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>
49 #define CREATE_TRACE_POINTS
50 #include <trace/events/oom.h>
52 int sysctl_panic_on_oom;
53 int sysctl_oom_kill_allocating_task;
54 int sysctl_oom_dump_tasks = 1;
56 DEFINE_MUTEX(oom_lock);
60 * has_intersects_mems_allowed() - check task eligiblity for kill
61 * @start: task struct of which task to consider
62 * @mask: nodemask passed to page allocator for mempolicy ooms
64 * Task eligibility is determined by whether or not a candidate task, @tsk,
65 * shares the same mempolicy nodes as current if it is bound by such a policy
66 * and whether or not it has the same set of allowed cpuset nodes.
68 static bool has_intersects_mems_allowed(struct task_struct *start,
69 const nodemask_t *mask)
71 struct task_struct *tsk;
75 for_each_thread(start, tsk) {
78 * If this is a mempolicy constrained oom, tsk's
79 * cpuset is irrelevant. Only return true if its
80 * mempolicy intersects current, otherwise it may be
83 ret = mempolicy_nodemask_intersects(tsk, mask);
86 * This is not a mempolicy constrained oom, so only
87 * check the mems of tsk's cpuset.
89 ret = cpuset_mems_allowed_intersects(current, tsk);
99 static bool has_intersects_mems_allowed(struct task_struct *tsk,
100 const nodemask_t *mask)
104 #endif /* CONFIG_NUMA */
107 * The process p may have detached its own ->mm while exiting or through
108 * use_mm(), but one or more of its subthreads may still have a valid
109 * pointer. Return p, or any of its subthreads with a valid ->mm, with
112 struct task_struct *find_lock_task_mm(struct task_struct *p)
114 struct task_struct *t;
118 for_each_thread(p, t) {
132 * order == -1 means the oom kill is required by sysrq, otherwise only
133 * for display purposes.
135 static inline bool is_sysrq_oom(struct oom_control *oc)
137 return oc->order == -1;
140 static inline bool is_memcg_oom(struct oom_control *oc)
142 return oc->memcg != NULL;
145 /* return true if the task is not adequate as candidate victim task. */
146 static bool oom_unkillable_task(struct task_struct *p,
147 struct mem_cgroup *memcg, const nodemask_t *nodemask)
149 if (is_global_init(p))
151 if (p->flags & PF_KTHREAD)
154 /* When mem_cgroup_out_of_memory() and p is not member of the group */
155 if (memcg && !task_in_mem_cgroup(p, memcg))
158 /* p may not have freeable memory in nodemask */
159 if (!has_intersects_mems_allowed(p, nodemask))
166 * Print out unreclaimble slabs info when unreclaimable slabs amount is greater
167 * than all user memory (LRU pages)
169 static bool is_dump_unreclaim_slabs(void)
171 unsigned long nr_lru;
173 nr_lru = global_node_page_state(NR_ACTIVE_ANON) +
174 global_node_page_state(NR_INACTIVE_ANON) +
175 global_node_page_state(NR_ACTIVE_FILE) +
176 global_node_page_state(NR_INACTIVE_FILE) +
177 global_node_page_state(NR_ISOLATED_ANON) +
178 global_node_page_state(NR_ISOLATED_FILE) +
179 global_node_page_state(NR_UNEVICTABLE);
181 return (global_node_page_state(NR_SLAB_UNRECLAIMABLE) > nr_lru);
185 * oom_badness - heuristic function to determine which candidate task to kill
186 * @p: task struct of which task we should calculate
187 * @totalpages: total present RAM allowed for page allocation
189 * The heuristic for determining which task to kill is made to be as simple and
190 * predictable as possible. The goal is to return the highest value for the
191 * task consuming the most memory to avoid subsequent oom failures.
193 unsigned long oom_badness(struct task_struct *p, struct mem_cgroup *memcg,
194 const nodemask_t *nodemask, unsigned long totalpages)
199 if (oom_unkillable_task(p, memcg, nodemask))
202 p = find_lock_task_mm(p);
207 * Do not even consider tasks which are explicitly marked oom
208 * unkillable or have been already oom reaped or the are in
209 * the middle of vfork
211 adj = (long)p->signal->oom_score_adj;
212 if (adj == OOM_SCORE_ADJ_MIN ||
213 test_bit(MMF_OOM_SKIP, &p->mm->flags) ||
220 * The baseline for the badness score is the proportion of RAM that each
221 * task's rss, pagetable and swap space use.
223 points = get_mm_rss(p->mm) + get_mm_counter(p->mm, MM_SWAPENTS) +
224 mm_nr_ptes(p->mm) + mm_nr_pmds(p->mm) + mm_nr_puds(p->mm);
228 * Root processes get 3% bonus, just like the __vm_enough_memory()
229 * implementation used by LSMs.
231 if (has_capability_noaudit(p, CAP_SYS_ADMIN))
232 points -= (points * 3) / 100;
234 /* Normalize to oom_score_adj units */
235 adj *= totalpages / 1000;
239 * Never return 0 for an eligible task regardless of the root bonus and
240 * oom_score_adj (oom_score_adj can't be OOM_SCORE_ADJ_MIN here).
242 return points > 0 ? points : 1;
245 enum oom_constraint {
248 CONSTRAINT_MEMORY_POLICY,
253 * Determine the type of allocation constraint.
255 static enum oom_constraint constrained_alloc(struct oom_control *oc)
259 enum zone_type high_zoneidx = gfp_zone(oc->gfp_mask);
260 bool cpuset_limited = false;
263 if (is_memcg_oom(oc)) {
264 oc->totalpages = mem_cgroup_get_limit(oc->memcg) ?: 1;
265 return CONSTRAINT_MEMCG;
268 /* Default to all available memory */
269 oc->totalpages = totalram_pages + total_swap_pages;
271 if (!IS_ENABLED(CONFIG_NUMA))
272 return CONSTRAINT_NONE;
275 return CONSTRAINT_NONE;
277 * Reach here only when __GFP_NOFAIL is used. So, we should avoid
278 * to kill current.We have to random task kill in this case.
279 * Hopefully, CONSTRAINT_THISNODE...but no way to handle it, now.
281 if (oc->gfp_mask & __GFP_THISNODE)
282 return CONSTRAINT_NONE;
285 * This is not a __GFP_THISNODE allocation, so a truncated nodemask in
286 * the page allocator means a mempolicy is in effect. Cpuset policy
287 * is enforced in get_page_from_freelist().
290 !nodes_subset(node_states[N_MEMORY], *oc->nodemask)) {
291 oc->totalpages = total_swap_pages;
292 for_each_node_mask(nid, *oc->nodemask)
293 oc->totalpages += node_spanned_pages(nid);
294 return CONSTRAINT_MEMORY_POLICY;
297 /* Check this allocation failure is caused by cpuset's wall function */
298 for_each_zone_zonelist_nodemask(zone, z, oc->zonelist,
299 high_zoneidx, oc->nodemask)
300 if (!cpuset_zone_allowed(zone, oc->gfp_mask))
301 cpuset_limited = true;
303 if (cpuset_limited) {
304 oc->totalpages = total_swap_pages;
305 for_each_node_mask(nid, cpuset_current_mems_allowed)
306 oc->totalpages += node_spanned_pages(nid);
307 return CONSTRAINT_CPUSET;
309 return CONSTRAINT_NONE;
312 static int oom_evaluate_task(struct task_struct *task, void *arg)
314 struct oom_control *oc = arg;
315 unsigned long points;
317 if (oom_unkillable_task(task, NULL, oc->nodemask))
321 * This task already has access to memory reserves and is being killed.
322 * Don't allow any other task to have access to the reserves unless
323 * the task has MMF_OOM_SKIP because chances that it would release
324 * any memory is quite low.
326 if (!is_sysrq_oom(oc) && tsk_is_oom_victim(task)) {
327 if (test_bit(MMF_OOM_SKIP, &task->signal->oom_mm->flags))
333 * If task is allocating a lot of memory and has been marked to be
334 * killed first if it triggers an oom, then select it.
336 if (oom_task_origin(task)) {
341 points = oom_badness(task, NULL, oc->nodemask, oc->totalpages);
342 if (!points || points < oc->chosen_points)
345 /* Prefer thread group leaders for display purposes */
346 if (points == oc->chosen_points && thread_group_leader(oc->chosen))
350 put_task_struct(oc->chosen);
351 get_task_struct(task);
353 oc->chosen_points = points;
358 put_task_struct(oc->chosen);
359 oc->chosen = (void *)-1UL;
364 * Simple selection loop. We choose the process with the highest number of
365 * 'points'. In case scan was aborted, oc->chosen is set to -1.
367 static void select_bad_process(struct oom_control *oc)
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))
381 oc->chosen_points = oc->chosen_points * 1000 / oc->totalpages;
385 * dump_tasks - dump current memory state of all system tasks
386 * @memcg: current's memory controller, if constrained
387 * @nodemask: nodemask passed to page allocator for mempolicy ooms
389 * Dumps the current memory state of all eligible tasks. Tasks not in the same
390 * memcg, not in the same cpuset, or bound to a disjoint set of mempolicy nodes
392 * State information includes task's pid, uid, tgid, vm size, rss, nr_ptes,
393 * swapents, oom_score_adj value, and name.
395 static void dump_tasks(struct mem_cgroup *memcg, const nodemask_t *nodemask)
397 struct task_struct *p;
398 struct task_struct *task;
400 pr_info("[ pid ] uid tgid total_vm rss nr_ptes nr_pmds nr_puds swapents oom_score_adj name\n");
402 for_each_process(p) {
403 if (oom_unkillable_task(p, memcg, nodemask))
406 task = find_lock_task_mm(p);
409 * This is a kthread or all of p's threads have already
410 * detached their mm's. There's no need to report
411 * them; they can't be oom killed anyway.
416 pr_info("[%5d] %5d %5d %8lu %8lu %7ld %7ld %7ld %8lu %5hd %s\n",
417 task->pid, from_kuid(&init_user_ns, task_uid(task)),
418 task->tgid, task->mm->total_vm, get_mm_rss(task->mm),
419 mm_nr_ptes(task->mm),
420 mm_nr_pmds(task->mm),
421 mm_nr_puds(task->mm),
422 get_mm_counter(task->mm, MM_SWAPENTS),
423 task->signal->oom_score_adj, task->comm);
429 static void dump_header(struct oom_control *oc, struct task_struct *p)
431 pr_warn("%s invoked oom-killer: gfp_mask=%#x(%pGg), nodemask=",
432 current->comm, oc->gfp_mask, &oc->gfp_mask);
434 pr_cont("%*pbl", nodemask_pr_args(oc->nodemask));
437 pr_cont(", order=%d, oom_score_adj=%hd\n",
438 oc->order, current->signal->oom_score_adj);
439 if (!IS_ENABLED(CONFIG_COMPACTION) && oc->order)
440 pr_warn("COMPACTION is disabled!!!\n");
442 cpuset_print_current_mems_allowed();
444 if (is_memcg_oom(oc))
445 mem_cgroup_print_oom_info(oc->memcg, p);
447 show_mem(SHOW_MEM_FILTER_NODES, oc->nodemask);
448 if (is_dump_unreclaim_slabs())
449 dump_unreclaimable_slab();
451 if (sysctl_oom_dump_tasks)
452 dump_tasks(oc->memcg, oc->nodemask);
456 * Number of OOM victims in flight
458 static atomic_t oom_victims = ATOMIC_INIT(0);
459 static DECLARE_WAIT_QUEUE_HEAD(oom_victims_wait);
461 static bool oom_killer_disabled __read_mostly;
463 #define K(x) ((x) << (PAGE_SHIFT-10))
466 * task->mm can be NULL if the task is the exited group leader. So to
467 * determine whether the task is using a particular mm, we examine all the
468 * task's threads: if one of those is using this mm then this task was also
471 bool process_shares_mm(struct task_struct *p, struct mm_struct *mm)
473 struct task_struct *t;
475 for_each_thread(p, t) {
476 struct mm_struct *t_mm = READ_ONCE(t->mm);
486 * OOM Reaper kernel thread which tries to reap the memory used by the OOM
487 * victim (if that is possible) to help the OOM killer to move on.
489 static struct task_struct *oom_reaper_th;
490 static DECLARE_WAIT_QUEUE_HEAD(oom_reaper_wait);
491 static struct task_struct *oom_reaper_list;
492 static DEFINE_SPINLOCK(oom_reaper_lock);
494 static bool __oom_reap_task_mm(struct task_struct *tsk, struct mm_struct *mm)
496 struct mmu_gather tlb;
497 struct vm_area_struct *vma;
501 * We have to make sure to not race with the victim exit path
502 * and cause premature new oom victim selection:
503 * __oom_reap_task_mm exit_mm
506 * atomic_dec_and_test
511 * # no TIF_MEMDIE task selects new victim
512 * unmap_page_range # frees some memory
514 mutex_lock(&oom_lock);
516 if (!down_read_trylock(&mm->mmap_sem)) {
518 trace_skip_task_reaping(tsk->pid);
523 * If the mm has notifiers then we would need to invalidate them around
524 * unmap_page_range and that is risky because notifiers can sleep and
525 * what they do is basically undeterministic. So let's have a short
526 * sleep to give the oom victim some more time.
527 * TODO: we really want to get rid of this ugly hack and make sure that
528 * notifiers cannot block for unbounded amount of time and add
529 * mmu_notifier_invalidate_range_{start,end} around unmap_page_range
531 if (mm_has_notifiers(mm)) {
532 up_read(&mm->mmap_sem);
533 schedule_timeout_idle(HZ);
538 * MMF_OOM_SKIP is set by exit_mmap when the OOM reaper can't
539 * work on the mm anymore. The check for MMF_OOM_SKIP must run
540 * under mmap_sem for reading because it serializes against the
541 * down_write();up_write() cycle in exit_mmap().
543 if (test_bit(MMF_OOM_SKIP, &mm->flags)) {
544 up_read(&mm->mmap_sem);
545 trace_skip_task_reaping(tsk->pid);
549 trace_start_task_reaping(tsk->pid);
552 * Tell all users of get_user/copy_from_user etc... that the content
553 * is no longer stable. No barriers really needed because unmapping
554 * should imply barriers already and the reader would hit a page fault
555 * if it stumbled over a reaped memory.
557 set_bit(MMF_UNSTABLE, &mm->flags);
559 tlb_gather_mmu(&tlb, mm, 0, -1);
560 for (vma = mm->mmap ; vma; vma = vma->vm_next) {
561 if (!can_madv_dontneed_vma(vma))
565 * Only anonymous pages have a good chance to be dropped
566 * without additional steps which we cannot afford as we
569 * We do not even care about fs backed pages because all
570 * which are reclaimable have already been reclaimed and
571 * we do not want to block exit_mmap by keeping mm ref
572 * count elevated without a good reason.
574 if (vma_is_anonymous(vma) || !(vma->vm_flags & VM_SHARED))
575 unmap_page_range(&tlb, vma, vma->vm_start, vma->vm_end,
578 tlb_finish_mmu(&tlb, 0, -1);
579 pr_info("oom_reaper: reaped process %d (%s), now anon-rss:%lukB, file-rss:%lukB, shmem-rss:%lukB\n",
580 task_pid_nr(tsk), tsk->comm,
581 K(get_mm_counter(mm, MM_ANONPAGES)),
582 K(get_mm_counter(mm, MM_FILEPAGES)),
583 K(get_mm_counter(mm, MM_SHMEMPAGES)));
584 up_read(&mm->mmap_sem);
586 trace_finish_task_reaping(tsk->pid);
588 mutex_unlock(&oom_lock);
592 #define MAX_OOM_REAP_RETRIES 10
593 static void oom_reap_task(struct task_struct *tsk)
596 struct mm_struct *mm = tsk->signal->oom_mm;
598 /* Retry the down_read_trylock(mmap_sem) a few times */
599 while (attempts++ < MAX_OOM_REAP_RETRIES && !__oom_reap_task_mm(tsk, mm))
600 schedule_timeout_idle(HZ/10);
602 if (attempts <= MAX_OOM_REAP_RETRIES)
606 pr_info("oom_reaper: unable to reap pid:%d (%s)\n",
607 task_pid_nr(tsk), tsk->comm);
608 debug_show_all_locks();
611 tsk->oom_reaper_list = NULL;
614 * Hide this mm from OOM killer because it has been either reaped or
615 * somebody can't call up_write(mmap_sem).
617 set_bit(MMF_OOM_SKIP, &mm->flags);
619 /* Drop a reference taken by wake_oom_reaper */
620 put_task_struct(tsk);
623 static int oom_reaper(void *unused)
626 struct task_struct *tsk = NULL;
628 wait_event_freezable(oom_reaper_wait, oom_reaper_list != NULL);
629 spin_lock(&oom_reaper_lock);
630 if (oom_reaper_list != NULL) {
631 tsk = oom_reaper_list;
632 oom_reaper_list = tsk->oom_reaper_list;
634 spin_unlock(&oom_reaper_lock);
643 static void wake_oom_reaper(struct task_struct *tsk)
648 /* tsk is already queued? */
649 if (tsk == oom_reaper_list || tsk->oom_reaper_list)
652 get_task_struct(tsk);
654 spin_lock(&oom_reaper_lock);
655 tsk->oom_reaper_list = oom_reaper_list;
656 oom_reaper_list = tsk;
657 spin_unlock(&oom_reaper_lock);
658 trace_wake_reaper(tsk->pid);
659 wake_up(&oom_reaper_wait);
662 static int __init oom_init(void)
664 oom_reaper_th = kthread_run(oom_reaper, NULL, "oom_reaper");
665 if (IS_ERR(oom_reaper_th)) {
666 pr_err("Unable to start OOM reaper %ld. Continuing regardless\n",
667 PTR_ERR(oom_reaper_th));
668 oom_reaper_th = NULL;
672 subsys_initcall(oom_init)
674 static inline void wake_oom_reaper(struct task_struct *tsk)
677 #endif /* CONFIG_MMU */
680 * mark_oom_victim - mark the given task as OOM victim
683 * Has to be called with oom_lock held and never after
684 * oom has been disabled already.
686 * tsk->mm has to be non NULL and caller has to guarantee it is stable (either
687 * under task_lock or operate on the current).
689 static void mark_oom_victim(struct task_struct *tsk)
691 struct mm_struct *mm = tsk->mm;
693 WARN_ON(oom_killer_disabled);
694 /* OOM killer might race with memcg OOM */
695 if (test_and_set_tsk_thread_flag(tsk, TIF_MEMDIE))
698 /* oom_mm is bound to the signal struct life time. */
699 if (!cmpxchg(&tsk->signal->oom_mm, NULL, mm))
700 mmgrab(tsk->signal->oom_mm);
703 * Make sure that the task is woken up from uninterruptible sleep
704 * if it is frozen because OOM killer wouldn't be able to free
705 * any memory and livelock. freezing_slow_path will tell the freezer
706 * that TIF_MEMDIE tasks should be ignored.
709 atomic_inc(&oom_victims);
710 trace_mark_victim(tsk->pid);
714 * exit_oom_victim - note the exit of an OOM victim
716 void exit_oom_victim(void)
718 clear_thread_flag(TIF_MEMDIE);
720 if (!atomic_dec_return(&oom_victims))
721 wake_up_all(&oom_victims_wait);
725 * oom_killer_enable - enable OOM killer
727 void oom_killer_enable(void)
729 oom_killer_disabled = false;
730 pr_info("OOM killer enabled.\n");
734 * oom_killer_disable - disable OOM killer
735 * @timeout: maximum timeout to wait for oom victims in jiffies
737 * Forces all page allocations to fail rather than trigger OOM killer.
738 * Will block and wait until all OOM victims are killed or the given
741 * The function cannot be called when there are runnable user tasks because
742 * the userspace would see unexpected allocation failures as a result. Any
743 * new usage of this function should be consulted with MM people.
745 * Returns true if successful and false if the OOM killer cannot be
748 bool oom_killer_disable(signed long timeout)
753 * Make sure to not race with an ongoing OOM killer. Check that the
754 * current is not killed (possibly due to sharing the victim's memory).
756 if (mutex_lock_killable(&oom_lock))
758 oom_killer_disabled = true;
759 mutex_unlock(&oom_lock);
761 ret = wait_event_interruptible_timeout(oom_victims_wait,
762 !atomic_read(&oom_victims), timeout);
767 pr_info("OOM killer disabled.\n");
772 static inline bool __task_will_free_mem(struct task_struct *task)
774 struct signal_struct *sig = task->signal;
777 * A coredumping process may sleep for an extended period in exit_mm(),
778 * so the oom killer cannot assume that the process will promptly exit
779 * and release memory.
781 if (sig->flags & SIGNAL_GROUP_COREDUMP)
784 if (sig->flags & SIGNAL_GROUP_EXIT)
787 if (thread_group_empty(task) && (task->flags & PF_EXITING))
794 * Checks whether the given task is dying or exiting and likely to
795 * release its address space. This means that all threads and processes
796 * sharing the same mm have to be killed or exiting.
797 * Caller has to make sure that task->mm is stable (hold task_lock or
798 * it operates on the current).
800 static bool task_will_free_mem(struct task_struct *task)
802 struct mm_struct *mm = task->mm;
803 struct task_struct *p;
807 * Skip tasks without mm because it might have passed its exit_mm and
808 * exit_oom_victim. oom_reaper could have rescued that but do not rely
809 * on that for now. We can consider find_lock_task_mm in future.
814 if (!__task_will_free_mem(task))
818 * This task has already been drained by the oom reaper so there are
819 * only small chances it will free some more
821 if (test_bit(MMF_OOM_SKIP, &mm->flags))
824 if (atomic_read(&mm->mm_users) <= 1)
828 * Make sure that all tasks which share the mm with the given tasks
829 * are dying as well to make sure that a) nobody pins its mm and
830 * b) the task is also reapable by the oom reaper.
833 for_each_process(p) {
834 if (!process_shares_mm(p, mm))
836 if (same_thread_group(task, p))
838 ret = __task_will_free_mem(p);
847 static void oom_kill_process(struct oom_control *oc, const char *message)
849 struct task_struct *p = oc->chosen;
850 unsigned int points = oc->chosen_points;
851 struct task_struct *victim = p;
852 struct task_struct *child;
853 struct task_struct *t;
854 struct mm_struct *mm;
855 unsigned int victim_points = 0;
856 static DEFINE_RATELIMIT_STATE(oom_rs, DEFAULT_RATELIMIT_INTERVAL,
857 DEFAULT_RATELIMIT_BURST);
858 bool can_oom_reap = true;
861 * If the task is already exiting, don't alarm the sysadmin or kill
862 * its children or threads, just give it access to memory reserves
863 * so it can die quickly
866 if (task_will_free_mem(p)) {
875 if (__ratelimit(&oom_rs))
878 pr_err("%s: Kill process %d (%s) score %u or sacrifice child\n",
879 message, task_pid_nr(p), p->comm, points);
882 * If any of p's children has a different mm and is eligible for kill,
883 * the one with the highest oom_badness() score is sacrificed for its
884 * parent. This attempts to lose the minimal amount of work done while
885 * still freeing memory.
887 read_lock(&tasklist_lock);
888 for_each_thread(p, t) {
889 list_for_each_entry(child, &t->children, sibling) {
890 unsigned int child_points;
892 if (process_shares_mm(child, p->mm))
895 * oom_badness() returns 0 if the thread is unkillable
897 child_points = oom_badness(child,
898 oc->memcg, oc->nodemask, oc->totalpages);
899 if (child_points > victim_points) {
900 put_task_struct(victim);
902 victim_points = child_points;
903 get_task_struct(victim);
907 read_unlock(&tasklist_lock);
909 p = find_lock_task_mm(victim);
911 put_task_struct(victim);
913 } else if (victim != p) {
915 put_task_struct(victim);
919 /* Get a reference to safely compare mm after task_unlock(victim) */
923 /* Raise event before sending signal: task reaper must see this */
924 count_vm_event(OOM_KILL);
925 count_memcg_event_mm(mm, OOM_KILL);
928 * We should send SIGKILL before granting access to memory reserves
929 * in order to prevent the OOM victim from depleting the memory
930 * reserves from the user space under its control.
932 do_send_sig_info(SIGKILL, SEND_SIG_FORCED, victim, true);
933 mark_oom_victim(victim);
934 pr_err("Killed process %d (%s) total-vm:%lukB, anon-rss:%lukB, file-rss:%lukB, shmem-rss:%lukB\n",
935 task_pid_nr(victim), victim->comm, K(victim->mm->total_vm),
936 K(get_mm_counter(victim->mm, MM_ANONPAGES)),
937 K(get_mm_counter(victim->mm, MM_FILEPAGES)),
938 K(get_mm_counter(victim->mm, MM_SHMEMPAGES)));
942 * Kill all user processes sharing victim->mm in other thread groups, if
943 * any. They don't get access to memory reserves, though, to avoid
944 * depletion of all memory. This prevents mm->mmap_sem livelock when an
945 * oom killed thread cannot exit because it requires the semaphore and
946 * its contended by another thread trying to allocate memory itself.
947 * That thread will now get access to memory reserves since it has a
948 * pending fatal signal.
951 for_each_process(p) {
952 if (!process_shares_mm(p, mm))
954 if (same_thread_group(p, victim))
956 if (is_global_init(p)) {
957 can_oom_reap = false;
958 set_bit(MMF_OOM_SKIP, &mm->flags);
959 pr_info("oom killer %d (%s) has mm pinned by %d (%s)\n",
960 task_pid_nr(victim), victim->comm,
961 task_pid_nr(p), p->comm);
965 * No use_mm() user needs to read from the userspace so we are
968 if (unlikely(p->flags & PF_KTHREAD))
970 do_send_sig_info(SIGKILL, SEND_SIG_FORCED, p, true);
975 wake_oom_reaper(victim);
978 put_task_struct(victim);
983 * Determines whether the kernel must panic because of the panic_on_oom sysctl.
985 static void check_panic_on_oom(struct oom_control *oc,
986 enum oom_constraint constraint)
988 if (likely(!sysctl_panic_on_oom))
990 if (sysctl_panic_on_oom != 2) {
992 * panic_on_oom == 1 only affects CONSTRAINT_NONE, the kernel
993 * does not panic for cpuset, mempolicy, or memcg allocation
996 if (constraint != CONSTRAINT_NONE)
999 /* Do not panic for oom kills triggered by sysrq */
1000 if (is_sysrq_oom(oc))
1002 dump_header(oc, NULL);
1003 panic("Out of memory: %s panic_on_oom is enabled\n",
1004 sysctl_panic_on_oom == 2 ? "compulsory" : "system-wide");
1007 static BLOCKING_NOTIFIER_HEAD(oom_notify_list);
1009 int register_oom_notifier(struct notifier_block *nb)
1011 return blocking_notifier_chain_register(&oom_notify_list, nb);
1013 EXPORT_SYMBOL_GPL(register_oom_notifier);
1015 int unregister_oom_notifier(struct notifier_block *nb)
1017 return blocking_notifier_chain_unregister(&oom_notify_list, nb);
1019 EXPORT_SYMBOL_GPL(unregister_oom_notifier);
1022 * out_of_memory - kill the "best" process when we run out of memory
1023 * @oc: pointer to struct oom_control
1025 * If we run out of memory, we have the choice between either
1026 * killing a random task (bad), letting the system crash (worse)
1027 * OR try to be smart about which process to kill. Note that we
1028 * don't have to be perfect here, we just have to be good.
1030 bool out_of_memory(struct oom_control *oc)
1032 unsigned long freed = 0;
1033 enum oom_constraint constraint = CONSTRAINT_NONE;
1035 if (oom_killer_disabled)
1038 if (!is_memcg_oom(oc)) {
1039 blocking_notifier_call_chain(&oom_notify_list, 0, &freed);
1041 /* Got some memory back in the last second. */
1046 * If current has a pending SIGKILL or is exiting, then automatically
1047 * select it. The goal is to allow it to allocate so that it may
1048 * quickly exit and free its memory.
1050 if (task_will_free_mem(current)) {
1051 mark_oom_victim(current);
1052 wake_oom_reaper(current);
1057 * The OOM killer does not compensate for IO-less reclaim.
1058 * pagefault_out_of_memory lost its gfp context so we have to
1059 * make sure exclude 0 mask - all other users should have at least
1060 * ___GFP_DIRECT_RECLAIM to get here.
1062 if (oc->gfp_mask && !(oc->gfp_mask & __GFP_FS))
1066 * Check if there were limitations on the allocation (only relevant for
1067 * NUMA and memcg) that may require different handling.
1069 constraint = constrained_alloc(oc);
1070 if (constraint != CONSTRAINT_MEMORY_POLICY)
1071 oc->nodemask = NULL;
1072 check_panic_on_oom(oc, constraint);
1074 if (!is_memcg_oom(oc) && sysctl_oom_kill_allocating_task &&
1075 current->mm && !oom_unkillable_task(current, NULL, oc->nodemask) &&
1076 current->signal->oom_score_adj != OOM_SCORE_ADJ_MIN) {
1077 get_task_struct(current);
1078 oc->chosen = current;
1079 oom_kill_process(oc, "Out of memory (oom_kill_allocating_task)");
1083 select_bad_process(oc);
1084 /* Found nothing?!?! Either we hang forever, or we panic. */
1085 if (!oc->chosen && !is_sysrq_oom(oc) && !is_memcg_oom(oc)) {
1086 dump_header(oc, NULL);
1087 panic("Out of memory and no killable processes...\n");
1089 if (oc->chosen && oc->chosen != (void *)-1UL) {
1090 oom_kill_process(oc, !is_memcg_oom(oc) ? "Out of memory" :
1091 "Memory cgroup out of memory");
1093 * Give the killed process a good chance to exit before trying
1094 * to allocate memory again.
1096 schedule_timeout_killable(1);
1098 return !!oc->chosen;
1102 * The pagefault handler calls here because it is out of memory, so kill a
1103 * memory-hogging task. If oom_lock is held by somebody else, a parallel oom
1104 * killing is already in progress so do nothing.
1106 void pagefault_out_of_memory(void)
1108 struct oom_control oc = {
1116 if (mem_cgroup_oom_synchronize(true))
1119 if (!mutex_trylock(&oom_lock))
1122 mutex_unlock(&oom_lock);