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>
52 #define CREATE_TRACE_POINTS
53 #include <trace/events/oom.h>
55 static int sysctl_panic_on_oom
;
56 static int sysctl_oom_kill_allocating_task
;
57 static int sysctl_oom_dump_tasks
= 1;
60 * Serializes oom killer invocations (out_of_memory()) from all contexts to
61 * prevent from over eager oom killing (e.g. when the oom killer is invoked
62 * from different domains).
64 * oom_killer_disable() relies on this lock to stabilize oom_killer_disabled
67 DEFINE_MUTEX(oom_lock
);
68 /* Serializes oom_score_adj and oom_score_adj_min updates */
69 DEFINE_MUTEX(oom_adj_mutex
);
71 static inline bool is_memcg_oom(struct oom_control
*oc
)
73 return oc
->memcg
!= NULL
;
78 * oom_cpuset_eligible() - check task eligibility for kill
79 * @start: task struct of which task to consider
80 * @oc: pointer to struct oom_control
82 * Task eligibility is determined by whether or not a candidate task, @tsk,
83 * shares the same mempolicy nodes as current if it is bound by such a policy
84 * and whether or not it has the same set of allowed cpuset nodes.
86 * This function is assuming oom-killer context and 'current' has triggered
89 static bool oom_cpuset_eligible(struct task_struct
*start
,
90 struct oom_control
*oc
)
92 struct task_struct
*tsk
;
94 const nodemask_t
*mask
= oc
->nodemask
;
97 for_each_thread(start
, tsk
) {
100 * If this is a mempolicy constrained oom, tsk's
101 * cpuset is irrelevant. Only return true if its
102 * mempolicy intersects current, otherwise it may be
105 ret
= mempolicy_in_oom_domain(tsk
, mask
);
108 * This is not a mempolicy constrained oom, so only
109 * check the mems of tsk's cpuset.
111 ret
= cpuset_mems_allowed_intersects(current
, tsk
);
121 static bool oom_cpuset_eligible(struct task_struct
*tsk
, struct oom_control
*oc
)
125 #endif /* CONFIG_NUMA */
128 * The process p may have detached its own ->mm while exiting or through
129 * kthread_use_mm(), but one or more of its subthreads may still have a valid
130 * pointer. Return p, or any of its subthreads with a valid ->mm, with
133 struct task_struct
*find_lock_task_mm(struct task_struct
*p
)
135 struct task_struct
*t
;
139 for_each_thread(p
, t
) {
153 * order == -1 means the oom kill is required by sysrq, otherwise only
154 * for display purposes.
156 static inline bool is_sysrq_oom(struct oom_control
*oc
)
158 return oc
->order
== -1;
161 /* return true if the task is not adequate as candidate victim task. */
162 static bool oom_unkillable_task(struct task_struct
*p
)
164 if (is_global_init(p
))
166 if (p
->flags
& PF_KTHREAD
)
172 * Check whether unreclaimable slab amount is greater than
173 * all user memory(LRU pages).
174 * dump_unreclaimable_slab() could help in the case that
175 * oom due to too much unreclaimable slab used by kernel.
177 static bool should_dump_unreclaim_slab(void)
179 unsigned long nr_lru
;
181 nr_lru
= global_node_page_state(NR_ACTIVE_ANON
) +
182 global_node_page_state(NR_INACTIVE_ANON
) +
183 global_node_page_state(NR_ACTIVE_FILE
) +
184 global_node_page_state(NR_INACTIVE_FILE
) +
185 global_node_page_state(NR_ISOLATED_ANON
) +
186 global_node_page_state(NR_ISOLATED_FILE
) +
187 global_node_page_state(NR_UNEVICTABLE
);
189 return (global_node_page_state_pages(NR_SLAB_UNRECLAIMABLE_B
) > nr_lru
);
193 * oom_badness - heuristic function to determine which candidate task to kill
194 * @p: task struct of which task we should calculate
195 * @totalpages: total present RAM allowed for page allocation
197 * The heuristic for determining which task to kill is made to be as simple and
198 * predictable as possible. The goal is to return the highest value for the
199 * task consuming the most memory to avoid subsequent oom failures.
201 long oom_badness(struct task_struct
*p
, unsigned long totalpages
)
206 if (oom_unkillable_task(p
))
209 p
= find_lock_task_mm(p
);
214 * Do not even consider tasks which are explicitly marked oom
215 * unkillable or have been already oom reaped or the are in
216 * the middle of vfork
218 adj
= (long)p
->signal
->oom_score_adj
;
219 if (adj
== OOM_SCORE_ADJ_MIN
||
220 test_bit(MMF_OOM_SKIP
, &p
->mm
->flags
) ||
227 * The baseline for the badness score is the proportion of RAM that each
228 * task's rss, pagetable and swap space use.
230 points
= get_mm_rss(p
->mm
) + get_mm_counter(p
->mm
, MM_SWAPENTS
) +
231 mm_pgtables_bytes(p
->mm
) / PAGE_SIZE
;
234 /* Normalize to oom_score_adj units */
235 adj
*= totalpages
/ 1000;
241 static const char * const oom_constraint_text
[] = {
242 [CONSTRAINT_NONE
] = "CONSTRAINT_NONE",
243 [CONSTRAINT_CPUSET
] = "CONSTRAINT_CPUSET",
244 [CONSTRAINT_MEMORY_POLICY
] = "CONSTRAINT_MEMORY_POLICY",
245 [CONSTRAINT_MEMCG
] = "CONSTRAINT_MEMCG",
249 * Determine the type of allocation constraint.
251 static enum oom_constraint
constrained_alloc(struct oom_control
*oc
)
255 enum zone_type highest_zoneidx
= gfp_zone(oc
->gfp_mask
);
256 bool cpuset_limited
= false;
259 if (is_memcg_oom(oc
)) {
260 oc
->totalpages
= mem_cgroup_get_max(oc
->memcg
) ?: 1;
261 return CONSTRAINT_MEMCG
;
264 /* Default to all available memory */
265 oc
->totalpages
= totalram_pages() + total_swap_pages
;
267 if (!IS_ENABLED(CONFIG_NUMA
))
268 return CONSTRAINT_NONE
;
271 return CONSTRAINT_NONE
;
273 * Reach here only when __GFP_NOFAIL is used. So, we should avoid
274 * to kill current.We have to random task kill in this case.
275 * Hopefully, CONSTRAINT_THISNODE...but no way to handle it, now.
277 if (oc
->gfp_mask
& __GFP_THISNODE
)
278 return CONSTRAINT_NONE
;
281 * This is not a __GFP_THISNODE allocation, so a truncated nodemask in
282 * the page allocator means a mempolicy is in effect. Cpuset policy
283 * is enforced in get_page_from_freelist().
286 !nodes_subset(node_states
[N_MEMORY
], *oc
->nodemask
)) {
287 oc
->totalpages
= total_swap_pages
;
288 for_each_node_mask(nid
, *oc
->nodemask
)
289 oc
->totalpages
+= node_present_pages(nid
);
290 return CONSTRAINT_MEMORY_POLICY
;
293 /* Check this allocation failure is caused by cpuset's wall function */
294 for_each_zone_zonelist_nodemask(zone
, z
, oc
->zonelist
,
295 highest_zoneidx
, oc
->nodemask
)
296 if (!cpuset_zone_allowed(zone
, oc
->gfp_mask
))
297 cpuset_limited
= true;
299 if (cpuset_limited
) {
300 oc
->totalpages
= total_swap_pages
;
301 for_each_node_mask(nid
, cpuset_current_mems_allowed
)
302 oc
->totalpages
+= node_present_pages(nid
);
303 return CONSTRAINT_CPUSET
;
305 return CONSTRAINT_NONE
;
308 static int oom_evaluate_task(struct task_struct
*task
, void *arg
)
310 struct oom_control
*oc
= arg
;
313 if (oom_unkillable_task(task
))
316 /* p may not have freeable memory in nodemask */
317 if (!is_memcg_oom(oc
) && !oom_cpuset_eligible(task
, oc
))
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
, oc
->totalpages
);
342 if (points
== LONG_MIN
|| points
< oc
->chosen_points
)
347 put_task_struct(oc
->chosen
);
348 get_task_struct(task
);
350 oc
->chosen_points
= points
;
355 put_task_struct(oc
->chosen
);
356 oc
->chosen
= (void *)-1UL;
361 * Simple selection loop. We choose the process with the highest number of
362 * 'points'. In case scan was aborted, oc->chosen is set to -1.
364 static void select_bad_process(struct oom_control
*oc
)
366 oc
->chosen_points
= LONG_MIN
;
368 if (is_memcg_oom(oc
))
369 mem_cgroup_scan_tasks(oc
->memcg
, oom_evaluate_task
, oc
);
371 struct task_struct
*p
;
375 if (oom_evaluate_task(p
, oc
))
381 static int dump_task(struct task_struct
*p
, void *arg
)
383 struct oom_control
*oc
= arg
;
384 struct task_struct
*task
;
386 if (oom_unkillable_task(p
))
389 /* p may not have freeable memory in nodemask */
390 if (!is_memcg_oom(oc
) && !oom_cpuset_eligible(p
, oc
))
393 task
= find_lock_task_mm(p
);
396 * All of p's threads have already detached their mm's. There's
397 * no need to report them; they can't be oom killed anyway.
402 pr_info("[%7d] %5d %5d %8lu %8lu %8ld %8lu %5hd %s\n",
403 task
->pid
, from_kuid(&init_user_ns
, task_uid(task
)),
404 task
->tgid
, task
->mm
->total_vm
, get_mm_rss(task
->mm
),
405 mm_pgtables_bytes(task
->mm
),
406 get_mm_counter(task
->mm
, MM_SWAPENTS
),
407 task
->signal
->oom_score_adj
, task
->comm
);
414 * dump_tasks - dump current memory state of all system tasks
415 * @oc: pointer to struct oom_control
417 * Dumps the current memory state of all eligible tasks. Tasks not in the same
418 * memcg, not in the same cpuset, or bound to a disjoint set of mempolicy nodes
420 * State information includes task's pid, uid, tgid, vm size, rss,
421 * pgtables_bytes, swapents, oom_score_adj value, and name.
423 static void dump_tasks(struct oom_control
*oc
)
425 pr_info("Tasks state (memory values in pages):\n");
426 pr_info("[ pid ] uid tgid total_vm rss pgtables_bytes swapents oom_score_adj name\n");
428 if (is_memcg_oom(oc
))
429 mem_cgroup_scan_tasks(oc
->memcg
, dump_task
, oc
);
431 struct task_struct
*p
;
440 static void dump_oom_summary(struct oom_control
*oc
, struct task_struct
*victim
)
442 /* one line summary of the oom killer context. */
443 pr_info("oom-kill:constraint=%s,nodemask=%*pbl",
444 oom_constraint_text
[oc
->constraint
],
445 nodemask_pr_args(oc
->nodemask
));
446 cpuset_print_current_mems_allowed();
447 mem_cgroup_print_oom_context(oc
->memcg
, victim
);
448 pr_cont(",task=%s,pid=%d,uid=%d\n", victim
->comm
, victim
->pid
,
449 from_kuid(&init_user_ns
, task_uid(victim
)));
452 static void dump_header(struct oom_control
*oc
, struct task_struct
*p
)
454 pr_warn("%s invoked oom-killer: gfp_mask=%#x(%pGg), order=%d, oom_score_adj=%hd\n",
455 current
->comm
, oc
->gfp_mask
, &oc
->gfp_mask
, oc
->order
,
456 current
->signal
->oom_score_adj
);
457 if (!IS_ENABLED(CONFIG_COMPACTION
) && oc
->order
)
458 pr_warn("COMPACTION is disabled!!!\n");
461 if (is_memcg_oom(oc
))
462 mem_cgroup_print_oom_meminfo(oc
->memcg
);
464 show_mem(SHOW_MEM_FILTER_NODES
, oc
->nodemask
);
465 if (should_dump_unreclaim_slab())
466 dump_unreclaimable_slab();
468 if (sysctl_oom_dump_tasks
)
471 dump_oom_summary(oc
, p
);
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
;
482 #define K(x) ((x) << (PAGE_SHIFT-10))
485 * task->mm can be NULL if the task is the exited group leader. So to
486 * determine whether the task is using a particular mm, we examine all the
487 * task's threads: if one of those is using this mm then this task was also
490 bool process_shares_mm(struct task_struct
*p
, struct mm_struct
*mm
)
492 struct task_struct
*t
;
494 for_each_thread(p
, t
) {
495 struct mm_struct
*t_mm
= READ_ONCE(t
->mm
);
504 * OOM Reaper kernel thread which tries to reap the memory used by the OOM
505 * victim (if that is possible) to help the OOM killer to move on.
507 static struct task_struct
*oom_reaper_th
;
508 static DECLARE_WAIT_QUEUE_HEAD(oom_reaper_wait
);
509 static struct task_struct
*oom_reaper_list
;
510 static DEFINE_SPINLOCK(oom_reaper_lock
);
512 bool __oom_reap_task_mm(struct mm_struct
*mm
)
514 struct vm_area_struct
*vma
;
518 * Tell all users of get_user/copy_from_user etc... that the content
519 * is no longer stable. No barriers really needed because unmapping
520 * should imply barriers already and the reader would hit a page fault
521 * if it stumbled over a reaped memory.
523 set_bit(MMF_UNSTABLE
, &mm
->flags
);
525 for (vma
= mm
->mmap
; vma
; vma
= vma
->vm_next
) {
526 if (vma
->vm_flags
& (VM_HUGETLB
|VM_PFNMAP
))
530 * Only anonymous pages have a good chance to be dropped
531 * without additional steps which we cannot afford as we
534 * We do not even care about fs backed pages because all
535 * which are reclaimable have already been reclaimed and
536 * we do not want to block exit_mmap by keeping mm ref
537 * count elevated without a good reason.
539 if (vma_is_anonymous(vma
) || !(vma
->vm_flags
& VM_SHARED
)) {
540 struct mmu_notifier_range range
;
541 struct mmu_gather tlb
;
543 mmu_notifier_range_init(&range
, MMU_NOTIFY_UNMAP
, 0,
544 vma
, mm
, vma
->vm_start
,
546 tlb_gather_mmu(&tlb
, mm
);
547 if (mmu_notifier_invalidate_range_start_nonblock(&range
)) {
548 tlb_finish_mmu(&tlb
);
552 unmap_page_range(&tlb
, vma
, range
.start
, range
.end
, NULL
);
553 mmu_notifier_invalidate_range_end(&range
);
554 tlb_finish_mmu(&tlb
);
562 * Reaps the address space of the give task.
564 * Returns true on success and false if none or part of the address space
565 * has been reclaimed and the caller should retry later.
567 static bool oom_reap_task_mm(struct task_struct
*tsk
, struct mm_struct
*mm
)
571 if (!mmap_read_trylock(mm
)) {
572 trace_skip_task_reaping(tsk
->pid
);
577 * MMF_OOM_SKIP is set by exit_mmap when the OOM reaper can't
578 * work on the mm anymore. The check for MMF_OOM_SKIP must run
579 * under mmap_lock for reading because it serializes against the
580 * mmap_write_lock();mmap_write_unlock() cycle in exit_mmap().
582 if (test_bit(MMF_OOM_SKIP
, &mm
->flags
)) {
583 trace_skip_task_reaping(tsk
->pid
);
587 trace_start_task_reaping(tsk
->pid
);
589 /* failed to reap part of the address space. Try again later */
590 ret
= __oom_reap_task_mm(mm
);
594 pr_info("oom_reaper: reaped process %d (%s), now anon-rss:%lukB, file-rss:%lukB, shmem-rss:%lukB\n",
595 task_pid_nr(tsk
), tsk
->comm
,
596 K(get_mm_counter(mm
, MM_ANONPAGES
)),
597 K(get_mm_counter(mm
, MM_FILEPAGES
)),
598 K(get_mm_counter(mm
, MM_SHMEMPAGES
)));
600 trace_finish_task_reaping(tsk
->pid
);
602 mmap_read_unlock(mm
);
607 #define MAX_OOM_REAP_RETRIES 10
608 static void oom_reap_task(struct task_struct
*tsk
)
611 struct mm_struct
*mm
= tsk
->signal
->oom_mm
;
613 /* Retry the mmap_read_trylock(mm) a few times */
614 while (attempts
++ < MAX_OOM_REAP_RETRIES
&& !oom_reap_task_mm(tsk
, mm
))
615 schedule_timeout_idle(HZ
/10);
617 if (attempts
<= MAX_OOM_REAP_RETRIES
||
618 test_bit(MMF_OOM_SKIP
, &mm
->flags
))
621 pr_info("oom_reaper: unable to reap pid:%d (%s)\n",
622 task_pid_nr(tsk
), tsk
->comm
);
623 sched_show_task(tsk
);
624 debug_show_all_locks();
627 tsk
->oom_reaper_list
= NULL
;
630 * Hide this mm from OOM killer because it has been either reaped or
631 * somebody can't call mmap_write_unlock(mm).
633 set_bit(MMF_OOM_SKIP
, &mm
->flags
);
635 /* Drop a reference taken by queue_oom_reaper */
636 put_task_struct(tsk
);
639 static int oom_reaper(void *unused
)
644 struct task_struct
*tsk
= NULL
;
646 wait_event_freezable(oom_reaper_wait
, oom_reaper_list
!= NULL
);
647 spin_lock_irq(&oom_reaper_lock
);
648 if (oom_reaper_list
!= NULL
) {
649 tsk
= oom_reaper_list
;
650 oom_reaper_list
= tsk
->oom_reaper_list
;
652 spin_unlock_irq(&oom_reaper_lock
);
661 static void wake_oom_reaper(struct timer_list
*timer
)
663 struct task_struct
*tsk
= container_of(timer
, struct task_struct
,
665 struct mm_struct
*mm
= tsk
->signal
->oom_mm
;
668 /* The victim managed to terminate on its own - see exit_mmap */
669 if (test_bit(MMF_OOM_SKIP
, &mm
->flags
)) {
670 put_task_struct(tsk
);
674 spin_lock_irqsave(&oom_reaper_lock
, flags
);
675 tsk
->oom_reaper_list
= oom_reaper_list
;
676 oom_reaper_list
= tsk
;
677 spin_unlock_irqrestore(&oom_reaper_lock
, flags
);
678 trace_wake_reaper(tsk
->pid
);
679 wake_up(&oom_reaper_wait
);
683 * Give the OOM victim time to exit naturally before invoking the oom_reaping.
684 * The timers timeout is arbitrary... the longer it is, the longer the worst
685 * case scenario for the OOM can take. If it is too small, the oom_reaper can
686 * get in the way and release resources needed by the process exit path.
687 * e.g. The futex robust list can sit in Anon|Private memory that gets reaped
688 * before the exit path is able to wake the futex waiters.
690 #define OOM_REAPER_DELAY (2*HZ)
691 static void queue_oom_reaper(struct task_struct
*tsk
)
693 /* mm is already queued? */
694 if (test_and_set_bit(MMF_OOM_REAP_QUEUED
, &tsk
->signal
->oom_mm
->flags
))
697 get_task_struct(tsk
);
698 timer_setup(&tsk
->oom_reaper_timer
, wake_oom_reaper
, 0);
699 tsk
->oom_reaper_timer
.expires
= jiffies
+ OOM_REAPER_DELAY
;
700 add_timer(&tsk
->oom_reaper_timer
);
704 static struct ctl_table vm_oom_kill_table
[] = {
706 .procname
= "panic_on_oom",
707 .data
= &sysctl_panic_on_oom
,
708 .maxlen
= sizeof(sysctl_panic_on_oom
),
710 .proc_handler
= proc_dointvec_minmax
,
711 .extra1
= SYSCTL_ZERO
,
712 .extra2
= SYSCTL_TWO
,
715 .procname
= "oom_kill_allocating_task",
716 .data
= &sysctl_oom_kill_allocating_task
,
717 .maxlen
= sizeof(sysctl_oom_kill_allocating_task
),
719 .proc_handler
= proc_dointvec
,
722 .procname
= "oom_dump_tasks",
723 .data
= &sysctl_oom_dump_tasks
,
724 .maxlen
= sizeof(sysctl_oom_dump_tasks
),
726 .proc_handler
= proc_dointvec
,
732 static int __init
oom_init(void)
734 oom_reaper_th
= kthread_run(oom_reaper
, NULL
, "oom_reaper");
736 register_sysctl_init("vm", vm_oom_kill_table
);
740 subsys_initcall(oom_init
)
742 static inline void queue_oom_reaper(struct task_struct
*tsk
)
745 #endif /* CONFIG_MMU */
748 * mark_oom_victim - mark the given task as OOM victim
751 * Has to be called with oom_lock held and never after
752 * oom has been disabled already.
754 * tsk->mm has to be non NULL and caller has to guarantee it is stable (either
755 * under task_lock or operate on the current).
757 static void mark_oom_victim(struct task_struct
*tsk
)
759 struct mm_struct
*mm
= tsk
->mm
;
761 WARN_ON(oom_killer_disabled
);
762 /* OOM killer might race with memcg OOM */
763 if (test_and_set_tsk_thread_flag(tsk
, TIF_MEMDIE
))
766 /* oom_mm is bound to the signal struct life time. */
767 if (!cmpxchg(&tsk
->signal
->oom_mm
, NULL
, mm
)) {
768 mmgrab(tsk
->signal
->oom_mm
);
769 set_bit(MMF_OOM_VICTIM
, &mm
->flags
);
773 * Make sure that the task is woken up from uninterruptible sleep
774 * if it is frozen because OOM killer wouldn't be able to free
775 * any memory and livelock. freezing_slow_path will tell the freezer
776 * that TIF_MEMDIE tasks should be ignored.
779 atomic_inc(&oom_victims
);
780 trace_mark_victim(tsk
->pid
);
784 * exit_oom_victim - note the exit of an OOM victim
786 void exit_oom_victim(void)
788 clear_thread_flag(TIF_MEMDIE
);
790 if (!atomic_dec_return(&oom_victims
))
791 wake_up_all(&oom_victims_wait
);
795 * oom_killer_enable - enable OOM killer
797 void oom_killer_enable(void)
799 oom_killer_disabled
= false;
800 pr_info("OOM killer enabled.\n");
804 * oom_killer_disable - disable OOM killer
805 * @timeout: maximum timeout to wait for oom victims in jiffies
807 * Forces all page allocations to fail rather than trigger OOM killer.
808 * Will block and wait until all OOM victims are killed or the given
811 * The function cannot be called when there are runnable user tasks because
812 * the userspace would see unexpected allocation failures as a result. Any
813 * new usage of this function should be consulted with MM people.
815 * Returns true if successful and false if the OOM killer cannot be
818 bool oom_killer_disable(signed long timeout
)
823 * Make sure to not race with an ongoing OOM killer. Check that the
824 * current is not killed (possibly due to sharing the victim's memory).
826 if (mutex_lock_killable(&oom_lock
))
828 oom_killer_disabled
= true;
829 mutex_unlock(&oom_lock
);
831 ret
= wait_event_interruptible_timeout(oom_victims_wait
,
832 !atomic_read(&oom_victims
), timeout
);
837 pr_info("OOM killer disabled.\n");
842 static inline bool __task_will_free_mem(struct task_struct
*task
)
844 struct signal_struct
*sig
= task
->signal
;
847 * A coredumping process may sleep for an extended period in
848 * coredump_task_exit(), so the oom killer cannot assume that
849 * the process will promptly exit and release memory.
854 if (sig
->flags
& SIGNAL_GROUP_EXIT
)
857 if (thread_group_empty(task
) && (task
->flags
& PF_EXITING
))
864 * Checks whether the given task is dying or exiting and likely to
865 * release its address space. This means that all threads and processes
866 * sharing the same mm have to be killed or exiting.
867 * Caller has to make sure that task->mm is stable (hold task_lock or
868 * it operates on the current).
870 static bool task_will_free_mem(struct task_struct
*task
)
872 struct mm_struct
*mm
= task
->mm
;
873 struct task_struct
*p
;
877 * Skip tasks without mm because it might have passed its exit_mm and
878 * exit_oom_victim. oom_reaper could have rescued that but do not rely
879 * on that for now. We can consider find_lock_task_mm in future.
884 if (!__task_will_free_mem(task
))
888 * This task has already been drained by the oom reaper so there are
889 * only small chances it will free some more
891 if (test_bit(MMF_OOM_SKIP
, &mm
->flags
))
894 if (atomic_read(&mm
->mm_users
) <= 1)
898 * Make sure that all tasks which share the mm with the given tasks
899 * are dying as well to make sure that a) nobody pins its mm and
900 * b) the task is also reapable by the oom reaper.
903 for_each_process(p
) {
904 if (!process_shares_mm(p
, mm
))
906 if (same_thread_group(task
, p
))
908 ret
= __task_will_free_mem(p
);
917 static void __oom_kill_process(struct task_struct
*victim
, const char *message
)
919 struct task_struct
*p
;
920 struct mm_struct
*mm
;
921 bool can_oom_reap
= true;
923 p
= find_lock_task_mm(victim
);
925 pr_info("%s: OOM victim %d (%s) is already exiting. Skip killing the task\n",
926 message
, task_pid_nr(victim
), victim
->comm
);
927 put_task_struct(victim
);
929 } else if (victim
!= p
) {
931 put_task_struct(victim
);
935 /* Get a reference to safely compare mm after task_unlock(victim) */
939 /* Raise event before sending signal: task reaper must see this */
940 count_vm_event(OOM_KILL
);
941 memcg_memory_event_mm(mm
, MEMCG_OOM_KILL
);
944 * We should send SIGKILL before granting access to memory reserves
945 * in order to prevent the OOM victim from depleting the memory
946 * reserves from the user space under its control.
948 do_send_sig_info(SIGKILL
, SEND_SIG_PRIV
, victim
, PIDTYPE_TGID
);
949 mark_oom_victim(victim
);
950 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",
951 message
, task_pid_nr(victim
), victim
->comm
, K(mm
->total_vm
),
952 K(get_mm_counter(mm
, MM_ANONPAGES
)),
953 K(get_mm_counter(mm
, MM_FILEPAGES
)),
954 K(get_mm_counter(mm
, MM_SHMEMPAGES
)),
955 from_kuid(&init_user_ns
, task_uid(victim
)),
956 mm_pgtables_bytes(mm
) >> 10, victim
->signal
->oom_score_adj
);
960 * Kill all user processes sharing victim->mm in other thread groups, if
961 * any. They don't get access to memory reserves, though, to avoid
962 * depletion of all memory. This prevents mm->mmap_lock livelock when an
963 * oom killed thread cannot exit because it requires the semaphore and
964 * its contended by another thread trying to allocate memory itself.
965 * That thread will now get access to memory reserves since it has a
966 * pending fatal signal.
969 for_each_process(p
) {
970 if (!process_shares_mm(p
, mm
))
972 if (same_thread_group(p
, victim
))
974 if (is_global_init(p
)) {
975 can_oom_reap
= false;
976 set_bit(MMF_OOM_SKIP
, &mm
->flags
);
977 pr_info("oom killer %d (%s) has mm pinned by %d (%s)\n",
978 task_pid_nr(victim
), victim
->comm
,
979 task_pid_nr(p
), p
->comm
);
983 * No kthread_use_mm() user needs to read from the userspace so
984 * we are ok to reap it.
986 if (unlikely(p
->flags
& PF_KTHREAD
))
988 do_send_sig_info(SIGKILL
, SEND_SIG_PRIV
, p
, PIDTYPE_TGID
);
993 queue_oom_reaper(victim
);
996 put_task_struct(victim
);
1001 * Kill provided task unless it's secured by setting
1002 * oom_score_adj to OOM_SCORE_ADJ_MIN.
1004 static int oom_kill_memcg_member(struct task_struct
*task
, void *message
)
1006 if (task
->signal
->oom_score_adj
!= OOM_SCORE_ADJ_MIN
&&
1007 !is_global_init(task
)) {
1008 get_task_struct(task
);
1009 __oom_kill_process(task
, message
);
1014 static void oom_kill_process(struct oom_control
*oc
, const char *message
)
1016 struct task_struct
*victim
= oc
->chosen
;
1017 struct mem_cgroup
*oom_group
;
1018 static DEFINE_RATELIMIT_STATE(oom_rs
, DEFAULT_RATELIMIT_INTERVAL
,
1019 DEFAULT_RATELIMIT_BURST
);
1022 * If the task is already exiting, don't alarm the sysadmin or kill
1023 * its children or threads, just give it access to memory reserves
1024 * so it can die quickly
1027 if (task_will_free_mem(victim
)) {
1028 mark_oom_victim(victim
);
1029 queue_oom_reaper(victim
);
1030 task_unlock(victim
);
1031 put_task_struct(victim
);
1034 task_unlock(victim
);
1036 if (__ratelimit(&oom_rs
))
1037 dump_header(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
))
1079 dump_header(oc
, NULL
);
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 * pagefault_out_of_memory lost its gfp context so we have to
1135 * make sure exclude 0 mask - all other users should have at least
1136 * ___GFP_DIRECT_RECLAIM to get here. But mem_cgroup_oom() has to
1137 * invoke the OOM killer even if it is a GFP_NOFS allocation.
1139 if (oc
->gfp_mask
&& !(oc
->gfp_mask
& __GFP_FS
) && !is_memcg_oom(oc
))
1143 * Check if there were limitations on the allocation (only relevant for
1144 * NUMA and memcg) that may require different handling.
1146 oc
->constraint
= constrained_alloc(oc
);
1147 if (oc
->constraint
!= CONSTRAINT_MEMORY_POLICY
)
1148 oc
->nodemask
= NULL
;
1149 check_panic_on_oom(oc
);
1151 if (!is_memcg_oom(oc
) && sysctl_oom_kill_allocating_task
&&
1152 current
->mm
&& !oom_unkillable_task(current
) &&
1153 oom_cpuset_eligible(current
, oc
) &&
1154 current
->signal
->oom_score_adj
!= OOM_SCORE_ADJ_MIN
) {
1155 get_task_struct(current
);
1156 oc
->chosen
= current
;
1157 oom_kill_process(oc
, "Out of memory (oom_kill_allocating_task)");
1161 select_bad_process(oc
);
1162 /* Found nothing?!?! */
1164 dump_header(oc
, NULL
);
1165 pr_warn("Out of memory and no killable processes...\n");
1167 * If we got here due to an actual allocation at the
1168 * system level, we cannot survive this and will enter
1169 * an endless loop in the allocator. Bail out now.
1171 if (!is_sysrq_oom(oc
) && !is_memcg_oom(oc
))
1172 panic("System is deadlocked on memory\n");
1174 if (oc
->chosen
&& oc
->chosen
!= (void *)-1UL)
1175 oom_kill_process(oc
, !is_memcg_oom(oc
) ? "Out of memory" :
1176 "Memory cgroup out of memory");
1177 return !!oc
->chosen
;
1181 * The pagefault handler calls here because some allocation has failed. We have
1182 * to take care of the memcg OOM here because this is the only safe context without
1183 * any locks held but let the oom killer triggered from the allocation context care
1184 * about the global OOM.
1186 void pagefault_out_of_memory(void)
1188 static DEFINE_RATELIMIT_STATE(pfoom_rs
, DEFAULT_RATELIMIT_INTERVAL
,
1189 DEFAULT_RATELIMIT_BURST
);
1191 if (mem_cgroup_oom_synchronize(true))
1194 if (fatal_signal_pending(current
))
1197 if (__ratelimit(&pfoom_rs
))
1198 pr_warn("Huh VM_FAULT_OOM leaked out to the #PF handler. Retrying PF\n");
1201 SYSCALL_DEFINE2(process_mrelease
, int, pidfd
, unsigned int, flags
)
1204 struct mm_struct
*mm
= NULL
;
1205 struct task_struct
*task
;
1206 struct task_struct
*p
;
1207 unsigned int f_flags
;
1214 task
= pidfd_get_task(pidfd
, &f_flags
);
1216 return PTR_ERR(task
);
1219 * Make sure to choose a thread which still has a reference to mm
1220 * during the group exit
1222 p
= find_lock_task_mm(task
);
1231 if (task_will_free_mem(p
))
1234 /* Error only if the work has not been done already */
1235 if (!test_bit(MMF_OOM_SKIP
, &mm
->flags
))
1243 if (mmap_read_lock_killable(mm
)) {
1248 * Check MMF_OOM_SKIP again under mmap_read_lock protection to ensure
1249 * possible change in exit_mmap is seen
1251 if (!test_bit(MMF_OOM_SKIP
, &mm
->flags
) && !__oom_reap_task_mm(mm
))
1253 mmap_read_unlock(mm
);
1258 put_task_struct(task
);
1262 #endif /* CONFIG_MMU */