1 // SPDX-License-Identifier: GPL-2.0-only
5 * Copyright (C) 1998,2000 Rik van Riel
6 * Thanks go out to Claus Fischer for some serious inspiration and
7 * for goading me into coding this file...
8 * Copyright (C) 2010 Google, Inc.
9 * Rewritten by David Rientjes
11 * The routines in this file are used to kill a process when
12 * we're seriously out of memory. This gets called from __alloc_pages()
13 * in mm/page_alloc.c when we really run out of memory.
15 * Since we won't call these routines often (on a well-configured
16 * machine) this file will double as a 'coding guide' and a signpost
17 * for newbie kernel hackers. It features several pointers to major
18 * kernel subsystems and hints as to where to find out what things do.
21 #include <linux/oom.h>
23 #include <linux/err.h>
24 #include <linux/gfp.h>
25 #include <linux/sched.h>
26 #include <linux/sched/mm.h>
27 #include <linux/sched/coredump.h>
28 #include <linux/sched/task.h>
29 #include <linux/sched/debug.h>
30 #include <linux/swap.h>
31 #include <linux/syscalls.h>
32 #include <linux/timex.h>
33 #include <linux/jiffies.h>
34 #include <linux/cpuset.h>
35 #include <linux/export.h>
36 #include <linux/notifier.h>
37 #include <linux/memcontrol.h>
38 #include <linux/mempolicy.h>
39 #include <linux/security.h>
40 #include <linux/ptrace.h>
41 #include <linux/freezer.h>
42 #include <linux/ftrace.h>
43 #include <linux/ratelimit.h>
44 #include <linux/kthread.h>
45 #include <linux/init.h>
46 #include <linux/mmu_notifier.h>
47 #include <linux/cred.h>
53 #define CREATE_TRACE_POINTS
54 #include <trace/events/oom.h>
56 static int sysctl_panic_on_oom
;
57 static int sysctl_oom_kill_allocating_task
;
58 static int sysctl_oom_dump_tasks
= 1;
61 * Serializes oom killer invocations (out_of_memory()) from all contexts to
62 * prevent from over eager oom killing (e.g. when the oom killer is invoked
63 * from different domains).
65 * oom_killer_disable() relies on this lock to stabilize oom_killer_disabled
68 DEFINE_MUTEX(oom_lock
);
69 /* Serializes oom_score_adj and oom_score_adj_min updates */
70 DEFINE_MUTEX(oom_adj_mutex
);
72 static inline bool is_memcg_oom(struct oom_control
*oc
)
74 return oc
->memcg
!= NULL
;
79 * oom_cpuset_eligible() - check task eligibility for kill
80 * @start: task struct of which task to consider
81 * @oc: pointer to struct oom_control
83 * Task eligibility is determined by whether or not a candidate task, @tsk,
84 * shares the same mempolicy nodes as current if it is bound by such a policy
85 * and whether or not it has the same set of allowed cpuset nodes.
87 * This function is assuming oom-killer context and 'current' has triggered
90 static bool oom_cpuset_eligible(struct task_struct
*start
,
91 struct oom_control
*oc
)
93 struct task_struct
*tsk
;
95 const nodemask_t
*mask
= oc
->nodemask
;
98 for_each_thread(start
, tsk
) {
101 * If this is a mempolicy constrained oom, tsk's
102 * cpuset is irrelevant. Only return true if its
103 * mempolicy intersects current, otherwise it may be
106 ret
= mempolicy_in_oom_domain(tsk
, mask
);
109 * This is not a mempolicy constrained oom, so only
110 * check the mems of tsk's cpuset.
112 ret
= cpuset_mems_allowed_intersects(current
, tsk
);
122 static bool oom_cpuset_eligible(struct task_struct
*tsk
, struct oom_control
*oc
)
126 #endif /* CONFIG_NUMA */
129 * The process p may have detached its own ->mm while exiting or through
130 * kthread_use_mm(), but one or more of its subthreads may still have a valid
131 * pointer. Return p, or any of its subthreads with a valid ->mm, with
134 struct task_struct
*find_lock_task_mm(struct task_struct
*p
)
136 struct task_struct
*t
;
140 for_each_thread(p
, t
) {
154 * order == -1 means the oom kill is required by sysrq, otherwise only
155 * for display purposes.
157 static inline bool is_sysrq_oom(struct oom_control
*oc
)
159 return oc
->order
== -1;
162 /* return true if the task is not adequate as candidate victim task. */
163 static bool oom_unkillable_task(struct task_struct
*p
)
165 if (is_global_init(p
))
167 if (p
->flags
& PF_KTHREAD
)
173 * Check whether unreclaimable slab amount is greater than
174 * all user memory(LRU pages).
175 * dump_unreclaimable_slab() could help in the case that
176 * oom due to too much unreclaimable slab used by kernel.
178 static bool should_dump_unreclaim_slab(void)
180 unsigned long nr_lru
;
182 nr_lru
= global_node_page_state(NR_ACTIVE_ANON
) +
183 global_node_page_state(NR_INACTIVE_ANON
) +
184 global_node_page_state(NR_ACTIVE_FILE
) +
185 global_node_page_state(NR_INACTIVE_FILE
) +
186 global_node_page_state(NR_ISOLATED_ANON
) +
187 global_node_page_state(NR_ISOLATED_FILE
) +
188 global_node_page_state(NR_UNEVICTABLE
);
190 return (global_node_page_state_pages(NR_SLAB_UNRECLAIMABLE_B
) > nr_lru
);
194 * oom_badness - heuristic function to determine which candidate task to kill
195 * @p: task struct of which task we should calculate
196 * @totalpages: total present RAM allowed for page allocation
198 * The heuristic for determining which task to kill is made to be as simple and
199 * predictable as possible. The goal is to return the highest value for the
200 * task consuming the most memory to avoid subsequent oom failures.
202 long oom_badness(struct task_struct
*p
, unsigned long totalpages
)
207 if (oom_unkillable_task(p
))
210 p
= find_lock_task_mm(p
);
215 * Do not even consider tasks which are explicitly marked oom
216 * unkillable or have been already oom reaped or the are in
217 * the middle of vfork
219 adj
= (long)p
->signal
->oom_score_adj
;
220 if (adj
== OOM_SCORE_ADJ_MIN
||
221 test_bit(MMF_OOM_SKIP
, &p
->mm
->flags
) ||
228 * The baseline for the badness score is the proportion of RAM that each
229 * task's rss, pagetable and swap space use.
231 points
= get_mm_rss(p
->mm
) + get_mm_counter(p
->mm
, MM_SWAPENTS
) +
232 mm_pgtables_bytes(p
->mm
) / PAGE_SIZE
;
235 /* Normalize to oom_score_adj units */
236 adj
*= totalpages
/ 1000;
242 static const char * const oom_constraint_text
[] = {
243 [CONSTRAINT_NONE
] = "CONSTRAINT_NONE",
244 [CONSTRAINT_CPUSET
] = "CONSTRAINT_CPUSET",
245 [CONSTRAINT_MEMORY_POLICY
] = "CONSTRAINT_MEMORY_POLICY",
246 [CONSTRAINT_MEMCG
] = "CONSTRAINT_MEMCG",
250 * Determine the type of allocation constraint.
252 static enum oom_constraint
constrained_alloc(struct oom_control
*oc
)
256 enum zone_type highest_zoneidx
= gfp_zone(oc
->gfp_mask
);
257 bool cpuset_limited
= false;
260 if (is_memcg_oom(oc
)) {
261 oc
->totalpages
= mem_cgroup_get_max(oc
->memcg
) ?: 1;
262 return CONSTRAINT_MEMCG
;
265 /* Default to all available memory */
266 oc
->totalpages
= totalram_pages() + total_swap_pages
;
268 if (!IS_ENABLED(CONFIG_NUMA
))
269 return CONSTRAINT_NONE
;
272 return CONSTRAINT_NONE
;
274 * Reach here only when __GFP_NOFAIL is used. So, we should avoid
275 * to kill current.We have to random task kill in this case.
276 * Hopefully, CONSTRAINT_THISNODE...but no way to handle it, now.
278 if (oc
->gfp_mask
& __GFP_THISNODE
)
279 return CONSTRAINT_NONE
;
282 * This is not a __GFP_THISNODE allocation, so a truncated nodemask in
283 * the page allocator means a mempolicy is in effect. Cpuset policy
284 * is enforced in get_page_from_freelist().
287 !nodes_subset(node_states
[N_MEMORY
], *oc
->nodemask
)) {
288 oc
->totalpages
= total_swap_pages
;
289 for_each_node_mask(nid
, *oc
->nodemask
)
290 oc
->totalpages
+= node_present_pages(nid
);
291 return CONSTRAINT_MEMORY_POLICY
;
294 /* Check this allocation failure is caused by cpuset's wall function */
295 for_each_zone_zonelist_nodemask(zone
, z
, oc
->zonelist
,
296 highest_zoneidx
, oc
->nodemask
)
297 if (!cpuset_zone_allowed(zone
, oc
->gfp_mask
))
298 cpuset_limited
= true;
300 if (cpuset_limited
) {
301 oc
->totalpages
= total_swap_pages
;
302 for_each_node_mask(nid
, cpuset_current_mems_allowed
)
303 oc
->totalpages
+= node_present_pages(nid
);
304 return CONSTRAINT_CPUSET
;
306 return CONSTRAINT_NONE
;
309 static int oom_evaluate_task(struct task_struct
*task
, void *arg
)
311 struct oom_control
*oc
= arg
;
314 if (oom_unkillable_task(task
))
317 /* p may not have freeable memory in nodemask */
318 if (!is_memcg_oom(oc
) && !oom_cpuset_eligible(task
, oc
))
322 * This task already has access to memory reserves and is being killed.
323 * Don't allow any other task to have access to the reserves unless
324 * the task has MMF_OOM_SKIP because chances that it would release
325 * any memory is quite low.
327 if (!is_sysrq_oom(oc
) && tsk_is_oom_victim(task
)) {
328 if (test_bit(MMF_OOM_SKIP
, &task
->signal
->oom_mm
->flags
))
334 * If task is allocating a lot of memory and has been marked to be
335 * killed first if it triggers an oom, then select it.
337 if (oom_task_origin(task
)) {
342 points
= oom_badness(task
, oc
->totalpages
);
343 if (points
== LONG_MIN
|| points
< oc
->chosen_points
)
348 put_task_struct(oc
->chosen
);
349 get_task_struct(task
);
351 oc
->chosen_points
= points
;
356 put_task_struct(oc
->chosen
);
357 oc
->chosen
= (void *)-1UL;
362 * Simple selection loop. We choose the process with the highest number of
363 * 'points'. In case scan was aborted, oc->chosen is set to -1.
365 static void select_bad_process(struct oom_control
*oc
)
367 oc
->chosen_points
= LONG_MIN
;
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
))
382 static int dump_task(struct task_struct
*p
, void *arg
)
384 struct oom_control
*oc
= arg
;
385 struct task_struct
*task
;
387 if (oom_unkillable_task(p
))
390 /* p may not have freeable memory in nodemask */
391 if (!is_memcg_oom(oc
) && !oom_cpuset_eligible(p
, oc
))
394 task
= find_lock_task_mm(p
);
397 * All of p's threads have already detached their mm's. There's
398 * no need to report them; they can't be oom killed anyway.
403 pr_info("[%7d] %5d %5d %8lu %8lu %8lu %8lu %9lu %8ld %8lu %5hd %s\n",
404 task
->pid
, from_kuid(&init_user_ns
, task_uid(task
)),
405 task
->tgid
, task
->mm
->total_vm
, get_mm_rss(task
->mm
),
406 get_mm_counter(task
->mm
, MM_ANONPAGES
), get_mm_counter(task
->mm
, MM_FILEPAGES
),
407 get_mm_counter(task
->mm
, MM_SHMEMPAGES
), mm_pgtables_bytes(task
->mm
),
408 get_mm_counter(task
->mm
, MM_SWAPENTS
),
409 task
->signal
->oom_score_adj
, task
->comm
);
416 * dump_tasks - dump current memory state of all system tasks
417 * @oc: pointer to struct oom_control
419 * Dumps the current memory state of all eligible tasks. Tasks not in the same
420 * memcg, not in the same cpuset, or bound to a disjoint set of mempolicy nodes
422 * State information includes task's pid, uid, tgid, vm size, rss,
423 * pgtables_bytes, swapents, oom_score_adj value, and name.
425 static void dump_tasks(struct oom_control
*oc
)
427 pr_info("Tasks state (memory values in pages):\n");
428 pr_info("[ pid ] uid tgid total_vm rss rss_anon rss_file rss_shmem pgtables_bytes swapents oom_score_adj name\n");
430 if (is_memcg_oom(oc
))
431 mem_cgroup_scan_tasks(oc
->memcg
, dump_task
, oc
);
433 struct task_struct
*p
;
442 static void dump_oom_victim(struct oom_control
*oc
, struct task_struct
*victim
)
444 /* one line summary of the oom killer context. */
445 pr_info("oom-kill:constraint=%s,nodemask=%*pbl",
446 oom_constraint_text
[oc
->constraint
],
447 nodemask_pr_args(oc
->nodemask
));
448 cpuset_print_current_mems_allowed();
449 mem_cgroup_print_oom_context(oc
->memcg
, victim
);
450 pr_cont(",task=%s,pid=%d,uid=%d\n", victim
->comm
, victim
->pid
,
451 from_kuid(&init_user_ns
, task_uid(victim
)));
454 static void dump_header(struct oom_control
*oc
)
456 pr_warn("%s invoked oom-killer: gfp_mask=%#x(%pGg), order=%d, oom_score_adj=%hd\n",
457 current
->comm
, oc
->gfp_mask
, &oc
->gfp_mask
, oc
->order
,
458 current
->signal
->oom_score_adj
);
459 if (!IS_ENABLED(CONFIG_COMPACTION
) && oc
->order
)
460 pr_warn("COMPACTION is disabled!!!\n");
463 if (is_memcg_oom(oc
))
464 mem_cgroup_print_oom_meminfo(oc
->memcg
);
466 __show_mem(SHOW_MEM_FILTER_NODES
, oc
->nodemask
, gfp_zone(oc
->gfp_mask
));
467 if (should_dump_unreclaim_slab())
468 dump_unreclaimable_slab();
470 if (sysctl_oom_dump_tasks
)
475 * Number of OOM victims in flight
477 static atomic_t oom_victims
= ATOMIC_INIT(0);
478 static DECLARE_WAIT_QUEUE_HEAD(oom_victims_wait
);
480 static bool oom_killer_disabled __read_mostly
;
483 * task->mm can be NULL if the task is the exited group leader. So to
484 * determine whether the task is using a particular mm, we examine all the
485 * task's threads: if one of those is using this mm then this task was also
488 bool process_shares_mm(struct task_struct
*p
, struct mm_struct
*mm
)
490 struct task_struct
*t
;
492 for_each_thread(p
, t
) {
493 struct mm_struct
*t_mm
= READ_ONCE(t
->mm
);
502 * OOM Reaper kernel thread which tries to reap the memory used by the OOM
503 * victim (if that is possible) to help the OOM killer to move on.
505 static struct task_struct
*oom_reaper_th
;
506 static DECLARE_WAIT_QUEUE_HEAD(oom_reaper_wait
);
507 static struct task_struct
*oom_reaper_list
;
508 static DEFINE_SPINLOCK(oom_reaper_lock
);
510 static bool __oom_reap_task_mm(struct mm_struct
*mm
)
512 struct vm_area_struct
*vma
;
514 VMA_ITERATOR(vmi
, mm
, 0);
517 * Tell all users of get_user/copy_from_user etc... that the content
518 * is no longer stable. No barriers really needed because unmapping
519 * should imply barriers already and the reader would hit a page fault
520 * if it stumbled over a reaped memory.
522 set_bit(MMF_UNSTABLE
, &mm
->flags
);
524 for_each_vma(vmi
, vma
) {
525 if (vma
->vm_flags
& (VM_HUGETLB
|VM_PFNMAP
))
529 * Only anonymous pages have a good chance to be dropped
530 * without additional steps which we cannot afford as we
533 * We do not even care about fs backed pages because all
534 * which are reclaimable have already been reclaimed and
535 * we do not want to block exit_mmap by keeping mm ref
536 * count elevated without a good reason.
538 if (vma_is_anonymous(vma
) || !(vma
->vm_flags
& VM_SHARED
)) {
539 struct mmu_notifier_range range
;
540 struct mmu_gather tlb
;
542 mmu_notifier_range_init(&range
, MMU_NOTIFY_UNMAP
, 0,
545 tlb_gather_mmu(&tlb
, mm
);
546 if (mmu_notifier_invalidate_range_start_nonblock(&range
)) {
547 tlb_finish_mmu(&tlb
);
551 unmap_page_range(&tlb
, vma
, range
.start
, range
.end
, NULL
);
552 mmu_notifier_invalidate_range_end(&range
);
553 tlb_finish_mmu(&tlb
);
561 * Reaps the address space of the give task.
563 * Returns true on success and false if none or part of the address space
564 * has been reclaimed and the caller should retry later.
566 static bool oom_reap_task_mm(struct task_struct
*tsk
, struct mm_struct
*mm
)
570 if (!mmap_read_trylock(mm
)) {
571 trace_skip_task_reaping(tsk
->pid
);
576 * MMF_OOM_SKIP is set by exit_mmap when the OOM reaper can't
577 * work on the mm anymore. The check for MMF_OOM_SKIP must run
578 * under mmap_lock for reading because it serializes against the
579 * mmap_write_lock();mmap_write_unlock() cycle in exit_mmap().
581 if (test_bit(MMF_OOM_SKIP
, &mm
->flags
)) {
582 trace_skip_task_reaping(tsk
->pid
);
586 trace_start_task_reaping(tsk
->pid
);
588 /* failed to reap part of the address space. Try again later */
589 ret
= __oom_reap_task_mm(mm
);
593 pr_info("oom_reaper: reaped process %d (%s), now anon-rss:%lukB, file-rss:%lukB, shmem-rss:%lukB\n",
594 task_pid_nr(tsk
), tsk
->comm
,
595 K(get_mm_counter(mm
, MM_ANONPAGES
)),
596 K(get_mm_counter(mm
, MM_FILEPAGES
)),
597 K(get_mm_counter(mm
, MM_SHMEMPAGES
)));
599 trace_finish_task_reaping(tsk
->pid
);
601 mmap_read_unlock(mm
);
606 #define MAX_OOM_REAP_RETRIES 10
607 static void oom_reap_task(struct task_struct
*tsk
)
610 struct mm_struct
*mm
= tsk
->signal
->oom_mm
;
612 /* Retry the mmap_read_trylock(mm) a few times */
613 while (attempts
++ < MAX_OOM_REAP_RETRIES
&& !oom_reap_task_mm(tsk
, mm
))
614 schedule_timeout_idle(HZ
/10);
616 if (attempts
<= MAX_OOM_REAP_RETRIES
||
617 test_bit(MMF_OOM_SKIP
, &mm
->flags
))
620 pr_info("oom_reaper: unable to reap pid:%d (%s)\n",
621 task_pid_nr(tsk
), tsk
->comm
);
622 sched_show_task(tsk
);
623 debug_show_all_locks();
626 tsk
->oom_reaper_list
= NULL
;
629 * Hide this mm from OOM killer because it has been either reaped or
630 * somebody can't call mmap_write_unlock(mm).
632 set_bit(MMF_OOM_SKIP
, &mm
->flags
);
634 /* Drop a reference taken by queue_oom_reaper */
635 put_task_struct(tsk
);
638 static int oom_reaper(void *unused
)
643 struct task_struct
*tsk
= NULL
;
645 wait_event_freezable(oom_reaper_wait
, oom_reaper_list
!= NULL
);
646 spin_lock_irq(&oom_reaper_lock
);
647 if (oom_reaper_list
!= NULL
) {
648 tsk
= oom_reaper_list
;
649 oom_reaper_list
= tsk
->oom_reaper_list
;
651 spin_unlock_irq(&oom_reaper_lock
);
660 static void wake_oom_reaper(struct timer_list
*timer
)
662 struct task_struct
*tsk
= container_of(timer
, struct task_struct
,
664 struct mm_struct
*mm
= tsk
->signal
->oom_mm
;
667 /* The victim managed to terminate on its own - see exit_mmap */
668 if (test_bit(MMF_OOM_SKIP
, &mm
->flags
)) {
669 put_task_struct(tsk
);
673 spin_lock_irqsave(&oom_reaper_lock
, flags
);
674 tsk
->oom_reaper_list
= oom_reaper_list
;
675 oom_reaper_list
= tsk
;
676 spin_unlock_irqrestore(&oom_reaper_lock
, flags
);
677 trace_wake_reaper(tsk
->pid
);
678 wake_up(&oom_reaper_wait
);
682 * Give the OOM victim time to exit naturally before invoking the oom_reaping.
683 * The timers timeout is arbitrary... the longer it is, the longer the worst
684 * case scenario for the OOM can take. If it is too small, the oom_reaper can
685 * get in the way and release resources needed by the process exit path.
686 * e.g. The futex robust list can sit in Anon|Private memory that gets reaped
687 * before the exit path is able to wake the futex waiters.
689 #define OOM_REAPER_DELAY (2*HZ)
690 static void queue_oom_reaper(struct task_struct
*tsk
)
692 /* mm is already queued? */
693 if (test_and_set_bit(MMF_OOM_REAP_QUEUED
, &tsk
->signal
->oom_mm
->flags
))
696 get_task_struct(tsk
);
697 timer_setup(&tsk
->oom_reaper_timer
, wake_oom_reaper
, 0);
698 tsk
->oom_reaper_timer
.expires
= jiffies
+ OOM_REAPER_DELAY
;
699 add_timer(&tsk
->oom_reaper_timer
);
703 static struct ctl_table vm_oom_kill_table
[] = {
705 .procname
= "panic_on_oom",
706 .data
= &sysctl_panic_on_oom
,
707 .maxlen
= sizeof(sysctl_panic_on_oom
),
709 .proc_handler
= proc_dointvec_minmax
,
710 .extra1
= SYSCTL_ZERO
,
711 .extra2
= SYSCTL_TWO
,
714 .procname
= "oom_kill_allocating_task",
715 .data
= &sysctl_oom_kill_allocating_task
,
716 .maxlen
= sizeof(sysctl_oom_kill_allocating_task
),
718 .proc_handler
= proc_dointvec
,
721 .procname
= "oom_dump_tasks",
722 .data
= &sysctl_oom_dump_tasks
,
723 .maxlen
= sizeof(sysctl_oom_dump_tasks
),
725 .proc_handler
= proc_dointvec
,
730 static int __init
oom_init(void)
732 oom_reaper_th
= kthread_run(oom_reaper
, NULL
, "oom_reaper");
734 register_sysctl_init("vm", vm_oom_kill_table
);
738 subsys_initcall(oom_init
)
740 static inline void queue_oom_reaper(struct task_struct
*tsk
)
743 #endif /* CONFIG_MMU */
746 * mark_oom_victim - mark the given task as OOM victim
749 * Has to be called with oom_lock held and never after
750 * oom has been disabled already.
752 * tsk->mm has to be non NULL and caller has to guarantee it is stable (either
753 * under task_lock or operate on the current).
755 static void mark_oom_victim(struct task_struct
*tsk
)
757 const struct cred
*cred
;
758 struct mm_struct
*mm
= tsk
->mm
;
760 WARN_ON(oom_killer_disabled
);
761 /* OOM killer might race with memcg OOM */
762 if (test_and_set_tsk_thread_flag(tsk
, TIF_MEMDIE
))
765 /* oom_mm is bound to the signal struct life time. */
766 if (!cmpxchg(&tsk
->signal
->oom_mm
, NULL
, mm
))
767 mmgrab(tsk
->signal
->oom_mm
);
770 * Make sure that the task is woken up from uninterruptible sleep
771 * if it is frozen because OOM killer wouldn't be able to free
772 * any memory and livelock. freezing_slow_path will tell the freezer
773 * that TIF_MEMDIE tasks should be ignored.
776 atomic_inc(&oom_victims
);
777 cred
= get_task_cred(tsk
);
778 trace_mark_victim(tsk
, cred
->uid
.val
);
783 * exit_oom_victim - note the exit of an OOM victim
785 void exit_oom_victim(void)
787 clear_thread_flag(TIF_MEMDIE
);
789 if (!atomic_dec_return(&oom_victims
))
790 wake_up_all(&oom_victims_wait
);
794 * oom_killer_enable - enable OOM killer
796 void oom_killer_enable(void)
798 oom_killer_disabled
= false;
799 pr_info("OOM killer enabled.\n");
803 * oom_killer_disable - disable OOM killer
804 * @timeout: maximum timeout to wait for oom victims in jiffies
806 * Forces all page allocations to fail rather than trigger OOM killer.
807 * Will block and wait until all OOM victims are killed or the given
810 * The function cannot be called when there are runnable user tasks because
811 * the userspace would see unexpected allocation failures as a result. Any
812 * new usage of this function should be consulted with MM people.
814 * Returns true if successful and false if the OOM killer cannot be
817 bool oom_killer_disable(signed long timeout
)
822 * Make sure to not race with an ongoing OOM killer. Check that the
823 * current is not killed (possibly due to sharing the victim's memory).
825 if (mutex_lock_killable(&oom_lock
))
827 oom_killer_disabled
= true;
828 mutex_unlock(&oom_lock
);
830 ret
= wait_event_interruptible_timeout(oom_victims_wait
,
831 !atomic_read(&oom_victims
), timeout
);
836 pr_info("OOM killer disabled.\n");
841 static inline bool __task_will_free_mem(struct task_struct
*task
)
843 struct signal_struct
*sig
= task
->signal
;
846 * A coredumping process may sleep for an extended period in
847 * coredump_task_exit(), so the oom killer cannot assume that
848 * the process will promptly exit and release memory.
853 if (sig
->flags
& SIGNAL_GROUP_EXIT
)
856 if (thread_group_empty(task
) && (task
->flags
& PF_EXITING
))
863 * Checks whether the given task is dying or exiting and likely to
864 * release its address space. This means that all threads and processes
865 * sharing the same mm have to be killed or exiting.
866 * Caller has to make sure that task->mm is stable (hold task_lock or
867 * it operates on the current).
869 static bool task_will_free_mem(struct task_struct
*task
)
871 struct mm_struct
*mm
= task
->mm
;
872 struct task_struct
*p
;
876 * Skip tasks without mm because it might have passed its exit_mm and
877 * exit_oom_victim. oom_reaper could have rescued that but do not rely
878 * on that for now. We can consider find_lock_task_mm in future.
883 if (!__task_will_free_mem(task
))
887 * This task has already been drained by the oom reaper so there are
888 * only small chances it will free some more
890 if (test_bit(MMF_OOM_SKIP
, &mm
->flags
))
893 if (atomic_read(&mm
->mm_users
) <= 1)
897 * Make sure that all tasks which share the mm with the given tasks
898 * are dying as well to make sure that a) nobody pins its mm and
899 * b) the task is also reapable by the oom reaper.
902 for_each_process(p
) {
903 if (!process_shares_mm(p
, mm
))
905 if (same_thread_group(task
, p
))
907 ret
= __task_will_free_mem(p
);
916 static void __oom_kill_process(struct task_struct
*victim
, const char *message
)
918 struct task_struct
*p
;
919 struct mm_struct
*mm
;
920 bool can_oom_reap
= true;
922 p
= find_lock_task_mm(victim
);
924 pr_info("%s: OOM victim %d (%s) is already exiting. Skip killing the task\n",
925 message
, task_pid_nr(victim
), victim
->comm
);
926 put_task_struct(victim
);
928 } else if (victim
!= p
) {
930 put_task_struct(victim
);
934 /* Get a reference to safely compare mm after task_unlock(victim) */
938 /* Raise event before sending signal: task reaper must see this */
939 count_vm_event(OOM_KILL
);
940 memcg_memory_event_mm(mm
, MEMCG_OOM_KILL
);
943 * We should send SIGKILL before granting access to memory reserves
944 * in order to prevent the OOM victim from depleting the memory
945 * reserves from the user space under its control.
947 do_send_sig_info(SIGKILL
, SEND_SIG_PRIV
, victim
, PIDTYPE_TGID
);
948 mark_oom_victim(victim
);
949 pr_err("%s: Killed process %d (%s) total-vm:%lukB, anon-rss:%lukB, file-rss:%lukB, shmem-rss:%lukB, UID:%u pgtables:%lukB oom_score_adj:%hd\n",
950 message
, task_pid_nr(victim
), victim
->comm
, K(mm
->total_vm
),
951 K(get_mm_counter(mm
, MM_ANONPAGES
)),
952 K(get_mm_counter(mm
, MM_FILEPAGES
)),
953 K(get_mm_counter(mm
, MM_SHMEMPAGES
)),
954 from_kuid(&init_user_ns
, task_uid(victim
)),
955 mm_pgtables_bytes(mm
) >> 10, victim
->signal
->oom_score_adj
);
959 * Kill all user processes sharing victim->mm in other thread groups, if
960 * any. They don't get access to memory reserves, though, to avoid
961 * depletion of all memory. This prevents mm->mmap_lock livelock when an
962 * oom killed thread cannot exit because it requires the semaphore and
963 * its contended by another thread trying to allocate memory itself.
964 * That thread will now get access to memory reserves since it has a
965 * pending fatal signal.
968 for_each_process(p
) {
969 if (!process_shares_mm(p
, mm
))
971 if (same_thread_group(p
, victim
))
973 if (is_global_init(p
)) {
974 can_oom_reap
= false;
975 set_bit(MMF_OOM_SKIP
, &mm
->flags
);
976 pr_info("oom killer %d (%s) has mm pinned by %d (%s)\n",
977 task_pid_nr(victim
), victim
->comm
,
978 task_pid_nr(p
), p
->comm
);
982 * No kthread_use_mm() user needs to read from the userspace so
983 * we are ok to reap it.
985 if (unlikely(p
->flags
& PF_KTHREAD
))
987 do_send_sig_info(SIGKILL
, SEND_SIG_PRIV
, p
, PIDTYPE_TGID
);
992 queue_oom_reaper(victim
);
995 put_task_struct(victim
);
999 * Kill provided task unless it's secured by setting
1000 * oom_score_adj to OOM_SCORE_ADJ_MIN.
1002 static int oom_kill_memcg_member(struct task_struct
*task
, void *message
)
1004 if (task
->signal
->oom_score_adj
!= OOM_SCORE_ADJ_MIN
&&
1005 !is_global_init(task
)) {
1006 get_task_struct(task
);
1007 __oom_kill_process(task
, message
);
1012 static void oom_kill_process(struct oom_control
*oc
, const char *message
)
1014 struct task_struct
*victim
= oc
->chosen
;
1015 struct mem_cgroup
*oom_group
;
1016 static DEFINE_RATELIMIT_STATE(oom_rs
, DEFAULT_RATELIMIT_INTERVAL
,
1017 DEFAULT_RATELIMIT_BURST
);
1020 * If the task is already exiting, don't alarm the sysadmin or kill
1021 * its children or threads, just give it access to memory reserves
1022 * so it can die quickly
1025 if (task_will_free_mem(victim
)) {
1026 mark_oom_victim(victim
);
1027 queue_oom_reaper(victim
);
1028 task_unlock(victim
);
1029 put_task_struct(victim
);
1032 task_unlock(victim
);
1034 if (__ratelimit(&oom_rs
)) {
1036 dump_oom_victim(oc
, victim
);
1040 * Do we need to kill the entire memory cgroup?
1041 * Or even one of the ancestor memory cgroups?
1042 * Check this out before killing the victim task.
1044 oom_group
= mem_cgroup_get_oom_group(victim
, oc
->memcg
);
1046 __oom_kill_process(victim
, message
);
1049 * If necessary, kill all tasks in the selected memory cgroup.
1052 memcg_memory_event(oom_group
, MEMCG_OOM_GROUP_KILL
);
1053 mem_cgroup_print_oom_group(oom_group
);
1054 mem_cgroup_scan_tasks(oom_group
, oom_kill_memcg_member
,
1056 mem_cgroup_put(oom_group
);
1061 * Determines whether the kernel must panic because of the panic_on_oom sysctl.
1063 static void check_panic_on_oom(struct oom_control
*oc
)
1065 if (likely(!sysctl_panic_on_oom
))
1067 if (sysctl_panic_on_oom
!= 2) {
1069 * panic_on_oom == 1 only affects CONSTRAINT_NONE, the kernel
1070 * does not panic for cpuset, mempolicy, or memcg allocation
1073 if (oc
->constraint
!= CONSTRAINT_NONE
)
1076 /* Do not panic for oom kills triggered by sysrq */
1077 if (is_sysrq_oom(oc
))
1080 panic("Out of memory: %s panic_on_oom is enabled\n",
1081 sysctl_panic_on_oom
== 2 ? "compulsory" : "system-wide");
1084 static BLOCKING_NOTIFIER_HEAD(oom_notify_list
);
1086 int register_oom_notifier(struct notifier_block
*nb
)
1088 return blocking_notifier_chain_register(&oom_notify_list
, nb
);
1090 EXPORT_SYMBOL_GPL(register_oom_notifier
);
1092 int unregister_oom_notifier(struct notifier_block
*nb
)
1094 return blocking_notifier_chain_unregister(&oom_notify_list
, nb
);
1096 EXPORT_SYMBOL_GPL(unregister_oom_notifier
);
1099 * out_of_memory - kill the "best" process when we run out of memory
1100 * @oc: pointer to struct oom_control
1102 * If we run out of memory, we have the choice between either
1103 * killing a random task (bad), letting the system crash (worse)
1104 * OR try to be smart about which process to kill. Note that we
1105 * don't have to be perfect here, we just have to be good.
1107 bool out_of_memory(struct oom_control
*oc
)
1109 unsigned long freed
= 0;
1111 if (oom_killer_disabled
)
1114 if (!is_memcg_oom(oc
)) {
1115 blocking_notifier_call_chain(&oom_notify_list
, 0, &freed
);
1116 if (freed
> 0 && !is_sysrq_oom(oc
))
1117 /* Got some memory back in the last second. */
1122 * If current has a pending SIGKILL or is exiting, then automatically
1123 * select it. The goal is to allow it to allocate so that it may
1124 * quickly exit and free its memory.
1126 if (task_will_free_mem(current
)) {
1127 mark_oom_victim(current
);
1128 queue_oom_reaper(current
);
1133 * The OOM killer does not compensate for IO-less reclaim.
1134 * But mem_cgroup_oom() has to invoke the OOM killer even
1135 * if it is a GFP_NOFS allocation.
1137 if (!(oc
->gfp_mask
& __GFP_FS
) && !is_memcg_oom(oc
))
1141 * Check if there were limitations on the allocation (only relevant for
1142 * NUMA and memcg) that may require different handling.
1144 oc
->constraint
= constrained_alloc(oc
);
1145 if (oc
->constraint
!= CONSTRAINT_MEMORY_POLICY
)
1146 oc
->nodemask
= NULL
;
1147 check_panic_on_oom(oc
);
1149 if (!is_memcg_oom(oc
) && sysctl_oom_kill_allocating_task
&&
1150 current
->mm
&& !oom_unkillable_task(current
) &&
1151 oom_cpuset_eligible(current
, oc
) &&
1152 current
->signal
->oom_score_adj
!= OOM_SCORE_ADJ_MIN
) {
1153 get_task_struct(current
);
1154 oc
->chosen
= current
;
1155 oom_kill_process(oc
, "Out of memory (oom_kill_allocating_task)");
1159 select_bad_process(oc
);
1160 /* Found nothing?!?! */
1163 pr_warn("Out of memory and no killable processes...\n");
1165 * If we got here due to an actual allocation at the
1166 * system level, we cannot survive this and will enter
1167 * an endless loop in the allocator. Bail out now.
1169 if (!is_sysrq_oom(oc
) && !is_memcg_oom(oc
))
1170 panic("System is deadlocked on memory\n");
1172 if (oc
->chosen
&& oc
->chosen
!= (void *)-1UL)
1173 oom_kill_process(oc
, !is_memcg_oom(oc
) ? "Out of memory" :
1174 "Memory cgroup out of memory");
1175 return !!oc
->chosen
;
1179 * The pagefault handler calls here because some allocation has failed. We have
1180 * to take care of the memcg OOM here because this is the only safe context without
1181 * any locks held but let the oom killer triggered from the allocation context care
1182 * about the global OOM.
1184 void pagefault_out_of_memory(void)
1186 static DEFINE_RATELIMIT_STATE(pfoom_rs
, DEFAULT_RATELIMIT_INTERVAL
,
1187 DEFAULT_RATELIMIT_BURST
);
1189 if (mem_cgroup_oom_synchronize(true))
1192 if (fatal_signal_pending(current
))
1195 if (__ratelimit(&pfoom_rs
))
1196 pr_warn("Huh VM_FAULT_OOM leaked out to the #PF handler. Retrying PF\n");
1199 SYSCALL_DEFINE2(process_mrelease
, int, pidfd
, unsigned int, flags
)
1202 struct mm_struct
*mm
= NULL
;
1203 struct task_struct
*task
;
1204 struct task_struct
*p
;
1205 unsigned int f_flags
;
1212 task
= pidfd_get_task(pidfd
, &f_flags
);
1214 return PTR_ERR(task
);
1217 * Make sure to choose a thread which still has a reference to mm
1218 * during the group exit
1220 p
= find_lock_task_mm(task
);
1229 if (task_will_free_mem(p
))
1232 /* Error only if the work has not been done already */
1233 if (!test_bit(MMF_OOM_SKIP
, &mm
->flags
))
1241 if (mmap_read_lock_killable(mm
)) {
1246 * Check MMF_OOM_SKIP again under mmap_read_lock protection to ensure
1247 * possible change in exit_mmap is seen
1249 if (!test_bit(MMF_OOM_SKIP
, &mm
->flags
) && !__oom_reap_task_mm(mm
))
1251 mmap_read_unlock(mm
);
1256 put_task_struct(task
);
1260 #endif /* CONFIG_MMU */