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
);
478 atomic_inc(&mm
->mm_users
);
481 if (!down_read_trylock(&mm
->mmap_sem
)) {
486 tlb_gather_mmu(&tlb
, mm
, 0, -1);
487 for (vma
= mm
->mmap
; vma
; vma
= vma
->vm_next
) {
488 if (is_vm_hugetlb_page(vma
))
492 * mlocked VMAs require explicit munlocking before unmap.
493 * Let's keep it simple here and skip such VMAs.
495 if (vma
->vm_flags
& VM_LOCKED
)
499 * Only anonymous pages have a good chance to be dropped
500 * without additional steps which we cannot afford as we
503 * We do not even care about fs backed pages because all
504 * which are reclaimable have already been reclaimed and
505 * we do not want to block exit_mmap by keeping mm ref
506 * count elevated without a good reason.
508 if (vma_is_anonymous(vma
) || !(vma
->vm_flags
& VM_SHARED
))
509 unmap_page_range(&tlb
, vma
, vma
->vm_start
, vma
->vm_end
,
512 tlb_finish_mmu(&tlb
, 0, -1);
513 pr_info("oom_reaper: reaped process %d (%s), now anon-rss:%lukB, file-rss:%lukB, shmem-rss:%lukB\n",
514 task_pid_nr(tsk
), tsk
->comm
,
515 K(get_mm_counter(mm
, MM_ANONPAGES
)),
516 K(get_mm_counter(mm
, MM_FILEPAGES
)),
517 K(get_mm_counter(mm
, MM_SHMEMPAGES
)));
518 up_read(&mm
->mmap_sem
);
521 * This task can be safely ignored because we cannot do much more
522 * to release its memory.
524 set_bit(MMF_OOM_REAPED
, &mm
->flags
);
526 mutex_unlock(&oom_lock
);
528 * Drop our reference but make sure the mmput slow path is called from a
529 * different context because we shouldn't risk we get stuck there and
530 * put the oom_reaper out of the way.
537 #define MAX_OOM_REAP_RETRIES 10
538 static void oom_reap_task(struct task_struct
*tsk
)
542 /* Retry the down_read_trylock(mmap_sem) a few times */
543 while (attempts
++ < MAX_OOM_REAP_RETRIES
&& !__oom_reap_task(tsk
))
544 schedule_timeout_idle(HZ
/10);
546 if (attempts
> MAX_OOM_REAP_RETRIES
) {
547 pr_info("oom_reaper: unable to reap pid:%d (%s)\n",
548 task_pid_nr(tsk
), tsk
->comm
);
549 debug_show_all_locks();
553 * Clear TIF_MEMDIE because the task shouldn't be sitting on a
554 * reasonably reclaimable memory anymore or it is not a good candidate
555 * for the oom victim right now because it cannot release its memory
556 * itself nor by the oom reaper.
558 tsk
->oom_reaper_list
= NULL
;
559 exit_oom_victim(tsk
);
561 /* Drop a reference taken by wake_oom_reaper */
562 put_task_struct(tsk
);
565 static int oom_reaper(void *unused
)
570 struct task_struct
*tsk
= NULL
;
572 wait_event_freezable(oom_reaper_wait
, oom_reaper_list
!= NULL
);
573 spin_lock(&oom_reaper_lock
);
574 if (oom_reaper_list
!= NULL
) {
575 tsk
= oom_reaper_list
;
576 oom_reaper_list
= tsk
->oom_reaper_list
;
578 spin_unlock(&oom_reaper_lock
);
587 static void wake_oom_reaper(struct task_struct
*tsk
)
592 /* tsk is already queued? */
593 if (tsk
== oom_reaper_list
|| tsk
->oom_reaper_list
)
596 get_task_struct(tsk
);
598 spin_lock(&oom_reaper_lock
);
599 tsk
->oom_reaper_list
= oom_reaper_list
;
600 oom_reaper_list
= tsk
;
601 spin_unlock(&oom_reaper_lock
);
602 wake_up(&oom_reaper_wait
);
605 /* Check if we can reap the given task. This has to be called with stable
608 void try_oom_reaper(struct task_struct
*tsk
)
610 struct mm_struct
*mm
= tsk
->mm
;
611 struct task_struct
*p
;
617 * There might be other threads/processes which are either not
618 * dying or even not killable.
620 if (atomic_read(&mm
->mm_users
) > 1) {
622 for_each_process(p
) {
623 if (!process_shares_mm(p
, mm
))
625 if (fatal_signal_pending(p
))
629 * If the task is exiting make sure the whole thread group
630 * is exiting and cannot acces mm anymore.
632 if (signal_group_exit(p
->signal
))
642 wake_oom_reaper(tsk
);
645 static int __init
oom_init(void)
647 oom_reaper_th
= kthread_run(oom_reaper
, NULL
, "oom_reaper");
648 if (IS_ERR(oom_reaper_th
)) {
649 pr_err("Unable to start OOM reaper %ld. Continuing regardless\n",
650 PTR_ERR(oom_reaper_th
));
651 oom_reaper_th
= NULL
;
655 subsys_initcall(oom_init
)
657 static void wake_oom_reaper(struct task_struct
*tsk
)
663 * mark_oom_victim - mark the given task as OOM victim
666 * Has to be called with oom_lock held and never after
667 * oom has been disabled already.
669 void mark_oom_victim(struct task_struct
*tsk
)
671 WARN_ON(oom_killer_disabled
);
672 /* OOM killer might race with memcg OOM */
673 if (test_and_set_tsk_thread_flag(tsk
, TIF_MEMDIE
))
675 atomic_inc(&tsk
->signal
->oom_victims
);
677 * Make sure that the task is woken up from uninterruptible sleep
678 * if it is frozen because OOM killer wouldn't be able to free
679 * any memory and livelock. freezing_slow_path will tell the freezer
680 * that TIF_MEMDIE tasks should be ignored.
683 atomic_inc(&oom_victims
);
687 * exit_oom_victim - note the exit of an OOM victim
689 void exit_oom_victim(struct task_struct
*tsk
)
691 if (!test_and_clear_tsk_thread_flag(tsk
, TIF_MEMDIE
))
693 atomic_dec(&tsk
->signal
->oom_victims
);
695 if (!atomic_dec_return(&oom_victims
))
696 wake_up_all(&oom_victims_wait
);
700 * oom_killer_disable - disable OOM killer
702 * Forces all page allocations to fail rather than trigger OOM killer.
703 * Will block and wait until all OOM victims are killed.
705 * The function cannot be called when there are runnable user tasks because
706 * the userspace would see unexpected allocation failures as a result. Any
707 * new usage of this function should be consulted with MM people.
709 * Returns true if successful and false if the OOM killer cannot be
712 bool oom_killer_disable(void)
715 * Make sure to not race with an ongoing OOM killer. Check that the
716 * current is not killed (possibly due to sharing the victim's memory).
718 if (mutex_lock_killable(&oom_lock
))
720 oom_killer_disabled
= true;
721 mutex_unlock(&oom_lock
);
723 wait_event(oom_victims_wait
, !atomic_read(&oom_victims
));
729 * oom_killer_enable - enable OOM killer
731 void oom_killer_enable(void)
733 oom_killer_disabled
= false;
737 * Must be called while holding a reference to p, which will be released upon
740 void oom_kill_process(struct oom_control
*oc
, struct task_struct
*p
,
741 unsigned int points
, unsigned long totalpages
,
742 struct mem_cgroup
*memcg
, const char *message
)
744 struct task_struct
*victim
= p
;
745 struct task_struct
*child
;
746 struct task_struct
*t
;
747 struct mm_struct
*mm
;
748 unsigned int victim_points
= 0;
749 static DEFINE_RATELIMIT_STATE(oom_rs
, DEFAULT_RATELIMIT_INTERVAL
,
750 DEFAULT_RATELIMIT_BURST
);
751 bool can_oom_reap
= true;
754 * If the task is already exiting, don't alarm the sysadmin or kill
755 * its children or threads, just set TIF_MEMDIE so it can die quickly
758 if (p
->mm
&& task_will_free_mem(p
)) {
767 if (__ratelimit(&oom_rs
))
768 dump_header(oc
, p
, memcg
);
770 pr_err("%s: Kill process %d (%s) score %u or sacrifice child\n",
771 message
, task_pid_nr(p
), p
->comm
, points
);
774 * If any of p's children has a different mm and is eligible for kill,
775 * the one with the highest oom_badness() score is sacrificed for its
776 * parent. This attempts to lose the minimal amount of work done while
777 * still freeing memory.
779 read_lock(&tasklist_lock
);
780 for_each_thread(p
, t
) {
781 list_for_each_entry(child
, &t
->children
, sibling
) {
782 unsigned int child_points
;
784 if (process_shares_mm(child
, p
->mm
))
787 * oom_badness() returns 0 if the thread is unkillable
789 child_points
= oom_badness(child
, memcg
, oc
->nodemask
,
791 if (child_points
> victim_points
) {
792 put_task_struct(victim
);
794 victim_points
= child_points
;
795 get_task_struct(victim
);
799 read_unlock(&tasklist_lock
);
801 p
= find_lock_task_mm(victim
);
803 put_task_struct(victim
);
805 } else if (victim
!= p
) {
807 put_task_struct(victim
);
811 /* Get a reference to safely compare mm after task_unlock(victim) */
813 atomic_inc(&mm
->mm_count
);
815 * We should send SIGKILL before setting TIF_MEMDIE in order to prevent
816 * the OOM victim from depleting the memory reserves from the user
817 * space under its control.
819 do_send_sig_info(SIGKILL
, SEND_SIG_FORCED
, victim
, true);
820 mark_oom_victim(victim
);
821 pr_err("Killed process %d (%s) total-vm:%lukB, anon-rss:%lukB, file-rss:%lukB, shmem-rss:%lukB\n",
822 task_pid_nr(victim
), victim
->comm
, K(victim
->mm
->total_vm
),
823 K(get_mm_counter(victim
->mm
, MM_ANONPAGES
)),
824 K(get_mm_counter(victim
->mm
, MM_FILEPAGES
)),
825 K(get_mm_counter(victim
->mm
, MM_SHMEMPAGES
)));
829 * Kill all user processes sharing victim->mm in other thread groups, if
830 * any. They don't get access to memory reserves, though, to avoid
831 * depletion of all memory. This prevents mm->mmap_sem livelock when an
832 * oom killed thread cannot exit because it requires the semaphore and
833 * its contended by another thread trying to allocate memory itself.
834 * That thread will now get access to memory reserves since it has a
835 * pending fatal signal.
838 for_each_process(p
) {
839 if (!process_shares_mm(p
, mm
))
841 if (same_thread_group(p
, victim
))
843 if (unlikely(p
->flags
& PF_KTHREAD
) || is_global_init(p
) ||
844 p
->signal
->oom_score_adj
== OOM_SCORE_ADJ_MIN
) {
846 * We cannot use oom_reaper for the mm shared by this
847 * process because it wouldn't get killed and so the
848 * memory might be still used.
850 can_oom_reap
= false;
853 do_send_sig_info(SIGKILL
, SEND_SIG_FORCED
, p
, true);
858 wake_oom_reaper(victim
);
861 put_task_struct(victim
);
866 * Determines whether the kernel must panic because of the panic_on_oom sysctl.
868 void check_panic_on_oom(struct oom_control
*oc
, enum oom_constraint constraint
,
869 struct mem_cgroup
*memcg
)
871 if (likely(!sysctl_panic_on_oom
))
873 if (sysctl_panic_on_oom
!= 2) {
875 * panic_on_oom == 1 only affects CONSTRAINT_NONE, the kernel
876 * does not panic for cpuset, mempolicy, or memcg allocation
879 if (constraint
!= CONSTRAINT_NONE
)
882 /* Do not panic for oom kills triggered by sysrq */
883 if (is_sysrq_oom(oc
))
885 dump_header(oc
, NULL
, memcg
);
886 panic("Out of memory: %s panic_on_oom is enabled\n",
887 sysctl_panic_on_oom
== 2 ? "compulsory" : "system-wide");
890 static BLOCKING_NOTIFIER_HEAD(oom_notify_list
);
892 int register_oom_notifier(struct notifier_block
*nb
)
894 return blocking_notifier_chain_register(&oom_notify_list
, nb
);
896 EXPORT_SYMBOL_GPL(register_oom_notifier
);
898 int unregister_oom_notifier(struct notifier_block
*nb
)
900 return blocking_notifier_chain_unregister(&oom_notify_list
, nb
);
902 EXPORT_SYMBOL_GPL(unregister_oom_notifier
);
905 * out_of_memory - kill the "best" process when we run out of memory
906 * @oc: pointer to struct oom_control
908 * If we run out of memory, we have the choice between either
909 * killing a random task (bad), letting the system crash (worse)
910 * OR try to be smart about which process to kill. Note that we
911 * don't have to be perfect here, we just have to be good.
913 bool out_of_memory(struct oom_control
*oc
)
915 struct task_struct
*p
;
916 unsigned long totalpages
;
917 unsigned long freed
= 0;
918 unsigned int uninitialized_var(points
);
919 enum oom_constraint constraint
= CONSTRAINT_NONE
;
921 if (oom_killer_disabled
)
924 blocking_notifier_call_chain(&oom_notify_list
, 0, &freed
);
926 /* Got some memory back in the last second. */
930 * If current has a pending SIGKILL or is exiting, then automatically
931 * select it. The goal is to allow it to allocate so that it may
932 * quickly exit and free its memory.
934 * But don't select if current has already released its mm and cleared
935 * TIF_MEMDIE flag at exit_mm(), otherwise an OOM livelock may occur.
938 (fatal_signal_pending(current
) || task_will_free_mem(current
))) {
939 mark_oom_victim(current
);
940 try_oom_reaper(current
);
945 * The OOM killer does not compensate for IO-less reclaim.
946 * pagefault_out_of_memory lost its gfp context so we have to
947 * make sure exclude 0 mask - all other users should have at least
948 * ___GFP_DIRECT_RECLAIM to get here.
950 if (oc
->gfp_mask
&& !(oc
->gfp_mask
& (__GFP_FS
|__GFP_NOFAIL
)))
954 * Check if there were limitations on the allocation (only relevant for
955 * NUMA) that may require different handling.
957 constraint
= constrained_alloc(oc
, &totalpages
);
958 if (constraint
!= CONSTRAINT_MEMORY_POLICY
)
960 check_panic_on_oom(oc
, constraint
, NULL
);
962 if (sysctl_oom_kill_allocating_task
&& current
->mm
&&
963 !oom_unkillable_task(current
, NULL
, oc
->nodemask
) &&
964 current
->signal
->oom_score_adj
!= OOM_SCORE_ADJ_MIN
) {
965 get_task_struct(current
);
966 oom_kill_process(oc
, current
, 0, totalpages
, NULL
,
967 "Out of memory (oom_kill_allocating_task)");
971 p
= select_bad_process(oc
, &points
, totalpages
);
972 /* Found nothing?!?! Either we hang forever, or we panic. */
973 if (!p
&& !is_sysrq_oom(oc
)) {
974 dump_header(oc
, NULL
, NULL
);
975 panic("Out of memory and no killable processes...\n");
977 if (p
&& p
!= (void *)-1UL) {
978 oom_kill_process(oc
, p
, points
, totalpages
, NULL
,
981 * Give the killed process a good chance to exit before trying
982 * to allocate memory again.
984 schedule_timeout_killable(1);
990 * The pagefault handler calls here because it is out of memory, so kill a
991 * memory-hogging task. If any populated zone has ZONE_OOM_LOCKED set, a
992 * parallel oom killing is already in progress so do nothing.
994 void pagefault_out_of_memory(void)
996 struct oom_control oc
= {
1003 if (mem_cgroup_oom_synchronize(true))
1006 if (!mutex_trylock(&oom_lock
))
1009 if (!out_of_memory(&oc
)) {
1011 * There shouldn't be any user tasks runnable while the
1012 * OOM killer is disabled, so the current task has to
1013 * be a racing OOM victim for which oom_killer_disable()
1016 WARN_ON(test_thread_flag(TIF_MEMDIE
));
1019 mutex_unlock(&oom_lock
);