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_pgtables_bytes(p
->mm
) / PAGE_SIZE
;
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,
393 * pgtables_bytes, 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 pgtables_bytes 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 %8ld %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_pgtables_bytes(task
->mm
),
420 get_mm_counter(task
->mm
, MM_SWAPENTS
),
421 task
->signal
->oom_score_adj
, task
->comm
);
427 static void dump_header(struct oom_control
*oc
, struct task_struct
*p
)
429 pr_warn("%s invoked oom-killer: gfp_mask=%#x(%pGg), nodemask=%*pbl, order=%d, oom_score_adj=%hd\n",
430 current
->comm
, oc
->gfp_mask
, &oc
->gfp_mask
,
431 nodemask_pr_args(oc
->nodemask
), oc
->order
,
432 current
->signal
->oom_score_adj
);
433 if (!IS_ENABLED(CONFIG_COMPACTION
) && oc
->order
)
434 pr_warn("COMPACTION is disabled!!!\n");
436 cpuset_print_current_mems_allowed();
438 if (is_memcg_oom(oc
))
439 mem_cgroup_print_oom_info(oc
->memcg
, p
);
441 show_mem(SHOW_MEM_FILTER_NODES
, oc
->nodemask
);
442 if (is_dump_unreclaim_slabs())
443 dump_unreclaimable_slab();
445 if (sysctl_oom_dump_tasks
)
446 dump_tasks(oc
->memcg
, oc
->nodemask
);
450 * Number of OOM victims in flight
452 static atomic_t oom_victims
= ATOMIC_INIT(0);
453 static DECLARE_WAIT_QUEUE_HEAD(oom_victims_wait
);
455 static bool oom_killer_disabled __read_mostly
;
457 #define K(x) ((x) << (PAGE_SHIFT-10))
460 * task->mm can be NULL if the task is the exited group leader. So to
461 * determine whether the task is using a particular mm, we examine all the
462 * task's threads: if one of those is using this mm then this task was also
465 bool process_shares_mm(struct task_struct
*p
, struct mm_struct
*mm
)
467 struct task_struct
*t
;
469 for_each_thread(p
, t
) {
470 struct mm_struct
*t_mm
= READ_ONCE(t
->mm
);
480 * OOM Reaper kernel thread which tries to reap the memory used by the OOM
481 * victim (if that is possible) to help the OOM killer to move on.
483 static struct task_struct
*oom_reaper_th
;
484 static DECLARE_WAIT_QUEUE_HEAD(oom_reaper_wait
);
485 static struct task_struct
*oom_reaper_list
;
486 static DEFINE_SPINLOCK(oom_reaper_lock
);
488 static bool __oom_reap_task_mm(struct task_struct
*tsk
, struct mm_struct
*mm
)
490 struct mmu_gather tlb
;
491 struct vm_area_struct
*vma
;
495 * We have to make sure to not race with the victim exit path
496 * and cause premature new oom victim selection:
497 * __oom_reap_task_mm exit_mm
500 * atomic_dec_and_test
505 * # no TIF_MEMDIE task selects new victim
506 * unmap_page_range # frees some memory
508 mutex_lock(&oom_lock
);
510 if (!down_read_trylock(&mm
->mmap_sem
)) {
512 trace_skip_task_reaping(tsk
->pid
);
517 * If the mm has invalidate_{start,end}() notifiers that could block,
518 * sleep to give the oom victim some more time.
519 * TODO: we really want to get rid of this ugly hack and make sure that
520 * notifiers cannot block for unbounded amount of time
522 if (mm_has_blockable_invalidate_notifiers(mm
)) {
523 up_read(&mm
->mmap_sem
);
524 schedule_timeout_idle(HZ
);
529 * MMF_OOM_SKIP is set by exit_mmap when the OOM reaper can't
530 * work on the mm anymore. The check for MMF_OOM_SKIP must run
531 * under mmap_sem for reading because it serializes against the
532 * down_write();up_write() cycle in exit_mmap().
534 if (test_bit(MMF_OOM_SKIP
, &mm
->flags
)) {
535 up_read(&mm
->mmap_sem
);
536 trace_skip_task_reaping(tsk
->pid
);
540 trace_start_task_reaping(tsk
->pid
);
543 * Tell all users of get_user/copy_from_user etc... that the content
544 * is no longer stable. No barriers really needed because unmapping
545 * should imply barriers already and the reader would hit a page fault
546 * if it stumbled over a reaped memory.
548 set_bit(MMF_UNSTABLE
, &mm
->flags
);
550 for (vma
= mm
->mmap
; vma
; vma
= vma
->vm_next
) {
551 if (!can_madv_dontneed_vma(vma
))
555 * Only anonymous pages have a good chance to be dropped
556 * without additional steps which we cannot afford as we
559 * We do not even care about fs backed pages because all
560 * which are reclaimable have already been reclaimed and
561 * we do not want to block exit_mmap by keeping mm ref
562 * count elevated without a good reason.
564 if (vma_is_anonymous(vma
) || !(vma
->vm_flags
& VM_SHARED
)) {
565 const unsigned long start
= vma
->vm_start
;
566 const unsigned long end
= vma
->vm_end
;
568 tlb_gather_mmu(&tlb
, mm
, start
, end
);
569 mmu_notifier_invalidate_range_start(mm
, start
, end
);
570 unmap_page_range(&tlb
, vma
, start
, end
, NULL
);
571 mmu_notifier_invalidate_range_end(mm
, start
, end
);
572 tlb_finish_mmu(&tlb
, start
, end
);
575 pr_info("oom_reaper: reaped process %d (%s), now anon-rss:%lukB, file-rss:%lukB, shmem-rss:%lukB\n",
576 task_pid_nr(tsk
), tsk
->comm
,
577 K(get_mm_counter(mm
, MM_ANONPAGES
)),
578 K(get_mm_counter(mm
, MM_FILEPAGES
)),
579 K(get_mm_counter(mm
, MM_SHMEMPAGES
)));
580 up_read(&mm
->mmap_sem
);
582 trace_finish_task_reaping(tsk
->pid
);
584 mutex_unlock(&oom_lock
);
588 #define MAX_OOM_REAP_RETRIES 10
589 static void oom_reap_task(struct task_struct
*tsk
)
592 struct mm_struct
*mm
= tsk
->signal
->oom_mm
;
594 /* Retry the down_read_trylock(mmap_sem) a few times */
595 while (attempts
++ < MAX_OOM_REAP_RETRIES
&& !__oom_reap_task_mm(tsk
, mm
))
596 schedule_timeout_idle(HZ
/10);
598 if (attempts
<= MAX_OOM_REAP_RETRIES
)
602 pr_info("oom_reaper: unable to reap pid:%d (%s)\n",
603 task_pid_nr(tsk
), tsk
->comm
);
604 debug_show_all_locks();
607 tsk
->oom_reaper_list
= NULL
;
610 * Hide this mm from OOM killer because it has been either reaped or
611 * somebody can't call up_write(mmap_sem).
613 set_bit(MMF_OOM_SKIP
, &mm
->flags
);
615 /* Drop a reference taken by wake_oom_reaper */
616 put_task_struct(tsk
);
619 static int oom_reaper(void *unused
)
622 struct task_struct
*tsk
= NULL
;
624 wait_event_freezable(oom_reaper_wait
, oom_reaper_list
!= NULL
);
625 spin_lock(&oom_reaper_lock
);
626 if (oom_reaper_list
!= NULL
) {
627 tsk
= oom_reaper_list
;
628 oom_reaper_list
= tsk
->oom_reaper_list
;
630 spin_unlock(&oom_reaper_lock
);
639 static void wake_oom_reaper(struct task_struct
*tsk
)
641 /* tsk is already queued? */
642 if (tsk
== oom_reaper_list
|| tsk
->oom_reaper_list
)
645 get_task_struct(tsk
);
647 spin_lock(&oom_reaper_lock
);
648 tsk
->oom_reaper_list
= oom_reaper_list
;
649 oom_reaper_list
= tsk
;
650 spin_unlock(&oom_reaper_lock
);
651 trace_wake_reaper(tsk
->pid
);
652 wake_up(&oom_reaper_wait
);
655 static int __init
oom_init(void)
657 oom_reaper_th
= kthread_run(oom_reaper
, NULL
, "oom_reaper");
660 subsys_initcall(oom_init
)
662 static inline void wake_oom_reaper(struct task_struct
*tsk
)
665 #endif /* CONFIG_MMU */
668 * mark_oom_victim - mark the given task as OOM victim
671 * Has to be called with oom_lock held and never after
672 * oom has been disabled already.
674 * tsk->mm has to be non NULL and caller has to guarantee it is stable (either
675 * under task_lock or operate on the current).
677 static void mark_oom_victim(struct task_struct
*tsk
)
679 struct mm_struct
*mm
= tsk
->mm
;
681 WARN_ON(oom_killer_disabled
);
682 /* OOM killer might race with memcg OOM */
683 if (test_and_set_tsk_thread_flag(tsk
, TIF_MEMDIE
))
686 /* oom_mm is bound to the signal struct life time. */
687 if (!cmpxchg(&tsk
->signal
->oom_mm
, NULL
, mm
)) {
688 mmgrab(tsk
->signal
->oom_mm
);
689 set_bit(MMF_OOM_VICTIM
, &mm
->flags
);
693 * Make sure that the task is woken up from uninterruptible sleep
694 * if it is frozen because OOM killer wouldn't be able to free
695 * any memory and livelock. freezing_slow_path will tell the freezer
696 * that TIF_MEMDIE tasks should be ignored.
699 atomic_inc(&oom_victims
);
700 trace_mark_victim(tsk
->pid
);
704 * exit_oom_victim - note the exit of an OOM victim
706 void exit_oom_victim(void)
708 clear_thread_flag(TIF_MEMDIE
);
710 if (!atomic_dec_return(&oom_victims
))
711 wake_up_all(&oom_victims_wait
);
715 * oom_killer_enable - enable OOM killer
717 void oom_killer_enable(void)
719 oom_killer_disabled
= false;
720 pr_info("OOM killer enabled.\n");
724 * oom_killer_disable - disable OOM killer
725 * @timeout: maximum timeout to wait for oom victims in jiffies
727 * Forces all page allocations to fail rather than trigger OOM killer.
728 * Will block and wait until all OOM victims are killed or the given
731 * The function cannot be called when there are runnable user tasks because
732 * the userspace would see unexpected allocation failures as a result. Any
733 * new usage of this function should be consulted with MM people.
735 * Returns true if successful and false if the OOM killer cannot be
738 bool oom_killer_disable(signed long timeout
)
743 * Make sure to not race with an ongoing OOM killer. Check that the
744 * current is not killed (possibly due to sharing the victim's memory).
746 if (mutex_lock_killable(&oom_lock
))
748 oom_killer_disabled
= true;
749 mutex_unlock(&oom_lock
);
751 ret
= wait_event_interruptible_timeout(oom_victims_wait
,
752 !atomic_read(&oom_victims
), timeout
);
757 pr_info("OOM killer disabled.\n");
762 static inline bool __task_will_free_mem(struct task_struct
*task
)
764 struct signal_struct
*sig
= task
->signal
;
767 * A coredumping process may sleep for an extended period in exit_mm(),
768 * so the oom killer cannot assume that the process will promptly exit
769 * and release memory.
771 if (sig
->flags
& SIGNAL_GROUP_COREDUMP
)
774 if (sig
->flags
& SIGNAL_GROUP_EXIT
)
777 if (thread_group_empty(task
) && (task
->flags
& PF_EXITING
))
784 * Checks whether the given task is dying or exiting and likely to
785 * release its address space. This means that all threads and processes
786 * sharing the same mm have to be killed or exiting.
787 * Caller has to make sure that task->mm is stable (hold task_lock or
788 * it operates on the current).
790 static bool task_will_free_mem(struct task_struct
*task
)
792 struct mm_struct
*mm
= task
->mm
;
793 struct task_struct
*p
;
797 * Skip tasks without mm because it might have passed its exit_mm and
798 * exit_oom_victim. oom_reaper could have rescued that but do not rely
799 * on that for now. We can consider find_lock_task_mm in future.
804 if (!__task_will_free_mem(task
))
808 * This task has already been drained by the oom reaper so there are
809 * only small chances it will free some more
811 if (test_bit(MMF_OOM_SKIP
, &mm
->flags
))
814 if (atomic_read(&mm
->mm_users
) <= 1)
818 * Make sure that all tasks which share the mm with the given tasks
819 * are dying as well to make sure that a) nobody pins its mm and
820 * b) the task is also reapable by the oom reaper.
823 for_each_process(p
) {
824 if (!process_shares_mm(p
, mm
))
826 if (same_thread_group(task
, p
))
828 ret
= __task_will_free_mem(p
);
837 static void oom_kill_process(struct oom_control
*oc
, const char *message
)
839 struct task_struct
*p
= oc
->chosen
;
840 unsigned int points
= oc
->chosen_points
;
841 struct task_struct
*victim
= p
;
842 struct task_struct
*child
;
843 struct task_struct
*t
;
844 struct mm_struct
*mm
;
845 unsigned int victim_points
= 0;
846 static DEFINE_RATELIMIT_STATE(oom_rs
, DEFAULT_RATELIMIT_INTERVAL
,
847 DEFAULT_RATELIMIT_BURST
);
848 bool can_oom_reap
= true;
851 * If the task is already exiting, don't alarm the sysadmin or kill
852 * its children or threads, just give it access to memory reserves
853 * so it can die quickly
856 if (task_will_free_mem(p
)) {
865 if (__ratelimit(&oom_rs
))
868 pr_err("%s: Kill process %d (%s) score %u or sacrifice child\n",
869 message
, task_pid_nr(p
), p
->comm
, points
);
872 * If any of p's children has a different mm and is eligible for kill,
873 * the one with the highest oom_badness() score is sacrificed for its
874 * parent. This attempts to lose the minimal amount of work done while
875 * still freeing memory.
877 read_lock(&tasklist_lock
);
878 for_each_thread(p
, t
) {
879 list_for_each_entry(child
, &t
->children
, sibling
) {
880 unsigned int child_points
;
882 if (process_shares_mm(child
, p
->mm
))
885 * oom_badness() returns 0 if the thread is unkillable
887 child_points
= oom_badness(child
,
888 oc
->memcg
, oc
->nodemask
, oc
->totalpages
);
889 if (child_points
> victim_points
) {
890 put_task_struct(victim
);
892 victim_points
= child_points
;
893 get_task_struct(victim
);
897 read_unlock(&tasklist_lock
);
899 p
= find_lock_task_mm(victim
);
901 put_task_struct(victim
);
903 } else if (victim
!= p
) {
905 put_task_struct(victim
);
909 /* Get a reference to safely compare mm after task_unlock(victim) */
913 /* Raise event before sending signal: task reaper must see this */
914 count_vm_event(OOM_KILL
);
915 count_memcg_event_mm(mm
, OOM_KILL
);
918 * We should send SIGKILL before granting access to memory reserves
919 * in order to prevent the OOM victim from depleting the memory
920 * reserves from the user space under its control.
922 do_send_sig_info(SIGKILL
, SEND_SIG_FORCED
, victim
, true);
923 mark_oom_victim(victim
);
924 pr_err("Killed process %d (%s) total-vm:%lukB, anon-rss:%lukB, file-rss:%lukB, shmem-rss:%lukB\n",
925 task_pid_nr(victim
), victim
->comm
, K(victim
->mm
->total_vm
),
926 K(get_mm_counter(victim
->mm
, MM_ANONPAGES
)),
927 K(get_mm_counter(victim
->mm
, MM_FILEPAGES
)),
928 K(get_mm_counter(victim
->mm
, MM_SHMEMPAGES
)));
932 * Kill all user processes sharing victim->mm in other thread groups, if
933 * any. They don't get access to memory reserves, though, to avoid
934 * depletion of all memory. This prevents mm->mmap_sem livelock when an
935 * oom killed thread cannot exit because it requires the semaphore and
936 * its contended by another thread trying to allocate memory itself.
937 * That thread will now get access to memory reserves since it has a
938 * pending fatal signal.
941 for_each_process(p
) {
942 if (!process_shares_mm(p
, mm
))
944 if (same_thread_group(p
, victim
))
946 if (is_global_init(p
)) {
947 can_oom_reap
= false;
948 set_bit(MMF_OOM_SKIP
, &mm
->flags
);
949 pr_info("oom killer %d (%s) has mm pinned by %d (%s)\n",
950 task_pid_nr(victim
), victim
->comm
,
951 task_pid_nr(p
), p
->comm
);
955 * No use_mm() user needs to read from the userspace so we are
958 if (unlikely(p
->flags
& PF_KTHREAD
))
960 do_send_sig_info(SIGKILL
, SEND_SIG_FORCED
, p
, true);
965 wake_oom_reaper(victim
);
968 put_task_struct(victim
);
973 * Determines whether the kernel must panic because of the panic_on_oom sysctl.
975 static void check_panic_on_oom(struct oom_control
*oc
,
976 enum oom_constraint constraint
)
978 if (likely(!sysctl_panic_on_oom
))
980 if (sysctl_panic_on_oom
!= 2) {
982 * panic_on_oom == 1 only affects CONSTRAINT_NONE, the kernel
983 * does not panic for cpuset, mempolicy, or memcg allocation
986 if (constraint
!= CONSTRAINT_NONE
)
989 /* Do not panic for oom kills triggered by sysrq */
990 if (is_sysrq_oom(oc
))
992 dump_header(oc
, NULL
);
993 panic("Out of memory: %s panic_on_oom is enabled\n",
994 sysctl_panic_on_oom
== 2 ? "compulsory" : "system-wide");
997 static BLOCKING_NOTIFIER_HEAD(oom_notify_list
);
999 int register_oom_notifier(struct notifier_block
*nb
)
1001 return blocking_notifier_chain_register(&oom_notify_list
, nb
);
1003 EXPORT_SYMBOL_GPL(register_oom_notifier
);
1005 int unregister_oom_notifier(struct notifier_block
*nb
)
1007 return blocking_notifier_chain_unregister(&oom_notify_list
, nb
);
1009 EXPORT_SYMBOL_GPL(unregister_oom_notifier
);
1012 * out_of_memory - kill the "best" process when we run out of memory
1013 * @oc: pointer to struct oom_control
1015 * If we run out of memory, we have the choice between either
1016 * killing a random task (bad), letting the system crash (worse)
1017 * OR try to be smart about which process to kill. Note that we
1018 * don't have to be perfect here, we just have to be good.
1020 bool out_of_memory(struct oom_control
*oc
)
1022 unsigned long freed
= 0;
1023 enum oom_constraint constraint
= CONSTRAINT_NONE
;
1025 if (oom_killer_disabled
)
1028 if (!is_memcg_oom(oc
)) {
1029 blocking_notifier_call_chain(&oom_notify_list
, 0, &freed
);
1031 /* Got some memory back in the last second. */
1036 * If current has a pending SIGKILL or is exiting, then automatically
1037 * select it. The goal is to allow it to allocate so that it may
1038 * quickly exit and free its memory.
1040 if (task_will_free_mem(current
)) {
1041 mark_oom_victim(current
);
1042 wake_oom_reaper(current
);
1047 * The OOM killer does not compensate for IO-less reclaim.
1048 * pagefault_out_of_memory lost its gfp context so we have to
1049 * make sure exclude 0 mask - all other users should have at least
1050 * ___GFP_DIRECT_RECLAIM to get here.
1052 if (oc
->gfp_mask
&& !(oc
->gfp_mask
& __GFP_FS
))
1056 * Check if there were limitations on the allocation (only relevant for
1057 * NUMA and memcg) that may require different handling.
1059 constraint
= constrained_alloc(oc
);
1060 if (constraint
!= CONSTRAINT_MEMORY_POLICY
)
1061 oc
->nodemask
= NULL
;
1062 check_panic_on_oom(oc
, constraint
);
1064 if (!is_memcg_oom(oc
) && sysctl_oom_kill_allocating_task
&&
1065 current
->mm
&& !oom_unkillable_task(current
, NULL
, oc
->nodemask
) &&
1066 current
->signal
->oom_score_adj
!= OOM_SCORE_ADJ_MIN
) {
1067 get_task_struct(current
);
1068 oc
->chosen
= current
;
1069 oom_kill_process(oc
, "Out of memory (oom_kill_allocating_task)");
1073 select_bad_process(oc
);
1074 /* Found nothing?!?! Either we hang forever, or we panic. */
1075 if (!oc
->chosen
&& !is_sysrq_oom(oc
) && !is_memcg_oom(oc
)) {
1076 dump_header(oc
, NULL
);
1077 panic("Out of memory and no killable processes...\n");
1079 if (oc
->chosen
&& oc
->chosen
!= (void *)-1UL) {
1080 oom_kill_process(oc
, !is_memcg_oom(oc
) ? "Out of memory" :
1081 "Memory cgroup out of memory");
1083 * Give the killed process a good chance to exit before trying
1084 * to allocate memory again.
1086 schedule_timeout_killable(1);
1088 return !!oc
->chosen
;
1092 * The pagefault handler calls here because it is out of memory, so kill a
1093 * memory-hogging task. If oom_lock is held by somebody else, a parallel oom
1094 * killing is already in progress so do nothing.
1096 void pagefault_out_of_memory(void)
1098 struct oom_control oc
= {
1106 if (mem_cgroup_oom_synchronize(true))
1109 if (!mutex_trylock(&oom_lock
))
1112 mutex_unlock(&oom_lock
);