4 * Copyright (C) 1998,2000 Rik van Riel
5 * Thanks go out to Claus Fischer for some serious inspiration and
6 * for goading me into coding this file...
7 * Copyright (C) 2010 Google, Inc.
8 * Rewritten by David Rientjes
10 * The routines in this file are used to kill a process when
11 * we're seriously out of memory. This gets called from __alloc_pages()
12 * in mm/page_alloc.c when we really run out of memory.
14 * Since we won't call these routines often (on a well-configured
15 * machine) this file will double as a 'coding guide' and a signpost
16 * for newbie kernel hackers. It features several pointers to major
17 * kernel subsystems and hints as to where to find out what things do.
20 #include <linux/oom.h>
22 #include <linux/err.h>
23 #include <linux/gfp.h>
24 #include <linux/sched.h>
25 #include <linux/sched/mm.h>
26 #include <linux/sched/coredump.h>
27 #include <linux/sched/task.h>
28 #include <linux/swap.h>
29 #include <linux/timex.h>
30 #include <linux/jiffies.h>
31 #include <linux/cpuset.h>
32 #include <linux/export.h>
33 #include <linux/notifier.h>
34 #include <linux/memcontrol.h>
35 #include <linux/mempolicy.h>
36 #include <linux/security.h>
37 #include <linux/ptrace.h>
38 #include <linux/freezer.h>
39 #include <linux/ftrace.h>
40 #include <linux/ratelimit.h>
41 #include <linux/kthread.h>
42 #include <linux/init.h>
43 #include <linux/mmu_notifier.h>
48 #define CREATE_TRACE_POINTS
49 #include <trace/events/oom.h>
51 int sysctl_panic_on_oom;
52 int sysctl_oom_kill_allocating_task;
53 int sysctl_oom_dump_tasks = 1;
55 DEFINE_MUTEX(oom_lock);
59 * has_intersects_mems_allowed() - check task eligiblity for kill
60 * @start: task struct of which task to consider
61 * @mask: nodemask passed to page allocator for mempolicy ooms
63 * Task eligibility is determined by whether or not a candidate task, @tsk,
64 * shares the same mempolicy nodes as current if it is bound by such a policy
65 * and whether or not it has the same set of allowed cpuset nodes.
67 static bool has_intersects_mems_allowed(struct task_struct *start,
68 const nodemask_t *mask)
70 struct task_struct *tsk;
74 for_each_thread(start, tsk) {
77 * If this is a mempolicy constrained oom, tsk's
78 * cpuset is irrelevant. Only return true if its
79 * mempolicy intersects current, otherwise it may be
82 ret = mempolicy_nodemask_intersects(tsk, mask);
85 * This is not a mempolicy constrained oom, so only
86 * check the mems of tsk's cpuset.
88 ret = cpuset_mems_allowed_intersects(current, tsk);
98 static bool has_intersects_mems_allowed(struct task_struct *tsk,
99 const nodemask_t *mask)
103 #endif /* CONFIG_NUMA */
106 * The process p may have detached its own ->mm while exiting or through
107 * use_mm(), but one or more of its subthreads may still have a valid
108 * pointer. Return p, or any of its subthreads with a valid ->mm, with
111 struct task_struct *find_lock_task_mm(struct task_struct *p)
113 struct task_struct *t;
117 for_each_thread(p, t) {
131 * order == -1 means the oom kill is required by sysrq, otherwise only
132 * for display purposes.
134 static inline bool is_sysrq_oom(struct oom_control *oc)
136 return oc->order == -1;
139 static inline bool is_memcg_oom(struct oom_control *oc)
141 return oc->memcg != NULL;
144 /* return true if the task is not adequate as candidate victim task. */
145 static bool oom_unkillable_task(struct task_struct *p,
146 struct mem_cgroup *memcg, const nodemask_t *nodemask)
148 if (is_global_init(p))
150 if (p->flags & PF_KTHREAD)
153 /* When mem_cgroup_out_of_memory() and p is not member of the group */
154 if (memcg && !task_in_mem_cgroup(p, memcg))
157 /* p may not have freeable memory in nodemask */
158 if (!has_intersects_mems_allowed(p, nodemask))
165 * oom_badness - heuristic function to determine which candidate task to kill
166 * @p: task struct of which task we should calculate
167 * @totalpages: total present RAM allowed for page allocation
169 * The heuristic for determining which task to kill is made to be as simple and
170 * predictable as possible. The goal is to return the highest value for the
171 * task consuming the most memory to avoid subsequent oom failures.
173 unsigned long oom_badness(struct task_struct *p, struct mem_cgroup *memcg,
174 const nodemask_t *nodemask, unsigned long totalpages)
179 if (oom_unkillable_task(p, memcg, nodemask))
182 p = find_lock_task_mm(p);
187 * Do not even consider tasks which are explicitly marked oom
188 * unkillable or have been already oom reaped or the are in
189 * the middle of vfork
191 adj = (long)p->signal->oom_score_adj;
192 if (adj == OOM_SCORE_ADJ_MIN ||
193 test_bit(MMF_OOM_SKIP, &p->mm->flags) ||
200 * The baseline for the badness score is the proportion of RAM that each
201 * task's rss, pagetable and swap space use.
203 points = get_mm_rss(p->mm) + get_mm_counter(p->mm, MM_SWAPENTS) +
204 atomic_long_read(&p->mm->nr_ptes) + mm_nr_pmds(p->mm);
208 * Root processes get 3% bonus, just like the __vm_enough_memory()
209 * implementation used by LSMs.
211 if (has_capability_noaudit(p, CAP_SYS_ADMIN))
212 points -= (points * 3) / 100;
214 /* Normalize to oom_score_adj units */
215 adj *= totalpages / 1000;
219 * Never return 0 for an eligible task regardless of the root bonus and
220 * oom_score_adj (oom_score_adj can't be OOM_SCORE_ADJ_MIN here).
222 return points > 0 ? points : 1;
225 enum oom_constraint {
228 CONSTRAINT_MEMORY_POLICY,
233 * Determine the type of allocation constraint.
235 static enum oom_constraint constrained_alloc(struct oom_control *oc)
239 enum zone_type high_zoneidx = gfp_zone(oc->gfp_mask);
240 bool cpuset_limited = false;
243 if (is_memcg_oom(oc)) {
244 oc->totalpages = mem_cgroup_get_limit(oc->memcg) ?: 1;
245 return CONSTRAINT_MEMCG;
248 /* Default to all available memory */
249 oc->totalpages = totalram_pages + total_swap_pages;
251 if (!IS_ENABLED(CONFIG_NUMA))
252 return CONSTRAINT_NONE;
255 return CONSTRAINT_NONE;
257 * Reach here only when __GFP_NOFAIL is used. So, we should avoid
258 * to kill current.We have to random task kill in this case.
259 * Hopefully, CONSTRAINT_THISNODE...but no way to handle it, now.
261 if (oc->gfp_mask & __GFP_THISNODE)
262 return CONSTRAINT_NONE;
265 * This is not a __GFP_THISNODE allocation, so a truncated nodemask in
266 * the page allocator means a mempolicy is in effect. Cpuset policy
267 * is enforced in get_page_from_freelist().
270 !nodes_subset(node_states[N_MEMORY], *oc->nodemask)) {
271 oc->totalpages = total_swap_pages;
272 for_each_node_mask(nid, *oc->nodemask)
273 oc->totalpages += node_spanned_pages(nid);
274 return CONSTRAINT_MEMORY_POLICY;
277 /* Check this allocation failure is caused by cpuset's wall function */
278 for_each_zone_zonelist_nodemask(zone, z, oc->zonelist,
279 high_zoneidx, oc->nodemask)
280 if (!cpuset_zone_allowed(zone, oc->gfp_mask))
281 cpuset_limited = true;
283 if (cpuset_limited) {
284 oc->totalpages = total_swap_pages;
285 for_each_node_mask(nid, cpuset_current_mems_allowed)
286 oc->totalpages += node_spanned_pages(nid);
287 return CONSTRAINT_CPUSET;
289 return CONSTRAINT_NONE;
292 static int oom_evaluate_task(struct task_struct *task, void *arg)
294 struct oom_control *oc = arg;
295 unsigned long points;
297 if (oom_unkillable_task(task, NULL, oc->nodemask))
301 * This task already has access to memory reserves and is being killed.
302 * Don't allow any other task to have access to the reserves unless
303 * the task has MMF_OOM_SKIP because chances that it would release
304 * any memory is quite low.
306 if (!is_sysrq_oom(oc) && tsk_is_oom_victim(task)) {
307 if (test_bit(MMF_OOM_SKIP, &task->signal->oom_mm->flags))
313 * If task is allocating a lot of memory and has been marked to be
314 * killed first if it triggers an oom, then select it.
316 if (oom_task_origin(task)) {
321 points = oom_badness(task, NULL, oc->nodemask, oc->totalpages);
322 if (!points || points < oc->chosen_points)
325 /* Prefer thread group leaders for display purposes */
326 if (points == oc->chosen_points && thread_group_leader(oc->chosen))
330 put_task_struct(oc->chosen);
331 get_task_struct(task);
333 oc->chosen_points = points;
338 put_task_struct(oc->chosen);
339 oc->chosen = (void *)-1UL;
344 * Simple selection loop. We choose the process with the highest number of
345 * 'points'. In case scan was aborted, oc->chosen is set to -1.
347 static void select_bad_process(struct oom_control *oc)
349 if (is_memcg_oom(oc))
350 mem_cgroup_scan_tasks(oc->memcg, oom_evaluate_task, oc);
352 struct task_struct *p;
356 if (oom_evaluate_task(p, oc))
361 oc->chosen_points = oc->chosen_points * 1000 / oc->totalpages;
365 * dump_tasks - dump current memory state of all system tasks
366 * @memcg: current's memory controller, if constrained
367 * @nodemask: nodemask passed to page allocator for mempolicy ooms
369 * Dumps the current memory state of all eligible tasks. Tasks not in the same
370 * memcg, not in the same cpuset, or bound to a disjoint set of mempolicy nodes
372 * State information includes task's pid, uid, tgid, vm size, rss, nr_ptes,
373 * swapents, oom_score_adj value, and name.
375 static void dump_tasks(struct mem_cgroup *memcg, const nodemask_t *nodemask)
377 struct task_struct *p;
378 struct task_struct *task;
380 pr_info("[ pid ] uid tgid total_vm rss nr_ptes nr_pmds swapents oom_score_adj name\n");
382 for_each_process(p) {
383 if (oom_unkillable_task(p, memcg, nodemask))
386 task = find_lock_task_mm(p);
389 * This is a kthread or all of p's threads have already
390 * detached their mm's. There's no need to report
391 * them; they can't be oom killed anyway.
396 pr_info("[%5d] %5d %5d %8lu %8lu %7ld %7ld %8lu %5hd %s\n",
397 task->pid, from_kuid(&init_user_ns, task_uid(task)),
398 task->tgid, task->mm->total_vm, get_mm_rss(task->mm),
399 atomic_long_read(&task->mm->nr_ptes),
400 mm_nr_pmds(task->mm),
401 get_mm_counter(task->mm, MM_SWAPENTS),
402 task->signal->oom_score_adj, task->comm);
408 static void dump_header(struct oom_control *oc, struct task_struct *p)
410 pr_warn("%s invoked oom-killer: gfp_mask=%#x(%pGg), nodemask=",
411 current->comm, oc->gfp_mask, &oc->gfp_mask);
413 pr_cont("%*pbl", nodemask_pr_args(oc->nodemask));
416 pr_cont(", order=%d, oom_score_adj=%hd\n",
417 oc->order, current->signal->oom_score_adj);
418 if (!IS_ENABLED(CONFIG_COMPACTION) && oc->order)
419 pr_warn("COMPACTION is disabled!!!\n");
421 cpuset_print_current_mems_allowed();
424 mem_cgroup_print_oom_info(oc->memcg, p);
426 show_mem(SHOW_MEM_FILTER_NODES, oc->nodemask);
427 if (sysctl_oom_dump_tasks)
428 dump_tasks(oc->memcg, oc->nodemask);
432 * Number of OOM victims in flight
434 static atomic_t oom_victims = ATOMIC_INIT(0);
435 static DECLARE_WAIT_QUEUE_HEAD(oom_victims_wait);
437 static bool oom_killer_disabled __read_mostly;
439 #define K(x) ((x) << (PAGE_SHIFT-10))
442 * task->mm can be NULL if the task is the exited group leader. So to
443 * determine whether the task is using a particular mm, we examine all the
444 * task's threads: if one of those is using this mm then this task was also
447 bool process_shares_mm(struct task_struct *p, struct mm_struct *mm)
449 struct task_struct *t;
451 for_each_thread(p, t) {
452 struct mm_struct *t_mm = READ_ONCE(t->mm);
462 * OOM Reaper kernel thread which tries to reap the memory used by the OOM
463 * victim (if that is possible) to help the OOM killer to move on.
465 static struct task_struct *oom_reaper_th;
466 static DECLARE_WAIT_QUEUE_HEAD(oom_reaper_wait);
467 static struct task_struct *oom_reaper_list;
468 static DEFINE_SPINLOCK(oom_reaper_lock);
470 static bool __oom_reap_task_mm(struct task_struct *tsk, struct mm_struct *mm)
472 struct mmu_gather tlb;
473 struct vm_area_struct *vma;
477 * We have to make sure to not race with the victim exit path
478 * and cause premature new oom victim selection:
479 * __oom_reap_task_mm exit_mm
482 * atomic_dec_and_test
487 * # no TIF_MEMDIE task selects new victim
488 * unmap_page_range # frees some memory
490 mutex_lock(&oom_lock);
492 if (!down_read_trylock(&mm->mmap_sem)) {
494 trace_skip_task_reaping(tsk->pid);
499 * If the mm has notifiers then we would need to invalidate them around
500 * unmap_page_range and that is risky because notifiers can sleep and
501 * what they do is basically undeterministic. So let's have a short
502 * sleep to give the oom victim some more time.
503 * TODO: we really want to get rid of this ugly hack and make sure that
504 * notifiers cannot block for unbounded amount of time and add
505 * mmu_notifier_invalidate_range_{start,end} around unmap_page_range
507 if (mm_has_notifiers(mm)) {
508 up_read(&mm->mmap_sem);
509 schedule_timeout_idle(HZ);
514 * MMF_OOM_SKIP is set by exit_mmap when the OOM reaper can't
515 * work on the mm anymore. The check for MMF_OOM_SKIP must run
516 * under mmap_sem for reading because it serializes against the
517 * down_write();up_write() cycle in exit_mmap().
519 if (test_bit(MMF_OOM_SKIP, &mm->flags)) {
520 up_read(&mm->mmap_sem);
521 trace_skip_task_reaping(tsk->pid);
525 trace_start_task_reaping(tsk->pid);
528 * Tell all users of get_user/copy_from_user etc... that the content
529 * is no longer stable. No barriers really needed because unmapping
530 * should imply barriers already and the reader would hit a page fault
531 * if it stumbled over a reaped memory.
533 set_bit(MMF_UNSTABLE, &mm->flags);
535 for (vma = mm->mmap ; vma; vma = vma->vm_next) {
536 if (!can_madv_dontneed_vma(vma))
540 * Only anonymous pages have a good chance to be dropped
541 * without additional steps which we cannot afford as we
544 * We do not even care about fs backed pages because all
545 * which are reclaimable have already been reclaimed and
546 * we do not want to block exit_mmap by keeping mm ref
547 * count elevated without a good reason.
549 if (vma_is_anonymous(vma) || !(vma->vm_flags & VM_SHARED)) {
550 tlb_gather_mmu(&tlb, mm, vma->vm_start, vma->vm_end);
551 unmap_page_range(&tlb, vma, vma->vm_start, vma->vm_end,
553 tlb_finish_mmu(&tlb, vma->vm_start, vma->vm_end);
556 pr_info("oom_reaper: reaped process %d (%s), now anon-rss:%lukB, file-rss:%lukB, shmem-rss:%lukB\n",
557 task_pid_nr(tsk), tsk->comm,
558 K(get_mm_counter(mm, MM_ANONPAGES)),
559 K(get_mm_counter(mm, MM_FILEPAGES)),
560 K(get_mm_counter(mm, MM_SHMEMPAGES)));
561 up_read(&mm->mmap_sem);
563 trace_finish_task_reaping(tsk->pid);
565 mutex_unlock(&oom_lock);
569 #define MAX_OOM_REAP_RETRIES 10
570 static void oom_reap_task(struct task_struct *tsk)
573 struct mm_struct *mm = tsk->signal->oom_mm;
575 /* Retry the down_read_trylock(mmap_sem) a few times */
576 while (attempts++ < MAX_OOM_REAP_RETRIES && !__oom_reap_task_mm(tsk, mm))
577 schedule_timeout_idle(HZ/10);
579 if (attempts <= MAX_OOM_REAP_RETRIES)
583 pr_info("oom_reaper: unable to reap pid:%d (%s)\n",
584 task_pid_nr(tsk), tsk->comm);
585 debug_show_all_locks();
588 tsk->oom_reaper_list = NULL;
591 * Hide this mm from OOM killer because it has been either reaped or
592 * somebody can't call up_write(mmap_sem).
594 set_bit(MMF_OOM_SKIP, &mm->flags);
596 /* Drop a reference taken by wake_oom_reaper */
597 put_task_struct(tsk);
600 static int oom_reaper(void *unused)
603 struct task_struct *tsk = NULL;
605 wait_event_freezable(oom_reaper_wait, oom_reaper_list != NULL);
606 spin_lock(&oom_reaper_lock);
607 if (oom_reaper_list != NULL) {
608 tsk = oom_reaper_list;
609 oom_reaper_list = tsk->oom_reaper_list;
611 spin_unlock(&oom_reaper_lock);
620 static void wake_oom_reaper(struct task_struct *tsk)
625 /* tsk is already queued? */
626 if (tsk == oom_reaper_list || tsk->oom_reaper_list)
629 get_task_struct(tsk);
631 spin_lock(&oom_reaper_lock);
632 tsk->oom_reaper_list = oom_reaper_list;
633 oom_reaper_list = tsk;
634 spin_unlock(&oom_reaper_lock);
635 trace_wake_reaper(tsk->pid);
636 wake_up(&oom_reaper_wait);
639 static int __init oom_init(void)
641 oom_reaper_th = kthread_run(oom_reaper, NULL, "oom_reaper");
642 if (IS_ERR(oom_reaper_th)) {
643 pr_err("Unable to start OOM reaper %ld. Continuing regardless\n",
644 PTR_ERR(oom_reaper_th));
645 oom_reaper_th = NULL;
649 subsys_initcall(oom_init)
651 static inline void wake_oom_reaper(struct task_struct *tsk)
654 #endif /* CONFIG_MMU */
657 * mark_oom_victim - mark the given task as OOM victim
660 * Has to be called with oom_lock held and never after
661 * oom has been disabled already.
663 * tsk->mm has to be non NULL and caller has to guarantee it is stable (either
664 * under task_lock or operate on the current).
666 static void mark_oom_victim(struct task_struct *tsk)
668 struct mm_struct *mm = tsk->mm;
670 WARN_ON(oom_killer_disabled);
671 /* OOM killer might race with memcg OOM */
672 if (test_and_set_tsk_thread_flag(tsk, TIF_MEMDIE))
675 /* oom_mm is bound to the signal struct life time. */
676 if (!cmpxchg(&tsk->signal->oom_mm, NULL, mm)) {
677 mmgrab(tsk->signal->oom_mm);
678 set_bit(MMF_OOM_VICTIM, &mm->flags);
682 * Make sure that the task is woken up from uninterruptible sleep
683 * if it is frozen because OOM killer wouldn't be able to free
684 * any memory and livelock. freezing_slow_path will tell the freezer
685 * that TIF_MEMDIE tasks should be ignored.
688 atomic_inc(&oom_victims);
689 trace_mark_victim(tsk->pid);
693 * exit_oom_victim - note the exit of an OOM victim
695 void exit_oom_victim(void)
697 clear_thread_flag(TIF_MEMDIE);
699 if (!atomic_dec_return(&oom_victims))
700 wake_up_all(&oom_victims_wait);
704 * oom_killer_enable - enable OOM killer
706 void oom_killer_enable(void)
708 oom_killer_disabled = false;
709 pr_info("OOM killer enabled.\n");
713 * oom_killer_disable - disable OOM killer
714 * @timeout: maximum timeout to wait for oom victims in jiffies
716 * Forces all page allocations to fail rather than trigger OOM killer.
717 * Will block and wait until all OOM victims are killed or the given
720 * The function cannot be called when there are runnable user tasks because
721 * the userspace would see unexpected allocation failures as a result. Any
722 * new usage of this function should be consulted with MM people.
724 * Returns true if successful and false if the OOM killer cannot be
727 bool oom_killer_disable(signed long timeout)
732 * Make sure to not race with an ongoing OOM killer. Check that the
733 * current is not killed (possibly due to sharing the victim's memory).
735 if (mutex_lock_killable(&oom_lock))
737 oom_killer_disabled = true;
738 mutex_unlock(&oom_lock);
740 ret = wait_event_interruptible_timeout(oom_victims_wait,
741 !atomic_read(&oom_victims), timeout);
746 pr_info("OOM killer disabled.\n");
751 static inline bool __task_will_free_mem(struct task_struct *task)
753 struct signal_struct *sig = task->signal;
756 * A coredumping process may sleep for an extended period in exit_mm(),
757 * so the oom killer cannot assume that the process will promptly exit
758 * and release memory.
760 if (sig->flags & SIGNAL_GROUP_COREDUMP)
763 if (sig->flags & SIGNAL_GROUP_EXIT)
766 if (thread_group_empty(task) && (task->flags & PF_EXITING))
773 * Checks whether the given task is dying or exiting and likely to
774 * release its address space. This means that all threads and processes
775 * sharing the same mm have to be killed or exiting.
776 * Caller has to make sure that task->mm is stable (hold task_lock or
777 * it operates on the current).
779 static bool task_will_free_mem(struct task_struct *task)
781 struct mm_struct *mm = task->mm;
782 struct task_struct *p;
786 * Skip tasks without mm because it might have passed its exit_mm and
787 * exit_oom_victim. oom_reaper could have rescued that but do not rely
788 * on that for now. We can consider find_lock_task_mm in future.
793 if (!__task_will_free_mem(task))
797 * This task has already been drained by the oom reaper so there are
798 * only small chances it will free some more
800 if (test_bit(MMF_OOM_SKIP, &mm->flags))
803 if (atomic_read(&mm->mm_users) <= 1)
807 * Make sure that all tasks which share the mm with the given tasks
808 * are dying as well to make sure that a) nobody pins its mm and
809 * b) the task is also reapable by the oom reaper.
812 for_each_process(p) {
813 if (!process_shares_mm(p, mm))
815 if (same_thread_group(task, p))
817 ret = __task_will_free_mem(p);
826 static void oom_kill_process(struct oom_control *oc, const char *message)
828 struct task_struct *p = oc->chosen;
829 unsigned int points = oc->chosen_points;
830 struct task_struct *victim = p;
831 struct task_struct *child;
832 struct task_struct *t;
833 struct mm_struct *mm;
834 unsigned int victim_points = 0;
835 static DEFINE_RATELIMIT_STATE(oom_rs, DEFAULT_RATELIMIT_INTERVAL,
836 DEFAULT_RATELIMIT_BURST);
837 bool can_oom_reap = true;
840 * If the task is already exiting, don't alarm the sysadmin or kill
841 * its children or threads, just give it access to memory reserves
842 * so it can die quickly
845 if (task_will_free_mem(p)) {
854 if (__ratelimit(&oom_rs))
857 pr_err("%s: Kill process %d (%s) score %u or sacrifice child\n",
858 message, task_pid_nr(p), p->comm, points);
861 * If any of p's children has a different mm and is eligible for kill,
862 * the one with the highest oom_badness() score is sacrificed for its
863 * parent. This attempts to lose the minimal amount of work done while
864 * still freeing memory.
866 read_lock(&tasklist_lock);
867 for_each_thread(p, t) {
868 list_for_each_entry(child, &t->children, sibling) {
869 unsigned int child_points;
871 if (process_shares_mm(child, p->mm))
874 * oom_badness() returns 0 if the thread is unkillable
876 child_points = oom_badness(child,
877 oc->memcg, oc->nodemask, oc->totalpages);
878 if (child_points > victim_points) {
879 put_task_struct(victim);
881 victim_points = child_points;
882 get_task_struct(victim);
886 read_unlock(&tasklist_lock);
888 p = find_lock_task_mm(victim);
890 put_task_struct(victim);
892 } else if (victim != p) {
894 put_task_struct(victim);
898 /* Get a reference to safely compare mm after task_unlock(victim) */
902 /* Raise event before sending signal: task reaper must see this */
903 count_vm_event(OOM_KILL);
904 count_memcg_event_mm(mm, OOM_KILL);
907 * We should send SIGKILL before granting access to memory reserves
908 * in order to prevent the OOM victim from depleting the memory
909 * reserves from the user space under its control.
911 do_send_sig_info(SIGKILL, SEND_SIG_FORCED, victim, true);
912 mark_oom_victim(victim);
913 pr_err("Killed process %d (%s) total-vm:%lukB, anon-rss:%lukB, file-rss:%lukB, shmem-rss:%lukB\n",
914 task_pid_nr(victim), victim->comm, K(victim->mm->total_vm),
915 K(get_mm_counter(victim->mm, MM_ANONPAGES)),
916 K(get_mm_counter(victim->mm, MM_FILEPAGES)),
917 K(get_mm_counter(victim->mm, MM_SHMEMPAGES)));
921 * Kill all user processes sharing victim->mm in other thread groups, if
922 * any. They don't get access to memory reserves, though, to avoid
923 * depletion of all memory. This prevents mm->mmap_sem livelock when an
924 * oom killed thread cannot exit because it requires the semaphore and
925 * its contended by another thread trying to allocate memory itself.
926 * That thread will now get access to memory reserves since it has a
927 * pending fatal signal.
930 for_each_process(p) {
931 if (!process_shares_mm(p, mm))
933 if (same_thread_group(p, victim))
935 if (is_global_init(p)) {
936 can_oom_reap = false;
937 set_bit(MMF_OOM_SKIP, &mm->flags);
938 pr_info("oom killer %d (%s) has mm pinned by %d (%s)\n",
939 task_pid_nr(victim), victim->comm,
940 task_pid_nr(p), p->comm);
944 * No use_mm() user needs to read from the userspace so we are
947 if (unlikely(p->flags & PF_KTHREAD))
949 do_send_sig_info(SIGKILL, SEND_SIG_FORCED, p, true);
954 wake_oom_reaper(victim);
957 put_task_struct(victim);
962 * Determines whether the kernel must panic because of the panic_on_oom sysctl.
964 static void check_panic_on_oom(struct oom_control *oc,
965 enum oom_constraint constraint)
967 if (likely(!sysctl_panic_on_oom))
969 if (sysctl_panic_on_oom != 2) {
971 * panic_on_oom == 1 only affects CONSTRAINT_NONE, the kernel
972 * does not panic for cpuset, mempolicy, or memcg allocation
975 if (constraint != CONSTRAINT_NONE)
978 /* Do not panic for oom kills triggered by sysrq */
979 if (is_sysrq_oom(oc))
981 dump_header(oc, NULL);
982 panic("Out of memory: %s panic_on_oom is enabled\n",
983 sysctl_panic_on_oom == 2 ? "compulsory" : "system-wide");
986 static BLOCKING_NOTIFIER_HEAD(oom_notify_list);
988 int register_oom_notifier(struct notifier_block *nb)
990 return blocking_notifier_chain_register(&oom_notify_list, nb);
992 EXPORT_SYMBOL_GPL(register_oom_notifier);
994 int unregister_oom_notifier(struct notifier_block *nb)
996 return blocking_notifier_chain_unregister(&oom_notify_list, nb);
998 EXPORT_SYMBOL_GPL(unregister_oom_notifier);
1001 * out_of_memory - kill the "best" process when we run out of memory
1002 * @oc: pointer to struct oom_control
1004 * If we run out of memory, we have the choice between either
1005 * killing a random task (bad), letting the system crash (worse)
1006 * OR try to be smart about which process to kill. Note that we
1007 * don't have to be perfect here, we just have to be good.
1009 bool out_of_memory(struct oom_control *oc)
1011 unsigned long freed = 0;
1012 enum oom_constraint constraint = CONSTRAINT_NONE;
1014 if (oom_killer_disabled)
1017 if (!is_memcg_oom(oc)) {
1018 blocking_notifier_call_chain(&oom_notify_list, 0, &freed);
1020 /* Got some memory back in the last second. */
1025 * If current has a pending SIGKILL or is exiting, then automatically
1026 * select it. The goal is to allow it to allocate so that it may
1027 * quickly exit and free its memory.
1029 if (task_will_free_mem(current)) {
1030 mark_oom_victim(current);
1031 wake_oom_reaper(current);
1036 * The OOM killer does not compensate for IO-less reclaim.
1037 * pagefault_out_of_memory lost its gfp context so we have to
1038 * make sure exclude 0 mask - all other users should have at least
1039 * ___GFP_DIRECT_RECLAIM to get here.
1041 if (oc->gfp_mask && !(oc->gfp_mask & __GFP_FS))
1045 * Check if there were limitations on the allocation (only relevant for
1046 * NUMA and memcg) that may require different handling.
1048 constraint = constrained_alloc(oc);
1049 if (constraint != CONSTRAINT_MEMORY_POLICY)
1050 oc->nodemask = NULL;
1051 check_panic_on_oom(oc, constraint);
1053 if (!is_memcg_oom(oc) && sysctl_oom_kill_allocating_task &&
1054 current->mm && !oom_unkillable_task(current, NULL, oc->nodemask) &&
1055 current->signal->oom_score_adj != OOM_SCORE_ADJ_MIN) {
1056 get_task_struct(current);
1057 oc->chosen = current;
1058 oom_kill_process(oc, "Out of memory (oom_kill_allocating_task)");
1062 select_bad_process(oc);
1063 /* Found nothing?!?! Either we hang forever, or we panic. */
1064 if (!oc->chosen && !is_sysrq_oom(oc) && !is_memcg_oom(oc)) {
1065 dump_header(oc, NULL);
1066 panic("Out of memory and no killable processes...\n");
1068 if (oc->chosen && oc->chosen != (void *)-1UL) {
1069 oom_kill_process(oc, !is_memcg_oom(oc) ? "Out of memory" :
1070 "Memory cgroup out of memory");
1072 * Give the killed process a good chance to exit before trying
1073 * to allocate memory again.
1075 schedule_timeout_killable(1);
1077 return !!oc->chosen;
1081 * The pagefault handler calls here because it is out of memory, so kill a
1082 * memory-hogging task. If oom_lock is held by somebody else, a parallel oom
1083 * killing is already in progress so do nothing.
1085 void pagefault_out_of_memory(void)
1087 struct oom_control oc = {
1095 if (mem_cgroup_oom_synchronize(true))
1098 if (!mutex_trylock(&oom_lock))
1101 mutex_unlock(&oom_lock);