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 static inline bool is_memcg_oom(struct oom_control
*oc
)
137 return oc
->memcg
!= NULL
;
140 /* return true if the task is not adequate as candidate victim task. */
141 static bool oom_unkillable_task(struct task_struct
*p
,
142 struct mem_cgroup
*memcg
, const nodemask_t
*nodemask
)
144 if (is_global_init(p
))
146 if (p
->flags
& PF_KTHREAD
)
149 /* When mem_cgroup_out_of_memory() and p is not member of the group */
150 if (memcg
&& !task_in_mem_cgroup(p
, memcg
))
153 /* p may not have freeable memory in nodemask */
154 if (!has_intersects_mems_allowed(p
, nodemask
))
161 * oom_badness - heuristic function to determine which candidate task to kill
162 * @p: task struct of which task we should calculate
163 * @totalpages: total present RAM allowed for page allocation
165 * The heuristic for determining which task to kill is made to be as simple and
166 * predictable as possible. The goal is to return the highest value for the
167 * task consuming the most memory to avoid subsequent oom failures.
169 unsigned long oom_badness(struct task_struct
*p
, struct mem_cgroup
*memcg
,
170 const nodemask_t
*nodemask
, unsigned long totalpages
)
175 if (oom_unkillable_task(p
, memcg
, nodemask
))
178 p
= find_lock_task_mm(p
);
183 * Do not even consider tasks which are explicitly marked oom
184 * unkillable or have been already oom reaped or the are in
185 * the middle of vfork
187 adj
= (long)p
->signal
->oom_score_adj
;
188 if (adj
== OOM_SCORE_ADJ_MIN
||
189 test_bit(MMF_OOM_SKIP
, &p
->mm
->flags
) ||
196 * The baseline for the badness score is the proportion of RAM that each
197 * task's rss, pagetable and swap space use.
199 points
= get_mm_rss(p
->mm
) + get_mm_counter(p
->mm
, MM_SWAPENTS
) +
200 atomic_long_read(&p
->mm
->nr_ptes
) + mm_nr_pmds(p
->mm
);
204 * Root processes get 3% bonus, just like the __vm_enough_memory()
205 * implementation used by LSMs.
207 if (has_capability_noaudit(p
, CAP_SYS_ADMIN
))
208 points
-= (points
* 3) / 100;
210 /* Normalize to oom_score_adj units */
211 adj
*= totalpages
/ 1000;
215 * Never return 0 for an eligible task regardless of the root bonus and
216 * oom_score_adj (oom_score_adj can't be OOM_SCORE_ADJ_MIN here).
218 return points
> 0 ? points
: 1;
221 enum oom_constraint
{
224 CONSTRAINT_MEMORY_POLICY
,
229 * Determine the type of allocation constraint.
231 static enum oom_constraint
constrained_alloc(struct oom_control
*oc
)
235 enum zone_type high_zoneidx
= gfp_zone(oc
->gfp_mask
);
236 bool cpuset_limited
= false;
239 if (is_memcg_oom(oc
)) {
240 oc
->totalpages
= mem_cgroup_get_limit(oc
->memcg
) ?: 1;
241 return CONSTRAINT_MEMCG
;
244 /* Default to all available memory */
245 oc
->totalpages
= totalram_pages
+ total_swap_pages
;
247 if (!IS_ENABLED(CONFIG_NUMA
))
248 return CONSTRAINT_NONE
;
251 return CONSTRAINT_NONE
;
253 * Reach here only when __GFP_NOFAIL is used. So, we should avoid
254 * to kill current.We have to random task kill in this case.
255 * Hopefully, CONSTRAINT_THISNODE...but no way to handle it, now.
257 if (oc
->gfp_mask
& __GFP_THISNODE
)
258 return CONSTRAINT_NONE
;
261 * This is not a __GFP_THISNODE allocation, so a truncated nodemask in
262 * the page allocator means a mempolicy is in effect. Cpuset policy
263 * is enforced in get_page_from_freelist().
266 !nodes_subset(node_states
[N_MEMORY
], *oc
->nodemask
)) {
267 oc
->totalpages
= total_swap_pages
;
268 for_each_node_mask(nid
, *oc
->nodemask
)
269 oc
->totalpages
+= node_spanned_pages(nid
);
270 return CONSTRAINT_MEMORY_POLICY
;
273 /* Check this allocation failure is caused by cpuset's wall function */
274 for_each_zone_zonelist_nodemask(zone
, z
, oc
->zonelist
,
275 high_zoneidx
, oc
->nodemask
)
276 if (!cpuset_zone_allowed(zone
, oc
->gfp_mask
))
277 cpuset_limited
= true;
279 if (cpuset_limited
) {
280 oc
->totalpages
= total_swap_pages
;
281 for_each_node_mask(nid
, cpuset_current_mems_allowed
)
282 oc
->totalpages
+= node_spanned_pages(nid
);
283 return CONSTRAINT_CPUSET
;
285 return CONSTRAINT_NONE
;
288 static int oom_evaluate_task(struct task_struct
*task
, void *arg
)
290 struct oom_control
*oc
= arg
;
291 unsigned long points
;
293 if (oom_unkillable_task(task
, NULL
, oc
->nodemask
))
297 * This task already has access to memory reserves and is being killed.
298 * Don't allow any other task to have access to the reserves unless
299 * the task has MMF_OOM_SKIP because chances that it would release
300 * any memory is quite low.
302 if (!is_sysrq_oom(oc
) && tsk_is_oom_victim(task
)) {
303 if (test_bit(MMF_OOM_SKIP
, &task
->signal
->oom_mm
->flags
))
309 * If task is allocating a lot of memory and has been marked to be
310 * killed first if it triggers an oom, then select it.
312 if (oom_task_origin(task
)) {
317 points
= oom_badness(task
, NULL
, oc
->nodemask
, oc
->totalpages
);
318 if (!points
|| points
< oc
->chosen_points
)
321 /* Prefer thread group leaders for display purposes */
322 if (points
== oc
->chosen_points
&& thread_group_leader(oc
->chosen
))
326 put_task_struct(oc
->chosen
);
327 get_task_struct(task
);
329 oc
->chosen_points
= points
;
334 put_task_struct(oc
->chosen
);
335 oc
->chosen
= (void *)-1UL;
340 * Simple selection loop. We choose the process with the highest number of
341 * 'points'. In case scan was aborted, oc->chosen is set to -1.
343 static void select_bad_process(struct oom_control
*oc
)
345 if (is_memcg_oom(oc
))
346 mem_cgroup_scan_tasks(oc
->memcg
, oom_evaluate_task
, oc
);
348 struct task_struct
*p
;
352 if (oom_evaluate_task(p
, oc
))
357 oc
->chosen_points
= oc
->chosen_points
* 1000 / oc
->totalpages
;
361 * dump_tasks - dump current memory state of all system tasks
362 * @memcg: current's memory controller, if constrained
363 * @nodemask: nodemask passed to page allocator for mempolicy ooms
365 * Dumps the current memory state of all eligible tasks. Tasks not in the same
366 * memcg, not in the same cpuset, or bound to a disjoint set of mempolicy nodes
368 * State information includes task's pid, uid, tgid, vm size, rss, nr_ptes,
369 * swapents, oom_score_adj value, and name.
371 static void dump_tasks(struct mem_cgroup
*memcg
, const nodemask_t
*nodemask
)
373 struct task_struct
*p
;
374 struct task_struct
*task
;
376 pr_info("[ pid ] uid tgid total_vm rss nr_ptes nr_pmds swapents oom_score_adj name\n");
378 for_each_process(p
) {
379 if (oom_unkillable_task(p
, memcg
, nodemask
))
382 task
= find_lock_task_mm(p
);
385 * This is a kthread or all of p's threads have already
386 * detached their mm's. There's no need to report
387 * them; they can't be oom killed anyway.
392 pr_info("[%5d] %5d %5d %8lu %8lu %7ld %7ld %8lu %5hd %s\n",
393 task
->pid
, from_kuid(&init_user_ns
, task_uid(task
)),
394 task
->tgid
, task
->mm
->total_vm
, get_mm_rss(task
->mm
),
395 atomic_long_read(&task
->mm
->nr_ptes
),
396 mm_nr_pmds(task
->mm
),
397 get_mm_counter(task
->mm
, MM_SWAPENTS
),
398 task
->signal
->oom_score_adj
, task
->comm
);
404 static void dump_header(struct oom_control
*oc
, struct task_struct
*p
)
406 pr_warn("%s invoked oom-killer: gfp_mask=%#x(%pGg), order=%d, oom_score_adj=%hd\n",
407 current
->comm
, oc
->gfp_mask
, &oc
->gfp_mask
, oc
->order
,
408 current
->signal
->oom_score_adj
);
410 cpuset_print_current_mems_allowed();
413 mem_cgroup_print_oom_info(oc
->memcg
, p
);
415 show_mem(SHOW_MEM_FILTER_NODES
);
416 if (sysctl_oom_dump_tasks
)
417 dump_tasks(oc
->memcg
, oc
->nodemask
);
421 * Number of OOM victims in flight
423 static atomic_t oom_victims
= ATOMIC_INIT(0);
424 static DECLARE_WAIT_QUEUE_HEAD(oom_victims_wait
);
426 static bool oom_killer_disabled __read_mostly
;
428 #define K(x) ((x) << (PAGE_SHIFT-10))
431 * task->mm can be NULL if the task is the exited group leader. So to
432 * determine whether the task is using a particular mm, we examine all the
433 * task's threads: if one of those is using this mm then this task was also
436 bool process_shares_mm(struct task_struct
*p
, struct mm_struct
*mm
)
438 struct task_struct
*t
;
440 for_each_thread(p
, t
) {
441 struct mm_struct
*t_mm
= READ_ONCE(t
->mm
);
451 * OOM Reaper kernel thread which tries to reap the memory used by the OOM
452 * victim (if that is possible) to help the OOM killer to move on.
454 static struct task_struct
*oom_reaper_th
;
455 static DECLARE_WAIT_QUEUE_HEAD(oom_reaper_wait
);
456 static struct task_struct
*oom_reaper_list
;
457 static DEFINE_SPINLOCK(oom_reaper_lock
);
459 static bool __oom_reap_task_mm(struct task_struct
*tsk
, struct mm_struct
*mm
)
461 struct mmu_gather tlb
;
462 struct vm_area_struct
*vma
;
463 struct zap_details details
= {.check_swap_entries
= true,
464 .ignore_dirty
= true};
468 * We have to make sure to not race with the victim exit path
469 * and cause premature new oom victim selection:
470 * __oom_reap_task_mm exit_mm
473 * atomic_dec_and_test
478 * # no TIF_MEMDIE task selects new victim
479 * unmap_page_range # frees some memory
481 mutex_lock(&oom_lock
);
483 if (!down_read_trylock(&mm
->mmap_sem
)) {
489 * increase mm_users only after we know we will reap something so
490 * that the mmput_async is called only when we have reaped something
491 * and delayed __mmput doesn't matter that much
493 if (!mmget_not_zero(mm
)) {
494 up_read(&mm
->mmap_sem
);
498 tlb_gather_mmu(&tlb
, mm
, 0, -1);
499 for (vma
= mm
->mmap
; vma
; vma
= vma
->vm_next
) {
500 if (is_vm_hugetlb_page(vma
))
504 * mlocked VMAs require explicit munlocking before unmap.
505 * Let's keep it simple here and skip such VMAs.
507 if (vma
->vm_flags
& VM_LOCKED
)
511 * Only anonymous pages have a good chance to be dropped
512 * without additional steps which we cannot afford as we
515 * We do not even care about fs backed pages because all
516 * which are reclaimable have already been reclaimed and
517 * we do not want to block exit_mmap by keeping mm ref
518 * count elevated without a good reason.
520 if (vma_is_anonymous(vma
) || !(vma
->vm_flags
& VM_SHARED
))
521 unmap_page_range(&tlb
, vma
, vma
->vm_start
, vma
->vm_end
,
524 tlb_finish_mmu(&tlb
, 0, -1);
525 pr_info("oom_reaper: reaped process %d (%s), now anon-rss:%lukB, file-rss:%lukB, shmem-rss:%lukB\n",
526 task_pid_nr(tsk
), tsk
->comm
,
527 K(get_mm_counter(mm
, MM_ANONPAGES
)),
528 K(get_mm_counter(mm
, MM_FILEPAGES
)),
529 K(get_mm_counter(mm
, MM_SHMEMPAGES
)));
530 up_read(&mm
->mmap_sem
);
533 * Drop our reference but make sure the mmput slow path is called from a
534 * different context because we shouldn't risk we get stuck there and
535 * put the oom_reaper out of the way.
539 mutex_unlock(&oom_lock
);
543 #define MAX_OOM_REAP_RETRIES 10
544 static void oom_reap_task(struct task_struct
*tsk
)
547 struct mm_struct
*mm
= tsk
->signal
->oom_mm
;
549 /* Retry the down_read_trylock(mmap_sem) a few times */
550 while (attempts
++ < MAX_OOM_REAP_RETRIES
&& !__oom_reap_task_mm(tsk
, mm
))
551 schedule_timeout_idle(HZ
/10);
553 if (attempts
<= MAX_OOM_REAP_RETRIES
)
557 pr_info("oom_reaper: unable to reap pid:%d (%s)\n",
558 task_pid_nr(tsk
), tsk
->comm
);
559 debug_show_all_locks();
562 tsk
->oom_reaper_list
= NULL
;
565 * Hide this mm from OOM killer because it has been either reaped or
566 * somebody can't call up_write(mmap_sem).
568 set_bit(MMF_OOM_SKIP
, &mm
->flags
);
570 /* Drop a reference taken by wake_oom_reaper */
571 put_task_struct(tsk
);
574 static int oom_reaper(void *unused
)
577 struct task_struct
*tsk
= NULL
;
579 wait_event_freezable(oom_reaper_wait
, oom_reaper_list
!= NULL
);
580 spin_lock(&oom_reaper_lock
);
581 if (oom_reaper_list
!= NULL
) {
582 tsk
= oom_reaper_list
;
583 oom_reaper_list
= tsk
->oom_reaper_list
;
585 spin_unlock(&oom_reaper_lock
);
594 static void wake_oom_reaper(struct task_struct
*tsk
)
599 /* tsk is already queued? */
600 if (tsk
== oom_reaper_list
|| tsk
->oom_reaper_list
)
603 get_task_struct(tsk
);
605 spin_lock(&oom_reaper_lock
);
606 tsk
->oom_reaper_list
= oom_reaper_list
;
607 oom_reaper_list
= tsk
;
608 spin_unlock(&oom_reaper_lock
);
609 wake_up(&oom_reaper_wait
);
612 static int __init
oom_init(void)
614 oom_reaper_th
= kthread_run(oom_reaper
, NULL
, "oom_reaper");
615 if (IS_ERR(oom_reaper_th
)) {
616 pr_err("Unable to start OOM reaper %ld. Continuing regardless\n",
617 PTR_ERR(oom_reaper_th
));
618 oom_reaper_th
= NULL
;
622 subsys_initcall(oom_init
)
624 static inline void wake_oom_reaper(struct task_struct
*tsk
)
627 #endif /* CONFIG_MMU */
630 * mark_oom_victim - mark the given task as OOM victim
633 * Has to be called with oom_lock held and never after
634 * oom has been disabled already.
636 * tsk->mm has to be non NULL and caller has to guarantee it is stable (either
637 * under task_lock or operate on the current).
639 static void mark_oom_victim(struct task_struct
*tsk
)
641 struct mm_struct
*mm
= tsk
->mm
;
643 WARN_ON(oom_killer_disabled
);
644 /* OOM killer might race with memcg OOM */
645 if (test_and_set_tsk_thread_flag(tsk
, TIF_MEMDIE
))
648 /* oom_mm is bound to the signal struct life time. */
649 if (!cmpxchg(&tsk
->signal
->oom_mm
, NULL
, mm
))
650 atomic_inc(&tsk
->signal
->oom_mm
->mm_count
);
653 * Make sure that the task is woken up from uninterruptible sleep
654 * if it is frozen because OOM killer wouldn't be able to free
655 * any memory and livelock. freezing_slow_path will tell the freezer
656 * that TIF_MEMDIE tasks should be ignored.
659 atomic_inc(&oom_victims
);
663 * exit_oom_victim - note the exit of an OOM victim
665 void exit_oom_victim(void)
667 clear_thread_flag(TIF_MEMDIE
);
669 if (!atomic_dec_return(&oom_victims
))
670 wake_up_all(&oom_victims_wait
);
674 * oom_killer_enable - enable OOM killer
676 void oom_killer_enable(void)
678 oom_killer_disabled
= false;
682 * oom_killer_disable - disable OOM killer
683 * @timeout: maximum timeout to wait for oom victims in jiffies
685 * Forces all page allocations to fail rather than trigger OOM killer.
686 * Will block and wait until all OOM victims are killed or the given
689 * The function cannot be called when there are runnable user tasks because
690 * the userspace would see unexpected allocation failures as a result. Any
691 * new usage of this function should be consulted with MM people.
693 * Returns true if successful and false if the OOM killer cannot be
696 bool oom_killer_disable(signed long timeout
)
701 * Make sure to not race with an ongoing OOM killer. Check that the
702 * current is not killed (possibly due to sharing the victim's memory).
704 if (mutex_lock_killable(&oom_lock
))
706 oom_killer_disabled
= true;
707 mutex_unlock(&oom_lock
);
709 ret
= wait_event_interruptible_timeout(oom_victims_wait
,
710 !atomic_read(&oom_victims
), timeout
);
719 static inline bool __task_will_free_mem(struct task_struct
*task
)
721 struct signal_struct
*sig
= task
->signal
;
724 * A coredumping process may sleep for an extended period in exit_mm(),
725 * so the oom killer cannot assume that the process will promptly exit
726 * and release memory.
728 if (sig
->flags
& SIGNAL_GROUP_COREDUMP
)
731 if (sig
->flags
& SIGNAL_GROUP_EXIT
)
734 if (thread_group_empty(task
) && (task
->flags
& PF_EXITING
))
741 * Checks whether the given task is dying or exiting and likely to
742 * release its address space. This means that all threads and processes
743 * sharing the same mm have to be killed or exiting.
744 * Caller has to make sure that task->mm is stable (hold task_lock or
745 * it operates on the current).
747 static bool task_will_free_mem(struct task_struct
*task
)
749 struct mm_struct
*mm
= task
->mm
;
750 struct task_struct
*p
;
754 * Skip tasks without mm because it might have passed its exit_mm and
755 * exit_oom_victim. oom_reaper could have rescued that but do not rely
756 * on that for now. We can consider find_lock_task_mm in future.
761 if (!__task_will_free_mem(task
))
765 * This task has already been drained by the oom reaper so there are
766 * only small chances it will free some more
768 if (test_bit(MMF_OOM_SKIP
, &mm
->flags
))
771 if (atomic_read(&mm
->mm_users
) <= 1)
775 * Make sure that all tasks which share the mm with the given tasks
776 * are dying as well to make sure that a) nobody pins its mm and
777 * b) the task is also reapable by the oom reaper.
780 for_each_process(p
) {
781 if (!process_shares_mm(p
, mm
))
783 if (same_thread_group(task
, p
))
785 ret
= __task_will_free_mem(p
);
794 static void oom_kill_process(struct oom_control
*oc
, const char *message
)
796 struct task_struct
*p
= oc
->chosen
;
797 unsigned int points
= oc
->chosen_points
;
798 struct task_struct
*victim
= p
;
799 struct task_struct
*child
;
800 struct task_struct
*t
;
801 struct mm_struct
*mm
;
802 unsigned int victim_points
= 0;
803 static DEFINE_RATELIMIT_STATE(oom_rs
, DEFAULT_RATELIMIT_INTERVAL
,
804 DEFAULT_RATELIMIT_BURST
);
805 bool can_oom_reap
= true;
808 * If the task is already exiting, don't alarm the sysadmin or kill
809 * its children or threads, just set TIF_MEMDIE so it can die quickly
812 if (task_will_free_mem(p
)) {
821 if (__ratelimit(&oom_rs
))
824 pr_err("%s: Kill process %d (%s) score %u or sacrifice child\n",
825 message
, task_pid_nr(p
), p
->comm
, points
);
828 * If any of p's children has a different mm and is eligible for kill,
829 * the one with the highest oom_badness() score is sacrificed for its
830 * parent. This attempts to lose the minimal amount of work done while
831 * still freeing memory.
833 read_lock(&tasklist_lock
);
834 for_each_thread(p
, t
) {
835 list_for_each_entry(child
, &t
->children
, sibling
) {
836 unsigned int child_points
;
838 if (process_shares_mm(child
, p
->mm
))
841 * oom_badness() returns 0 if the thread is unkillable
843 child_points
= oom_badness(child
,
844 oc
->memcg
, oc
->nodemask
, oc
->totalpages
);
845 if (child_points
> victim_points
) {
846 put_task_struct(victim
);
848 victim_points
= child_points
;
849 get_task_struct(victim
);
853 read_unlock(&tasklist_lock
);
855 p
= find_lock_task_mm(victim
);
857 put_task_struct(victim
);
859 } else if (victim
!= p
) {
861 put_task_struct(victim
);
865 /* Get a reference to safely compare mm after task_unlock(victim) */
867 atomic_inc(&mm
->mm_count
);
869 * We should send SIGKILL before setting TIF_MEMDIE in order to prevent
870 * the OOM victim from depleting the memory reserves from the user
871 * space under its control.
873 do_send_sig_info(SIGKILL
, SEND_SIG_FORCED
, victim
, true);
874 mark_oom_victim(victim
);
875 pr_err("Killed process %d (%s) total-vm:%lukB, anon-rss:%lukB, file-rss:%lukB, shmem-rss:%lukB\n",
876 task_pid_nr(victim
), victim
->comm
, K(victim
->mm
->total_vm
),
877 K(get_mm_counter(victim
->mm
, MM_ANONPAGES
)),
878 K(get_mm_counter(victim
->mm
, MM_FILEPAGES
)),
879 K(get_mm_counter(victim
->mm
, MM_SHMEMPAGES
)));
883 * Kill all user processes sharing victim->mm in other thread groups, if
884 * any. They don't get access to memory reserves, though, to avoid
885 * depletion of all memory. This prevents mm->mmap_sem livelock when an
886 * oom killed thread cannot exit because it requires the semaphore and
887 * its contended by another thread trying to allocate memory itself.
888 * That thread will now get access to memory reserves since it has a
889 * pending fatal signal.
892 for_each_process(p
) {
893 if (!process_shares_mm(p
, mm
))
895 if (same_thread_group(p
, victim
))
897 if (unlikely(p
->flags
& PF_KTHREAD
) || is_global_init(p
)) {
899 * We cannot use oom_reaper for the mm shared by this
900 * process because it wouldn't get killed and so the
901 * memory might be still used. Hide the mm from the oom
902 * killer to guarantee OOM forward progress.
904 can_oom_reap
= false;
905 set_bit(MMF_OOM_SKIP
, &mm
->flags
);
906 pr_info("oom killer %d (%s) has mm pinned by %d (%s)\n",
907 task_pid_nr(victim
), victim
->comm
,
908 task_pid_nr(p
), p
->comm
);
911 do_send_sig_info(SIGKILL
, SEND_SIG_FORCED
, p
, true);
916 wake_oom_reaper(victim
);
919 put_task_struct(victim
);
924 * Determines whether the kernel must panic because of the panic_on_oom sysctl.
926 static void check_panic_on_oom(struct oom_control
*oc
,
927 enum oom_constraint constraint
)
929 if (likely(!sysctl_panic_on_oom
))
931 if (sysctl_panic_on_oom
!= 2) {
933 * panic_on_oom == 1 only affects CONSTRAINT_NONE, the kernel
934 * does not panic for cpuset, mempolicy, or memcg allocation
937 if (constraint
!= CONSTRAINT_NONE
)
940 /* Do not panic for oom kills triggered by sysrq */
941 if (is_sysrq_oom(oc
))
943 dump_header(oc
, NULL
);
944 panic("Out of memory: %s panic_on_oom is enabled\n",
945 sysctl_panic_on_oom
== 2 ? "compulsory" : "system-wide");
948 static BLOCKING_NOTIFIER_HEAD(oom_notify_list
);
950 int register_oom_notifier(struct notifier_block
*nb
)
952 return blocking_notifier_chain_register(&oom_notify_list
, nb
);
954 EXPORT_SYMBOL_GPL(register_oom_notifier
);
956 int unregister_oom_notifier(struct notifier_block
*nb
)
958 return blocking_notifier_chain_unregister(&oom_notify_list
, nb
);
960 EXPORT_SYMBOL_GPL(unregister_oom_notifier
);
963 * out_of_memory - kill the "best" process when we run out of memory
964 * @oc: pointer to struct oom_control
966 * If we run out of memory, we have the choice between either
967 * killing a random task (bad), letting the system crash (worse)
968 * OR try to be smart about which process to kill. Note that we
969 * don't have to be perfect here, we just have to be good.
971 bool out_of_memory(struct oom_control
*oc
)
973 unsigned long freed
= 0;
974 enum oom_constraint constraint
= CONSTRAINT_NONE
;
976 if (oom_killer_disabled
)
979 if (!is_memcg_oom(oc
)) {
980 blocking_notifier_call_chain(&oom_notify_list
, 0, &freed
);
982 /* Got some memory back in the last second. */
987 * If current has a pending SIGKILL or is exiting, then automatically
988 * select it. The goal is to allow it to allocate so that it may
989 * quickly exit and free its memory.
991 if (task_will_free_mem(current
)) {
992 mark_oom_victim(current
);
993 wake_oom_reaper(current
);
998 * The OOM killer does not compensate for IO-less reclaim.
999 * pagefault_out_of_memory lost its gfp context so we have to
1000 * make sure exclude 0 mask - all other users should have at least
1001 * ___GFP_DIRECT_RECLAIM to get here.
1003 if (oc
->gfp_mask
&& !(oc
->gfp_mask
& (__GFP_FS
|__GFP_NOFAIL
)))
1007 * Check if there were limitations on the allocation (only relevant for
1008 * NUMA and memcg) that may require different handling.
1010 constraint
= constrained_alloc(oc
);
1011 if (constraint
!= CONSTRAINT_MEMORY_POLICY
)
1012 oc
->nodemask
= NULL
;
1013 check_panic_on_oom(oc
, constraint
);
1015 if (!is_memcg_oom(oc
) && sysctl_oom_kill_allocating_task
&&
1016 current
->mm
&& !oom_unkillable_task(current
, NULL
, oc
->nodemask
) &&
1017 current
->signal
->oom_score_adj
!= OOM_SCORE_ADJ_MIN
) {
1018 get_task_struct(current
);
1019 oc
->chosen
= current
;
1020 oom_kill_process(oc
, "Out of memory (oom_kill_allocating_task)");
1024 select_bad_process(oc
);
1025 /* Found nothing?!?! Either we hang forever, or we panic. */
1026 if (!oc
->chosen
&& !is_sysrq_oom(oc
) && !is_memcg_oom(oc
)) {
1027 dump_header(oc
, NULL
);
1028 panic("Out of memory and no killable processes...\n");
1030 if (oc
->chosen
&& oc
->chosen
!= (void *)-1UL) {
1031 oom_kill_process(oc
, !is_memcg_oom(oc
) ? "Out of memory" :
1032 "Memory cgroup out of memory");
1034 * Give the killed process a good chance to exit before trying
1035 * to allocate memory again.
1037 schedule_timeout_killable(1);
1039 return !!oc
->chosen
;
1043 * The pagefault handler calls here because it is out of memory, so kill a
1044 * memory-hogging task. If oom_lock is held by somebody else, a parallel oom
1045 * killing is already in progress so do nothing.
1047 void pagefault_out_of_memory(void)
1049 struct oom_control oc
= {
1057 if (mem_cgroup_oom_synchronize(true))
1060 if (!mutex_trylock(&oom_lock
))
1063 if (!out_of_memory(&oc
)) {
1065 * There shouldn't be any user tasks runnable while the
1066 * OOM killer is disabled, so the current task has to
1067 * be a racing OOM victim for which oom_killer_disable()
1070 WARN_ON(test_thread_flag(TIF_MEMDIE
));
1073 mutex_unlock(&oom_lock
);