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/swap.h>
26 #include <linux/timex.h>
27 #include <linux/jiffies.h>
28 #include <linux/cpuset.h>
29 #include <linux/export.h>
30 #include <linux/notifier.h>
31 #include <linux/memcontrol.h>
32 #include <linux/mempolicy.h>
33 #include <linux/security.h>
34 #include <linux/ptrace.h>
35 #include <linux/freezer.h>
36 #include <linux/ftrace.h>
37 #include <linux/ratelimit.h>
38 #include <linux/kthread.h>
39 #include <linux/init.h>
44 #define CREATE_TRACE_POINTS
45 #include <trace/events/oom.h>
47 int sysctl_panic_on_oom;
48 int sysctl_oom_kill_allocating_task;
49 int sysctl_oom_dump_tasks = 1;
51 DEFINE_MUTEX(oom_lock);
55 * has_intersects_mems_allowed() - check task eligiblity for kill
56 * @start: task struct of which task to consider
57 * @mask: nodemask passed to page allocator for mempolicy ooms
59 * Task eligibility is determined by whether or not a candidate task, @tsk,
60 * shares the same mempolicy nodes as current if it is bound by such a policy
61 * and whether or not it has the same set of allowed cpuset nodes.
63 static bool has_intersects_mems_allowed(struct task_struct *start,
64 const nodemask_t *mask)
66 struct task_struct *tsk;
70 for_each_thread(start, tsk) {
73 * If this is a mempolicy constrained oom, tsk's
74 * cpuset is irrelevant. Only return true if its
75 * mempolicy intersects current, otherwise it may be
78 ret = mempolicy_nodemask_intersects(tsk, mask);
81 * This is not a mempolicy constrained oom, so only
82 * check the mems of tsk's cpuset.
84 ret = cpuset_mems_allowed_intersects(current, tsk);
94 static bool has_intersects_mems_allowed(struct task_struct *tsk,
95 const nodemask_t *mask)
99 #endif /* CONFIG_NUMA */
102 * The process p may have detached its own ->mm while exiting or through
103 * use_mm(), but one or more of its subthreads may still have a valid
104 * pointer. Return p, or any of its subthreads with a valid ->mm, with
107 struct task_struct *find_lock_task_mm(struct task_struct *p)
109 struct task_struct *t;
113 for_each_thread(p, t) {
127 * order == -1 means the oom kill is required by sysrq, otherwise only
128 * for display purposes.
130 static inline bool is_sysrq_oom(struct oom_control *oc)
132 return oc->order == -1;
135 /* return true if the task is not adequate as candidate victim task. */
136 static bool oom_unkillable_task(struct task_struct *p,
137 struct mem_cgroup *memcg, const nodemask_t *nodemask)
139 if (is_global_init(p))
141 if (p->flags & PF_KTHREAD)
144 /* When mem_cgroup_out_of_memory() and p is not member of the group */
145 if (memcg && !task_in_mem_cgroup(p, memcg))
148 /* p may not have freeable memory in nodemask */
149 if (!has_intersects_mems_allowed(p, nodemask))
156 * oom_badness - heuristic function to determine which candidate task to kill
157 * @p: task struct of which task we should calculate
158 * @totalpages: total present RAM allowed for page allocation
160 * The heuristic for determining which task to kill is made to be as simple and
161 * predictable as possible. The goal is to return the highest value for the
162 * task consuming the most memory to avoid subsequent oom failures.
164 unsigned long oom_badness(struct task_struct *p, struct mem_cgroup *memcg,
165 const nodemask_t *nodemask, unsigned long totalpages)
170 if (oom_unkillable_task(p, memcg, nodemask))
173 p = find_lock_task_mm(p);
178 * Do not even consider tasks which are explicitly marked oom
179 * unkillable or have been already oom reaped.
181 adj = (long)p->signal->oom_score_adj;
182 if (adj == OOM_SCORE_ADJ_MIN ||
183 test_bit(MMF_OOM_REAPED, &p->mm->flags)) {
189 * The baseline for the badness score is the proportion of RAM that each
190 * task's rss, pagetable and swap space use.
192 points = get_mm_rss(p->mm) + get_mm_counter(p->mm, MM_SWAPENTS) +
193 atomic_long_read(&p->mm->nr_ptes) + mm_nr_pmds(p->mm);
197 * Root processes get 3% bonus, just like the __vm_enough_memory()
198 * implementation used by LSMs.
200 if (has_capability_noaudit(p, CAP_SYS_ADMIN))
201 points -= (points * 3) / 100;
203 /* Normalize to oom_score_adj units */
204 adj *= totalpages / 1000;
208 * Never return 0 for an eligible task regardless of the root bonus and
209 * oom_score_adj (oom_score_adj can't be OOM_SCORE_ADJ_MIN here).
211 return points > 0 ? points : 1;
215 * Determine the type of allocation constraint.
218 static enum oom_constraint constrained_alloc(struct oom_control *oc,
219 unsigned long *totalpages)
223 enum zone_type high_zoneidx = gfp_zone(oc->gfp_mask);
224 bool cpuset_limited = false;
227 /* Default to all available memory */
228 *totalpages = totalram_pages + total_swap_pages;
231 return CONSTRAINT_NONE;
233 * Reach here only when __GFP_NOFAIL is used. So, we should avoid
234 * to kill current.We have to random task kill in this case.
235 * Hopefully, CONSTRAINT_THISNODE...but no way to handle it, now.
237 if (oc->gfp_mask & __GFP_THISNODE)
238 return CONSTRAINT_NONE;
241 * This is not a __GFP_THISNODE allocation, so a truncated nodemask in
242 * the page allocator means a mempolicy is in effect. Cpuset policy
243 * is enforced in get_page_from_freelist().
246 !nodes_subset(node_states[N_MEMORY], *oc->nodemask)) {
247 *totalpages = total_swap_pages;
248 for_each_node_mask(nid, *oc->nodemask)
249 *totalpages += node_spanned_pages(nid);
250 return CONSTRAINT_MEMORY_POLICY;
253 /* Check this allocation failure is caused by cpuset's wall function */
254 for_each_zone_zonelist_nodemask(zone, z, oc->zonelist,
255 high_zoneidx, oc->nodemask)
256 if (!cpuset_zone_allowed(zone, oc->gfp_mask))
257 cpuset_limited = true;
259 if (cpuset_limited) {
260 *totalpages = total_swap_pages;
261 for_each_node_mask(nid, cpuset_current_mems_allowed)
262 *totalpages += node_spanned_pages(nid);
263 return CONSTRAINT_CPUSET;
265 return CONSTRAINT_NONE;
268 static enum oom_constraint constrained_alloc(struct oom_control *oc,
269 unsigned long *totalpages)
271 *totalpages = totalram_pages + total_swap_pages;
272 return CONSTRAINT_NONE;
276 enum oom_scan_t oom_scan_process_thread(struct oom_control *oc,
277 struct task_struct *task, unsigned long totalpages)
279 if (oom_unkillable_task(task, NULL, oc->nodemask))
280 return OOM_SCAN_CONTINUE;
283 * This task already has access to memory reserves and is being killed.
284 * Don't allow any other task to have access to the reserves.
286 if (!is_sysrq_oom(oc) && atomic_read(&task->signal->oom_victims))
287 return OOM_SCAN_ABORT;
290 * If task is allocating a lot of memory and has been marked to be
291 * killed first if it triggers an oom, then select it.
293 if (oom_task_origin(task))
294 return OOM_SCAN_SELECT;
300 * Simple selection loop. We chose the process with the highest
301 * number of 'points'. Returns -1 on scan abort.
303 static struct task_struct *select_bad_process(struct oom_control *oc,
304 unsigned int *ppoints, unsigned long totalpages)
306 struct task_struct *p;
307 struct task_struct *chosen = NULL;
308 unsigned long chosen_points = 0;
311 for_each_process(p) {
314 switch (oom_scan_process_thread(oc, p, totalpages)) {
315 case OOM_SCAN_SELECT:
317 chosen_points = ULONG_MAX;
319 case OOM_SCAN_CONTINUE:
323 return (struct task_struct *)(-1UL);
327 points = oom_badness(p, NULL, oc->nodemask, totalpages);
328 if (!points || points < chosen_points)
332 chosen_points = points;
335 get_task_struct(chosen);
338 *ppoints = chosen_points * 1000 / totalpages;
343 * dump_tasks - dump current memory state of all system tasks
344 * @memcg: current's memory controller, if constrained
345 * @nodemask: nodemask passed to page allocator for mempolicy ooms
347 * Dumps the current memory state of all eligible tasks. Tasks not in the same
348 * memcg, not in the same cpuset, or bound to a disjoint set of mempolicy nodes
350 * State information includes task's pid, uid, tgid, vm size, rss, nr_ptes,
351 * swapents, oom_score_adj value, and name.
353 static void dump_tasks(struct mem_cgroup *memcg, const nodemask_t *nodemask)
355 struct task_struct *p;
356 struct task_struct *task;
358 pr_info("[ pid ] uid tgid total_vm rss nr_ptes nr_pmds swapents oom_score_adj name\n");
360 for_each_process(p) {
361 if (oom_unkillable_task(p, memcg, nodemask))
364 task = find_lock_task_mm(p);
367 * This is a kthread or all of p's threads have already
368 * detached their mm's. There's no need to report
369 * them; they can't be oom killed anyway.
374 pr_info("[%5d] %5d %5d %8lu %8lu %7ld %7ld %8lu %5hd %s\n",
375 task->pid, from_kuid(&init_user_ns, task_uid(task)),
376 task->tgid, task->mm->total_vm, get_mm_rss(task->mm),
377 atomic_long_read(&task->mm->nr_ptes),
378 mm_nr_pmds(task->mm),
379 get_mm_counter(task->mm, MM_SWAPENTS),
380 task->signal->oom_score_adj, task->comm);
386 static void dump_header(struct oom_control *oc, struct task_struct *p,
387 struct mem_cgroup *memcg)
389 pr_warn("%s invoked oom-killer: gfp_mask=%#x(%pGg), order=%d, oom_score_adj=%hd\n",
390 current->comm, oc->gfp_mask, &oc->gfp_mask, oc->order,
391 current->signal->oom_score_adj);
393 cpuset_print_current_mems_allowed();
396 mem_cgroup_print_oom_info(memcg, p);
398 show_mem(SHOW_MEM_FILTER_NODES);
399 if (sysctl_oom_dump_tasks)
400 dump_tasks(memcg, oc->nodemask);
404 * Number of OOM victims in flight
406 static atomic_t oom_victims = ATOMIC_INIT(0);
407 static DECLARE_WAIT_QUEUE_HEAD(oom_victims_wait);
409 bool oom_killer_disabled __read_mostly;
411 #define K(x) ((x) << (PAGE_SHIFT-10))
414 * task->mm can be NULL if the task is the exited group leader. So to
415 * determine whether the task is using a particular mm, we examine all the
416 * task's threads: if one of those is using this mm then this task was also
419 static bool process_shares_mm(struct task_struct *p, struct mm_struct *mm)
421 struct task_struct *t;
423 for_each_thread(p, t) {
424 struct mm_struct *t_mm = READ_ONCE(t->mm);
434 * OOM Reaper kernel thread which tries to reap the memory used by the OOM
435 * victim (if that is possible) to help the OOM killer to move on.
437 static struct task_struct *oom_reaper_th;
438 static DECLARE_WAIT_QUEUE_HEAD(oom_reaper_wait);
439 static struct task_struct *oom_reaper_list;
440 static DEFINE_SPINLOCK(oom_reaper_lock);
442 static bool __oom_reap_task(struct task_struct *tsk)
444 struct mmu_gather tlb;
445 struct vm_area_struct *vma;
446 struct mm_struct *mm = NULL;
447 struct task_struct *p;
448 struct zap_details details = {.check_swap_entries = true,
449 .ignore_dirty = true};
453 * We have to make sure to not race with the victim exit path
454 * and cause premature new oom victim selection:
455 * __oom_reap_task exit_mm
456 * atomic_inc_not_zero
458 * atomic_dec_and_test
463 * # no TIF_MEMDIE task selects new victim
464 * unmap_page_range # frees some memory
466 mutex_lock(&oom_lock);
469 * Make sure we find the associated mm_struct even when the particular
470 * thread has already terminated and cleared its mm.
471 * We might have race with exit path so consider our work done if there
474 p = find_lock_task_mm(tsk);
479 if (!atomic_inc_not_zero(&mm->mm_users)) {
487 if (!down_read_trylock(&mm->mmap_sem)) {
492 tlb_gather_mmu(&tlb, mm, 0, -1);
493 for (vma = mm->mmap ; vma; vma = vma->vm_next) {
494 if (is_vm_hugetlb_page(vma))
498 * mlocked VMAs require explicit munlocking before unmap.
499 * Let's keep it simple here and skip such VMAs.
501 if (vma->vm_flags & VM_LOCKED)
505 * Only anonymous pages have a good chance to be dropped
506 * without additional steps which we cannot afford as we
509 * We do not even care about fs backed pages because all
510 * which are reclaimable have already been reclaimed and
511 * we do not want to block exit_mmap by keeping mm ref
512 * count elevated without a good reason.
514 if (vma_is_anonymous(vma) || !(vma->vm_flags & VM_SHARED))
515 unmap_page_range(&tlb, vma, vma->vm_start, vma->vm_end,
518 tlb_finish_mmu(&tlb, 0, -1);
519 pr_info("oom_reaper: reaped process %d (%s), now anon-rss:%lukB, file-rss:%lukB, shmem-rss:%lukB\n",
520 task_pid_nr(tsk), tsk->comm,
521 K(get_mm_counter(mm, MM_ANONPAGES)),
522 K(get_mm_counter(mm, MM_FILEPAGES)),
523 K(get_mm_counter(mm, MM_SHMEMPAGES)));
524 up_read(&mm->mmap_sem);
527 * This task can be safely ignored because we cannot do much more
528 * to release its memory.
530 set_bit(MMF_OOM_REAPED, &mm->flags);
532 mutex_unlock(&oom_lock);
534 * Drop our reference but make sure the mmput slow path is called from a
535 * different context because we shouldn't risk we get stuck there and
536 * put the oom_reaper out of the way.
543 #define MAX_OOM_REAP_RETRIES 10
544 static void oom_reap_task(struct task_struct *tsk)
548 /* Retry the down_read_trylock(mmap_sem) a few times */
549 while (attempts++ < MAX_OOM_REAP_RETRIES && !__oom_reap_task(tsk))
550 schedule_timeout_idle(HZ/10);
552 if (attempts > MAX_OOM_REAP_RETRIES) {
553 pr_info("oom_reaper: unable to reap pid:%d (%s)\n",
554 task_pid_nr(tsk), tsk->comm);
555 debug_show_all_locks();
559 * Clear TIF_MEMDIE because the task shouldn't be sitting on a
560 * reasonably reclaimable memory anymore or it is not a good candidate
561 * for the oom victim right now because it cannot release its memory
562 * itself nor by the oom reaper.
564 tsk->oom_reaper_list = NULL;
565 exit_oom_victim(tsk);
567 /* Drop a reference taken by wake_oom_reaper */
568 put_task_struct(tsk);
571 static int oom_reaper(void *unused)
576 struct task_struct *tsk = NULL;
578 wait_event_freezable(oom_reaper_wait, oom_reaper_list != NULL);
579 spin_lock(&oom_reaper_lock);
580 if (oom_reaper_list != NULL) {
581 tsk = oom_reaper_list;
582 oom_reaper_list = tsk->oom_reaper_list;
584 spin_unlock(&oom_reaper_lock);
593 static void wake_oom_reaper(struct task_struct *tsk)
598 /* tsk is already queued? */
599 if (tsk == oom_reaper_list || tsk->oom_reaper_list)
602 get_task_struct(tsk);
604 spin_lock(&oom_reaper_lock);
605 tsk->oom_reaper_list = oom_reaper_list;
606 oom_reaper_list = tsk;
607 spin_unlock(&oom_reaper_lock);
608 wake_up(&oom_reaper_wait);
611 /* Check if we can reap the given task. This has to be called with stable
614 void try_oom_reaper(struct task_struct *tsk)
616 struct mm_struct *mm = tsk->mm;
617 struct task_struct *p;
623 * There might be other threads/processes which are either not
624 * dying or even not killable.
626 if (atomic_read(&mm->mm_users) > 1) {
628 for_each_process(p) {
629 if (!process_shares_mm(p, mm))
631 if (fatal_signal_pending(p))
635 * If the task is exiting make sure the whole thread group
636 * is exiting and cannot acces mm anymore.
638 if (signal_group_exit(p->signal))
648 wake_oom_reaper(tsk);
651 static int __init oom_init(void)
653 oom_reaper_th = kthread_run(oom_reaper, NULL, "oom_reaper");
654 if (IS_ERR(oom_reaper_th)) {
655 pr_err("Unable to start OOM reaper %ld. Continuing regardless\n",
656 PTR_ERR(oom_reaper_th));
657 oom_reaper_th = NULL;
661 subsys_initcall(oom_init)
663 static void wake_oom_reaper(struct task_struct *tsk)
669 * mark_oom_victim - mark the given task as OOM victim
672 * Has to be called with oom_lock held and never after
673 * oom has been disabled already.
675 void mark_oom_victim(struct task_struct *tsk)
677 WARN_ON(oom_killer_disabled);
678 /* OOM killer might race with memcg OOM */
679 if (test_and_set_tsk_thread_flag(tsk, TIF_MEMDIE))
681 atomic_inc(&tsk->signal->oom_victims);
683 * Make sure that the task is woken up from uninterruptible sleep
684 * if it is frozen because OOM killer wouldn't be able to free
685 * any memory and livelock. freezing_slow_path will tell the freezer
686 * that TIF_MEMDIE tasks should be ignored.
689 atomic_inc(&oom_victims);
693 * exit_oom_victim - note the exit of an OOM victim
695 void exit_oom_victim(struct task_struct *tsk)
697 if (!test_and_clear_tsk_thread_flag(tsk, TIF_MEMDIE))
699 atomic_dec(&tsk->signal->oom_victims);
701 if (!atomic_dec_return(&oom_victims))
702 wake_up_all(&oom_victims_wait);
706 * oom_killer_disable - disable OOM killer
708 * Forces all page allocations to fail rather than trigger OOM killer.
709 * Will block and wait until all OOM victims are killed.
711 * The function cannot be called when there are runnable user tasks because
712 * the userspace would see unexpected allocation failures as a result. Any
713 * new usage of this function should be consulted with MM people.
715 * Returns true if successful and false if the OOM killer cannot be
718 bool oom_killer_disable(void)
721 * Make sure to not race with an ongoing OOM killer. Check that the
722 * current is not killed (possibly due to sharing the victim's memory).
724 if (mutex_lock_killable(&oom_lock))
726 oom_killer_disabled = true;
727 mutex_unlock(&oom_lock);
729 wait_event(oom_victims_wait, !atomic_read(&oom_victims));
735 * oom_killer_enable - enable OOM killer
737 void oom_killer_enable(void)
739 oom_killer_disabled = false;
743 * Must be called while holding a reference to p, which will be released upon
746 void oom_kill_process(struct oom_control *oc, struct task_struct *p,
747 unsigned int points, unsigned long totalpages,
748 struct mem_cgroup *memcg, const char *message)
750 struct task_struct *victim = p;
751 struct task_struct *child;
752 struct task_struct *t;
753 struct mm_struct *mm;
754 unsigned int victim_points = 0;
755 static DEFINE_RATELIMIT_STATE(oom_rs, DEFAULT_RATELIMIT_INTERVAL,
756 DEFAULT_RATELIMIT_BURST);
757 bool can_oom_reap = true;
760 * If the task is already exiting, don't alarm the sysadmin or kill
761 * its children or threads, just set TIF_MEMDIE so it can die quickly
764 if (p->mm && task_will_free_mem(p)) {
773 if (__ratelimit(&oom_rs))
774 dump_header(oc, p, memcg);
776 pr_err("%s: Kill process %d (%s) score %u or sacrifice child\n",
777 message, task_pid_nr(p), p->comm, points);
780 * If any of p's children has a different mm and is eligible for kill,
781 * the one with the highest oom_badness() score is sacrificed for its
782 * parent. This attempts to lose the minimal amount of work done while
783 * still freeing memory.
785 read_lock(&tasklist_lock);
786 for_each_thread(p, t) {
787 list_for_each_entry(child, &t->children, sibling) {
788 unsigned int child_points;
790 if (process_shares_mm(child, p->mm))
793 * oom_badness() returns 0 if the thread is unkillable
795 child_points = oom_badness(child, memcg, oc->nodemask,
797 if (child_points > victim_points) {
798 put_task_struct(victim);
800 victim_points = child_points;
801 get_task_struct(victim);
805 read_unlock(&tasklist_lock);
807 p = find_lock_task_mm(victim);
809 put_task_struct(victim);
811 } else if (victim != p) {
813 put_task_struct(victim);
817 /* Get a reference to safely compare mm after task_unlock(victim) */
819 atomic_inc(&mm->mm_count);
821 * We should send SIGKILL before setting TIF_MEMDIE in order to prevent
822 * the OOM victim from depleting the memory reserves from the user
823 * space under its control.
825 do_send_sig_info(SIGKILL, SEND_SIG_FORCED, victim, true);
826 mark_oom_victim(victim);
827 pr_err("Killed process %d (%s) total-vm:%lukB, anon-rss:%lukB, file-rss:%lukB, shmem-rss:%lukB\n",
828 task_pid_nr(victim), victim->comm, K(victim->mm->total_vm),
829 K(get_mm_counter(victim->mm, MM_ANONPAGES)),
830 K(get_mm_counter(victim->mm, MM_FILEPAGES)),
831 K(get_mm_counter(victim->mm, MM_SHMEMPAGES)));
835 * Kill all user processes sharing victim->mm in other thread groups, if
836 * any. They don't get access to memory reserves, though, to avoid
837 * depletion of all memory. This prevents mm->mmap_sem livelock when an
838 * oom killed thread cannot exit because it requires the semaphore and
839 * its contended by another thread trying to allocate memory itself.
840 * That thread will now get access to memory reserves since it has a
841 * pending fatal signal.
844 for_each_process(p) {
845 if (!process_shares_mm(p, mm))
847 if (same_thread_group(p, victim))
849 if (unlikely(p->flags & PF_KTHREAD) || is_global_init(p) ||
850 p->signal->oom_score_adj == OOM_SCORE_ADJ_MIN) {
852 * We cannot use oom_reaper for the mm shared by this
853 * process because it wouldn't get killed and so the
854 * memory might be still used.
856 can_oom_reap = false;
859 do_send_sig_info(SIGKILL, SEND_SIG_FORCED, p, true);
864 wake_oom_reaper(victim);
867 put_task_struct(victim);
872 * Determines whether the kernel must panic because of the panic_on_oom sysctl.
874 void check_panic_on_oom(struct oom_control *oc, enum oom_constraint constraint,
875 struct mem_cgroup *memcg)
877 if (likely(!sysctl_panic_on_oom))
879 if (sysctl_panic_on_oom != 2) {
881 * panic_on_oom == 1 only affects CONSTRAINT_NONE, the kernel
882 * does not panic for cpuset, mempolicy, or memcg allocation
885 if (constraint != CONSTRAINT_NONE)
888 /* Do not panic for oom kills triggered by sysrq */
889 if (is_sysrq_oom(oc))
891 dump_header(oc, NULL, memcg);
892 panic("Out of memory: %s panic_on_oom is enabled\n",
893 sysctl_panic_on_oom == 2 ? "compulsory" : "system-wide");
896 static BLOCKING_NOTIFIER_HEAD(oom_notify_list);
898 int register_oom_notifier(struct notifier_block *nb)
900 return blocking_notifier_chain_register(&oom_notify_list, nb);
902 EXPORT_SYMBOL_GPL(register_oom_notifier);
904 int unregister_oom_notifier(struct notifier_block *nb)
906 return blocking_notifier_chain_unregister(&oom_notify_list, nb);
908 EXPORT_SYMBOL_GPL(unregister_oom_notifier);
911 * out_of_memory - kill the "best" process when we run out of memory
912 * @oc: pointer to struct oom_control
914 * If we run out of memory, we have the choice between either
915 * killing a random task (bad), letting the system crash (worse)
916 * OR try to be smart about which process to kill. Note that we
917 * don't have to be perfect here, we just have to be good.
919 bool out_of_memory(struct oom_control *oc)
921 struct task_struct *p;
922 unsigned long totalpages;
923 unsigned long freed = 0;
924 unsigned int uninitialized_var(points);
925 enum oom_constraint constraint = CONSTRAINT_NONE;
927 if (oom_killer_disabled)
930 blocking_notifier_call_chain(&oom_notify_list, 0, &freed);
932 /* Got some memory back in the last second. */
936 * If current has a pending SIGKILL or is exiting, then automatically
937 * select it. The goal is to allow it to allocate so that it may
938 * quickly exit and free its memory.
940 * But don't select if current has already released its mm and cleared
941 * TIF_MEMDIE flag at exit_mm(), otherwise an OOM livelock may occur.
944 (fatal_signal_pending(current) || task_will_free_mem(current))) {
945 mark_oom_victim(current);
946 try_oom_reaper(current);
951 * The OOM killer does not compensate for IO-less reclaim.
952 * pagefault_out_of_memory lost its gfp context so we have to
953 * make sure exclude 0 mask - all other users should have at least
954 * ___GFP_DIRECT_RECLAIM to get here.
956 if (oc->gfp_mask && !(oc->gfp_mask & (__GFP_FS|__GFP_NOFAIL)))
960 * Check if there were limitations on the allocation (only relevant for
961 * NUMA) that may require different handling.
963 constraint = constrained_alloc(oc, &totalpages);
964 if (constraint != CONSTRAINT_MEMORY_POLICY)
966 check_panic_on_oom(oc, constraint, NULL);
968 if (sysctl_oom_kill_allocating_task && current->mm &&
969 !oom_unkillable_task(current, NULL, oc->nodemask) &&
970 current->signal->oom_score_adj != OOM_SCORE_ADJ_MIN) {
971 get_task_struct(current);
972 oom_kill_process(oc, current, 0, totalpages, NULL,
973 "Out of memory (oom_kill_allocating_task)");
977 p = select_bad_process(oc, &points, totalpages);
978 /* Found nothing?!?! Either we hang forever, or we panic. */
979 if (!p && !is_sysrq_oom(oc)) {
980 dump_header(oc, NULL, NULL);
981 panic("Out of memory and no killable processes...\n");
983 if (p && p != (void *)-1UL) {
984 oom_kill_process(oc, p, points, totalpages, NULL,
987 * Give the killed process a good chance to exit before trying
988 * to allocate memory again.
990 schedule_timeout_killable(1);
996 * The pagefault handler calls here because it is out of memory, so kill a
997 * memory-hogging task. If any populated zone has ZONE_OOM_LOCKED set, a
998 * parallel oom killing is already in progress so do nothing.
1000 void pagefault_out_of_memory(void)
1002 struct oom_control oc = {
1009 if (mem_cgroup_oom_synchronize(true))
1012 if (!mutex_trylock(&oom_lock))
1015 if (!out_of_memory(&oc)) {
1017 * There shouldn't be any user tasks runnable while the
1018 * OOM killer is disabled, so the current task has to
1019 * be a racing OOM victim for which oom_killer_disable()
1022 WARN_ON(test_thread_flag(TIF_MEMDIE));
1025 mutex_unlock(&oom_lock);