding rq->lock, the CPU isn't yet set to this CPU so the
9288 * lockdep check in task_group() will fail.
9290 * Similar case to sched_fork(). / Alternatively we could
9291 * use task_rq_lock() here and obtain the other rq->lock.
9296 __set_task_cpu(idle, cpu);
9300 rcu_assign_pointer(rq->curr, idle);
9301 idle->on_rq = TASK_ON_RQ_QUEUED;
9305 raw_spin_rq_unlock(rq);
9306 raw_spin_unlock_irqrestore(&idle->pi_lock, flags);
9308 /* Set the preempt count _outside_ the spinlocks! */
9309 init_idle_preempt_count(idle, cpu);
9312 * The idle tasks have their own, simple scheduling class:
9314 idle->sched_class = &idle_sched_class;
9315 ftrace_graph_init_idle_task(idle, cpu);
9316 vtime_init_idle(idle, cpu);
9318 sprintf(idle->comm, "%s/%d", INIT_TASK_COMM, cpu);
9324 int cpuset_cpumask_can_shrink(const struct cpumask *cur,
9325 const struct cpumask *trial)
9329 if (cpumask_empty(cur))
9332 ret = dl_cpuset_cpumask_can_shrink(cur, trial);
9337 int task_can_attach(struct task_struct *p)
9342 * Kthreads which disallow setaffinity shouldn't be moved
9343 * to a new cpuset; we don't want to change their CPU
9344 * affinity and isolating such threads by their set of
9345 * allowed nodes is unnecessary. Thus, cpusets are not
9346 * applicable for such threads. This prevents checking for
9347 * success of set_cpus_allowed_ptr() on all attached tasks
9348 * before cpus_mask may be changed.
9350 if (p->flags & PF_NO_SETAFFINITY)
9356 bool sched_smp_initialized __read_mostly;
9358 #ifdef CONFIG_NUMA_BALANCING
9359 /* Migrate current task p to target_cpu */
9360 int migrate_task_to(struct task_struct *p, int target_cpu)
9362 struct migration_arg arg = { p, target_cpu };
9363 int curr_cpu = task_cpu(p);
9365 if (curr_cpu == target_cpu)
9368 if (!cpumask_test_cpu(target_cpu, p->cpus_ptr))
9371 /* TODO: This is not properly updating schedstats */
9373 trace_sched_move_numa(p, curr_cpu, target_cpu);
9374 return stop_one_cpu(curr_cpu, migration_cpu_stop, &arg);
9378 * Requeue a task on a given node and accurately track the number of NUMA
9379 * tasks on the runqueues
9381 void sched_setnuma(struct task_struct *p, int nid)
9383 bool queued, running;
9387 rq = task_rq_lock(p, &rf);
9388 queued = task_on_rq_queued(p);
9389 running = task_current(rq, p);
9392 dequeue_task(rq, p, DEQUEUE_SAVE);
9394 put_prev_task(rq, p);
9396 p->numa_preferred_nid = nid;
9399 enqueue_task(rq, p, ENQUEUE_RESTORE | ENQUEUE_NOCLOCK);
9401 set_next_task(rq, p);
9402 task_rq_unlock(rq, p, &rf);
9404 #endif /* CONFIG_NUMA_BALANCING */
9406 #ifdef CONFIG_HOTPLUG_CPU
9408 * Ensure that the idle task is using init_mm right before its CPU goes
9411 void idle_task_exit(void)
9413 struct mm_struct *mm = current->active_mm;
9415 BUG_ON(cpu_online(smp_processor_id()));
9416 BUG_ON(current != this_rq()->idle);
9418 if (mm != &init_mm) {
9419 switch_mm(mm, &init_mm, current);
9420 finish_arch_post_lock_switch();
9423 /* finish_cpu(), as ran on the BP, will clean up the active_mm state */
9426 static int __balance_push_cpu_stop(void *arg)
9428 struct task_struct *p = arg;
9429 struct rq *rq = this_rq();
9433 raw_spin_lock_irq(&p->pi_lock);
9436 update_rq_clock(rq);
9438 if (task_rq(p) == rq && task_on_rq_queued(p)) {
9439 cpu = select_fallback_rq(rq->cpu, p);
9440 rq = __migrate_task(rq, &rf, p, cpu);
9444 raw_spin_unlock_irq(&p->pi_lock);
9451 static DEFINE_PER_CPU(struct cpu_stop_work, push_work);
9454 * Ensure we only run per-cpu kthreads once the CPU goes !active.
9456 * This is enabled below SCHED_AP_ACTIVE; when !cpu_active(), but only
9457 * effective when the hotplug motion is down.
9459 static void balance_push(struct rq *rq)
9461 struct task_struct *push_task = rq->curr;
9463 lockdep_assert_rq_held(rq);
9466 * Ensure the thing is persistent until balance_push_set(.on = false);
9468 rq->balance_callback = &balance_push_callback;
9471 * Only active while going offline and when invoked on the outgoing
9474 if (!cpu_dying(rq->cpu) || rq != this_rq())
9478 * Both the cpu-hotplug and stop task are in this case and are
9479 * required to complete the hotplug process.
9481 if (kthread_is_per_cpu(push_task) ||
9482 is_migration_disabled(push_task)) {
9485 * If this is the idle task on the outgoing CPU try to wake
9486 * up the hotplug control thread which might wait for the
9487 * last task to vanish. The rcuwait_active() check is
9488 * accurate here because the waiter is pinned on this CPU
9489 * and can't obviously be running in parallel.
9491 * On RT kernels this also has to check whether there are
9492 * pinned and scheduled out tasks on the runqueue. They
9493 * need to leave the migrate disabled section first.
9495 if (!rq->nr_running && !rq_has_pinned_tasks(rq) &&
9496 rcuwait_active(&rq->hotplug_wait)) {
9497 raw_spin_rq_unlock(rq);
9498 rcuwait_wake_up(&rq->hotplug_wait);
9499 raw_spin_rq_lock(rq);
9504 get_task_struct(push_task);
9506 * Temporarily drop rq->lock such that we can wake-up the stop task.
9507 * Both preemption and IRQs are still disabled.
9510 raw_spin_rq_unlock(rq);
9511 stop_one_cpu_nowait(rq->cpu, __balance_push_cpu_stop, push_task,
9512 this_cpu_ptr(&push_work));
9515 * At this point need_resched() is true and we'll take the loop in
9516 * schedule(). The next pick is obviously going to be the stop task
9517 * which kthread_is_per_cpu() and will push this task away.
9519 raw_spin_rq_lock(rq);
9522 static void balance_push_set(int cpu, bool on)
9524 struct rq *rq = cpu_rq(cpu);
9527 rq_lock_irqsave(rq, &rf);
9529 WARN_ON_ONCE(rq->balance_callback);
9530 rq->balance_callback = &balance_push_callback;
9531 } else if (rq->balance_callback == &balance_push_callback) {
9532 rq->balance_callback = NULL;
9534 rq_unlock_irqrestore(rq, &rf);
9538 * Invoked from a CPUs hotplug control thread after the CPU has been marked
9539 * inactive. All tasks which are not per CPU kernel threads are either
9540 * pushed off this CPU now via balance_push() or placed on a different CPU
9541 * during wakeup. Wait until the CPU is quiescent.
9543 static void balance_hotplug_wait(void)
9545 struct rq *rq = this_rq();
9547 rcuwait_wait_event(&rq->hotplug_wait,
9548 rq->nr_running == 1 && !rq_has_pinned_tasks(rq),
9549 TASK_UNINTERRUPTIBLE);
9554 static inline void balance_push(struct rq *rq)
9558 static inline void balance_push_set(int cpu, bool on)
9562 static inline void balance_hotplug_wait(void)
9566 #endif /* CONFIG_HOTPLUG_CPU */
9568 void set_rq_online(struct rq *rq)
9571 const struct sched_class *class;
9573 cpumask_set_cpu(rq->cpu, rq->rd->online);
9576 for_each_class(class) {
9577 if (class->rq_online)
9578 class->rq_online(rq);
9583 void set_rq_offline(struct rq *rq)
9586 const struct sched_class *class;
9588 update_rq_clock(rq);
9589 for_each_class(class) {
9590 if (class->rq_offline)
9591 class->rq_offline(rq);
9594 cpumask_clear_cpu(rq->cpu, rq->rd->online);
9600 * used to mark begin/end of suspend/resume:
9602 static int num_cpus_frozen;
9605 * Update cpusets according to cpu_active mask. If cpusets are
9606 * disabled, cpuset_update_active_cpus() becomes a simple wrapper
9607 * around partition_sched_domains().
9609 * If we come here as part of a suspend/resume, don't touch cpusets because we
9610 * want to restore it back to its original state upon resume anyway.
9612 static void cpuset_cpu_active(void)
9614 if (cpuhp_tasks_frozen) {
9616 * num_cpus_frozen tracks how many CPUs are involved in suspend
9617 * resume sequence. As long as this is not the last online
9618 * operation in the resume sequence, just build a single sched
9619 * domain, ignoring cpusets.
9621 partition_sched_domains(1, NULL, NULL);
9622 if (--num_cpus_frozen)
9625 * This is the last CPU online operation. So fall through and
9626 * restore the original sched domains by considering the
9627 * cpuset configurations.
9629 cpuset_force_rebuild();
9631 cpuset_update_active_cpus();
9634 static int cpuset_cpu_inactive(unsigned int cpu)
9636 if (!cpuhp_tasks_frozen) {
9637 int ret = dl_bw_check_overflow(cpu);
9641 cpuset_update_active_cpus();
9644 partition_sched_domains(1, NULL, NULL);
9649 int sched_cpu_activate(unsigned int cpu)
9651 struct rq *rq = cpu_rq(cpu);
9655 * Clear the balance_push callback and prepare to schedule
9658 balance_push_set(cpu, false);
9660 #ifdef CONFIG_SCHED_SMT
9662 * When going up, increment the number of cores with SMT present.
9664 if (cpumask_weight(cpu_smt_mask(cpu)) == 2)
9665 static_branch_inc_cpuslocked(&sched_smt_present);
9667 set_cpu_active(cpu, true);
9669 if (sched_smp_initialized) {
9670 sched_update_numa(cpu, true);
9671 sched_domains_numa_masks_set(cpu);
9672 cpuset_cpu_active();
9676 * Put the rq online, if not already. This happens:
9678 * 1) In the early boot process, because we build the real domains
9679 * after all CPUs have been brought up.
9681 * 2) At runtime, if cpuset_cpu_active() fails to rebuild the
9684 rq_lock_irqsave(rq, &rf);
9686 BUG_ON(!cpumask_test_cpu(cpu, rq->rd->span));
9689 rq_unlock_irqrestore(rq, &rf);
9694 int sched_cpu_deactivate(unsigned int cpu)
9696 struct rq *rq = cpu_rq(cpu);
9701 * Remove CPU from nohz.idle_cpus_mask to prevent participating in
9702 * load balancing when not active
9704 nohz_balance_exit_idle(rq);
9706 set_cpu_active(cpu, false);
9709 * From this point forward, this CPU will refuse to run any task that
9710 * is not: migrate_disable() or KTHREAD_IS_PER_CPU, and will actively
9711 * push those tasks away until this gets cleared, see
9712 * sched_cpu_dying().
9714 balance_push_set(cpu, true);
9717 * We've cleared cpu_active_mask / set balance_push, wait for all
9718 * preempt-disabled and RCU users of this state to go away such that
9719 * all new such users will observe it.
9721 * Specifically, we rely on ttwu to no longer target this CPU, see
9722 * ttwu_queue_cond() and is_cpu_allowed().
9724 * Do sync before park smpboot threads to take care the rcu boost case.
9728 rq_lock_irqsave(rq, &rf);
9730 BUG_ON(!cpumask_test_cpu(cpu, rq->rd->span));
9733 rq_unlock_irqrestore(rq, &rf);
9735 #ifdef CONFIG_SCHED_SMT
9737 * When going down, decrement the number of cores with SMT present.
9739 if (cpumask_weight(cpu_smt_mask(cpu)) == 2)
9740 static_branch_dec_cpuslocked(&sched_smt_present);
9742 sched_core_cpu_deactivate(cpu);
9745 if (!sched_smp_initialized)
9748 sched_update_numa(cpu, false);
9749 ret = cpuset_cpu_inactive(cpu);
9751 balance_push_set(cpu, false);
9752 set_cpu_active(cpu, true);
9753 sched_update_numa(cpu, true);
9756 sched_domains_numa_masks_clear(cpu);
9760 static void sched_rq_cpu_starting(unsigned int cpu)
9762 struct rq *rq = cpu_rq(cpu);
9764 rq->calc_load_update = calc_load_update;
9765 update_max_interval();
9768 int sched_cpu_starting(unsigned int cpu)
9770 sched_core_cpu_starting(cpu);
9771 sched_rq_cpu_starting(cpu);
9772 sched_tick_start(cpu);
9776 #ifdef CONFIG_HOTPLUG_CPU
9779 * Invoked immediately before the stopper thread is invoked to bring the
9780 * CPU down completely. At this point all per CPU kthreads except the
9781 * hotplug thread (current) and the stopper thread (inactive) have been
9782 * either parked or have been unbound from the outgoing CPU. Ensure that
9783 * any of those which might be on the way out are gone.
9785 * If after this point a bound task is being woken on this CPU then the
9786 * responsible hotplug callback has failed to do it's job.
9787 * sched_cpu_dying() will catch it with the appropriate fireworks.
9789 int sched_cpu_wait_empty(unsigned int cpu)
9791 balance_hotplug_wait();
9796 * Since this CPU is going 'away' for a while, fold any nr_active delta we
9797 * might have. Called from the CPU stopper task after ensuring that the
9798 * stopper is the last running task on the CPU, so nr_active count is
9799 * stable. We need to take the teardown thread which is calling this into
9800 * account, so we hand in adjust = 1 to the load calculation.
9802 * Also see the comment "Global load-average calculations".
9804 static void calc_load_migrate(struct rq *rq)
9806 long delta = calc_load_fold_active(rq, 1);
9809 atomic_long_add(delta, &calc_load_tasks);
9812 static void dump_rq_tasks(struct rq *rq, const char *loglvl)
9814 struct task_struct *g, *p;
9815 int cpu = cpu_of(rq);
9817 lockdep_assert_rq_held(rq);
9819 printk("%sCPU%d enqueued tasks (%u total):\n", loglvl, cpu, rq->nr_running);
9820 for_each_process_thread(g, p) {
9821 if (task_cpu(p) != cpu)
9824 if (!task_on_rq_queued(p))
9827 printk("%s\tpid: %d, name: %s\n", loglvl, p->pid, p->comm);
9831 int sched_cpu_dying(unsigned int cpu)
9833 struct rq *rq = cpu_rq(cpu);
9836 /* Handle pending wakeups and then migrate everything off */
9837 sched_tick_stop(cpu);
9839 rq_lock_irqsave(rq, &rf);
9840 if (rq->nr_running != 1 || rq_has_pinned_tasks(rq)) {
9841 WARN(true, "Dying CPU not properly vacated!");
9842 dump_rq_tasks(rq, KERN_WARNING);
9844 rq_unlock_irqrestore(rq, &rf);
9846 calc_load_migrate(rq);
9847 update_max_interval();
9849 sched_core_cpu_dying(cpu);
9854 void __init sched_init_smp(void)
9856 sched_init_numa(NUMA_NO_NODE);
9859 * There's no userspace yet to cause hotplug operations; hence all the
9860 * CPU masks are stable and all blatant races in the below code cannot
9863 mutex_lock(&sched_domains_mutex);
9864 sched_init_domains(cpu_active_mask);
9865 mutex_unlock(&sched_domains_mutex);
9867 /* Move init over to a non-isolated CPU */
9868 if (set_cpus_allowed_ptr(current, housekeeping_cpumask(HK_TYPE_DOMAIN)) < 0)
9870 current->flags &= ~PF_NO_SETAFFINITY;
9871 sched_init_granularity();
9873 init_sched_rt_class();
9874 init_sched_dl_class();
9876 sched_smp_initialized = true;
9879 static int __init migration_init(void)
9881 sched_cpu_starting(smp_processor_id());
9884 early_initcall(migration_init);
9887 void __init sched_init_smp(void)
9889 sched_init_granularity();
9891 #endif /* CONFIG_SMP */
9893 int in_sched_functions(unsigned long addr)
9895 return in_lock_functions(addr) ||
9896 (addr >= (unsigned long)__sched_text_start
9897 && addr < (unsigned long)__sched_text_end);
9900 #ifdef CONFIG_CGROUP_SCHED
9902 * Default task group.
9903 * Every task in system belongs to this group at bootup.
9905 struct task_group root_task_group;
9906 LIST_HEAD(task_groups);
9908 /* Cacheline aligned slab cache for task_group */
9909 static struct kmem_cache *task_group_cache __read_mostly;
9912 void __init sched_init(void)
9914 unsigned long ptr = 0;
9917 /* Make sure the linker didn't screw up */
9918 BUG_ON(&idle_sched_class != &fair_sched_class + 1 ||
9919 &fair_sched_class != &rt_sched_class + 1 ||
9920 &rt_sched_class != &dl_sched_class + 1);
9922 BUG_ON(&dl_sched_class != &stop_sched_class + 1);
9927 #ifdef CONFIG_FAIR_GROUP_SCHED
9928 ptr += 2 * nr_cpu_ids * sizeof(void **);
9930 #ifdef CONFIG_RT_GROUP_SCHED
9931 ptr += 2 * nr_cpu_ids * sizeof(void **);
9934 ptr = (unsigned long)kzalloc(ptr, GFP_NOWAIT);
9936 #ifdef CONFIG_FAIR_GROUP_SCHED
9937 root_task_group.se = (struct sched_entity **)ptr;
9938 ptr += nr_cpu_ids * sizeof(void **);
9940 root_task_group.cfs_rq = (struct cfs_rq **)ptr;
9941 ptr += nr_cpu_ids * sizeof(void **);
9943 root_task_group.shares = ROOT_TASK_GROUP_LOAD;
9944 init_cfs_bandwidth(&root_task_group.cfs_bandwidth, NULL);
9945 #endif /* CONFIG_FAIR_GROUP_SCHED */
9946 #ifdef CONFIG_RT_GROUP_SCHED
9947 root_task_group.rt_se = (struct sched_rt_entity **)ptr;
9948 ptr += nr_cpu_ids * sizeof(void **);
9950 root_task_group.rt_rq = (struct rt_rq **)ptr;
9951 ptr += nr_cpu_ids * sizeof(void **);
9953 #endif /* CONFIG_RT_GROUP_SCHED */
9956 init_rt_bandwidth(&def_rt_bandwidth, global_rt_period(), global_rt_runtime());
9959 init_defrootdomain();
9962 #ifdef CONFIG_RT_GROUP_SCHED
9963 init_rt_bandwidth(&root_task_group.rt_bandwidth,
9964 global_rt_period(), global_rt_runtime());
9965 #endif /* CONFIG_RT_GROUP_SCHED */
9967 #ifdef CONFIG_CGROUP_SCHED
9968 task_group_cache = KMEM_CACHE(task_group, 0);
9970 list_add(&root_task_group.list, &task_groups);
9971 INIT_LIST_HEAD(&root_task_group.children);
9972 INIT_LIST_HEAD(&root_task_group.siblings);
9973 autogroup_init(&init_task);
9974 #endif /* CONFIG_CGROUP_SCHED */
9976 for_each_possible_cpu(i) {
9980 raw_spin_lock_init(&rq->__lock);
9982 rq->calc_load_active = 0;
9983 rq->calc_load_update = jiffies + LOAD_FREQ;
9984 init_cfs_rq(&rq->cfs);
9985 init_rt_rq(&rq->rt);
9986 init_dl_rq(&rq->dl);
9987 #ifdef CONFIG_FAIR_GROUP_SCHED
9988 INIT_LIST_HEAD(&rq->leaf_cfs_rq_list);
9989 rq->tmp_alone_branch = &rq->leaf_cfs_rq_list;
9991 * How much CPU bandwidth does root_task_group get?
9993 * In case of task-groups formed thr' the cgroup filesystem, it
9994 * gets 100% of the CPU resources in the system. This overall
9995 * system CPU resource is divided among the tasks of
9996 * root_task_group and its child task-groups in a fair manner,
9997 * based on each entity's (task or task-group's) weight
9998 * (se->load.weight).
10000 * In other words, if root_task_group has 10 tasks of weight
10001 * 1024) and two child groups A0 and A1 (of weight 1024 each),
10002 * then A0's share of the CPU resource is:
10004 * A0's bandwidth = 1024 / (10*1024 + 1024 + 1024) = 8.33%
10006 * We achieve this by letting root_task_group's tasks sit
10007 * directly in rq->cfs (i.e root_task_group->se[] = NULL).
10009 init_tg_cfs_entry(&root_task_group, &rq->cfs, NULL, i, NULL);
10010 #endif /* CONFIG_FAIR_GROUP_SCHED */
10012 rq->rt.rt_runtime = def_rt_bandwidth.rt_runtime;
10013 #ifdef CONFIG_RT_GROUP_SCHED
10014 init_tg_rt_entry(&root_task_group, &rq->rt, NULL, i, NULL);
10019 rq->cpu_capacity = rq->cpu_capacity_orig = SCHED_CAPACITY_SCALE;
10020 rq->balance_callback = &balance_push_callback;
10021 rq->active_balance = 0;
10022 rq->next_balance = jiffies;
10026 rq->idle_stamp = 0;
10027 rq->avg_idle = 2*sysctl_sched_migration_cost;
10028 rq->wake_stamp = jiffies;
10029 rq->wake_avg_idle = rq->avg_idle;
10030 rq->max_idle_balance_cost = sysctl_sched_migration_cost;
10032 INIT_LIST_HEAD(&rq->cfs_tasks);
10034 rq_attach_root(rq, &def_root_domain);
10035 #ifdef CONFIG_NO_HZ_COMMON
10036 rq->last_blocked_load_update_tick = jiffies;
10037 atomic_set(&rq->nohz_flags, 0);
10039 INIT_CSD(&rq->nohz_csd, nohz_csd_func, rq);
10041 #ifdef CONFIG_HOTPLUG_CPU
10042 rcuwait_init(&rq->hotplug_wait);
10044 #endif /* CONFIG_SMP */
10045 hrtick_rq_init(rq);
10046 atomic_set(&rq->nr_iowait, 0);
10048 #ifdef CONFIG_SCHED_CORE
10050 rq->core_pick = NULL;
10051 rq->core_enabled = 0;
10052 rq->core_tree = RB_ROOT;
10053 rq->core_forceidle_count = 0;
10054 rq->core_forceidle_occupation = 0;
10055 rq->core_forceidle_start = 0;
10057 rq->core_cookie = 0UL;
10059 zalloc_cpumask_var_node(&rq->scratch_mask, GFP_KERNEL, cpu_to_node(i));
10062 set_load_weight(&init_task, false);
10065 * The boot idle thread does lazy MMU switching as well:
10067 mmgrab_lazy_tlb(&init_mm);
10068 enter_lazy_tlb(&init_mm, current);
10071 * The idle task doesn't need the kthread struct to function, but it
10072 * is dressed up as a per-CPU kthread and thus needs to play the part
10073 * if we want to avoid special-casing it in code that deals with per-CPU
10076 WARN_ON(!set_kthread_struct(current));
10079 * Make us the idle thread. Technically, schedule() should not be
10080 * called from this thread, however somewhere below it might be,
10081 * but because we are the idle thread, we just pick up running again
10082 * when this runqueue becomes "idle".
10084 init_idle(current, smp_processor_id());
10086 calc_load_update = jiffies + LOAD_FREQ;
10089 idle_thread_set_boot_cpu();
10090 balance_push_set(smp_processor_id(), false);
10092 init_sched_fair_class();
10098 preempt_dynamic_init();
10100 scheduler_running = 1;
10103 #ifdef CONFIG_DEBUG_ATOMIC_SLEEP
10105 void __might_sleep(const char *file, int line)
10107 unsigned int state = get_current_state();
10109 * Blocking primitives will set (and therefore destroy) current->state,
10110 * since we will exit with TASK_RUNNING make sure we enter with it,
10111 * otherwise we will destroy state.
10113 WARN_ONCE(state != TASK_RUNNING && current->task_state_change,
10114 "do not call blocking ops when !TASK_RUNNING; "
10115 "state=%x set at [<%p>] %pS\n", state,
10116 (void *)current->task_state_change,
10117 (void *)current->task_state_change);
10119 __might_resched(file, line, 0);
10121 EXPORT_SYMBOL(__might_sleep);
10123 static void print_preempt_disable_ip(int preempt_offset, unsigned long ip)
10125 if (!IS_ENABLED(CONFIG_DEBUG_PREEMPT))
10128 if (preempt_count() == preempt_offset)
10131 pr_err("Preemption disabled at:");
10132 print_ip_sym(KERN_ERR, ip);
10135 static inline bool resched_offsets_ok(unsigned int offsets)
10137 unsigned int nested = preempt_count();
10139 nested += rcu_preempt_depth() << MIGHT_RESCHED_RCU_SHIFT;
10141 return nested == offsets;
10144 void __might_resched(const char *file, int line, unsigned int offsets)
10146 /* Ratelimiting timestamp: */
10147 static unsigned long prev_jiffy;
10149 unsigned long preempt_disable_ip;
10151 /* WARN_ON_ONCE() by default, no rate limit required: */
10154 if ((resched_offsets_ok(offsets) && !irqs_disabled() &&
10155 !is_idle_task(current) && !current->non_block_count) ||
10156 system_state == SYSTEM_BOOTING || system_state > SYSTEM_RUNNING ||
10160 if (time_before(jiffies, prev_jiffy + HZ) && prev_jiffy)
10162 prev_jiffy = jiffies;
10164 /* Save this before calling printk(), since that will clobber it: */
10165 preempt_disable_ip = get_preempt_disable_ip(current);
10167 pr_err("BUG: sleeping function called from invalid context at %s:%d\n",
10169 pr_err("in_atomic(): %d, irqs_disabled(): %d, non_block: %d, pid: %d, name: %s\n",
10170 in_atomic(), irqs_disabled(), current->non_block_count,
10171 current->pid, current->comm);
10172 pr_err("preempt_count: %x, expected: %x\n", preempt_count(),
10173 offsets & MIGHT_RESCHED_PREEMPT_MASK);
10175 if (IS_ENABLED(CONFIG_PREEMPT_RCU)) {
10176 pr_err("RCU nest depth: %d, expected: %u\n",
10177 rcu_preempt_depth(), offsets >> MIGHT_RESCHED_RCU_SHIFT);
10180 if (task_stack_end_corrupted(current))
10181 pr_emerg("Thread overran stack, or stack corrupted\n");
10183 debug_show_held_locks(current);
10184 if (irqs_disabled())
10185 print_irqtrace_events(current);
10187 print_preempt_disable_ip(offsets & MIGHT_RESCHED_PREEMPT_MASK,
10188 preempt_disable_ip);
10191 add_taint(TAINT_WARN, LOCKDEP_STILL_OK);
10193 EXPORT_SYMBOL(__might_resched);
10195 void __cant_sleep(const char *file, int line, int preempt_offset)
10197 static unsigned long prev_jiffy;
10199 if (irqs_disabled())
10202 if (!IS_ENABLED(CONFIG_PREEMPT_COUNT))
10205 if (preempt_count() > preempt_offset)
10208 if (time_before(jiffies, prev_jiffy + HZ) && prev_jiffy)
10210 prev_jiffy = jiffies;
10212 printk(KERN_ERR "BUG: assuming atomic context at %s:%d\n", file, line);
10213 printk(KERN_ERR "in_atomic(): %d, irqs_disabled(): %d, pid: %d, name: %s\n",
10214 in_atomic(), irqs_disabled(),
10215 current->pid, current->comm);
10217 debug_show_held_locks(current);
10219 add_taint(TAINT_WARN, LOCKDEP_STILL_OK);
10221 EXPORT_SYMBOL_GPL(__cant_sleep);
10224 void __cant_migrate(const char *file, int line)
10226 static unsigned long prev_jiffy;
10228 if (irqs_disabled())
10231 if (is_migration_disabled(current))
10234 if (!IS_ENABLED(CONFIG_PREEMPT_COUNT))
10237 if (preempt_count() > 0)
10240 if (time_before(jiffies, prev_jiffy + HZ) && prev_jiffy)
10242 prev_jiffy = jiffies;
10244 pr_err("BUG: assuming non migratable context at %s:%d\n", file, line);
10245 pr_err("in_atomic(): %d, irqs_disabled(): %d, migration_disabled() %u pid: %d, name: %s\n",
10246 in_atomic(), irqs_disabled(), is_migration_disabled(current),
10247 current->pid, current->comm);
10249 debug_show_held_locks(current);
10251 add_taint(TAINT_WARN, LOCKDEP_STILL_OK);
10253 EXPORT_SYMBOL_GPL(__cant_migrate);
10257 #ifdef CONFIG_MAGIC_SYSRQ
10258 void normalize_rt_tasks(void)
10260 struct task_struct *g, *p;
10261 struct sched_attr attr = {
10262 .sched_policy = SCHED_NORMAL,
10265 read_lock(&tasklist_lock);
10266 for_each_process_thread(g, p) {
10268 * Only normalize user tasks:
10270 if (p->flags & PF_KTHREAD)
10273 p->se.exec_start = 0;
10274 schedstat_set(p->stats.wait_start, 0);
10275 schedstat_set(p->stats.sleep_start, 0);
10276 schedstat_set(p->stats.block_start, 0);
10278 if (!dl_task(p) && !rt_task(p)) {
10280 * Renice negative nice level userspace
10283 if (task_nice(p) < 0)
10284 set_user_nice(p, 0);
10288 __sched_setscheduler(p, &attr, false, false);
10290 read_unlock(&tasklist_lock);
10293 #endif /* CONFIG_MAGIC_SYSRQ */
10295 #if defined(CONFIG_IA64) || defined(CONFIG_KGDB_KDB)
10297 * These functions are only useful for the IA64 MCA handling, or kdb.
10299 * They can only be called when the whole system has been
10300 * stopped - every CPU needs to be quiescent, and no scheduling
10301 * activity can take place. Using them for anything else would
10302 * be a serious bug, and as a result, they aren't even visible
10303 * under any other configuration.
10307 * curr_task - return the current task for a given CPU.
10308 * @cpu: the processor in question.
10310 * ONLY VALID WHEN THE WHOLE SYSTEM IS STOPPED!
10312 * Return: The current task for @cpu.
10314 struct task_struct *curr_task(int cpu)
10316 return cpu_curr(cpu);
10319 #endif /* defined(CONFIG_IA64) || defined(CONFIG_KGDB_KDB) */
10323 * ia64_set_curr_task - set the current task for a given CPU.
10324 * @cpu: the processor in question.
10325 * @p: the task pointer to set.
10327 * Description: This function must only be used when non-maskable interrupts
10328 * are serviced on a separate stack. It allows the architecture to switch the
10329 * notion of the current task on a CPU in a non-blocking manner. This function
10330 * must be called with all CPU's synchronized, and interrupts disabled, the
10331 * and caller must save the original value of the current task (see
10332 * curr_task() above) and restore that value before reenabling interrupts and
10333 * re-starting the system.
10335 * ONLY VALID WHEN THE WHOLE SYSTEM IS STOPPED!
10337 void ia64_set_curr_task(int cpu, struct task_struct *p)
10344 #ifdef CONFIG_CGROUP_SCHED
10345 /* task_group_lock serializes the addition/removal of task groups */
10346 static DEFINE_SPINLOCK(task_group_lock);
10348 static inline void alloc_uclamp_sched_group(struct task_group *tg,
10349 struct task_group *parent)
10351 #ifdef CONFIG_UCLAMP_TASK_GROUP
10352 enum uclamp_id clamp_id;
10354 for_each_clamp_id(clamp_id) {
10355 uclamp_se_set(&tg->uclamp_req[clamp_id],
10356 uclamp_none(clamp_id), false);
10357 tg->uclamp[clamp_id] = parent->uclamp[clamp_id];
10362 static void sched_free_group(struct task_group *tg)
10364 free_fair_sched_group(tg);
10365 free_rt_sched_group(tg);
10366 autogroup_free(tg);
10367 kmem_cache_free(task_group_cache, tg);
10370 static void sched_free_group_rcu(struct rcu_head *rcu)
10372 sched_free_group(container_of(rcu, struct task_group, rcu));
10375 static void sched_unregister_group(struct task_group *tg)
10377 unregister_fair_sched_group(tg);
10378 unregister_rt_sched_group(tg);
10380 * We have to wait for yet another RCU grace period to expire, as
10381 * print_cfs_stats() might run concurrently.
10383 call_rcu(&tg->rcu, sched_free_group_rcu);
10386 /* allocate runqueue etc for a new task group */
10387 struct task_group *sched_create_group(struct task_group *parent)
10389 struct task_group *tg;
10391 tg = kmem_cache_alloc(task_group_cache, GFP_KERNEL | __GFP_ZERO);
10393 return ERR_PTR(-ENOMEM);
10395 if (!alloc_fair_sched_group(tg, parent))
10398 if (!alloc_rt_sched_group(tg, parent))
10401 alloc_uclamp_sched_group(tg, parent);
10406 sched_free_group(tg);
10407 return ERR_PTR(-ENOMEM);
10410 void sched_online_group(struct task_group *tg, struct task_group *parent)
10412 unsigned long flags;
10414 spin_lock_irqsave(&task_group_lock, flags);
10415 list_add_rcu(&tg->list, &task_groups);
10417 /* Root should already exist: */
10420 tg->parent = parent;
10421 INIT_LIST_HEAD(&tg->children);
10422 list_add_rcu(&tg->siblings, &parent->children);
10423 spin_unlock_irqrestore(&task_group_lock, flags);
10425 online_fair_sched_group(tg);
10428 /* rcu callback to free various structures associated with a task group */
10429 static void sched_unregister_group_rcu(struct rcu_head *rhp)
10431 /* Now it should be safe to free those cfs_rqs: */
10432 sched_unregister_group(container_of(rhp, struct task_group, rcu));
10435 void sched_destroy_group(struct task_group *tg)
10437 /* Wait for possible concurrent references to cfs_rqs complete: */
10438 call_rcu(&tg->rcu, sched_unregister_group_rcu);
10441 void sched_release_group(struct task_group *tg)
10443 unsigned long flags;
10446 * Unlink first, to avoid walk_tg_tree_from() from finding us (via
10447 * sched_cfs_period_timer()).
10449 * For this to be effective, we have to wait for all pending users of
10450 * this task group to leave their RCU critical section to ensure no new
10451 * user will see our dying task group any more. Specifically ensure
10452 * that tg_unthrottle_up() won't add decayed cfs_rq's to it.
10454 * We therefore defer calling unregister_fair_sched_group() to
10455 * sched_unregister_group() which is guarantied to get called only after the
10456 * current RCU grace period has expired.
10458 spin_lock_irqsave(&task_group_lock, flags);
10459 list_del_rcu(&tg->list);
10460 list_del_rcu(&tg->siblings);
10461 spin_unlock_irqrestore(&task_group_lock, flags);
10464 static struct task_group *sched_get_task_group(struct task_struct *tsk)
10466 struct task_group *tg;
10469 * All callers are synchronized by task_rq_lock(); we do not use RCU
10470 * which is pointless here. Thus, we pass "true" to task_css_check()
10471 * to prevent lockdep warnings.
10473 tg = container_of(task_css_check(tsk, cpu_cgrp_id, true),
10474 struct task_group, css);
10475 tg = autogroup_task_group(tsk, tg);
10480 static void sched_change_group(struct task_struct *tsk, struct task_group *group)
10482 tsk->sched_task_group = group;
10484 #ifdef CONFIG_FAIR_GROUP_SCHED
10485 if (tsk->sched_class->task_change_group)
10486 tsk->sched_class->task_change_group(tsk);
10489 set_task_rq(tsk, task_cpu(tsk));
10493 * Change task's runqueue when it moves between groups.
10495 * The caller of this function should have put the task in its new group by
10496 * now. This function just updates tsk->se.cfs_rq and tsk->se.parent to reflect
10499 void sched_move_task(struct task_struct *tsk)
10501 int queued, running, queue_flags =
10502 DEQUEUE_SAVE | DEQUEUE_MOVE | DEQUEUE_NOCLOCK;
10503 struct task_group *group;
10504 struct rq_flags rf;
10507 rq = task_rq_lock(tsk, &rf);
10509 * Esp. with SCHED_AUTOGROUP enabled it is possible to get superfluous
10512 group = sched_get_task_group(tsk);
10513 if (group == tsk->sched_task_group)
10516 update_rq_clock(rq);
10518 running = task_current(rq, tsk);
10519 queued = task_on_rq_queued(tsk);
10522 dequeue_task(rq, tsk, queue_flags);
10524 put_prev_task(rq, tsk);
10526 sched_change_group(tsk, group);
10529 enqueue_task(rq, tsk, queue_flags);
10531 set_next_task(rq, tsk);
10533 * After changing group, the running task may have joined a
10534 * throttled one but it's still the running task. Trigger a
10535 * resched to make sure that task can still run.
10541 task_rq_unlock(rq, tsk, &rf);
10544 static inline struct task_group *css_tg(struct cgroup_subsys_state *css)
10546 return css ? container_of(css, struct task_group, css) : NULL;
10549 static struct cgroup_subsys_state *
10550 cpu_cgroup_css_alloc(struct cgroup_subsys_state *parent_css)
10552 struct task_group *parent = css_tg(parent_css);
10553 struct task_group *tg;
10556 /* This is early initialization for the top cgroup */
10557 return &root_task_group.css;
10560 tg = sched_create_group(parent);
10562 return ERR_PTR(-ENOMEM);
10567 /* Expose task group only after completing cgroup initialization */
10568 static int cpu_cgroup_css_online(struct cgroup_subsys_state *css)
10570 struct task_group *tg = css_tg(css);
10571 struct task_group *parent = css_tg(css->parent);
10574 sched_online_group(tg, parent);
10576 #ifdef CONFIG_UCLAMP_TASK_GROUP
10577 /* Propagate the effective uclamp value for the new group */
10578 mutex_lock(&uclamp_mutex);
10580 cpu_util_update_eff(css);
10582 mutex_unlock(&uclamp_mutex);
10588 static void cpu_cgroup_css_released(struct cgroup_subsys_state *css)
10590 struct task_group *tg = css_tg(css);
10592 sched_release_group(tg);
10595 static void cpu_cgroup_css_free(struct cgroup_subsys_state *css)
10597 struct task_group *tg = css_tg(css);
10600 * Relies on the RCU grace period between css_released() and this.
10602 sched_unregister_group(tg);
10605 #ifdef CONFIG_RT_GROUP_SCHED
10606 static int cpu_cgroup_can_attach(struct cgroup_taskset *tset)
10608 struct task_struct *task;
10609 struct cgroup_subsys_state *css;
10611 cgroup_taskset_for_each(task, css, tset) {
10612 if (!sched_rt_can_attach(css_tg(css), task))
10619 static void cpu_cgroup_attach(struct cgroup_taskset *tset)
10621 struct task_struct *task;
10622 struct cgroup_subsys_state *css;
10624 cgroup_taskset_for_each(task, css, tset)
10625 sched_move_task(task);
10628 #ifdef CONFIG_UCLAMP_TASK_GROUP
10629 static void cpu_util_update_eff(struct cgroup_subsys_state *css)
10631 struct cgroup_subsys_state *top_css = css;
10632 struct uclamp_se *uc_parent = NULL;
10633 struct uclamp_se *uc_se = NULL;
10634 unsigned int eff[UCLAMP_CNT];
10635 enum uclamp_id clamp_id;
10636 unsigned int clamps;
10638 lockdep_assert_held(&uclamp_mutex);
10639 SCHED_WARN_ON(!rcu_read_lock_held());
10641 css_for_each_descendant_pre(css, top_css) {
10642 uc_parent = css_tg(css)->parent
10643 ? css_tg(css)->parent->uclamp : NULL;
10645 for_each_clamp_id(clamp_id) {
10646 /* Assume effective clamps matches requested clamps */
10647 eff[clamp_id] = css_tg(css)->uclamp_req[clamp_id].value;
10648 /* Cap effective clamps with parent's effective clamps */
10650 eff[clamp_id] > uc_parent[clamp_id].value) {
10651 eff[clamp_id] = uc_parent[clamp_id].value;
10654 /* Ensure protection is always capped by limit */
10655 eff[UCLAMP_MIN] = min(eff[UCLAMP_MIN], eff[UCLAMP_MAX]);
10657 /* Propagate most restrictive effective clamps */
10659 uc_se = css_tg(css)->uclamp;
10660 for_each_clamp_id(clamp_id) {
10661 if (eff[clamp_id] == uc_se[clamp_id].value)
10663 uc_se[clamp_id].value = eff[clamp_id];
10664 uc_se[clamp_id].bucket_id = uclamp_bucket_id(eff[clamp_id]);
10665 clamps |= (0x1 << clamp_id);
10668 css = css_rightmost_descendant(css);
10672 /* Immediately update descendants RUNNABLE tasks */
10673 uclamp_update_active_tasks(css);
10678 * Integer 10^N with a given N exponent by casting to integer the literal "1eN"
10679 * C expression. Since there is no way to convert a macro argument (N) into a
10680 * character constant, use two levels of macros.
10682 #define _POW10(exp) ((unsigned int)1e##exp)
10683 #define POW10(exp) _POW10(exp)
10685 struct uclamp_request {
10686 #define UCLAMP_PERCENT_SHIFT 2
10687 #define UCLAMP_PERCENT_SCALE (100 * POW10(UCLAMP_PERCENT_SHIFT))
10693 static inline struct uclamp_request
10694 capacity_from_percent(char *buf)
10696 struct uclamp_request req = {
10697 .percent = UCLAMP_PERCENT_SCALE,
10698 .util = SCHED_CAPACITY_SCALE,
10703 if (strcmp(buf, "max")) {
10704 req.ret = cgroup_parse_float(buf, UCLAMP_PERCENT_SHIFT,
10708 if ((u64)req.percent > UCLAMP_PERCENT_SCALE) {
10713 req.util = req.percent << SCHED_CAPACITY_SHIFT;
10714 req.util = DIV_ROUND_CLOSEST_ULL(req.util, UCLAMP_PERCENT_SCALE);
10720 static ssize_t cpu_uclamp_write(struct kernfs_open_file *of, char *buf,
10721 size_t nbytes, loff_t off,
10722 enum uclamp_id clamp_id)
10724 struct uclamp_request req;
10725 struct task_group *tg;
10727 req = capacity_from_percent(buf);
10731 static_branch_enable(&sched_uclamp_used);
10733 mutex_lock(&uclamp_mutex);
10736 tg = css_tg(of_css(of));
10737 if (tg->uclamp_req[clamp_id].value != req.util)
10738 uclamp_se_set(&tg->uclamp_req[clamp_id], req.util, false);
10741 * Because of not recoverable conversion rounding we keep track of the
10742 * exact requested value
10744 tg->uclamp_pct[clamp_id] = req.percent;
10746 /* Update effective clamps to track the most restrictive value */
10747 cpu_util_update_eff(of_css(of));
10750 mutex_unlock(&uclamp_mutex);
10755 static ssize_t cpu_uclamp_min_write(struct kernfs_open_file *of,
10756 char *buf, size_t nbytes,
10759 return cpu_uclamp_write(of, buf, nbytes, off, UCLAMP_MIN);
10762 static ssize_t cpu_uclamp_max_write(struct kernfs_open_file *of,
10763 char *buf, size_t nbytes,
10766 return cpu_uclamp_write(of, buf, nbytes, off, UCLAMP_MAX);
10769 static inline void cpu_uclamp_print(struct seq_file *sf,
10770 enum uclamp_id clamp_id)
10772 struct task_group *tg;
10778 tg = css_tg(seq_css(sf));
10779 util_clamp = tg->uclamp_req[clamp_id].value;
10782 if (util_clamp == SCHED_CAPACITY_SCALE) {
10783 seq_puts(sf, "max\n");
10787 percent = tg->uclamp_pct[clamp_id];
10788 percent = div_u64_rem(percent, POW10(UCLAMP_PERCENT_SHIFT), &rem);
10789 seq_printf(sf, "%llu.%0*u\n", percent, UCLAMP_PERCENT_SHIFT, rem);
10792 static int cpu_uclamp_min_show(struct seq_file *sf, void *v)
10794 cpu_uclamp_print(sf, UCLAMP_MIN);
10798 static int cpu_uclamp_max_show(struct seq_file *sf, void *v)
10800 cpu_uclamp_print(sf, UCLAMP_MAX);
10803 #endif /* CONFIG_UCLAMP_TASK_GROUP */
10805 #ifdef CONFIG_FAIR_GROUP_SCHED
10806 static int cpu_shares_write_u64(struct cgroup_subsys_state *css,
10807 struct cftype *cftype, u64 shareval)
10809 if (shareval > scale_load_down(ULONG_MAX))
10810 shareval = MAX_SHARES;
10811 return sched_group_set_shares(css_tg(css), scale_load(shareval));
10814 static u64 cpu_shares_read_u64(struct cgroup_subsys_state *css,
10815 struct cftype *cft)
10817 struct task_group *tg = css_tg(css);
10819 return (u64) scale_load_down(tg->shares);
10822 #ifdef CONFIG_CFS_BANDWIDTH
10823 static DEFINE_MUTEX(cfs_constraints_mutex);
10825 const u64 max_cfs_quota_period = 1 * NSEC_PER_SEC; /* 1s */
10826 static const u64 min_cfs_quota_period = 1 * NSEC_PER_MSEC; /* 1ms */
10827 /* More than 203 days if BW_SHIFT equals 20. */
10828 static const u64 max_cfs_runtime = MAX_BW * NSEC_PER_USEC;
10830 static int __cfs_schedulable(struct task_group *tg, u64 period, u64 runtime);
10832 static int tg_set_cfs_bandwidth(struct task_group *tg, u64 period, u64 quota,
10835 int i, ret = 0, runtime_enabled, runtime_was_enabled;
10836 struct cfs_bandwidth *cfs_b = &tg->cfs_bandwidth;
10838 if (tg == &root_task_group)
10842 * Ensure we have at some amount of bandwidth every period. This is
10843 * to prevent reaching a state of large arrears when throttled via
10844 * entity_tick() resulting in prolonged exit starvation.
10846 if (quota < min_cfs_quota_period || period < min_cfs_quota_period)
10850 * Likewise, bound things on the other side by preventing insane quota
10851 * periods. This also allows us to normalize in computing quota
10854 if (period > max_cfs_quota_period)
10858 * Bound quota to defend quota against overflow during bandwidth shift.
10860 if (quota != RUNTIME_INF && quota > max_cfs_runtime)
10863 if (quota != RUNTIME_INF && (burst > quota ||
10864 burst + quota > max_cfs_runtime))
10868 * Prevent race between setting of cfs_rq->runtime_enabled and
10869 * unthrottle_offline_cfs_rqs().
10871 guard(cpus_read_lock)();
10872 guard(mutex)(&cfs_constraints_mutex);
10874 ret = __cfs_schedulable(tg, period, quota);
10878 runtime_enabled = quota != RUNTIME_INF;
10879 runtime_was_enabled = cfs_b->quota != RUNTIME_INF;
10881 * If we need to toggle cfs_bandwidth_used, off->on must occur
10882 * before making related changes, and on->off must occur afterwards
10884 if (runtime_enabled && !runtime_was_enabled)
10885 cfs_bandwidth_usage_inc();
10887 scoped_guard (raw_spinlock_irq, &cfs_b->lock) {
10888 cfs_b->period = ns_to_ktime(period);
10889 cfs_b->quota = quota;
10890 cfs_b->burst = burst;
10892 __refill_cfs_bandwidth_runtime(cfs_b);
10895 * Restart the period timer (if active) to handle new
10898 if (runtime_enabled)
10899 start_cfs_bandwidth(cfs_b);
10902 for_each_online_cpu(i) {
10903 struct cfs_rq *cfs_rq = tg->cfs_rq[i];
10904 struct rq *rq = cfs_rq->rq;
10906 guard(rq_lock_irq)(rq);
10907 cfs_rq->runtime_enabled = runtime_enabled;
10908 cfs_rq->runtime_remaining = 0;
10910 if (cfs_rq->throttled)
10911 unthrottle_cfs_rq(cfs_rq);
10914 if (runtime_was_enabled && !runtime_enabled)
10915 cfs_bandwidth_usage_dec();
10920 static int tg_set_cfs_quota(struct task_group *tg, long cfs_quota_us)
10922 u64 quota, period, burst;
10924 period = ktime_to_ns(tg->cfs_bandwidth.period);
10925 burst = tg->cfs_bandwidth.burst;
10926 if (cfs_quota_us < 0)
10927 quota = RUNTIME_INF;
10928 else if ((u64)cfs_quota_us <= U64_MAX / NSEC_PER_USEC)
10929 quota = (u64)cfs_quota_us * NSEC_PER_USEC;
10933 return tg_set_cfs_bandwidth(tg, period, quota, burst);
10936 static long tg_get_cfs_quota(struct task_group *tg)
10940 if (tg->cfs_bandwidth.quota == RUNTIME_INF)
10943 quota_us = tg->cfs_bandwidth.quota;
10944 do_div(quota_us, NSEC_PER_USEC);
10949 static int tg_set_cfs_period(struct task_group *tg, long cfs_period_us)
10951 u64 quota, period, burst;
10953 if ((u64)cfs_period_us > U64_MAX / NSEC_PER_USEC)
10956 period = (u64)cfs_period_us * NSEC_PER_USEC;
10957 quota = tg->cfs_bandwidth.quota;
10958 burst = tg->cfs_bandwidth.burst;
10960 return tg_set_cfs_bandwidth(tg, period, quota, burst);
10963 static long tg_get_cfs_period(struct task_group *tg)
10967 cfs_period_us = ktime_to_ns(tg->cfs_bandwidth.period);
10968 do_div(cfs_period_us, NSEC_PER_USEC);
10970 return cfs_period_us;
10973 static int tg_set_cfs_burst(struct task_group *tg, long cfs_burst_us)
10975 u64 quota, period, burst;
10977 if ((u64)cfs_burst_us > U64_MAX / NSEC_PER_USEC)
10980 burst = (u64)cfs_burst_us * NSEC_PER_USEC;
10981 period = ktime_to_ns(tg->cfs_bandwidth.period);
10982 quota = tg->cfs_bandwidth.quota;
10984 return tg_set_cfs_bandwidth(tg, period, quota, burst);
10987 static long tg_get_cfs_burst(struct task_group *tg)
10991 burst_us = tg->cfs_bandwidth.burst;
10992 do_div(burst_us, NSEC_PER_USEC);
10997 static s64 cpu_cfs_quota_read_s64(struct cgroup_subsys_state *css,
10998 struct cftype *cft)
11000 return tg_get_cfs_quota(css_tg(css));
11003 static int cpu_cfs_quota_write_s64(struct cgroup_subsys_state *css,
11004 struct cftype *cftype, s64 cfs_quota_us)
11006 return tg_set_cfs_quota(css_tg(css), cfs_quota_us);
11009 static u64 cpu_cfs_period_read_u64(struct cgroup_subsys_state *css,
11010 struct cftype *cft)
11012 return tg_get_cfs_period(css_tg(css));
11015 static int cpu_cfs_period_write_u64(struct cgroup_subsys_state *css,
11016 struct cftype *cftype, u64 cfs_period_us)
11018 return tg_set_cfs_period(css_tg(css), cfs_period_us);
11021 static u64 cpu_cfs_burst_read_u64(struct cgroup_subsys_state *css,
11022 struct cftype *cft)
11024 return tg_get_cfs_burst(css_tg(css));
11027 static int cpu_cfs_burst_write_u64(struct cgroup_subsys_state *css,
11028 struct cftype *cftype, u64 cfs_burst_us)
11030 return tg_set_cfs_burst(css_tg(css), cfs_burst_us);
11033 struct cfs_schedulable_data {
11034 struct task_group *tg;
11039 * normalize group quota/period to be quota/max_period
11040 * note: units are usecs
11042 static u64 normalize_cfs_quota(struct task_group *tg,
11043 struct cfs_schedulable_data *d)
11048 period = d->period;
11051 period = tg_get_cfs_period(tg);
11052 quota = tg_get_cfs_quota(tg);
11055 /* note: these should typically be equivalent */
11056 if (quota == RUNTIME_INF || quota == -1)
11057 return RUNTIME_INF;
11059 return to_ratio(period, quota);
11062 static int tg_cfs_schedulable_down(struct task_group *tg, void *data)
11064 struct cfs_schedulable_data *d = data;
11065 struct cfs_bandwidth *cfs_b = &tg->cfs_bandwidth;
11066 s64 quota = 0, parent_quota = -1;
11069 quota = RUNTIME_INF;
11071 struct cfs_bandwidth *parent_b = &tg->parent->cfs_bandwidth;
11073 quota = normalize_cfs_quota(tg, d);
11074 parent_quota = parent_b->hierarchical_quota;
11077 * Ensure max(child_quota) <= parent_quota. On cgroup2,
11078 * always take the non-RUNTIME_INF min. On cgroup1, only
11079 * inherit when no limit is set. In both cases this is used
11080 * by the scheduler to determine if a given CFS task has a
11081 * bandwidth constraint at some higher level.
11083 if (cgroup_subsys_on_dfl(cpu_cgrp_subsys)) {
11084 if (quota == RUNTIME_INF)
11085 quota = parent_quota;
11086 else if (parent_quota != RUNTIME_INF)
11087 quota = min(quota, parent_quota);
11089 if (quota == RUNTIME_INF)
11090 quota = parent_quota;
11091 else if (parent_quota != RUNTIME_INF && quota > parent_quota)
11095 cfs_b->hierarchical_quota = quota;
11100 static int __cfs_schedulable(struct task_group *tg, u64 period, u64 quota)
11103 struct cfs_schedulable_data data = {
11109 if (quota != RUNTIME_INF) {
11110 do_div(data.period, NSEC_PER_USEC);
11111 do_div(data.quota, NSEC_PER_USEC);
11115 ret = walk_tg_tree(tg_cfs_schedulable_down, tg_nop, &data);
11121 static int cpu_cfs_stat_show(struct seq_file *sf, void *v)
11123 struct task_group *tg = css_tg(seq_css(sf));
11124 struct cfs_bandwidth *cfs_b = &tg->cfs_bandwidth;
11126 seq_printf(sf, "nr_periods %d\n", cfs_b->nr_periods);
11127 seq_printf(sf, "nr_throttled %d\n", cfs_b->nr_throttled);
11128 seq_printf(sf, "throttled_time %llu\n", cfs_b->throttled_time);
11130 if (schedstat_enabled() && tg != &root_task_group) {
11131 struct sched_statistics *stats;
11135 for_each_possible_cpu(i) {
11136 stats = __schedstats_from_se(tg->se[i]);
11137 ws += schedstat_val(stats->wait_sum);
11140 seq_printf(sf, "wait_sum %llu\n", ws);
11143 seq_printf(sf, "nr_bursts %d\n", cfs_b->nr_burst);
11144 seq_printf(sf, "burst_time %llu\n", cfs_b->burst_time);
11149 static u64 throttled_time_self(struct task_group *tg)
11154 for_each_possible_cpu(i) {
11155 total += READ_ONCE(tg->cfs_rq[i]->throttled_clock_self_time);
11161 static int cpu_cfs_local_stat_show(struct seq_file *sf, void *v)
11163 struct task_group *tg = css_tg(seq_css(sf));
11165 seq_printf(sf, "throttled_time %llu\n", throttled_time_self(tg));
11169 #endif /* CONFIG_CFS_BANDWIDTH */
11170 #endif /* CONFIG_FAIR_GROUP_SCHED */
11172 #ifdef CONFIG_RT_GROUP_SCHED
11173 static int cpu_rt_runtime_write(struct cgroup_subsys_state *css,
11174 struct cftype *cft, s64 val)
11176 return sched_group_set_rt_runtime(css_tg(css), val);
11179 static s64 cpu_rt_runtime_read(struct cgroup_subsys_state *css,
11180 struct cftype *cft)
11182 return sched_group_rt_runtime(css_tg(css));
11185 static int cpu_rt_period_write_uint(struct cgroup_subsys_state *css,
11186 struct cftype *cftype, u64 rt_period_us)
11188 return sched_group_set_rt_period(css_tg(css), rt_period_us);
11191 static u64 cpu_rt_period_read_uint(struct cgroup_subsys_state *css,
11192 struct cftype *cft)
11194 return sched_group_rt_period(css_tg(css));
11196 #endif /* CONFIG_RT_GROUP_SCHED */
11198 #ifdef CONFIG_FAIR_GROUP_SCHED
11199 static s64 cpu_idle_read_s64(struct cgroup_subsys_state *css,
11200 struct cftype *cft)
11202 return css_tg(css)->idle;
11205 static int cpu_idle_write_s64(struct cgroup_subsys_state *css,
11206 struct cftype *cft, s64 idle)
11208 return sched_group_set_idle(css_tg(css), idle);
11212 static struct cftype cpu_legacy_files[] = {
11213 #ifdef CONFIG_FAIR_GROUP_SCHED
11216 .read_u64 = cpu_shares_read_u64,
11217 .write_u64 = cpu_shares_write_u64,
11221 .read_s64 = cpu_idle_read_s64,
11222 .write_s64 = cpu_idle_write_s64,
11225 #ifdef CONFIG_CFS_BANDWIDTH
11227 .name = "cfs_quota_us",
11228 .read_s64 = cpu_cfs_quota_read_s64,
11229 .write_s64 = cpu_cfs_quota_write_s64,
11232 .name = "cfs_period_us",
11233 .read_u64 = cpu_cfs_period_read_u64,
11234 .write_u64 = cpu_cfs_period_write_u64,
11237 .name = "cfs_burst_us",
11238 .read_u64 = cpu_cfs_burst_read_u64,
11239 .write_u64 = cpu_cfs_burst_write_u64,
11243 .seq_show = cpu_cfs_stat_show,
11246 .name = "stat.local",
11247 .seq_show = cpu_cfs_local_stat_show,
11250 #ifdef CONFIG_RT_GROUP_SCHED
11252 .name = "rt_runtime_us",
11253 .read_s64 = cpu_rt_runtime_read,
11254 .write_s64 = cpu_rt_runtime_write,
11257 .name = "rt_period_us",
11258 .read_u64 = cpu_rt_period_read_uint,
11259 .write_u64 = cpu_rt_period_write_uint,
11262 #ifdef CONFIG_UCLAMP_TASK_GROUP
11264 .name = "uclamp.min",
11265 .flags = CFTYPE_NOT_ON_ROOT,
11266 .seq_show = cpu_uclamp_min_show,
11267 .write = cpu_uclamp_min_write,
11270 .name = "uclamp.max",
11271 .flags = CFTYPE_NOT_ON_ROOT,
11272 .seq_show = cpu_uclamp_max_show,
11273 .write = cpu_uclamp_max_write,
11276 { } /* Terminate */
11279 static int cpu_extra_stat_show(struct seq_file *sf,
11280 struct cgroup_subsys_state *css)
11282 #ifdef CONFIG_CFS_BANDWIDTH
11284 struct task_group *tg = css_tg(css);
11285 struct cfs_bandwidth *cfs_b = &tg->cfs_bandwidth;
11286 u64 throttled_usec, burst_usec;
11288 throttled_usec = cfs_b->throttled_time;
11289 do_div(throttled_usec, NSEC_PER_USEC);
11290 burst_usec = cfs_b->burst_time;
11291 do_div(burst_usec, NSEC_PER_USEC);
11293 seq_printf(sf, "nr_periods %d\n"
11294 "nr_throttled %d\n"
11295 "throttled_usec %llu\n"
11297 "burst_usec %llu\n",
11298 cfs_b->nr_periods, cfs_b->nr_throttled,
11299 throttled_usec, cfs_b->nr_burst, burst_usec);
11305 static int cpu_local_stat_show(struct seq_file *sf,
11306 struct cgroup_subsys_state *css)
11308 #ifdef CONFIG_CFS_BANDWIDTH
11310 struct task_group *tg = css_tg(css);
11311 u64 throttled_self_usec;
11313 throttled_self_usec = throttled_time_self(tg);
11314 do_div(throttled_self_usec, NSEC_PER_USEC);
11316 seq_printf(sf, "throttled_usec %llu\n",
11317 throttled_self_usec);
11323 #ifdef CONFIG_FAIR_GROUP_SCHED
11324 static u64 cpu_weight_read_u64(struct cgroup_subsys_state *css,
11325 struct cftype *cft)
11327 struct task_group *tg = css_tg(css);
11328 u64 weight = scale_load_down(tg->shares);
11330 return DIV_ROUND_CLOSEST_ULL(weight * CGROUP_WEIGHT_DFL, 1024);
11333 static int cpu_weight_write_u64(struct cgroup_subsys_state *css,
11334 struct cftype *cft, u64 weight)
11337 * cgroup weight knobs should use the common MIN, DFL and MAX
11338 * values which are 1, 100 and 10000 respectively. While it loses
11339 * a bit of range on both ends, it maps pretty well onto the shares
11340 * value used by scheduler and the round-trip conversions preserve
11341 * the original value over the entire range.
11343 if (weight < CGROUP_WEIGHT_MIN || weight > CGROUP_WEIGHT_MAX)
11346 weight = DIV_ROUND_CLOSEST_ULL(weight * 1024, CGROUP_WEIGHT_DFL);
11348 return sched_group_set_shares(css_tg(css), scale_load(weight));
11351 static s64 cpu_weight_nice_read_s64(struct cgroup_subsys_state *css,
11352 struct cftype *cft)
11354 unsigned long weight = scale_load_down(css_tg(css)->shares);
11355 int last_delta = INT_MAX;
11358 /* find the closest nice value to the current weight */
11359 for (prio = 0; prio < ARRAY_SIZE(sched_prio_to_weight); prio++) {
11360 delta = abs(sched_prio_to_weight[prio] - weight);
11361 if (delta >= last_delta)
11363 last_delta = delta;
11366 return PRIO_TO_NICE(prio - 1 + MAX_RT_PRIO);
11369 static int cpu_weight_nice_write_s64(struct cgroup_subsys_state *css,
11370 struct cftype *cft, s64 nice)
11372 unsigned long weight;
11375 if (nice < MIN_NICE || nice > MAX_NICE)
11378 idx = NICE_TO_PRIO(nice) - MAX_RT_PRIO;
11379 idx = array_index_nospec(idx, 40);
11380 weight = sched_prio_to_weight[idx];
11382 return sched_group_set_shares(css_tg(css), scale_load(weight));
11386 static void __maybe_unused cpu_period_quota_print(struct seq_file *sf,
11387 long period, long quota)
11390 seq_puts(sf, "max");
11392 seq_printf(sf, "%ld", quota);
11394 seq_printf(sf, " %ld\n", period);
11397 /* caller should put the current value in *@periodp before calling */
11398 static int __maybe_unused cpu_period_quota_parse(char *buf,
11399 u64 *periodp, u64 *quotap)
11401 char tok[21]; /* U64_MAX */
11403 if (sscanf(buf, "%20s %llu", tok, periodp) < 1)
11406 *periodp *= NSEC_PER_USEC;
11408 if (sscanf(tok, "%llu", quotap))
11409 *quotap *= NSEC_PER_USEC;
11410 else if (!strcmp(tok, "max"))
11411 *quotap = RUNTIME_INF;
11418 #ifdef CONFIG_CFS_BANDWIDTH
11419 static int cpu_max_show(struct seq_file *sf, void *v)
11421 struct task_group *tg = css_tg(seq_css(sf));
11423 cpu_period_quota_print(sf, tg_get_cfs_period(tg), tg_get_cfs_quota(tg));
11427 static ssize_t cpu_max_write(struct kernfs_open_file *of,
11428 char *buf, size_t nbytes, loff_t off)
11430 struct task_group *tg = css_tg(of_css(of));
11431 u64 period = tg_get_cfs_period(tg);
11432 u64 burst = tg_get_cfs_burst(tg);
11436 ret = cpu_period_quota_parse(buf, &period, "a);
11438 ret = tg_set_cfs_bandwidth(tg, period, quota, burst);
11439 return ret ?: nbytes;
11443 static struct cftype cpu_files[] = {
11444 #ifdef CONFIG_FAIR_GROUP_SCHED
11447 .flags = CFTYPE_NOT_ON_ROOT,
11448 .read_u64 = cpu_weight_read_u64,
11449 .write_u64 = cpu_weight_write_u64,
11452 .name = "weight.nice",
11453 .flags = CFTYPE_NOT_ON_ROOT,
11454 .read_s64 = cpu_weight_nice_read_s64,
11455 .write_s64 = cpu_weight_nice_write_s64,
11459 .flags = CFTYPE_NOT_ON_ROOT,
11460 .read_s64 = cpu_idle_read_s64,
11461 .write_s64 = cpu_idle_write_s64,
11464 #ifdef CONFIG_CFS_BANDWIDTH
11467 .flags = CFTYPE_NOT_ON_ROOT,
11468 .seq_show = cpu_max_show,
11469 .write = cpu_max_write,
11472 .name = "max.burst",
11473 .flags = CFTYPE_NOT_ON_ROOT,
11474 .read_u64 = cpu_cfs_burst_read_u64,
11475 .write_u64 = cpu_cfs_burst_write_u64,
11478 #ifdef CONFIG_UCLAMP_TASK_GROUP
11480 .name = "uclamp.min",
11481 .flags = CFTYPE_NOT_ON_ROOT,
11482 .seq_show = cpu_uclamp_min_show,
11483 .write = cpu_uclamp_min_write,
11486 .name = "uclamp.max",
11487 .flags = CFTYPE_NOT_ON_ROOT,
11488 .seq_show = cpu_uclamp_max_show,
11489 .write = cpu_uclamp_max_write,
11492 { } /* terminate */
11495 struct cgroup_subsys cpu_cgrp_subsys = {
11496 .css_alloc = cpu_cgroup_css_alloc,
11497 .css_online = cpu_cgroup_css_online,
11498 .css_released = cpu_cgroup_css_released,
11499 .css_free = cpu_cgroup_css_free,
11500 .css_extra_stat_show = cpu_extra_stat_show,
11501 .css_local_stat_show = cpu_local_stat_show,
11502 #ifdef CONFIG_RT_GROUP_SCHED
11503 .can_attach = cpu_cgroup_can_attach,
11505 .attach = cpu_cgroup_attach,
11506 .legacy_cftypes = cpu_legacy_files,
11507 .dfl_cftypes = cpu_files,
11508 .early_init = true,
11512 #endif /* CONFIG_CGROUP_SCHED */
11514 void dump_cpu_task(int cpu)
11516 if (cpu == smp_processor_id() && in_hardirq()) {
11517 struct pt_regs *regs;
11519 regs = get_irq_regs();
11526 if (trigger_single_cpu_backtrace(cpu))
11529 pr_info("Task dump for CPU %d:\n", cpu);
11530 sched_show_task(cpu_curr(cpu));
11534 * Nice levels are multiplicative, with a gentle 10% change for every
11535 * nice level changed. I.e. when a CPU-bound task goes from nice 0 to
11536 * nice 1, it will get ~10% less CPU time than another CPU-bound task
11537 * that remained on nice 0.
11539 * The "10% effect" is relative and cumulative: from _any_ nice level,
11540 * if you go up 1 level, it's -10% CPU usage, if you go down 1 level
11541 * it's +10% CPU usage. (to achieve that we use a multiplier of 1.25.
11542 * If a task goes up by ~10% and another task goes down by ~10% then
11543 * the relative distance between them is ~25%.)
11545 const int sched_prio_to_weight[40] = {
11546 /* -20 */ 88761, 71755, 56483, 46273, 36291,
11547 /* -15 */ 29154, 23254, 18705, 14949, 11916,
11548 /* -10 */ 9548, 7620, 6100, 4904, 3906,
11549 /* -5 */ 3121, 2501, 1991, 1586, 1277,
11550 /* 0 */ 1024, 820, 655, 526, 423,
11551 /* 5 */ 335, 272, 215, 172, 137,
11552 /* 10 */ 110, 87, 70, 56, 45,
11553 /* 15 */ 36, 29, 23, 18, 15,
11557 * Inverse (2^32/x) values of the sched_prio_to_weight[] array, precalculated.
11559 * In cases where the weight does not change often, we can use the
11560 * precalculated inverse to speed up arithmetics by turning divisions
11561 * into multiplications:
11563 const u32 sched_prio_to_wmult[40] = {
11564 /* -20 */ 48388, 59856, 76040, 92818, 118348,
11565 /* -15 */ 147320, 184698, 229616, 287308, 360437,
11566 /* -10 */ 449829, 563644, 704093, 875809, 1099582,
11567 /* -5 */ 1376151, 1717300, 2157191, 2708050, 3363326,
11568 /* 0 */ 4194304, 5237765, 6557202, 8165337, 10153587,
11569 /* 5 */ 12820798, 15790321, 19976592, 24970740, 31350126,
11570 /* 10 */ 39045157, 49367440, 61356676, 76695844, 95443717,
11571 /* 15 */ 119304647, 148102320, 186737708, 238609294, 286331153,
11574 void call_trace_sched_update_nr_running(struct rq *rq, int count)
11576 trace_sched_update_nr_running_tp(rq, count);
11579 #ifdef CONFIG_SCHED_MM_CID
11582 * @cid_lock: Guarantee forward-progress of cid allocation.
11584 * Concurrency ID allocation within a bitmap is mostly lock-free. The cid_lock
11585 * is only used when contention is detected by the lock-free allocation so
11586 * forward progress can be guaranteed.
11588 DEFINE_RAW_SPINLOCK(cid_lock);
11591 * @use_cid_lock: Select cid allocation behavior: lock-free vs spinlock.
11593 * When @use_cid_lock is 0, the cid allocation is lock-free. When contention is
11594 * detected, it is set to 1 to ensure that all newly coming allocations are
11595 * serialized by @cid_lock until the allocation which detected contention
11596 * completes and sets @use_cid_lock back to 0. This guarantees forward progress
11597 * of a cid allocation.
11602 * mm_cid remote-clear implements a lock-free algorithm to clear per-mm/cpu cid
11603 * concurrently with respect to the execution of the source runqueue context
11606 * There is one basic properties we want to guarantee here:
11608 * (1) Remote-clear should _never_ mark a per-cpu cid UNSET when it is actively
11609 * used by a task. That would lead to concurrent allocation of the cid and
11610 * userspace corruption.
11612 * Provide this guarantee by introducing a Dekker memory ordering to guarantee
11613 * that a pair of loads observe at least one of a pair of stores, which can be
11622 * Which guarantees that x==0 && y==0 is impossible. But rather than using
11623 * values 0 and 1, this algorithm cares about specific state transitions of the
11624 * runqueue current task (as updated by the scheduler context switch), and the
11625 * per-mm/cpu cid value.
11627 * Let's introduce task (Y) which has task->mm == mm and task (N) which has
11628 * task->mm != mm for the rest of the discussion. There are two scheduler state
11629 * transitions on context switch we care about:
11631 * (TSA) Store to rq->curr with transition from (N) to (Y)
11633 * (TSB) Store to rq->curr with transition from (Y) to (N)
11635 * On the remote-clear side, there is one transition we care about:
11637 * (TMA) cmpxchg to *pcpu_cid to set the LAZY flag
11639 * There is also a transition to UNSET state which can be performed from all
11640 * sides (scheduler, remote-clear). It is always performed with a cmpxchg which
11641 * guarantees that only a single thread will succeed:
11643 * (TMB) cmpxchg to *pcpu_cid to mark UNSET
11645 * Just to be clear, what we do _not_ want to happen is a transition to UNSET
11646 * when a thread is actively using the cid (property (1)).
11648 * Let's looks at the relevant combinations of TSA/TSB, and TMA transitions.
11650 * Scenario A) (TSA)+(TMA) (from next task perspective)
11654 * Context switch CS-1 Remote-clear
11655 * - store to rq->curr: (N)->(Y) (TSA) - cmpxchg to *pcpu_id to LAZY (TMA)
11656 * (implied barrier after cmpxchg)
11657 * - switch_mm_cid()
11658 * - memory barrier (see switch_mm_cid()
11659 * comment explaining how this barrier
11660 * is combined with other scheduler
11662 * - mm_cid_get (next)
11663 * - READ_ONCE(*pcpu_cid) - rcu_dereference(src_rq->curr)
11665 * This Dekker ensures that either task (Y) is observed by the
11666 * rcu_dereference() or the LAZY flag is observed by READ_ONCE(), or both are
11669 * If task (Y) store is observed by rcu_dereference(), it means that there is
11670 * still an active task on the cpu. Remote-clear will therefore not transition
11671 * to UNSET, which fulfills property (1).
11673 * If task (Y) is not observed, but the lazy flag is observed by READ_ONCE(),
11674 * it will move its state to UNSET, which clears the percpu cid perhaps
11675 * uselessly (which is not an issue for correctness). Because task (Y) is not
11676 * observed, CPU1 can move ahead to set the state to UNSET. Because moving
11677 * state to UNSET is done with a cmpxchg expecting that the old state has the
11678 * LAZY flag set, only one thread will successfully UNSET.
11680 * If both states (LAZY flag and task (Y)) are observed, the thread on CPU0
11681 * will observe the LAZY flag and transition to UNSET (perhaps uselessly), and
11682 * CPU1 will observe task (Y) and do nothing more, which is fine.
11684 * What we are effectively preventing with this Dekker is a scenario where
11685 * neither LAZY flag nor store (Y) are observed, which would fail property (1)
11686 * because this would UNSET a cid which is actively used.
11689 void sched_mm_cid_migrate_from(struct task_struct *t)
11691 t->migrate_from_cpu = task_cpu(t);
11695 int __sched_mm_cid_migrate_from_fetch_cid(struct rq *src_rq,
11696 struct task_struct *t,
11697 struct mm_cid *src_pcpu_cid)
11699 struct mm_struct *mm = t->mm;
11700 struct task_struct *src_task;
11701 int src_cid, last_mm_cid;
11706 last_mm_cid = t->last_mm_cid;
11708 * If the migrated task has no last cid, or if the current
11709 * task on src rq uses the cid, it means the source cid does not need
11710 * to be moved to the destination cpu.
11712 if (last_mm_cid == -1)
11714 src_cid = READ_ONCE(src_pcpu_cid->cid);
11715 if (!mm_cid_is_valid(src_cid) || last_mm_cid != src_cid)
11719 * If we observe an active task using the mm on this rq, it means we
11720 * are not the last task to be migrated from this cpu for this mm, so
11721 * there is no need to move src_cid to the destination cpu.
11724 src_task = rcu_dereference(src_rq->curr);
11725 if (READ_ONCE(src_task->mm_cid_active) && src_task->mm == mm) {
11727 t->last_mm_cid = -1;
11736 int __sched_mm_cid_migrate_from_try_steal_cid(struct rq *src_rq,
11737 struct task_struct *t,
11738 struct mm_cid *src_pcpu_cid,
11741 struct task_struct *src_task;
11742 struct mm_struct *mm = t->mm;
11749 * Attempt to clear the source cpu cid to move it to the destination
11752 lazy_cid = mm_cid_set_lazy_put(src_cid);
11753 if (!try_cmpxchg(&src_pcpu_cid->cid, &src_cid, lazy_cid))
11757 * The implicit barrier after cmpxchg per-mm/cpu cid before loading
11758 * rq->curr->mm matches the scheduler barrier in context_switch()
11759 * between store to rq->curr and load of prev and next task's
11762 * The implicit barrier after cmpxchg per-mm/cpu cid before loading
11763 * rq->curr->mm_cid_active matches the barrier in
11764 * sched_mm_cid_exit_signals(), sched_mm_cid_before_execve(), and
11765 * sched_mm_cid_after_execve() between store to t->mm_cid_active and
11766 * load of per-mm/cpu cid.
11770 * If we observe an active task using the mm on this rq after setting
11771 * the lazy-put flag, this task will be responsible for transitioning
11772 * from lazy-put flag set to MM_CID_UNSET.
11775 src_task = rcu_dereference(src_rq->curr);
11776 if (READ_ONCE(src_task->mm_cid_active) && src_task->mm == mm) {
11779 * We observed an active task for this mm, there is therefore
11780 * no point in moving this cid to the destination cpu.
11782 t->last_mm_cid = -1;
11788 * The src_cid is unused, so it can be unset.
11790 if (!try_cmpxchg(&src_pcpu_cid->cid, &lazy_cid, MM_CID_UNSET))
11796 * Migration to dst cpu. Called with dst_rq lock held.
11797 * Interrupts are disabled, which keeps the window of cid ownership without the
11798 * source rq lock held small.
11800 void sched_mm_cid_migrate_to(struct rq *dst_rq, struct task_struct *t)
11802 struct mm_cid *src_pcpu_cid, *dst_pcpu_cid;
11803 struct mm_struct *mm = t->mm;
11804 int src_cid, dst_cid, src_cpu;
11807 lockdep_assert_rq_held(dst_rq);
11811 src_cpu = t->migrate_from_cpu;
11812 if (src_cpu == -1) {
11813 t->last_mm_cid = -1;
11817 * Move the src cid if the dst cid is unset. This keeps id
11818 * allocation closest to 0 in cases where few threads migrate around
11821 * If destination cid is already set, we may have to just clear
11822 * the src cid to ensure compactness in frequent migrations
11825 * It is not useful to clear the src cid when the number of threads is
11826 * greater or equal to the number of allowed cpus, because user-space
11827 * can expect that the number of allowed cids can reach the number of
11830 dst_pcpu_cid = per_cpu_ptr(mm->pcpu_cid, cpu_of(dst_rq));
11831 dst_cid = READ_ONCE(dst_pcpu_cid->cid);
11832 if (!mm_cid_is_unset(dst_cid) &&
11833 atomic_read(&mm->mm_users) >= t->nr_cpus_allowed)
11835 src_pcpu_cid = per_cpu_ptr(mm->pcpu_cid, src_cpu);
11836 src_rq = cpu_rq(src_cpu);
11837 src_cid = __sched_mm_cid_migrate_from_fetch_cid(src_rq, t, src_pcpu_cid);
11840 src_cid = __sched_mm_cid_migrate_from_try_steal_cid(src_rq, t, src_pcpu_cid,
11844 if (!mm_cid_is_unset(dst_cid)) {
11845 __mm_cid_put(mm, src_cid);
11848 /* Move src_cid to dst cpu. */
11849 mm_cid_snapshot_time(dst_rq, mm);
11850 WRITE_ONCE(dst_pcpu_cid->cid, src_cid);
11853 static void sched_mm_cid_remote_clear(struct mm_struct *mm, struct mm_cid *pcpu_cid,
11856 struct rq *rq = cpu_rq(cpu);
11857 struct task_struct *t;
11858 unsigned long flags;
11861 cid = READ_ONCE(pcpu_cid->cid);
11862 if (!mm_cid_is_valid(cid))
11866 * Clear the cpu cid if it is set to keep cid allocation compact. If
11867 * there happens to be other tasks left on the source cpu using this
11868 * mm, the next task using this mm will reallocate its cid on context
11871 lazy_cid = mm_cid_set_lazy_put(cid);
11872 if (!try_cmpxchg(&pcpu_cid->cid, &cid, lazy_cid))
11876 * The implicit barrier after cmpxchg per-mm/cpu cid before loading
11877 * rq->curr->mm matches the scheduler barrier in context_switch()
11878 * between store to rq->curr and load of prev and next task's
11881 * The implicit barrier after cmpxchg per-mm/cpu cid before loading
11882 * rq->curr->mm_cid_active matches the barrier in
11883 * sched_mm_cid_exit_signals(), sched_mm_cid_before_execve(), and
11884 * sched_mm_cid_after_execve() between store to t->mm_cid_active and
11885 * load of per-mm/cpu cid.
11889 * If we observe an active task using the mm on this rq after setting
11890 * the lazy-put flag, that task will be responsible for transitioning
11891 * from lazy-put flag set to MM_CID_UNSET.
11894 t = rcu_dereference(rq->curr);
11895 if (READ_ONCE(t->mm_cid_active) && t->mm == mm) {
11902 * The cid is unused, so it can be unset.
11903 * Disable interrupts to keep the window of cid ownership without rq
11906 local_irq_save(flags);
11907 if (try_cmpxchg(&pcpu_cid->cid, &lazy_cid, MM_CID_UNSET))
11908 __mm_cid_put(mm, cid);
11909 local_irq_restore(flags);
11912 static void sched_mm_cid_remote_clear_old(struct mm_struct *mm, int cpu)
11914 struct rq *rq = cpu_rq(cpu);
11915 struct mm_cid *pcpu_cid;
11916 struct task_struct *curr;
11920 * rq->clock load is racy on 32-bit but one spurious clear once in a
11921 * while is irrelevant.
11923 rq_clock = READ_ONCE(rq->clock);
11924 pcpu_cid = per_cpu_ptr(mm->pcpu_cid, cpu);
11927 * In order to take care of infrequently scheduled tasks, bump the time
11928 * snapshot associated with this cid if an active task using the mm is
11929 * observed on this rq.
11932 curr = rcu_dereference(rq->curr);
11933 if (READ_ONCE(curr->mm_cid_active) && curr->mm == mm) {
11934 WRITE_ONCE(pcpu_cid->time, rq_clock);
11940 if (rq_clock < pcpu_cid->time + SCHED_MM_CID_PERIOD_NS)
11942 sched_mm_cid_remote_clear(mm, pcpu_cid, cpu);
11945 static void sched_mm_cid_remote_clear_weight(struct mm_struct *mm, int cpu,
11948 struct mm_cid *pcpu_cid;
11951 pcpu_cid = per_cpu_ptr(mm->pcpu_cid, cpu);
11952 cid = READ_ONCE(pcpu_cid->cid);
11953 if (!mm_cid_is_valid(cid) || cid < weight)
11955 sched_mm_cid_remote_clear(mm, pcpu_cid, cpu);
11958 static void task_mm_cid_work(struct callback_head *work)
11960 unsigned long now = jiffies, old_scan, next_scan;
11961 struct task_struct *t = current;
11962 struct cpumask *cidmask;
11963 struct mm_struct *mm;
11966 SCHED_WARN_ON(t != container_of(work, struct task_struct, cid_work));
11968 work->next = work; /* Prevent double-add */
11969 if (t->flags & PF_EXITING)
11974 old_scan = READ_ONCE(mm->mm_cid_next_scan);
11975 next_scan = now + msecs_to_jiffies(MM_CID_SCAN_DELAY);
11979 res = cmpxchg(&mm->mm_cid_next_scan, old_scan, next_scan);
11980 if (res != old_scan)
11983 old_scan = next_scan;
11985 if (time_before(now, old_scan))
11987 if (!try_cmpxchg(&mm->mm_cid_next_scan, &old_scan, next_scan))
11989 cidmask = mm_cidmask(mm);
11990 /* Clear cids that were not recently used. */
11991 for_each_possible_cpu(cpu)
11992 sched_mm_cid_remote_clear_old(mm, cpu);
11993 weight = cpumask_weight(cidmask);
11995 * Clear cids that are greater or equal to the cidmask weight to
11998 for_each_possible_cpu(cpu)
11999 sched_mm_cid_remote_clear_weight(mm, cpu, weight);
12002 void init_sched_mm_cid(struct task_struct *t)
12004 struct mm_struct *mm = t->mm;
12008 mm_users = atomic_read(&mm->mm_users);
12010 mm->mm_cid_next_scan = jiffies + msecs_to_jiffies(MM_CID_SCAN_DELAY);
12012 t->cid_work.next = &t->cid_work; /* Protect against double add */
12013 init_task_work(&t->cid_work, task_mm_cid_work);
12016 void task_tick_mm_cid(struct rq *rq, struct task_struct *curr)
12018 struct callback_head *work = &curr->cid_work;
12019 unsigned long now = jiffies;
12021 if (!curr->mm || (curr->flags & (PF_EXITING | PF_KTHREAD)) ||
12022 work->next != work)
12024 if (time_before(now, READ_ONCE(curr->mm->mm_cid_next_scan)))
12026 task_work_add(curr, work, TWA_RESUME);
12029 void sched_mm_cid_exit_signals(struct task_struct *t)
12031 struct mm_struct *mm = t->mm;
12032 struct rq_flags rf;
12040 rq_lock_irqsave(rq, &rf);
12041 preempt_enable_no_resched(); /* holding spinlock */
12042 WRITE_ONCE(t->mm_cid_active, 0);
12044 * Store t->mm_cid_active before loading per-mm/cpu cid.
12045 * Matches barrier in sched_mm_cid_remote_clear_old().
12049 t->last_mm_cid = t->mm_cid = -1;
12050 rq_unlock_irqrestore(rq, &rf);
12053 void sched_mm_cid_before_execve(struct task_struct *t)
12055 struct mm_struct *mm = t->mm;
12056 struct rq_flags rf;
12064 rq_lock_irqsave(rq, &rf);
12065 preempt_enable_no_resched(); /* holding spinlock */
12066 WRITE_ONCE(t->mm_cid_active, 0);
12068 * Store t->mm_cid_active before loading per-mm/cpu cid.
12069 * Matches barrier in sched_mm_cid_remote_clear_old().
12073 t->last_mm_cid = t->mm_cid = -1;
12074 rq_unlock_irqrestore(rq, &rf);
12077 void sched_mm_cid_after_execve(struct task_struct *t)
12079 struct mm_struct *mm = t->mm;
12080 struct rq_flags rf;
12088 rq_lock_irqsave(rq, &rf);
12089 preempt_enable_no_resched(); /* holding spinlock */
12090 WRITE_ONCE(t->mm_cid_active, 1);
12092 * Store t->mm_cid_active before loading per-mm/cpu cid.
12093 * Matches barrier in sched_mm_cid_remote_clear_old().
12096 t->last_mm_cid = t->mm_cid = mm_cid_get(rq, mm);
12097 rq_unlock_irqrestore(rq, &rf);
12098 rseq_set_notify_resume(t);
12101 void sched_mm_cid_fork(struct task_struct *t)
12103 WARN_ON_ONCE(!t->mm || t->mm_cid != -1);
12104 t->mm_cid_active = 1;