1 // SPDX-License-Identifier: GPL-2.0-only
5 * Copyright (C) 1998,2000 Rik van Riel
6 * Thanks go out to Claus Fischer for some serious inspiration and
7 * for goading me into coding this file...
8 * Copyright (C) 2010 Google, Inc.
9 * Rewritten by David Rientjes
11 * The routines in this file are used to kill a process when
12 * we're seriously out of memory. This gets called from __alloc_pages()
13 * in mm/page_alloc.c when we really run out of memory.
15 * Since we won't call these routines often (on a well-configured
16 * machine) this file will double as a 'coding guide' and a signpost
17 * for newbie kernel hackers. It features several pointers to major
18 * kernel subsystems and hints as to where to find out what things do.
21 #include <linux/oom.h>
23 #include <linux/err.h>
24 #include <linux/gfp.h>
25 #include <linux/sched.h>
26 #include <linux/sched/mm.h>
27 #include <linux/sched/coredump.h>
28 #include <linux/sched/task.h>
29 #include <linux/sched/debug.h>
30 #include <linux/swap.h>
31 #include <linux/syscalls.h>
32 #include <linux/timex.h>
33 #include <linux/jiffies.h>
34 #include <linux/cpuset.h>
35 #include <linux/export.h>
36 #include <linux/notifier.h>
37 #include <linux/memcontrol.h>
38 #include <linux/mempolicy.h>
39 #include <linux/security.h>
40 #include <linux/ptrace.h>
41 #include <linux/freezer.h>
42 #include <linux/ftrace.h>
43 #include <linux/ratelimit.h>
44 #include <linux/kthread.h>
45 #include <linux/init.h>
46 #include <linux/mmu_notifier.h>
47 #include <linux/cred.h>
53 #define CREATE_TRACE_POINTS
54 #include <trace/events/oom.h>
56 static int sysctl_panic_on_oom;
57 static int sysctl_oom_kill_allocating_task;
58 static int sysctl_oom_dump_tasks = 1;
61 * Serializes oom killer invocations (out_of_memory()) from all contexts to
62 * prevent from over eager oom killing (e.g. when the oom killer is invoked
63 * from different domains).
65 * oom_killer_disable() relies on this lock to stabilize oom_killer_disabled
68 DEFINE_MUTEX(oom_lock);
69 /* Serializes oom_score_adj and oom_score_adj_min updates */
70 DEFINE_MUTEX(oom_adj_mutex);
72 static inline bool is_memcg_oom(struct oom_control *oc)
74 return oc->memcg != NULL;
79 * oom_cpuset_eligible() - check task eligibility for kill
80 * @start: task struct of which task to consider
81 * @oc: pointer to struct oom_control
83 * Task eligibility is determined by whether or not a candidate task, @tsk,
84 * shares the same mempolicy nodes as current if it is bound by such a policy
85 * and whether or not it has the same set of allowed cpuset nodes.
87 * This function is assuming oom-killer context and 'current' has triggered
90 static bool oom_cpuset_eligible(struct task_struct *start,
91 struct oom_control *oc)
93 struct task_struct *tsk;
95 const nodemask_t *mask = oc->nodemask;
98 for_each_thread(start, tsk) {
101 * If this is a mempolicy constrained oom, tsk's
102 * cpuset is irrelevant. Only return true if its
103 * mempolicy intersects current, otherwise it may be
106 ret = mempolicy_in_oom_domain(tsk, mask);
109 * This is not a mempolicy constrained oom, so only
110 * check the mems of tsk's cpuset.
112 ret = cpuset_mems_allowed_intersects(current, tsk);
122 static bool oom_cpuset_eligible(struct task_struct *tsk, struct oom_control *oc)
126 #endif /* CONFIG_NUMA */
129 * The process p may have detached its own ->mm while exiting or through
130 * kthread_use_mm(), but one or more of its subthreads may still have a valid
131 * pointer. Return p, or any of its subthreads with a valid ->mm, with
134 struct task_struct *find_lock_task_mm(struct task_struct *p)
136 struct task_struct *t;
140 for_each_thread(p, t) {
154 * order == -1 means the oom kill is required by sysrq, otherwise only
155 * for display purposes.
157 static inline bool is_sysrq_oom(struct oom_control *oc)
159 return oc->order == -1;
162 /* return true if the task is not adequate as candidate victim task. */
163 static bool oom_unkillable_task(struct task_struct *p)
165 if (is_global_init(p))
167 if (p->flags & PF_KTHREAD)
173 * Check whether unreclaimable slab amount is greater than
174 * all user memory(LRU pages).
175 * dump_unreclaimable_slab() could help in the case that
176 * oom due to too much unreclaimable slab used by kernel.
178 static bool should_dump_unreclaim_slab(void)
180 unsigned long nr_lru;
182 nr_lru = global_node_page_state(NR_ACTIVE_ANON) +
183 global_node_page_state(NR_INACTIVE_ANON) +
184 global_node_page_state(NR_ACTIVE_FILE) +
185 global_node_page_state(NR_INACTIVE_FILE) +
186 global_node_page_state(NR_ISOLATED_ANON) +
187 global_node_page_state(NR_ISOLATED_FILE) +
188 global_node_page_state(NR_UNEVICTABLE);
190 return (global_node_page_state_pages(NR_SLAB_UNRECLAIMABLE_B) > nr_lru);
194 * oom_badness - heuristic function to determine which candidate task to kill
195 * @p: task struct of which task we should calculate
196 * @totalpages: total present RAM allowed for page allocation
198 * The heuristic for determining which task to kill is made to be as simple and
199 * predictable as possible. The goal is to return the highest value for the
200 * task consuming the most memory to avoid subsequent oom failures.
202 long oom_badness(struct task_struct *p, unsigned long totalpages)
207 if (oom_unkillable_task(p))
210 p = find_lock_task_mm(p);
215 * Do not even consider tasks which are explicitly marked oom
216 * unkillable or have been already oom reaped or the are in
217 * the middle of vfork
219 adj = (long)p->signal->oom_score_adj;
220 if (adj == OOM_SCORE_ADJ_MIN ||
221 test_bit(MMF_OOM_SKIP, &p->mm->flags) ||
228 * The baseline for the badness score is the proportion of RAM that each
229 * task's rss, pagetable and swap space use.
231 points = get_mm_rss(p->mm) + get_mm_counter(p->mm, MM_SWAPENTS) +
232 mm_pgtables_bytes(p->mm) / PAGE_SIZE;
235 /* Normalize to oom_score_adj units */
236 adj *= totalpages / 1000;
242 static const char * const oom_constraint_text[] = {
243 [CONSTRAINT_NONE] = "CONSTRAINT_NONE",
244 [CONSTRAINT_CPUSET] = "CONSTRAINT_CPUSET",
245 [CONSTRAINT_MEMORY_POLICY] = "CONSTRAINT_MEMORY_POLICY",
246 [CONSTRAINT_MEMCG] = "CONSTRAINT_MEMCG",
250 * Determine the type of allocation constraint.
252 static enum oom_constraint constrained_alloc(struct oom_control *oc)
256 enum zone_type highest_zoneidx = gfp_zone(oc->gfp_mask);
257 bool cpuset_limited = false;
260 if (is_memcg_oom(oc)) {
261 oc->totalpages = mem_cgroup_get_max(oc->memcg) ?: 1;
262 return CONSTRAINT_MEMCG;
265 /* Default to all available memory */
266 oc->totalpages = totalram_pages() + total_swap_pages;
268 if (!IS_ENABLED(CONFIG_NUMA))
269 return CONSTRAINT_NONE;
272 return CONSTRAINT_NONE;
274 * Reach here only when __GFP_NOFAIL is used. So, we should avoid
275 * to kill current.We have to random task kill in this case.
276 * Hopefully, CONSTRAINT_THISNODE...but no way to handle it, now.
278 if (oc->gfp_mask & __GFP_THISNODE)
279 return CONSTRAINT_NONE;
282 * This is not a __GFP_THISNODE allocation, so a truncated nodemask in
283 * the page allocator means a mempolicy is in effect. Cpuset policy
284 * is enforced in get_page_from_freelist().
287 !nodes_subset(node_states[N_MEMORY], *oc->nodemask)) {
288 oc->totalpages = total_swap_pages;
289 for_each_node_mask(nid, *oc->nodemask)
290 oc->totalpages += node_present_pages(nid);
291 return CONSTRAINT_MEMORY_POLICY;
294 /* Check this allocation failure is caused by cpuset's wall function */
295 for_each_zone_zonelist_nodemask(zone, z, oc->zonelist,
296 highest_zoneidx, oc->nodemask)
297 if (!cpuset_zone_allowed(zone, oc->gfp_mask))
298 cpuset_limited = true;
300 if (cpuset_limited) {
301 oc->totalpages = total_swap_pages;
302 for_each_node_mask(nid, cpuset_current_mems_allowed)
303 oc->totalpages += node_present_pages(nid);
304 return CONSTRAINT_CPUSET;
306 return CONSTRAINT_NONE;
309 static int oom_evaluate_task(struct task_struct *task, void *arg)
311 struct oom_control *oc = arg;
314 if (oom_unkillable_task(task))
317 /* p may not have freeable memory in nodemask */
318 if (!is_memcg_oom(oc) && !oom_cpuset_eligible(task, oc))
322 * This task already has access to memory reserves and is being killed.
323 * Don't allow any other task to have access to the reserves unless
324 * the task has MMF_OOM_SKIP because chances that it would release
325 * any memory is quite low.
327 if (!is_sysrq_oom(oc) && tsk_is_oom_victim(task)) {
328 if (test_bit(MMF_OOM_SKIP, &task->signal->oom_mm->flags))
334 * If task is allocating a lot of memory and has been marked to be
335 * killed first if it triggers an oom, then select it.
337 if (oom_task_origin(task)) {
342 points = oom_badness(task, oc->totalpages);
343 if (points == LONG_MIN || points < oc->chosen_points)
348 put_task_struct(oc->chosen);
349 get_task_struct(task);
351 oc->chosen_points = points;
356 put_task_struct(oc->chosen);
357 oc->chosen = (void *)-1UL;
362 * Simple selection loop. We choose the process with the highest number of
363 * 'points'. In case scan was aborted, oc->chosen is set to -1.
365 static void select_bad_process(struct oom_control *oc)
367 oc->chosen_points = LONG_MIN;
369 if (is_memcg_oom(oc))
370 mem_cgroup_scan_tasks(oc->memcg, oom_evaluate_task, oc);
372 struct task_struct *p;
376 if (oom_evaluate_task(p, oc))
382 static int dump_task(struct task_struct *p, void *arg)
384 struct oom_control *oc = arg;
385 struct task_struct *task;
387 if (oom_unkillable_task(p))
390 /* p may not have freeable memory in nodemask */
391 if (!is_memcg_oom(oc) && !oom_cpuset_eligible(p, oc))
394 task = find_lock_task_mm(p);
397 * All of p's threads have already detached their mm's. There's
398 * no need to report them; they can't be oom killed anyway.
403 pr_info("[%7d] %5d %5d %8lu %8lu %8lu %8lu %9lu %8ld %8lu %5hd %s\n",
404 task->pid, from_kuid(&init_user_ns, task_uid(task)),
405 task->tgid, task->mm->total_vm, get_mm_rss(task->mm),
406 get_mm_counter(task->mm, MM_ANONPAGES), get_mm_counter(task->mm, MM_FILEPAGES),
407 get_mm_counter(task->mm, MM_SHMEMPAGES), mm_pgtables_bytes(task->mm),
408 get_mm_counter(task->mm, MM_SWAPENTS),
409 task->signal->oom_score_adj, task->comm);
416 * dump_tasks - dump current memory state of all system tasks
417 * @oc: pointer to struct oom_control
419 * Dumps the current memory state of all eligible tasks. Tasks not in the same
420 * memcg, not in the same cpuset, or bound to a disjoint set of mempolicy nodes
422 * State information includes task's pid, uid, tgid, vm size, rss,
423 * pgtables_bytes, swapents, oom_score_adj value, and name.
425 static void dump_tasks(struct oom_control *oc)
427 pr_info("Tasks state (memory values in pages):\n");
428 pr_info("[ pid ] uid tgid total_vm rss rss_anon rss_file rss_shmem pgtables_bytes swapents oom_score_adj name\n");
430 if (is_memcg_oom(oc))
431 mem_cgroup_scan_tasks(oc->memcg, dump_task, oc);
433 struct task_struct *p;
442 static void dump_oom_victim(struct oom_control *oc, struct task_struct *victim)
444 /* one line summary of the oom killer context. */
445 pr_info("oom-kill:constraint=%s,nodemask=%*pbl",
446 oom_constraint_text[oc->constraint],
447 nodemask_pr_args(oc->nodemask));
448 cpuset_print_current_mems_allowed();
449 mem_cgroup_print_oom_context(oc->memcg, victim);
450 pr_cont(",task=%s,pid=%d,uid=%d\n", victim->comm, victim->pid,
451 from_kuid(&init_user_ns, task_uid(victim)));
454 static void dump_header(struct oom_control *oc)
456 pr_warn("%s invoked oom-killer: gfp_mask=%#x(%pGg), order=%d, oom_score_adj=%hd\n",
457 current->comm, oc->gfp_mask, &oc->gfp_mask, oc->order,
458 current->signal->oom_score_adj);
459 if (!IS_ENABLED(CONFIG_COMPACTION) && oc->order)
460 pr_warn("COMPACTION is disabled!!!\n");
463 if (is_memcg_oom(oc))
464 mem_cgroup_print_oom_meminfo(oc->memcg);
466 __show_mem(SHOW_MEM_FILTER_NODES, oc->nodemask, gfp_zone(oc->gfp_mask));
467 if (should_dump_unreclaim_slab())
468 dump_unreclaimable_slab();
470 if (sysctl_oom_dump_tasks)
475 * Number of OOM victims in flight
477 static atomic_t oom_victims = ATOMIC_INIT(0);
478 static DECLARE_WAIT_QUEUE_HEAD(oom_victims_wait);
480 static bool oom_killer_disabled __read_mostly;
483 * task->mm can be NULL if the task is the exited group leader. So to
484 * determine whether the task is using a particular mm, we examine all the
485 * task's threads: if one of those is using this mm then this task was also
488 bool process_shares_mm(struct task_struct *p, struct mm_struct *mm)
490 struct task_struct *t;
492 for_each_thread(p, t) {
493 struct mm_struct *t_mm = READ_ONCE(t->mm);
502 * OOM Reaper kernel thread which tries to reap the memory used by the OOM
503 * victim (if that is possible) to help the OOM killer to move on.
505 static struct task_struct *oom_reaper_th;
506 static DECLARE_WAIT_QUEUE_HEAD(oom_reaper_wait);
507 static struct task_struct *oom_reaper_list;
508 static DEFINE_SPINLOCK(oom_reaper_lock);
510 static bool __oom_reap_task_mm(struct mm_struct *mm)
512 struct vm_area_struct *vma;
514 VMA_ITERATOR(vmi, mm, 0);
517 * Tell all users of get_user/copy_from_user etc... that the content
518 * is no longer stable. No barriers really needed because unmapping
519 * should imply barriers already and the reader would hit a page fault
520 * if it stumbled over a reaped memory.
522 set_bit(MMF_UNSTABLE, &mm->flags);
524 for_each_vma(vmi, vma) {
525 if (vma->vm_flags & (VM_HUGETLB|VM_PFNMAP))
529 * Only anonymous pages have a good chance to be dropped
530 * without additional steps which we cannot afford as we
533 * We do not even care about fs backed pages because all
534 * which are reclaimable have already been reclaimed and
535 * we do not want to block exit_mmap by keeping mm ref
536 * count elevated without a good reason.
538 if (vma_is_anonymous(vma) || !(vma->vm_flags & VM_SHARED)) {
539 struct mmu_notifier_range range;
540 struct mmu_gather tlb;
542 mmu_notifier_range_init(&range, MMU_NOTIFY_UNMAP, 0,
545 tlb_gather_mmu(&tlb, mm);
546 if (mmu_notifier_invalidate_range_start_nonblock(&range)) {
547 tlb_finish_mmu(&tlb);
551 unmap_page_range(&tlb, vma, range.start, range.end, NULL);
552 mmu_notifier_invalidate_range_end(&range);
553 tlb_finish_mmu(&tlb);
561 * Reaps the address space of the give task.
563 * Returns true on success and false if none or part of the address space
564 * has been reclaimed and the caller should retry later.
566 static bool oom_reap_task_mm(struct task_struct *tsk, struct mm_struct *mm)
570 if (!mmap_read_trylock(mm)) {
571 trace_skip_task_reaping(tsk->pid);
576 * MMF_OOM_SKIP is set by exit_mmap when the OOM reaper can't
577 * work on the mm anymore. The check for MMF_OOM_SKIP must run
578 * under mmap_lock for reading because it serializes against the
579 * mmap_write_lock();mmap_write_unlock() cycle in exit_mmap().
581 if (test_bit(MMF_OOM_SKIP, &mm->flags)) {
582 trace_skip_task_reaping(tsk->pid);
586 trace_start_task_reaping(tsk->pid);
588 /* failed to reap part of the address space. Try again later */
589 ret = __oom_reap_task_mm(mm);
593 pr_info("oom_reaper: reaped process %d (%s), now anon-rss:%lukB, file-rss:%lukB, shmem-rss:%lukB\n",
594 task_pid_nr(tsk), tsk->comm,
595 K(get_mm_counter(mm, MM_ANONPAGES)),
596 K(get_mm_counter(mm, MM_FILEPAGES)),
597 K(get_mm_counter(mm, MM_SHMEMPAGES)));
599 trace_finish_task_reaping(tsk->pid);
601 mmap_read_unlock(mm);
606 #define MAX_OOM_REAP_RETRIES 10
607 static void oom_reap_task(struct task_struct *tsk)
610 struct mm_struct *mm = tsk->signal->oom_mm;
612 /* Retry the mmap_read_trylock(mm) a few times */
613 while (attempts++ < MAX_OOM_REAP_RETRIES && !oom_reap_task_mm(tsk, mm))
614 schedule_timeout_idle(HZ/10);
616 if (attempts <= MAX_OOM_REAP_RETRIES ||
617 test_bit(MMF_OOM_SKIP, &mm->flags))
620 pr_info("oom_reaper: unable to reap pid:%d (%s)\n",
621 task_pid_nr(tsk), tsk->comm);
622 sched_show_task(tsk);
623 debug_show_all_locks();
626 tsk->oom_reaper_list = NULL;
629 * Hide this mm from OOM killer because it has been either reaped or
630 * somebody can't call mmap_write_unlock(mm).
632 set_bit(MMF_OOM_SKIP, &mm->flags);
634 /* Drop a reference taken by queue_oom_reaper */
635 put_task_struct(tsk);
638 static int oom_reaper(void *unused)
643 struct task_struct *tsk = NULL;
645 wait_event_freezable(oom_reaper_wait, oom_reaper_list != NULL);
646 spin_lock_irq(&oom_reaper_lock);
647 if (oom_reaper_list != NULL) {
648 tsk = oom_reaper_list;
649 oom_reaper_list = tsk->oom_reaper_list;
651 spin_unlock_irq(&oom_reaper_lock);
660 static void wake_oom_reaper(struct timer_list *timer)
662 struct task_struct *tsk = container_of(timer, struct task_struct,
664 struct mm_struct *mm = tsk->signal->oom_mm;
667 /* The victim managed to terminate on its own - see exit_mmap */
668 if (test_bit(MMF_OOM_SKIP, &mm->flags)) {
669 put_task_struct(tsk);
673 spin_lock_irqsave(&oom_reaper_lock, flags);
674 tsk->oom_reaper_list = oom_reaper_list;
675 oom_reaper_list = tsk;
676 spin_unlock_irqrestore(&oom_reaper_lock, flags);
677 trace_wake_reaper(tsk->pid);
678 wake_up(&oom_reaper_wait);
682 * Give the OOM victim time to exit naturally before invoking the oom_reaping.
683 * The timers timeout is arbitrary... the longer it is, the longer the worst
684 * case scenario for the OOM can take. If it is too small, the oom_reaper can
685 * get in the way and release resources needed by the process exit path.
686 * e.g. The futex robust list can sit in Anon|Private memory that gets reaped
687 * before the exit path is able to wake the futex waiters.
689 #define OOM_REAPER_DELAY (2*HZ)
690 static void queue_oom_reaper(struct task_struct *tsk)
692 /* mm is already queued? */
693 if (test_and_set_bit(MMF_OOM_REAP_QUEUED, &tsk->signal->oom_mm->flags))
696 get_task_struct(tsk);
697 timer_setup(&tsk->oom_reaper_timer, wake_oom_reaper, 0);
698 tsk->oom_reaper_timer.expires = jiffies + OOM_REAPER_DELAY;
699 add_timer(&tsk->oom_reaper_timer);
703 static struct ctl_table vm_oom_kill_table[] = {
705 .procname = "panic_on_oom",
706 .data = &sysctl_panic_on_oom,
707 .maxlen = sizeof(sysctl_panic_on_oom),
709 .proc_handler = proc_dointvec_minmax,
710 .extra1 = SYSCTL_ZERO,
711 .extra2 = SYSCTL_TWO,
714 .procname = "oom_kill_allocating_task",
715 .data = &sysctl_oom_kill_allocating_task,
716 .maxlen = sizeof(sysctl_oom_kill_allocating_task),
718 .proc_handler = proc_dointvec,
721 .procname = "oom_dump_tasks",
722 .data = &sysctl_oom_dump_tasks,
723 .maxlen = sizeof(sysctl_oom_dump_tasks),
725 .proc_handler = proc_dointvec,
731 static int __init oom_init(void)
733 oom_reaper_th = kthread_run(oom_reaper, NULL, "oom_reaper");
735 register_sysctl_init("vm", vm_oom_kill_table);
739 subsys_initcall(oom_init)
741 static inline void queue_oom_reaper(struct task_struct *tsk)
744 #endif /* CONFIG_MMU */
747 * mark_oom_victim - mark the given task as OOM victim
750 * Has to be called with oom_lock held and never after
751 * oom has been disabled already.
753 * tsk->mm has to be non NULL and caller has to guarantee it is stable (either
754 * under task_lock or operate on the current).
756 static void mark_oom_victim(struct task_struct *tsk)
758 const struct cred *cred;
759 struct mm_struct *mm = tsk->mm;
761 WARN_ON(oom_killer_disabled);
762 /* OOM killer might race with memcg OOM */
763 if (test_and_set_tsk_thread_flag(tsk, TIF_MEMDIE))
766 /* oom_mm is bound to the signal struct life time. */
767 if (!cmpxchg(&tsk->signal->oom_mm, NULL, mm))
768 mmgrab(tsk->signal->oom_mm);
771 * Make sure that the task is woken up from uninterruptible sleep
772 * if it is frozen because OOM killer wouldn't be able to free
773 * any memory and livelock. freezing_slow_path will tell the freezer
774 * that TIF_MEMDIE tasks should be ignored.
777 atomic_inc(&oom_victims);
778 cred = get_task_cred(tsk);
779 trace_mark_victim(tsk, cred->uid.val);
784 * exit_oom_victim - note the exit of an OOM victim
786 void exit_oom_victim(void)
788 clear_thread_flag(TIF_MEMDIE);
790 if (!atomic_dec_return(&oom_victims))
791 wake_up_all(&oom_victims_wait);
795 * oom_killer_enable - enable OOM killer
797 void oom_killer_enable(void)
799 oom_killer_disabled = false;
800 pr_info("OOM killer enabled.\n");
804 * oom_killer_disable - disable OOM killer
805 * @timeout: maximum timeout to wait for oom victims in jiffies
807 * Forces all page allocations to fail rather than trigger OOM killer.
808 * Will block and wait until all OOM victims are killed or the given
811 * The function cannot be called when there are runnable user tasks because
812 * the userspace would see unexpected allocation failures as a result. Any
813 * new usage of this function should be consulted with MM people.
815 * Returns true if successful and false if the OOM killer cannot be
818 bool oom_killer_disable(signed long timeout)
823 * Make sure to not race with an ongoing OOM killer. Check that the
824 * current is not killed (possibly due to sharing the victim's memory).
826 if (mutex_lock_killable(&oom_lock))
828 oom_killer_disabled = true;
829 mutex_unlock(&oom_lock);
831 ret = wait_event_interruptible_timeout(oom_victims_wait,
832 !atomic_read(&oom_victims), timeout);
837 pr_info("OOM killer disabled.\n");
842 static inline bool __task_will_free_mem(struct task_struct *task)
844 struct signal_struct *sig = task->signal;
847 * A coredumping process may sleep for an extended period in
848 * coredump_task_exit(), so the oom killer cannot assume that
849 * the process will promptly exit and release memory.
854 if (sig->flags & SIGNAL_GROUP_EXIT)
857 if (thread_group_empty(task) && (task->flags & PF_EXITING))
864 * Checks whether the given task is dying or exiting and likely to
865 * release its address space. This means that all threads and processes
866 * sharing the same mm have to be killed or exiting.
867 * Caller has to make sure that task->mm is stable (hold task_lock or
868 * it operates on the current).
870 static bool task_will_free_mem(struct task_struct *task)
872 struct mm_struct *mm = task->mm;
873 struct task_struct *p;
877 * Skip tasks without mm because it might have passed its exit_mm and
878 * exit_oom_victim. oom_reaper could have rescued that but do not rely
879 * on that for now. We can consider find_lock_task_mm in future.
884 if (!__task_will_free_mem(task))
888 * This task has already been drained by the oom reaper so there are
889 * only small chances it will free some more
891 if (test_bit(MMF_OOM_SKIP, &mm->flags))
894 if (atomic_read(&mm->mm_users) <= 1)
898 * Make sure that all tasks which share the mm with the given tasks
899 * are dying as well to make sure that a) nobody pins its mm and
900 * b) the task is also reapable by the oom reaper.
903 for_each_process(p) {
904 if (!process_shares_mm(p, mm))
906 if (same_thread_group(task, p))
908 ret = __task_will_free_mem(p);
917 static void __oom_kill_process(struct task_struct *victim, const char *message)
919 struct task_struct *p;
920 struct mm_struct *mm;
921 bool can_oom_reap = true;
923 p = find_lock_task_mm(victim);
925 pr_info("%s: OOM victim %d (%s) is already exiting. Skip killing the task\n",
926 message, task_pid_nr(victim), victim->comm);
927 put_task_struct(victim);
929 } else if (victim != p) {
931 put_task_struct(victim);
935 /* Get a reference to safely compare mm after task_unlock(victim) */
939 /* Raise event before sending signal: task reaper must see this */
940 count_vm_event(OOM_KILL);
941 memcg_memory_event_mm(mm, MEMCG_OOM_KILL);
944 * We should send SIGKILL before granting access to memory reserves
945 * in order to prevent the OOM victim from depleting the memory
946 * reserves from the user space under its control.
948 do_send_sig_info(SIGKILL, SEND_SIG_PRIV, victim, PIDTYPE_TGID);
949 mark_oom_victim(victim);
950 pr_err("%s: Killed process %d (%s) total-vm:%lukB, anon-rss:%lukB, file-rss:%lukB, shmem-rss:%lukB, UID:%u pgtables:%lukB oom_score_adj:%hd\n",
951 message, task_pid_nr(victim), victim->comm, K(mm->total_vm),
952 K(get_mm_counter(mm, MM_ANONPAGES)),
953 K(get_mm_counter(mm, MM_FILEPAGES)),
954 K(get_mm_counter(mm, MM_SHMEMPAGES)),
955 from_kuid(&init_user_ns, task_uid(victim)),
956 mm_pgtables_bytes(mm) >> 10, victim->signal->oom_score_adj);
960 * Kill all user processes sharing victim->mm in other thread groups, if
961 * any. They don't get access to memory reserves, though, to avoid
962 * depletion of all memory. This prevents mm->mmap_lock livelock when an
963 * oom killed thread cannot exit because it requires the semaphore and
964 * its contended by another thread trying to allocate memory itself.
965 * That thread will now get access to memory reserves since it has a
966 * pending fatal signal.
969 for_each_process(p) {
970 if (!process_shares_mm(p, mm))
972 if (same_thread_group(p, victim))
974 if (is_global_init(p)) {
975 can_oom_reap = false;
976 set_bit(MMF_OOM_SKIP, &mm->flags);
977 pr_info("oom killer %d (%s) has mm pinned by %d (%s)\n",
978 task_pid_nr(victim), victim->comm,
979 task_pid_nr(p), p->comm);
983 * No kthread_use_mm() user needs to read from the userspace so
984 * we are ok to reap it.
986 if (unlikely(p->flags & PF_KTHREAD))
988 do_send_sig_info(SIGKILL, SEND_SIG_PRIV, p, PIDTYPE_TGID);
993 queue_oom_reaper(victim);
996 put_task_struct(victim);
1000 * Kill provided task unless it's secured by setting
1001 * oom_score_adj to OOM_SCORE_ADJ_MIN.
1003 static int oom_kill_memcg_member(struct task_struct *task, void *message)
1005 if (task->signal->oom_score_adj != OOM_SCORE_ADJ_MIN &&
1006 !is_global_init(task)) {
1007 get_task_struct(task);
1008 __oom_kill_process(task, message);
1013 static void oom_kill_process(struct oom_control *oc, const char *message)
1015 struct task_struct *victim = oc->chosen;
1016 struct mem_cgroup *oom_group;
1017 static DEFINE_RATELIMIT_STATE(oom_rs, DEFAULT_RATELIMIT_INTERVAL,
1018 DEFAULT_RATELIMIT_BURST);
1021 * If the task is already exiting, don't alarm the sysadmin or kill
1022 * its children or threads, just give it access to memory reserves
1023 * so it can die quickly
1026 if (task_will_free_mem(victim)) {
1027 mark_oom_victim(victim);
1028 queue_oom_reaper(victim);
1029 task_unlock(victim);
1030 put_task_struct(victim);
1033 task_unlock(victim);
1035 if (__ratelimit(&oom_rs)) {
1037 dump_oom_victim(oc, victim);
1041 * Do we need to kill the entire memory cgroup?
1042 * Or even one of the ancestor memory cgroups?
1043 * Check this out before killing the victim task.
1045 oom_group = mem_cgroup_get_oom_group(victim, oc->memcg);
1047 __oom_kill_process(victim, message);
1050 * If necessary, kill all tasks in the selected memory cgroup.
1053 memcg_memory_event(oom_group, MEMCG_OOM_GROUP_KILL);
1054 mem_cgroup_print_oom_group(oom_group);
1055 mem_cgroup_scan_tasks(oom_group, oom_kill_memcg_member,
1057 mem_cgroup_put(oom_group);
1062 * Determines whether the kernel must panic because of the panic_on_oom sysctl.
1064 static void check_panic_on_oom(struct oom_control *oc)
1066 if (likely(!sysctl_panic_on_oom))
1068 if (sysctl_panic_on_oom != 2) {
1070 * panic_on_oom == 1 only affects CONSTRAINT_NONE, the kernel
1071 * does not panic for cpuset, mempolicy, or memcg allocation
1074 if (oc->constraint != CONSTRAINT_NONE)
1077 /* Do not panic for oom kills triggered by sysrq */
1078 if (is_sysrq_oom(oc))
1081 panic("Out of memory: %s panic_on_oom is enabled\n",
1082 sysctl_panic_on_oom == 2 ? "compulsory" : "system-wide");
1085 static BLOCKING_NOTIFIER_HEAD(oom_notify_list);
1087 int register_oom_notifier(struct notifier_block *nb)
1089 return blocking_notifier_chain_register(&oom_notify_list, nb);
1091 EXPORT_SYMBOL_GPL(register_oom_notifier);
1093 int unregister_oom_notifier(struct notifier_block *nb)
1095 return blocking_notifier_chain_unregister(&oom_notify_list, nb);
1097 EXPORT_SYMBOL_GPL(unregister_oom_notifier);
1100 * out_of_memory - kill the "best" process when we run out of memory
1101 * @oc: pointer to struct oom_control
1103 * If we run out of memory, we have the choice between either
1104 * killing a random task (bad), letting the system crash (worse)
1105 * OR try to be smart about which process to kill. Note that we
1106 * don't have to be perfect here, we just have to be good.
1108 bool out_of_memory(struct oom_control *oc)
1110 unsigned long freed = 0;
1112 if (oom_killer_disabled)
1115 if (!is_memcg_oom(oc)) {
1116 blocking_notifier_call_chain(&oom_notify_list, 0, &freed);
1117 if (freed > 0 && !is_sysrq_oom(oc))
1118 /* Got some memory back in the last second. */
1123 * If current has a pending SIGKILL or is exiting, then automatically
1124 * select it. The goal is to allow it to allocate so that it may
1125 * quickly exit and free its memory.
1127 if (task_will_free_mem(current)) {
1128 mark_oom_victim(current);
1129 queue_oom_reaper(current);
1134 * The OOM killer does not compensate for IO-less reclaim.
1135 * But mem_cgroup_oom() has to invoke the OOM killer even
1136 * if it is a GFP_NOFS allocation.
1138 if (!(oc->gfp_mask & __GFP_FS) && !is_memcg_oom(oc))
1142 * Check if there were limitations on the allocation (only relevant for
1143 * NUMA and memcg) that may require different handling.
1145 oc->constraint = constrained_alloc(oc);
1146 if (oc->constraint != CONSTRAINT_MEMORY_POLICY)
1147 oc->nodemask = NULL;
1148 check_panic_on_oom(oc);
1150 if (!is_memcg_oom(oc) && sysctl_oom_kill_allocating_task &&
1151 current->mm && !oom_unkillable_task(current) &&
1152 oom_cpuset_eligible(current, oc) &&
1153 current->signal->oom_score_adj != OOM_SCORE_ADJ_MIN) {
1154 get_task_struct(current);
1155 oc->chosen = current;
1156 oom_kill_process(oc, "Out of memory (oom_kill_allocating_task)");
1160 select_bad_process(oc);
1161 /* Found nothing?!?! */
1164 pr_warn("Out of memory and no killable processes...\n");
1166 * If we got here due to an actual allocation at the
1167 * system level, we cannot survive this and will enter
1168 * an endless loop in the allocator. Bail out now.
1170 if (!is_sysrq_oom(oc) && !is_memcg_oom(oc))
1171 panic("System is deadlocked on memory\n");
1173 if (oc->chosen && oc->chosen != (void *)-1UL)
1174 oom_kill_process(oc, !is_memcg_oom(oc) ? "Out of memory" :
1175 "Memory cgroup out of memory");
1176 return !!oc->chosen;
1180 * The pagefault handler calls here because some allocation has failed. We have
1181 * to take care of the memcg OOM here because this is the only safe context without
1182 * any locks held but let the oom killer triggered from the allocation context care
1183 * about the global OOM.
1185 void pagefault_out_of_memory(void)
1187 static DEFINE_RATELIMIT_STATE(pfoom_rs, DEFAULT_RATELIMIT_INTERVAL,
1188 DEFAULT_RATELIMIT_BURST);
1190 if (mem_cgroup_oom_synchronize(true))
1193 if (fatal_signal_pending(current))
1196 if (__ratelimit(&pfoom_rs))
1197 pr_warn("Huh VM_FAULT_OOM leaked out to the #PF handler. Retrying PF\n");
1200 SYSCALL_DEFINE2(process_mrelease, int, pidfd, unsigned int, flags)
1203 struct mm_struct *mm = NULL;
1204 struct task_struct *task;
1205 struct task_struct *p;
1206 unsigned int f_flags;
1213 task = pidfd_get_task(pidfd, &f_flags);
1215 return PTR_ERR(task);
1218 * Make sure to choose a thread which still has a reference to mm
1219 * during the group exit
1221 p = find_lock_task_mm(task);
1230 if (task_will_free_mem(p))
1233 /* Error only if the work has not been done already */
1234 if (!test_bit(MMF_OOM_SKIP, &mm->flags))
1242 if (mmap_read_lock_killable(mm)) {
1247 * Check MMF_OOM_SKIP again under mmap_read_lock protection to ensure
1248 * possible change in exit_mmap is seen
1250 if (!test_bit(MMF_OOM_SKIP, &mm->flags) && !__oom_reap_task_mm(mm))
1252 mmap_read_unlock(mm);
1257 put_task_struct(task);
1261 #endif /* CONFIG_MMU */