USB: typec: Remove redundant license text
[linux-2.6/btrfs-unstable.git] / mm / oom_kill.c
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1 /*
2 * linux/mm/oom_kill.c
3 *
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>
21 #include <linux/mm.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>
45 #include <asm/tlb.h>
46 #include "internal.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);
57 #ifdef CONFIG_NUMA
58 /**
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;
71 bool ret = false;
73 rcu_read_lock();
74 for_each_thread(start, tsk) {
75 if (mask) {
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
80 * needlessly killed.
82 ret = mempolicy_nodemask_intersects(tsk, mask);
83 } else {
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);
90 if (ret)
91 break;
93 rcu_read_unlock();
95 return ret;
97 #else
98 static bool has_intersects_mems_allowed(struct task_struct *tsk,
99 const nodemask_t *mask)
101 return true;
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
109 * task_lock() held.
111 struct task_struct *find_lock_task_mm(struct task_struct *p)
113 struct task_struct *t;
115 rcu_read_lock();
117 for_each_thread(p, t) {
118 task_lock(t);
119 if (likely(t->mm))
120 goto found;
121 task_unlock(t);
123 t = NULL;
124 found:
125 rcu_read_unlock();
127 return 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))
149 return true;
150 if (p->flags & PF_KTHREAD)
151 return true;
153 /* When mem_cgroup_out_of_memory() and p is not member of the group */
154 if (memcg && !task_in_mem_cgroup(p, memcg))
155 return true;
157 /* p may not have freeable memory in nodemask */
158 if (!has_intersects_mems_allowed(p, nodemask))
159 return true;
161 return false;
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)
176 long points;
177 long adj;
179 if (oom_unkillable_task(p, memcg, nodemask))
180 return 0;
182 p = find_lock_task_mm(p);
183 if (!p)
184 return 0;
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) ||
194 in_vfork(p)) {
195 task_unlock(p);
196 return 0;
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);
205 task_unlock(p);
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;
216 points += adj;
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 {
226 CONSTRAINT_NONE,
227 CONSTRAINT_CPUSET,
228 CONSTRAINT_MEMORY_POLICY,
229 CONSTRAINT_MEMCG,
233 * Determine the type of allocation constraint.
235 static enum oom_constraint constrained_alloc(struct oom_control *oc)
237 struct zone *zone;
238 struct zoneref *z;
239 enum zone_type high_zoneidx = gfp_zone(oc->gfp_mask);
240 bool cpuset_limited = false;
241 int nid;
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;
254 if (!oc->zonelist)
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().
269 if (oc->nodemask &&
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))
298 goto next;
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))
308 goto next;
309 goto abort;
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)) {
317 points = ULONG_MAX;
318 goto select;
321 points = oom_badness(task, NULL, oc->nodemask, oc->totalpages);
322 if (!points || points < oc->chosen_points)
323 goto next;
325 /* Prefer thread group leaders for display purposes */
326 if (points == oc->chosen_points && thread_group_leader(oc->chosen))
327 goto next;
328 select:
329 if (oc->chosen)
330 put_task_struct(oc->chosen);
331 get_task_struct(task);
332 oc->chosen = task;
333 oc->chosen_points = points;
334 next:
335 return 0;
336 abort:
337 if (oc->chosen)
338 put_task_struct(oc->chosen);
339 oc->chosen = (void *)-1UL;
340 return 1;
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);
351 else {
352 struct task_struct *p;
354 rcu_read_lock();
355 for_each_process(p)
356 if (oom_evaluate_task(p, oc))
357 break;
358 rcu_read_unlock();
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
371 * are not shown.
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");
381 rcu_read_lock();
382 for_each_process(p) {
383 if (oom_unkillable_task(p, memcg, nodemask))
384 continue;
386 task = find_lock_task_mm(p);
387 if (!task) {
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.
393 continue;
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);
403 task_unlock(task);
405 rcu_read_unlock();
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);
412 if (oc->nodemask)
413 pr_cont("%*pbl", nodemask_pr_args(oc->nodemask));
414 else
415 pr_cont("(null)");
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();
422 dump_stack();
423 if (oc->memcg)
424 mem_cgroup_print_oom_info(oc->memcg, p);
425 else
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
445 * using it.
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);
453 if (t_mm)
454 return t_mm == mm;
456 return false;
460 #ifdef CONFIG_MMU
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;
474 bool ret = true;
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
480 * mmget_not_zero
481 * mmput
482 * atomic_dec_and_test
483 * exit_oom_victim
484 * [...]
485 * out_of_memory
486 * select_bad_process
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)) {
493 ret = false;
494 trace_skip_task_reaping(tsk->pid);
495 goto unlock_oom;
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);
510 goto unlock_oom;
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);
522 goto unlock_oom;
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 tlb_gather_mmu(&tlb, mm, 0, -1);
536 for (vma = mm->mmap ; vma; vma = vma->vm_next) {
537 if (!can_madv_dontneed_vma(vma))
538 continue;
541 * Only anonymous pages have a good chance to be dropped
542 * without additional steps which we cannot afford as we
543 * are OOM already.
545 * We do not even care about fs backed pages because all
546 * which are reclaimable have already been reclaimed and
547 * we do not want to block exit_mmap by keeping mm ref
548 * count elevated without a good reason.
550 if (vma_is_anonymous(vma) || !(vma->vm_flags & VM_SHARED))
551 unmap_page_range(&tlb, vma, vma->vm_start, vma->vm_end,
552 NULL);
554 tlb_finish_mmu(&tlb, 0, -1);
555 pr_info("oom_reaper: reaped process %d (%s), now anon-rss:%lukB, file-rss:%lukB, shmem-rss:%lukB\n",
556 task_pid_nr(tsk), tsk->comm,
557 K(get_mm_counter(mm, MM_ANONPAGES)),
558 K(get_mm_counter(mm, MM_FILEPAGES)),
559 K(get_mm_counter(mm, MM_SHMEMPAGES)));
560 up_read(&mm->mmap_sem);
562 trace_finish_task_reaping(tsk->pid);
563 unlock_oom:
564 mutex_unlock(&oom_lock);
565 return ret;
568 #define MAX_OOM_REAP_RETRIES 10
569 static void oom_reap_task(struct task_struct *tsk)
571 int attempts = 0;
572 struct mm_struct *mm = tsk->signal->oom_mm;
574 /* Retry the down_read_trylock(mmap_sem) a few times */
575 while (attempts++ < MAX_OOM_REAP_RETRIES && !__oom_reap_task_mm(tsk, mm))
576 schedule_timeout_idle(HZ/10);
578 if (attempts <= MAX_OOM_REAP_RETRIES)
579 goto done;
582 pr_info("oom_reaper: unable to reap pid:%d (%s)\n",
583 task_pid_nr(tsk), tsk->comm);
584 debug_show_all_locks();
586 done:
587 tsk->oom_reaper_list = NULL;
590 * Hide this mm from OOM killer because it has been either reaped or
591 * somebody can't call up_write(mmap_sem).
593 set_bit(MMF_OOM_SKIP, &mm->flags);
595 /* Drop a reference taken by wake_oom_reaper */
596 put_task_struct(tsk);
599 static int oom_reaper(void *unused)
601 while (true) {
602 struct task_struct *tsk = NULL;
604 wait_event_freezable(oom_reaper_wait, oom_reaper_list != NULL);
605 spin_lock(&oom_reaper_lock);
606 if (oom_reaper_list != NULL) {
607 tsk = oom_reaper_list;
608 oom_reaper_list = tsk->oom_reaper_list;
610 spin_unlock(&oom_reaper_lock);
612 if (tsk)
613 oom_reap_task(tsk);
616 return 0;
619 static void wake_oom_reaper(struct task_struct *tsk)
621 if (!oom_reaper_th)
622 return;
624 /* tsk is already queued? */
625 if (tsk == oom_reaper_list || tsk->oom_reaper_list)
626 return;
628 get_task_struct(tsk);
630 spin_lock(&oom_reaper_lock);
631 tsk->oom_reaper_list = oom_reaper_list;
632 oom_reaper_list = tsk;
633 spin_unlock(&oom_reaper_lock);
634 trace_wake_reaper(tsk->pid);
635 wake_up(&oom_reaper_wait);
638 static int __init oom_init(void)
640 oom_reaper_th = kthread_run(oom_reaper, NULL, "oom_reaper");
641 if (IS_ERR(oom_reaper_th)) {
642 pr_err("Unable to start OOM reaper %ld. Continuing regardless\n",
643 PTR_ERR(oom_reaper_th));
644 oom_reaper_th = NULL;
646 return 0;
648 subsys_initcall(oom_init)
649 #else
650 static inline void wake_oom_reaper(struct task_struct *tsk)
653 #endif /* CONFIG_MMU */
656 * mark_oom_victim - mark the given task as OOM victim
657 * @tsk: task to mark
659 * Has to be called with oom_lock held and never after
660 * oom has been disabled already.
662 * tsk->mm has to be non NULL and caller has to guarantee it is stable (either
663 * under task_lock or operate on the current).
665 static void mark_oom_victim(struct task_struct *tsk)
667 struct mm_struct *mm = tsk->mm;
669 WARN_ON(oom_killer_disabled);
670 /* OOM killer might race with memcg OOM */
671 if (test_and_set_tsk_thread_flag(tsk, TIF_MEMDIE))
672 return;
674 /* oom_mm is bound to the signal struct life time. */
675 if (!cmpxchg(&tsk->signal->oom_mm, NULL, mm))
676 mmgrab(tsk->signal->oom_mm);
679 * Make sure that the task is woken up from uninterruptible sleep
680 * if it is frozen because OOM killer wouldn't be able to free
681 * any memory and livelock. freezing_slow_path will tell the freezer
682 * that TIF_MEMDIE tasks should be ignored.
684 __thaw_task(tsk);
685 atomic_inc(&oom_victims);
686 trace_mark_victim(tsk->pid);
690 * exit_oom_victim - note the exit of an OOM victim
692 void exit_oom_victim(void)
694 clear_thread_flag(TIF_MEMDIE);
696 if (!atomic_dec_return(&oom_victims))
697 wake_up_all(&oom_victims_wait);
701 * oom_killer_enable - enable OOM killer
703 void oom_killer_enable(void)
705 oom_killer_disabled = false;
706 pr_info("OOM killer enabled.\n");
710 * oom_killer_disable - disable OOM killer
711 * @timeout: maximum timeout to wait for oom victims in jiffies
713 * Forces all page allocations to fail rather than trigger OOM killer.
714 * Will block and wait until all OOM victims are killed or the given
715 * timeout expires.
717 * The function cannot be called when there are runnable user tasks because
718 * the userspace would see unexpected allocation failures as a result. Any
719 * new usage of this function should be consulted with MM people.
721 * Returns true if successful and false if the OOM killer cannot be
722 * disabled.
724 bool oom_killer_disable(signed long timeout)
726 signed long ret;
729 * Make sure to not race with an ongoing OOM killer. Check that the
730 * current is not killed (possibly due to sharing the victim's memory).
732 if (mutex_lock_killable(&oom_lock))
733 return false;
734 oom_killer_disabled = true;
735 mutex_unlock(&oom_lock);
737 ret = wait_event_interruptible_timeout(oom_victims_wait,
738 !atomic_read(&oom_victims), timeout);
739 if (ret <= 0) {
740 oom_killer_enable();
741 return false;
743 pr_info("OOM killer disabled.\n");
745 return true;
748 static inline bool __task_will_free_mem(struct task_struct *task)
750 struct signal_struct *sig = task->signal;
753 * A coredumping process may sleep for an extended period in exit_mm(),
754 * so the oom killer cannot assume that the process will promptly exit
755 * and release memory.
757 if (sig->flags & SIGNAL_GROUP_COREDUMP)
758 return false;
760 if (sig->flags & SIGNAL_GROUP_EXIT)
761 return true;
763 if (thread_group_empty(task) && (task->flags & PF_EXITING))
764 return true;
766 return false;
770 * Checks whether the given task is dying or exiting and likely to
771 * release its address space. This means that all threads and processes
772 * sharing the same mm have to be killed or exiting.
773 * Caller has to make sure that task->mm is stable (hold task_lock or
774 * it operates on the current).
776 static bool task_will_free_mem(struct task_struct *task)
778 struct mm_struct *mm = task->mm;
779 struct task_struct *p;
780 bool ret = true;
783 * Skip tasks without mm because it might have passed its exit_mm and
784 * exit_oom_victim. oom_reaper could have rescued that but do not rely
785 * on that for now. We can consider find_lock_task_mm in future.
787 if (!mm)
788 return false;
790 if (!__task_will_free_mem(task))
791 return false;
794 * This task has already been drained by the oom reaper so there are
795 * only small chances it will free some more
797 if (test_bit(MMF_OOM_SKIP, &mm->flags))
798 return false;
800 if (atomic_read(&mm->mm_users) <= 1)
801 return true;
804 * Make sure that all tasks which share the mm with the given tasks
805 * are dying as well to make sure that a) nobody pins its mm and
806 * b) the task is also reapable by the oom reaper.
808 rcu_read_lock();
809 for_each_process(p) {
810 if (!process_shares_mm(p, mm))
811 continue;
812 if (same_thread_group(task, p))
813 continue;
814 ret = __task_will_free_mem(p);
815 if (!ret)
816 break;
818 rcu_read_unlock();
820 return ret;
823 static void oom_kill_process(struct oom_control *oc, const char *message)
825 struct task_struct *p = oc->chosen;
826 unsigned int points = oc->chosen_points;
827 struct task_struct *victim = p;
828 struct task_struct *child;
829 struct task_struct *t;
830 struct mm_struct *mm;
831 unsigned int victim_points = 0;
832 static DEFINE_RATELIMIT_STATE(oom_rs, DEFAULT_RATELIMIT_INTERVAL,
833 DEFAULT_RATELIMIT_BURST);
834 bool can_oom_reap = true;
837 * If the task is already exiting, don't alarm the sysadmin or kill
838 * its children or threads, just give it access to memory reserves
839 * so it can die quickly
841 task_lock(p);
842 if (task_will_free_mem(p)) {
843 mark_oom_victim(p);
844 wake_oom_reaper(p);
845 task_unlock(p);
846 put_task_struct(p);
847 return;
849 task_unlock(p);
851 if (__ratelimit(&oom_rs))
852 dump_header(oc, p);
854 pr_err("%s: Kill process %d (%s) score %u or sacrifice child\n",
855 message, task_pid_nr(p), p->comm, points);
858 * If any of p's children has a different mm and is eligible for kill,
859 * the one with the highest oom_badness() score is sacrificed for its
860 * parent. This attempts to lose the minimal amount of work done while
861 * still freeing memory.
863 read_lock(&tasklist_lock);
864 for_each_thread(p, t) {
865 list_for_each_entry(child, &t->children, sibling) {
866 unsigned int child_points;
868 if (process_shares_mm(child, p->mm))
869 continue;
871 * oom_badness() returns 0 if the thread is unkillable
873 child_points = oom_badness(child,
874 oc->memcg, oc->nodemask, oc->totalpages);
875 if (child_points > victim_points) {
876 put_task_struct(victim);
877 victim = child;
878 victim_points = child_points;
879 get_task_struct(victim);
883 read_unlock(&tasklist_lock);
885 p = find_lock_task_mm(victim);
886 if (!p) {
887 put_task_struct(victim);
888 return;
889 } else if (victim != p) {
890 get_task_struct(p);
891 put_task_struct(victim);
892 victim = p;
895 /* Get a reference to safely compare mm after task_unlock(victim) */
896 mm = victim->mm;
897 mmgrab(mm);
899 /* Raise event before sending signal: task reaper must see this */
900 count_vm_event(OOM_KILL);
901 count_memcg_event_mm(mm, OOM_KILL);
904 * We should send SIGKILL before granting access to memory reserves
905 * in order to prevent the OOM victim from depleting the memory
906 * reserves from the user space under its control.
908 do_send_sig_info(SIGKILL, SEND_SIG_FORCED, victim, true);
909 mark_oom_victim(victim);
910 pr_err("Killed process %d (%s) total-vm:%lukB, anon-rss:%lukB, file-rss:%lukB, shmem-rss:%lukB\n",
911 task_pid_nr(victim), victim->comm, K(victim->mm->total_vm),
912 K(get_mm_counter(victim->mm, MM_ANONPAGES)),
913 K(get_mm_counter(victim->mm, MM_FILEPAGES)),
914 K(get_mm_counter(victim->mm, MM_SHMEMPAGES)));
915 task_unlock(victim);
918 * Kill all user processes sharing victim->mm in other thread groups, if
919 * any. They don't get access to memory reserves, though, to avoid
920 * depletion of all memory. This prevents mm->mmap_sem livelock when an
921 * oom killed thread cannot exit because it requires the semaphore and
922 * its contended by another thread trying to allocate memory itself.
923 * That thread will now get access to memory reserves since it has a
924 * pending fatal signal.
926 rcu_read_lock();
927 for_each_process(p) {
928 if (!process_shares_mm(p, mm))
929 continue;
930 if (same_thread_group(p, victim))
931 continue;
932 if (is_global_init(p)) {
933 can_oom_reap = false;
934 set_bit(MMF_OOM_SKIP, &mm->flags);
935 pr_info("oom killer %d (%s) has mm pinned by %d (%s)\n",
936 task_pid_nr(victim), victim->comm,
937 task_pid_nr(p), p->comm);
938 continue;
941 * No use_mm() user needs to read from the userspace so we are
942 * ok to reap it.
944 if (unlikely(p->flags & PF_KTHREAD))
945 continue;
946 do_send_sig_info(SIGKILL, SEND_SIG_FORCED, p, true);
948 rcu_read_unlock();
950 if (can_oom_reap)
951 wake_oom_reaper(victim);
953 mmdrop(mm);
954 put_task_struct(victim);
956 #undef K
959 * Determines whether the kernel must panic because of the panic_on_oom sysctl.
961 static void check_panic_on_oom(struct oom_control *oc,
962 enum oom_constraint constraint)
964 if (likely(!sysctl_panic_on_oom))
965 return;
966 if (sysctl_panic_on_oom != 2) {
968 * panic_on_oom == 1 only affects CONSTRAINT_NONE, the kernel
969 * does not panic for cpuset, mempolicy, or memcg allocation
970 * failures.
972 if (constraint != CONSTRAINT_NONE)
973 return;
975 /* Do not panic for oom kills triggered by sysrq */
976 if (is_sysrq_oom(oc))
977 return;
978 dump_header(oc, NULL);
979 panic("Out of memory: %s panic_on_oom is enabled\n",
980 sysctl_panic_on_oom == 2 ? "compulsory" : "system-wide");
983 static BLOCKING_NOTIFIER_HEAD(oom_notify_list);
985 int register_oom_notifier(struct notifier_block *nb)
987 return blocking_notifier_chain_register(&oom_notify_list, nb);
989 EXPORT_SYMBOL_GPL(register_oom_notifier);
991 int unregister_oom_notifier(struct notifier_block *nb)
993 return blocking_notifier_chain_unregister(&oom_notify_list, nb);
995 EXPORT_SYMBOL_GPL(unregister_oom_notifier);
998 * out_of_memory - kill the "best" process when we run out of memory
999 * @oc: pointer to struct oom_control
1001 * If we run out of memory, we have the choice between either
1002 * killing a random task (bad), letting the system crash (worse)
1003 * OR try to be smart about which process to kill. Note that we
1004 * don't have to be perfect here, we just have to be good.
1006 bool out_of_memory(struct oom_control *oc)
1008 unsigned long freed = 0;
1009 enum oom_constraint constraint = CONSTRAINT_NONE;
1011 if (oom_killer_disabled)
1012 return false;
1014 if (!is_memcg_oom(oc)) {
1015 blocking_notifier_call_chain(&oom_notify_list, 0, &freed);
1016 if (freed > 0)
1017 /* Got some memory back in the last second. */
1018 return true;
1022 * If current has a pending SIGKILL or is exiting, then automatically
1023 * select it. The goal is to allow it to allocate so that it may
1024 * quickly exit and free its memory.
1026 if (task_will_free_mem(current)) {
1027 mark_oom_victim(current);
1028 wake_oom_reaper(current);
1029 return true;
1033 * The OOM killer does not compensate for IO-less reclaim.
1034 * pagefault_out_of_memory lost its gfp context so we have to
1035 * make sure exclude 0 mask - all other users should have at least
1036 * ___GFP_DIRECT_RECLAIM to get here.
1038 if (oc->gfp_mask && !(oc->gfp_mask & __GFP_FS))
1039 return true;
1042 * Check if there were limitations on the allocation (only relevant for
1043 * NUMA and memcg) that may require different handling.
1045 constraint = constrained_alloc(oc);
1046 if (constraint != CONSTRAINT_MEMORY_POLICY)
1047 oc->nodemask = NULL;
1048 check_panic_on_oom(oc, constraint);
1050 if (!is_memcg_oom(oc) && sysctl_oom_kill_allocating_task &&
1051 current->mm && !oom_unkillable_task(current, NULL, oc->nodemask) &&
1052 current->signal->oom_score_adj != OOM_SCORE_ADJ_MIN) {
1053 get_task_struct(current);
1054 oc->chosen = current;
1055 oom_kill_process(oc, "Out of memory (oom_kill_allocating_task)");
1056 return true;
1059 select_bad_process(oc);
1060 /* Found nothing?!?! Either we hang forever, or we panic. */
1061 if (!oc->chosen && !is_sysrq_oom(oc) && !is_memcg_oom(oc)) {
1062 dump_header(oc, NULL);
1063 panic("Out of memory and no killable processes...\n");
1065 if (oc->chosen && oc->chosen != (void *)-1UL) {
1066 oom_kill_process(oc, !is_memcg_oom(oc) ? "Out of memory" :
1067 "Memory cgroup out of memory");
1069 * Give the killed process a good chance to exit before trying
1070 * to allocate memory again.
1072 schedule_timeout_killable(1);
1074 return !!oc->chosen;
1078 * The pagefault handler calls here because it is out of memory, so kill a
1079 * memory-hogging task. If oom_lock is held by somebody else, a parallel oom
1080 * killing is already in progress so do nothing.
1082 void pagefault_out_of_memory(void)
1084 struct oom_control oc = {
1085 .zonelist = NULL,
1086 .nodemask = NULL,
1087 .memcg = NULL,
1088 .gfp_mask = 0,
1089 .order = 0,
1092 if (mem_cgroup_oom_synchronize(true))
1093 return;
1095 if (!mutex_trylock(&oom_lock))
1096 return;
1097 out_of_memory(&oc);
1098 mutex_unlock(&oom_lock);