1 /* Kernel thread helper functions.
2 * Copyright (C) 2004 IBM Corporation, Rusty Russell.
4 * Creation is done via kthreadd, so that we get a clean environment
5 * even if we're invoked from userspace (think modprobe, hotplug cpu,
8 #include <uapi/linux/sched/types.h>
9 #include <linux/sched.h>
10 #include <linux/sched/task.h>
11 #include <linux/kthread.h>
12 #include <linux/completion.h>
13 #include <linux/err.h>
14 #include <linux/cpuset.h>
15 #include <linux/unistd.h>
16 #include <linux/file.h>
17 #include <linux/export.h>
18 #include <linux/mutex.h>
19 #include <linux/slab.h>
20 #include <linux/freezer.h>
21 #include <linux/ptrace.h>
22 #include <linux/uaccess.h>
23 #include <linux/cgroup.h>
24 #include <trace/events/sched.h>
26 static DEFINE_SPINLOCK(kthread_create_lock);
27 static LIST_HEAD(kthread_create_list);
28 struct task_struct *kthreadd_task;
30 struct kthread_create_info
32 /* Information passed to kthread() from kthreadd. */
33 int (*threadfn)(void *data);
37 /* Result passed back to kthread_create() from kthreadd. */
38 struct task_struct *result;
39 struct completion *done;
41 struct list_head list;
48 struct completion parked;
49 struct completion exited;
53 KTHREAD_IS_PER_CPU = 0,
59 static inline void set_kthread_struct(void *kthread)
62 * We abuse ->set_child_tid to avoid the new member and because it
63 * can't be wrongly copied by copy_process(). We also rely on fact
64 * that the caller can't exec, so PF_KTHREAD can't be cleared.
66 current->set_child_tid = (__force void __user *)kthread;
69 static inline struct kthread *to_kthread(struct task_struct *k)
71 WARN_ON(!(k->flags & PF_KTHREAD));
72 return (__force void *)k->set_child_tid;
75 void free_kthread_struct(struct task_struct *k)
78 * Can be NULL if this kthread was created by kernel_thread()
79 * or if kmalloc() in kthread() failed.
85 * kthread_should_stop - should this kthread return now?
87 * When someone calls kthread_stop() on your kthread, it will be woken
88 * and this will return true. You should then return, and your return
89 * value will be passed through to kthread_stop().
91 bool kthread_should_stop(void)
93 return test_bit(KTHREAD_SHOULD_STOP, &to_kthread(current)->flags);
95 EXPORT_SYMBOL(kthread_should_stop);
98 * kthread_should_park - should this kthread park now?
100 * When someone calls kthread_park() on your kthread, it will be woken
101 * and this will return true. You should then do the necessary
102 * cleanup and call kthread_parkme()
104 * Similar to kthread_should_stop(), but this keeps the thread alive
105 * and in a park position. kthread_unpark() "restarts" the thread and
106 * calls the thread function again.
108 bool kthread_should_park(void)
110 return test_bit(KTHREAD_SHOULD_PARK, &to_kthread(current)->flags);
112 EXPORT_SYMBOL_GPL(kthread_should_park);
115 * kthread_freezable_should_stop - should this freezable kthread return now?
116 * @was_frozen: optional out parameter, indicates whether %current was frozen
118 * kthread_should_stop() for freezable kthreads, which will enter
119 * refrigerator if necessary. This function is safe from kthread_stop() /
120 * freezer deadlock and freezable kthreads should use this function instead
121 * of calling try_to_freeze() directly.
123 bool kthread_freezable_should_stop(bool *was_frozen)
129 if (unlikely(freezing(current)))
130 frozen = __refrigerator(true);
133 *was_frozen = frozen;
135 return kthread_should_stop();
137 EXPORT_SYMBOL_GPL(kthread_freezable_should_stop);
140 * kthread_data - return data value specified on kthread creation
141 * @task: kthread task in question
143 * Return the data value specified when kthread @task was created.
144 * The caller is responsible for ensuring the validity of @task when
145 * calling this function.
147 void *kthread_data(struct task_struct *task)
149 return to_kthread(task)->data;
153 * kthread_probe_data - speculative version of kthread_data()
154 * @task: possible kthread task in question
156 * @task could be a kthread task. Return the data value specified when it
157 * was created if accessible. If @task isn't a kthread task or its data is
158 * inaccessible for any reason, %NULL is returned. This function requires
159 * that @task itself is safe to dereference.
161 void *kthread_probe_data(struct task_struct *task)
163 struct kthread *kthread = to_kthread(task);
166 probe_kernel_read(&data, &kthread->data, sizeof(data));
170 static void __kthread_parkme(struct kthread *self)
173 set_current_state(TASK_PARKED);
174 if (!test_bit(KTHREAD_SHOULD_PARK, &self->flags))
176 if (!test_and_set_bit(KTHREAD_IS_PARKED, &self->flags))
177 complete(&self->parked);
180 clear_bit(KTHREAD_IS_PARKED, &self->flags);
181 __set_current_state(TASK_RUNNING);
184 void kthread_parkme(void)
186 __kthread_parkme(to_kthread(current));
188 EXPORT_SYMBOL_GPL(kthread_parkme);
190 static int kthread(void *_create)
192 /* Copy data: it's on kthread's stack */
193 struct kthread_create_info *create = _create;
194 int (*threadfn)(void *data) = create->threadfn;
195 void *data = create->data;
196 struct completion *done;
197 struct kthread *self;
200 self = kmalloc(sizeof(*self), GFP_KERNEL);
201 set_kthread_struct(self);
203 /* If user was SIGKILLed, I release the structure. */
204 done = xchg(&create->done, NULL);
211 create->result = ERR_PTR(-ENOMEM);
218 init_completion(&self->exited);
219 init_completion(&self->parked);
220 current->vfork_done = &self->exited;
222 /* OK, tell user we're spawned, wait for stop or wakeup */
223 __set_current_state(TASK_UNINTERRUPTIBLE);
224 create->result = current;
229 if (!test_bit(KTHREAD_SHOULD_STOP, &self->flags)) {
230 cgroup_kthread_ready();
231 __kthread_parkme(self);
232 ret = threadfn(data);
237 /* called from do_fork() to get node information for about to be created task */
238 int tsk_fork_get_node(struct task_struct *tsk)
241 if (tsk == kthreadd_task)
242 return tsk->pref_node_fork;
247 static void create_kthread(struct kthread_create_info *create)
252 current->pref_node_fork = create->node;
254 /* We want our own signal handler (we take no signals by default). */
255 pid = kernel_thread(kthread, create, CLONE_FS | CLONE_FILES | SIGCHLD);
257 /* If user was SIGKILLed, I release the structure. */
258 struct completion *done = xchg(&create->done, NULL);
264 create->result = ERR_PTR(pid);
269 static __printf(4, 0)
270 struct task_struct *__kthread_create_on_node(int (*threadfn)(void *data),
271 void *data, int node,
272 const char namefmt[],
275 DECLARE_COMPLETION_ONSTACK(done);
276 struct task_struct *task;
277 struct kthread_create_info *create = kmalloc(sizeof(*create),
281 return ERR_PTR(-ENOMEM);
282 create->threadfn = threadfn;
285 create->done = &done;
287 spin_lock(&kthread_create_lock);
288 list_add_tail(&create->list, &kthread_create_list);
289 spin_unlock(&kthread_create_lock);
291 wake_up_process(kthreadd_task);
293 * Wait for completion in killable state, for I might be chosen by
294 * the OOM killer while kthreadd is trying to allocate memory for
297 if (unlikely(wait_for_completion_killable(&done))) {
299 * If I was SIGKILLed before kthreadd (or new kernel thread)
300 * calls complete(), leave the cleanup of this structure to
303 if (xchg(&create->done, NULL))
304 return ERR_PTR(-EINTR);
306 * kthreadd (or new kernel thread) will call complete()
309 wait_for_completion(&done);
311 task = create->result;
313 static const struct sched_param param = { .sched_priority = 0 };
314 char name[TASK_COMM_LEN];
317 * task is already visible to other tasks, so updating
318 * COMM must be protected.
320 vsnprintf(name, sizeof(name), namefmt, args);
321 set_task_comm(task, name);
323 * root may have changed our (kthreadd's) priority or CPU mask.
324 * The kernel thread should not inherit these properties.
326 sched_setscheduler_nocheck(task, SCHED_NORMAL, ¶m);
327 set_cpus_allowed_ptr(task, cpu_all_mask);
334 * kthread_create_on_node - create a kthread.
335 * @threadfn: the function to run until signal_pending(current).
336 * @data: data ptr for @threadfn.
337 * @node: task and thread structures for the thread are allocated on this node
338 * @namefmt: printf-style name for the thread.
340 * Description: This helper function creates and names a kernel
341 * thread. The thread will be stopped: use wake_up_process() to start
342 * it. See also kthread_run(). The new thread has SCHED_NORMAL policy and
343 * is affine to all CPUs.
345 * If thread is going to be bound on a particular cpu, give its node
346 * in @node, to get NUMA affinity for kthread stack, or else give NUMA_NO_NODE.
347 * When woken, the thread will run @threadfn() with @data as its
348 * argument. @threadfn() can either call do_exit() directly if it is a
349 * standalone thread for which no one will call kthread_stop(), or
350 * return when 'kthread_should_stop()' is true (which means
351 * kthread_stop() has been called). The return value should be zero
352 * or a negative error number; it will be passed to kthread_stop().
354 * Returns a task_struct or ERR_PTR(-ENOMEM) or ERR_PTR(-EINTR).
356 struct task_struct *kthread_create_on_node(int (*threadfn)(void *data),
357 void *data, int node,
358 const char namefmt[],
361 struct task_struct *task;
364 va_start(args, namefmt);
365 task = __kthread_create_on_node(threadfn, data, node, namefmt, args);
370 EXPORT_SYMBOL(kthread_create_on_node);
372 static void __kthread_bind_mask(struct task_struct *p, const struct cpumask *mask, long state)
376 if (!wait_task_inactive(p, state)) {
381 /* It's safe because the task is inactive. */
382 raw_spin_lock_irqsave(&p->pi_lock, flags);
383 do_set_cpus_allowed(p, mask);
384 p->flags |= PF_NO_SETAFFINITY;
385 raw_spin_unlock_irqrestore(&p->pi_lock, flags);
388 static void __kthread_bind(struct task_struct *p, unsigned int cpu, long state)
390 __kthread_bind_mask(p, cpumask_of(cpu), state);
393 void kthread_bind_mask(struct task_struct *p, const struct cpumask *mask)
395 __kthread_bind_mask(p, mask, TASK_UNINTERRUPTIBLE);
399 * kthread_bind - bind a just-created kthread to a cpu.
400 * @p: thread created by kthread_create().
401 * @cpu: cpu (might not be online, must be possible) for @k to run on.
403 * Description: This function is equivalent to set_cpus_allowed(),
404 * except that @cpu doesn't need to be online, and the thread must be
405 * stopped (i.e., just returned from kthread_create()).
407 void kthread_bind(struct task_struct *p, unsigned int cpu)
409 __kthread_bind(p, cpu, TASK_UNINTERRUPTIBLE);
411 EXPORT_SYMBOL(kthread_bind);
414 * kthread_create_on_cpu - Create a cpu bound kthread
415 * @threadfn: the function to run until signal_pending(current).
416 * @data: data ptr for @threadfn.
417 * @cpu: The cpu on which the thread should be bound,
418 * @namefmt: printf-style name for the thread. Format is restricted
419 * to "name.*%u". Code fills in cpu number.
421 * Description: This helper function creates and names a kernel thread
422 * The thread will be woken and put into park mode.
424 struct task_struct *kthread_create_on_cpu(int (*threadfn)(void *data),
425 void *data, unsigned int cpu,
428 struct task_struct *p;
430 p = kthread_create_on_node(threadfn, data, cpu_to_node(cpu), namefmt,
434 kthread_bind(p, cpu);
435 /* CPU hotplug need to bind once again when unparking the thread. */
436 to_kthread(p)->cpu = cpu;
440 void kthread_set_per_cpu(struct task_struct *k, int cpu)
442 struct kthread *kthread = to_kthread(k);
446 WARN_ON_ONCE(!(k->flags & PF_NO_SETAFFINITY));
449 clear_bit(KTHREAD_IS_PER_CPU, &kthread->flags);
454 set_bit(KTHREAD_IS_PER_CPU, &kthread->flags);
457 bool kthread_is_per_cpu(struct task_struct *k)
459 struct kthread *kthread = to_kthread(k);
463 return test_bit(KTHREAD_IS_PER_CPU, &kthread->flags);
467 * kthread_unpark - unpark a thread created by kthread_create().
468 * @k: thread created by kthread_create().
470 * Sets kthread_should_park() for @k to return false, wakes it, and
471 * waits for it to return. If the thread is marked percpu then its
472 * bound to the cpu again.
474 void kthread_unpark(struct task_struct *k)
476 struct kthread *kthread = to_kthread(k);
478 clear_bit(KTHREAD_SHOULD_PARK, &kthread->flags);
480 * We clear the IS_PARKED bit here as we don't wait
481 * until the task has left the park code. So if we'd
482 * park before that happens we'd see the IS_PARKED bit
483 * which might be about to be cleared.
485 if (test_and_clear_bit(KTHREAD_IS_PARKED, &kthread->flags)) {
487 * Newly created kthread was parked when the CPU was offline.
488 * The binding was lost and we need to set it again.
490 if (test_bit(KTHREAD_IS_PER_CPU, &kthread->flags))
491 __kthread_bind(k, kthread->cpu, TASK_PARKED);
492 wake_up_state(k, TASK_PARKED);
495 EXPORT_SYMBOL_GPL(kthread_unpark);
498 * kthread_park - park a thread created by kthread_create().
499 * @k: thread created by kthread_create().
501 * Sets kthread_should_park() for @k to return true, wakes it, and
502 * waits for it to return. This can also be called after kthread_create()
503 * instead of calling wake_up_process(): the thread will park without
504 * calling threadfn().
506 * Returns 0 if the thread is parked, -ENOSYS if the thread exited.
507 * If called by the kthread itself just the park bit is set.
509 int kthread_park(struct task_struct *k)
511 struct kthread *kthread = to_kthread(k);
513 if (WARN_ON(k->flags & PF_EXITING))
516 if (!test_bit(KTHREAD_IS_PARKED, &kthread->flags)) {
517 set_bit(KTHREAD_SHOULD_PARK, &kthread->flags);
520 wait_for_completion(&kthread->parked);
526 EXPORT_SYMBOL_GPL(kthread_park);
529 * kthread_stop - stop a thread created by kthread_create().
530 * @k: thread created by kthread_create().
532 * Sets kthread_should_stop() for @k to return true, wakes it, and
533 * waits for it to exit. This can also be called after kthread_create()
534 * instead of calling wake_up_process(): the thread will exit without
535 * calling threadfn().
537 * If threadfn() may call do_exit() itself, the caller must ensure
538 * task_struct can't go away.
540 * Returns the result of threadfn(), or %-EINTR if wake_up_process()
543 int kthread_stop(struct task_struct *k)
545 struct kthread *kthread;
548 trace_sched_kthread_stop(k);
551 kthread = to_kthread(k);
552 set_bit(KTHREAD_SHOULD_STOP, &kthread->flags);
555 wait_for_completion(&kthread->exited);
559 trace_sched_kthread_stop_ret(ret);
562 EXPORT_SYMBOL(kthread_stop);
564 int kthreadd(void *unused)
566 struct task_struct *tsk = current;
568 /* Setup a clean context for our children to inherit. */
569 set_task_comm(tsk, "kthreadd");
571 set_cpus_allowed_ptr(tsk, cpu_all_mask);
572 set_mems_allowed(node_states[N_MEMORY]);
574 current->flags |= PF_NOFREEZE;
575 cgroup_init_kthreadd();
578 set_current_state(TASK_INTERRUPTIBLE);
579 if (list_empty(&kthread_create_list))
581 __set_current_state(TASK_RUNNING);
583 spin_lock(&kthread_create_lock);
584 while (!list_empty(&kthread_create_list)) {
585 struct kthread_create_info *create;
587 create = list_entry(kthread_create_list.next,
588 struct kthread_create_info, list);
589 list_del_init(&create->list);
590 spin_unlock(&kthread_create_lock);
592 create_kthread(create);
594 spin_lock(&kthread_create_lock);
596 spin_unlock(&kthread_create_lock);
602 void __kthread_init_worker(struct kthread_worker *worker,
604 struct lock_class_key *key)
606 memset(worker, 0, sizeof(struct kthread_worker));
607 spin_lock_init(&worker->lock);
608 lockdep_set_class_and_name(&worker->lock, key, name);
609 INIT_LIST_HEAD(&worker->work_list);
610 INIT_LIST_HEAD(&worker->delayed_work_list);
612 EXPORT_SYMBOL_GPL(__kthread_init_worker);
615 * kthread_worker_fn - kthread function to process kthread_worker
616 * @worker_ptr: pointer to initialized kthread_worker
618 * This function implements the main cycle of kthread worker. It processes
619 * work_list until it is stopped with kthread_stop(). It sleeps when the queue
622 * The works are not allowed to keep any locks, disable preemption or interrupts
623 * when they finish. There is defined a safe point for freezing when one work
624 * finishes and before a new one is started.
626 * Also the works must not be handled by more than one worker at the same time,
627 * see also kthread_queue_work().
629 int kthread_worker_fn(void *worker_ptr)
631 struct kthread_worker *worker = worker_ptr;
632 struct kthread_work *work;
635 * FIXME: Update the check and remove the assignment when all kthread
636 * worker users are created using kthread_create_worker*() functions.
638 WARN_ON(worker->task && worker->task != current);
639 worker->task = current;
641 if (worker->flags & KTW_FREEZABLE)
645 set_current_state(TASK_INTERRUPTIBLE); /* mb paired w/ kthread_stop */
647 if (kthread_should_stop()) {
648 __set_current_state(TASK_RUNNING);
649 spin_lock_irq(&worker->lock);
651 spin_unlock_irq(&worker->lock);
656 spin_lock_irq(&worker->lock);
657 if (!list_empty(&worker->work_list)) {
658 work = list_first_entry(&worker->work_list,
659 struct kthread_work, node);
660 list_del_init(&work->node);
662 worker->current_work = work;
663 spin_unlock_irq(&worker->lock);
666 __set_current_state(TASK_RUNNING);
668 } else if (!freezing(current))
675 EXPORT_SYMBOL_GPL(kthread_worker_fn);
677 static __printf(3, 0) struct kthread_worker *
678 __kthread_create_worker(int cpu, unsigned int flags,
679 const char namefmt[], va_list args)
681 struct kthread_worker *worker;
682 struct task_struct *task;
685 worker = kzalloc(sizeof(*worker), GFP_KERNEL);
687 return ERR_PTR(-ENOMEM);
689 kthread_init_worker(worker);
692 node = cpu_to_node(cpu);
694 task = __kthread_create_on_node(kthread_worker_fn, worker,
695 node, namefmt, args);
700 kthread_bind(task, cpu);
702 worker->flags = flags;
704 wake_up_process(task);
709 return ERR_CAST(task);
713 * kthread_create_worker - create a kthread worker
714 * @flags: flags modifying the default behavior of the worker
715 * @namefmt: printf-style name for the kthread worker (task).
717 * Returns a pointer to the allocated worker on success, ERR_PTR(-ENOMEM)
718 * when the needed structures could not get allocated, and ERR_PTR(-EINTR)
719 * when the worker was SIGKILLed.
721 struct kthread_worker *
722 kthread_create_worker(unsigned int flags, const char namefmt[], ...)
724 struct kthread_worker *worker;
727 va_start(args, namefmt);
728 worker = __kthread_create_worker(-1, flags, namefmt, args);
733 EXPORT_SYMBOL(kthread_create_worker);
736 * kthread_create_worker_on_cpu - create a kthread worker and bind it
737 * it to a given CPU and the associated NUMA node.
739 * @flags: flags modifying the default behavior of the worker
740 * @namefmt: printf-style name for the kthread worker (task).
742 * Use a valid CPU number if you want to bind the kthread worker
743 * to the given CPU and the associated NUMA node.
745 * A good practice is to add the cpu number also into the worker name.
746 * For example, use kthread_create_worker_on_cpu(cpu, "helper/%d", cpu).
748 * Returns a pointer to the allocated worker on success, ERR_PTR(-ENOMEM)
749 * when the needed structures could not get allocated, and ERR_PTR(-EINTR)
750 * when the worker was SIGKILLed.
752 struct kthread_worker *
753 kthread_create_worker_on_cpu(int cpu, unsigned int flags,
754 const char namefmt[], ...)
756 struct kthread_worker *worker;
759 va_start(args, namefmt);
760 worker = __kthread_create_worker(cpu, flags, namefmt, args);
765 EXPORT_SYMBOL(kthread_create_worker_on_cpu);
768 * Returns true when the work could not be queued at the moment.
769 * It happens when it is already pending in a worker list
770 * or when it is being cancelled.
772 static inline bool queuing_blocked(struct kthread_worker *worker,
773 struct kthread_work *work)
775 lockdep_assert_held(&worker->lock);
777 return !list_empty(&work->node) || work->canceling;
780 static void kthread_insert_work_sanity_check(struct kthread_worker *worker,
781 struct kthread_work *work)
783 lockdep_assert_held(&worker->lock);
784 WARN_ON_ONCE(!list_empty(&work->node));
785 /* Do not use a work with >1 worker, see kthread_queue_work() */
786 WARN_ON_ONCE(work->worker && work->worker != worker);
789 /* insert @work before @pos in @worker */
790 static void kthread_insert_work(struct kthread_worker *worker,
791 struct kthread_work *work,
792 struct list_head *pos)
794 kthread_insert_work_sanity_check(worker, work);
796 list_add_tail(&work->node, pos);
797 work->worker = worker;
798 if (!worker->current_work && likely(worker->task))
799 wake_up_process(worker->task);
803 * kthread_queue_work - queue a kthread_work
804 * @worker: target kthread_worker
805 * @work: kthread_work to queue
807 * Queue @work to work processor @task for async execution. @task
808 * must have been created with kthread_worker_create(). Returns %true
809 * if @work was successfully queued, %false if it was already pending.
811 * Reinitialize the work if it needs to be used by another worker.
812 * For example, when the worker was stopped and started again.
814 bool kthread_queue_work(struct kthread_worker *worker,
815 struct kthread_work *work)
820 spin_lock_irqsave(&worker->lock, flags);
821 if (!queuing_blocked(worker, work)) {
822 kthread_insert_work(worker, work, &worker->work_list);
825 spin_unlock_irqrestore(&worker->lock, flags);
828 EXPORT_SYMBOL_GPL(kthread_queue_work);
831 * kthread_delayed_work_timer_fn - callback that queues the associated kthread
832 * delayed work when the timer expires.
833 * @__data: pointer to the data associated with the timer
835 * The format of the function is defined by struct timer_list.
836 * It should have been called from irqsafe timer with irq already off.
838 void kthread_delayed_work_timer_fn(unsigned long __data)
840 struct kthread_delayed_work *dwork =
841 (struct kthread_delayed_work *)__data;
842 struct kthread_work *work = &dwork->work;
843 struct kthread_worker *worker = work->worker;
846 * This might happen when a pending work is reinitialized.
847 * It means that it is used a wrong way.
849 if (WARN_ON_ONCE(!worker))
852 spin_lock(&worker->lock);
853 /* Work must not be used with >1 worker, see kthread_queue_work(). */
854 WARN_ON_ONCE(work->worker != worker);
856 /* Move the work from worker->delayed_work_list. */
857 WARN_ON_ONCE(list_empty(&work->node));
858 list_del_init(&work->node);
859 if (!work->canceling)
860 kthread_insert_work(worker, work, &worker->work_list);
862 spin_unlock(&worker->lock);
864 EXPORT_SYMBOL(kthread_delayed_work_timer_fn);
866 void __kthread_queue_delayed_work(struct kthread_worker *worker,
867 struct kthread_delayed_work *dwork,
870 struct timer_list *timer = &dwork->timer;
871 struct kthread_work *work = &dwork->work;
873 WARN_ON_ONCE(timer->function != kthread_delayed_work_timer_fn ||
874 timer->data != (unsigned long)dwork);
877 * If @delay is 0, queue @dwork->work immediately. This is for
878 * both optimization and correctness. The earliest @timer can
879 * expire is on the closest next tick and delayed_work users depend
880 * on that there's no such delay when @delay is 0.
883 kthread_insert_work(worker, work, &worker->work_list);
887 /* Be paranoid and try to detect possible races already now. */
888 kthread_insert_work_sanity_check(worker, work);
890 list_add(&work->node, &worker->delayed_work_list);
891 work->worker = worker;
892 timer->expires = jiffies + delay;
897 * kthread_queue_delayed_work - queue the associated kthread work
899 * @worker: target kthread_worker
900 * @dwork: kthread_delayed_work to queue
901 * @delay: number of jiffies to wait before queuing
903 * If the work has not been pending it starts a timer that will queue
904 * the work after the given @delay. If @delay is zero, it queues the
907 * Return: %false if the @work has already been pending. It means that
908 * either the timer was running or the work was queued. It returns %true
911 bool kthread_queue_delayed_work(struct kthread_worker *worker,
912 struct kthread_delayed_work *dwork,
915 struct kthread_work *work = &dwork->work;
919 spin_lock_irqsave(&worker->lock, flags);
921 if (!queuing_blocked(worker, work)) {
922 __kthread_queue_delayed_work(worker, dwork, delay);
926 spin_unlock_irqrestore(&worker->lock, flags);
929 EXPORT_SYMBOL_GPL(kthread_queue_delayed_work);
931 struct kthread_flush_work {
932 struct kthread_work work;
933 struct completion done;
936 static void kthread_flush_work_fn(struct kthread_work *work)
938 struct kthread_flush_work *fwork =
939 container_of(work, struct kthread_flush_work, work);
940 complete(&fwork->done);
944 * kthread_flush_work - flush a kthread_work
945 * @work: work to flush
947 * If @work is queued or executing, wait for it to finish execution.
949 void kthread_flush_work(struct kthread_work *work)
951 struct kthread_flush_work fwork = {
952 KTHREAD_WORK_INIT(fwork.work, kthread_flush_work_fn),
953 COMPLETION_INITIALIZER_ONSTACK(fwork.done),
955 struct kthread_worker *worker;
958 worker = work->worker;
962 spin_lock_irq(&worker->lock);
963 /* Work must not be used with >1 worker, see kthread_queue_work(). */
964 WARN_ON_ONCE(work->worker != worker);
966 if (!list_empty(&work->node))
967 kthread_insert_work(worker, &fwork.work, work->node.next);
968 else if (worker->current_work == work)
969 kthread_insert_work(worker, &fwork.work,
970 worker->work_list.next);
974 spin_unlock_irq(&worker->lock);
977 wait_for_completion(&fwork.done);
979 EXPORT_SYMBOL_GPL(kthread_flush_work);
982 * Make sure that the timer is neither set nor running and could
983 * not manipulate the work list_head any longer.
985 * The function is called under worker->lock. The lock is temporary
986 * released but the timer can't be set again in the meantime.
988 static void kthread_cancel_delayed_work_timer(struct kthread_work *work,
989 unsigned long *flags)
991 struct kthread_delayed_work *dwork =
992 container_of(work, struct kthread_delayed_work, work);
993 struct kthread_worker *worker = work->worker;
996 * del_timer_sync() must be called to make sure that the timer
997 * callback is not running. The lock must be temporary released
998 * to avoid a deadlock with the callback. In the meantime,
999 * any queuing is blocked by setting the canceling counter.
1002 spin_unlock_irqrestore(&worker->lock, *flags);
1003 del_timer_sync(&dwork->timer);
1004 spin_lock_irqsave(&worker->lock, *flags);
1009 * This function removes the work from the worker queue.
1011 * It is called under worker->lock. The caller must make sure that
1012 * the timer used by delayed work is not running, e.g. by calling
1013 * kthread_cancel_delayed_work_timer().
1015 * The work might still be in use when this function finishes. See the
1016 * current_work proceed by the worker.
1018 * Return: %true if @work was pending and successfully canceled,
1019 * %false if @work was not pending
1021 static bool __kthread_cancel_work(struct kthread_work *work)
1024 * Try to remove the work from a worker list. It might either
1025 * be from worker->work_list or from worker->delayed_work_list.
1027 if (!list_empty(&work->node)) {
1028 list_del_init(&work->node);
1036 * kthread_mod_delayed_work - modify delay of or queue a kthread delayed work
1037 * @worker: kthread worker to use
1038 * @dwork: kthread delayed work to queue
1039 * @delay: number of jiffies to wait before queuing
1041 * If @dwork is idle, equivalent to kthread_queue_delayed_work(). Otherwise,
1042 * modify @dwork's timer so that it expires after @delay. If @delay is zero,
1043 * @work is guaranteed to be queued immediately.
1045 * Return: %true if @dwork was pending and its timer was modified,
1048 * A special case is when the work is being canceled in parallel.
1049 * It might be caused either by the real kthread_cancel_delayed_work_sync()
1050 * or yet another kthread_mod_delayed_work() call. We let the other command
1051 * win and return %false here. The caller is supposed to synchronize these
1052 * operations a reasonable way.
1054 * This function is safe to call from any context including IRQ handler.
1055 * See __kthread_cancel_work() and kthread_delayed_work_timer_fn()
1058 bool kthread_mod_delayed_work(struct kthread_worker *worker,
1059 struct kthread_delayed_work *dwork,
1060 unsigned long delay)
1062 struct kthread_work *work = &dwork->work;
1063 unsigned long flags;
1066 spin_lock_irqsave(&worker->lock, flags);
1068 /* Do not bother with canceling when never queued. */
1072 /* Work must not be used with >1 worker, see kthread_queue_work() */
1073 WARN_ON_ONCE(work->worker != worker);
1076 * Temporary cancel the work but do not fight with another command
1077 * that is canceling the work as well.
1079 * It is a bit tricky because of possible races with another
1080 * mod_delayed_work() and cancel_delayed_work() callers.
1082 * The timer must be canceled first because worker->lock is released
1083 * when doing so. But the work can be removed from the queue (list)
1084 * only when it can be queued again so that the return value can
1085 * be used for reference counting.
1087 kthread_cancel_delayed_work_timer(work, &flags);
1088 if (work->canceling)
1090 ret = __kthread_cancel_work(work);
1093 __kthread_queue_delayed_work(worker, dwork, delay);
1095 spin_unlock_irqrestore(&worker->lock, flags);
1098 EXPORT_SYMBOL_GPL(kthread_mod_delayed_work);
1100 static bool __kthread_cancel_work_sync(struct kthread_work *work, bool is_dwork)
1102 struct kthread_worker *worker = work->worker;
1103 unsigned long flags;
1109 spin_lock_irqsave(&worker->lock, flags);
1110 /* Work must not be used with >1 worker, see kthread_queue_work(). */
1111 WARN_ON_ONCE(work->worker != worker);
1114 kthread_cancel_delayed_work_timer(work, &flags);
1116 ret = __kthread_cancel_work(work);
1118 if (worker->current_work != work)
1122 * The work is in progress and we need to wait with the lock released.
1123 * In the meantime, block any queuing by setting the canceling counter.
1126 spin_unlock_irqrestore(&worker->lock, flags);
1127 kthread_flush_work(work);
1128 spin_lock_irqsave(&worker->lock, flags);
1132 spin_unlock_irqrestore(&worker->lock, flags);
1138 * kthread_cancel_work_sync - cancel a kthread work and wait for it to finish
1139 * @work: the kthread work to cancel
1141 * Cancel @work and wait for its execution to finish. This function
1142 * can be used even if the work re-queues itself. On return from this
1143 * function, @work is guaranteed to be not pending or executing on any CPU.
1145 * kthread_cancel_work_sync(&delayed_work->work) must not be used for
1146 * delayed_work's. Use kthread_cancel_delayed_work_sync() instead.
1148 * The caller must ensure that the worker on which @work was last
1149 * queued can't be destroyed before this function returns.
1151 * Return: %true if @work was pending, %false otherwise.
1153 bool kthread_cancel_work_sync(struct kthread_work *work)
1155 return __kthread_cancel_work_sync(work, false);
1157 EXPORT_SYMBOL_GPL(kthread_cancel_work_sync);
1160 * kthread_cancel_delayed_work_sync - cancel a kthread delayed work and
1161 * wait for it to finish.
1162 * @dwork: the kthread delayed work to cancel
1164 * This is kthread_cancel_work_sync() for delayed works.
1166 * Return: %true if @dwork was pending, %false otherwise.
1168 bool kthread_cancel_delayed_work_sync(struct kthread_delayed_work *dwork)
1170 return __kthread_cancel_work_sync(&dwork->work, true);
1172 EXPORT_SYMBOL_GPL(kthread_cancel_delayed_work_sync);
1175 * kthread_flush_worker - flush all current works on a kthread_worker
1176 * @worker: worker to flush
1178 * Wait until all currently executing or pending works on @worker are
1181 void kthread_flush_worker(struct kthread_worker *worker)
1183 struct kthread_flush_work fwork = {
1184 KTHREAD_WORK_INIT(fwork.work, kthread_flush_work_fn),
1185 COMPLETION_INITIALIZER_ONSTACK(fwork.done),
1188 kthread_queue_work(worker, &fwork.work);
1189 wait_for_completion(&fwork.done);
1191 EXPORT_SYMBOL_GPL(kthread_flush_worker);
1194 * kthread_destroy_worker - destroy a kthread worker
1195 * @worker: worker to be destroyed
1197 * Flush and destroy @worker. The simple flush is enough because the kthread
1198 * worker API is used only in trivial scenarios. There are no multi-step state
1201 void kthread_destroy_worker(struct kthread_worker *worker)
1203 struct task_struct *task;
1205 task = worker->task;
1209 kthread_flush_worker(worker);
1211 WARN_ON(!list_empty(&worker->work_list));
1214 EXPORT_SYMBOL(kthread_destroy_worker);