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1/*
2 * linux/mm/oom_kill.c
3 *
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
9 *
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.
13 *
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.
18 */
19
20#include <linux/oom.h>
21#include <linux/mm.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>
44
45#include <asm/tlb.h>
46#include "internal.h"
47#include "slab.h"
48
49#define CREATE_TRACE_POINTS
50#include <trace/events/oom.h>
51
52int sysctl_panic_on_oom;
53int sysctl_oom_kill_allocating_task;
54int sysctl_oom_dump_tasks = 1;
55
56DEFINE_MUTEX(oom_lock);
57
58#ifdef CONFIG_NUMA
59/**
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
63 *
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.
67 */
68static bool has_intersects_mems_allowed(struct task_struct *start,
69 const nodemask_t *mask)
70{
71 struct task_struct *tsk;
72 bool ret = false;
73
74 rcu_read_lock();
75 for_each_thread(start, tsk) {
76 if (mask) {
77 /*
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
81 * needlessly killed.
82 */
83 ret = mempolicy_nodemask_intersects(tsk, mask);
84 } else {
85 /*
86 * This is not a mempolicy constrained oom, so only
87 * check the mems of tsk's cpuset.
88 */
89 ret = cpuset_mems_allowed_intersects(current, tsk);
90 }
91 if (ret)
92 break;
93 }
94 rcu_read_unlock();
95
96 return ret;
97}
98#else
99static bool has_intersects_mems_allowed(struct task_struct *tsk,
100 const nodemask_t *mask)
101{
102 return true;
103}
104#endif /* CONFIG_NUMA */
105
106/*
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
110 * task_lock() held.
111 */
112struct task_struct *find_lock_task_mm(struct task_struct *p)
113{
114 struct task_struct *t;
115
116 rcu_read_lock();
117
118 for_each_thread(p, t) {
119 task_lock(t);
120 if (likely(t->mm))
121 goto found;
122 task_unlock(t);
123 }
124 t = NULL;
125found:
126 rcu_read_unlock();
127
128 return t;
129}
130
131/*
132 * order == -1 means the oom kill is required by sysrq, otherwise only
133 * for display purposes.
134 */
135static inline bool is_sysrq_oom(struct oom_control *oc)
136{
137 return oc->order == -1;
138}
139
140static inline bool is_memcg_oom(struct oom_control *oc)
141{
142 return oc->memcg != NULL;
143}
144
145/* return true if the task is not adequate as candidate victim task. */
146static bool oom_unkillable_task(struct task_struct *p,
147 struct mem_cgroup *memcg, const nodemask_t *nodemask)
148{
149 if (is_global_init(p))
150 return true;
151 if (p->flags & PF_KTHREAD)
152 return true;
153
154 /* When mem_cgroup_out_of_memory() and p is not member of the group */
155 if (memcg && !task_in_mem_cgroup(p, memcg))
156 return true;
157
158 /* p may not have freeable memory in nodemask */
159 if (!has_intersects_mems_allowed(p, nodemask))
160 return true;
161
162 return false;
163}
164
165/*
166 * Print out unreclaimble slabs info when unreclaimable slabs amount is greater
167 * than all user memory (LRU pages)
168 */
169static bool is_dump_unreclaim_slabs(void)
170{
171 unsigned long nr_lru;
172
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);
180
181 return (global_node_page_state(NR_SLAB_UNRECLAIMABLE) > nr_lru);
182}
183
184/**
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
188 * @memcg: task's memory controller, if constrained
189 * @nodemask: nodemask passed to page allocator for mempolicy ooms
190 *
191 * The heuristic for determining which task to kill is made to be as simple and
192 * predictable as possible. The goal is to return the highest value for the
193 * task consuming the most memory to avoid subsequent oom failures.
194 */
195unsigned long oom_badness(struct task_struct *p, struct mem_cgroup *memcg,
196 const nodemask_t *nodemask, unsigned long totalpages)
197{
198 long points;
199 long adj;
200
201 if (oom_unkillable_task(p, memcg, nodemask))
202 return 0;
203
204 p = find_lock_task_mm(p);
205 if (!p)
206 return 0;
207
208 /*
209 * Do not even consider tasks which are explicitly marked oom
210 * unkillable or have been already oom reaped or the are in
211 * the middle of vfork
212 */
213 adj = (long)p->signal->oom_score_adj;
214 if (adj == OOM_SCORE_ADJ_MIN ||
215 test_bit(MMF_OOM_SKIP, &p->mm->flags) ||
216 in_vfork(p)) {
217 task_unlock(p);
218 return 0;
219 }
220
221 /*
222 * The baseline for the badness score is the proportion of RAM that each
223 * task's rss, pagetable and swap space use.
224 */
225 points = get_mm_rss(p->mm) + get_mm_counter(p->mm, MM_SWAPENTS) +
226 mm_pgtables_bytes(p->mm) / PAGE_SIZE;
227 task_unlock(p);
228
229 /* Normalize to oom_score_adj units */
230 adj *= totalpages / 1000;
231 points += adj;
232
233 /*
234 * Never return 0 for an eligible task regardless of the root bonus and
235 * oom_score_adj (oom_score_adj can't be OOM_SCORE_ADJ_MIN here).
236 */
237 return points > 0 ? points : 1;
238}
239
240enum oom_constraint {
241 CONSTRAINT_NONE,
242 CONSTRAINT_CPUSET,
243 CONSTRAINT_MEMORY_POLICY,
244 CONSTRAINT_MEMCG,
245};
246
247/*
248 * Determine the type of allocation constraint.
249 */
250static enum oom_constraint constrained_alloc(struct oom_control *oc)
251{
252 struct zone *zone;
253 struct zoneref *z;
254 enum zone_type high_zoneidx = gfp_zone(oc->gfp_mask);
255 bool cpuset_limited = false;
256 int nid;
257
258 if (is_memcg_oom(oc)) {
259 oc->totalpages = mem_cgroup_get_limit(oc->memcg) ?: 1;
260 return CONSTRAINT_MEMCG;
261 }
262
263 /* Default to all available memory */
264 oc->totalpages = totalram_pages + total_swap_pages;
265
266 if (!IS_ENABLED(CONFIG_NUMA))
267 return CONSTRAINT_NONE;
268
269 if (!oc->zonelist)
270 return CONSTRAINT_NONE;
271 /*
272 * Reach here only when __GFP_NOFAIL is used. So, we should avoid
273 * to kill current.We have to random task kill in this case.
274 * Hopefully, CONSTRAINT_THISNODE...but no way to handle it, now.
275 */
276 if (oc->gfp_mask & __GFP_THISNODE)
277 return CONSTRAINT_NONE;
278
279 /*
280 * This is not a __GFP_THISNODE allocation, so a truncated nodemask in
281 * the page allocator means a mempolicy is in effect. Cpuset policy
282 * is enforced in get_page_from_freelist().
283 */
284 if (oc->nodemask &&
285 !nodes_subset(node_states[N_MEMORY], *oc->nodemask)) {
286 oc->totalpages = total_swap_pages;
287 for_each_node_mask(nid, *oc->nodemask)
288 oc->totalpages += node_spanned_pages(nid);
289 return CONSTRAINT_MEMORY_POLICY;
290 }
291
292 /* Check this allocation failure is caused by cpuset's wall function */
293 for_each_zone_zonelist_nodemask(zone, z, oc->zonelist,
294 high_zoneidx, oc->nodemask)
295 if (!cpuset_zone_allowed(zone, oc->gfp_mask))
296 cpuset_limited = true;
297
298 if (cpuset_limited) {
299 oc->totalpages = total_swap_pages;
300 for_each_node_mask(nid, cpuset_current_mems_allowed)
301 oc->totalpages += node_spanned_pages(nid);
302 return CONSTRAINT_CPUSET;
303 }
304 return CONSTRAINT_NONE;
305}
306
307static int oom_evaluate_task(struct task_struct *task, void *arg)
308{
309 struct oom_control *oc = arg;
310 unsigned long points;
311
312 if (oom_unkillable_task(task, NULL, oc->nodemask))
313 goto next;
314
315 /*
316 * This task already has access to memory reserves and is being killed.
317 * Don't allow any other task to have access to the reserves unless
318 * the task has MMF_OOM_SKIP because chances that it would release
319 * any memory is quite low.
320 */
321 if (!is_sysrq_oom(oc) && tsk_is_oom_victim(task)) {
322 if (test_bit(MMF_OOM_SKIP, &task->signal->oom_mm->flags))
323 goto next;
324 goto abort;
325 }
326
327 /*
328 * If task is allocating a lot of memory and has been marked to be
329 * killed first if it triggers an oom, then select it.
330 */
331 if (oom_task_origin(task)) {
332 points = ULONG_MAX;
333 goto select;
334 }
335
336 points = oom_badness(task, NULL, oc->nodemask, oc->totalpages);
337 if (!points || points < oc->chosen_points)
338 goto next;
339
340 /* Prefer thread group leaders for display purposes */
341 if (points == oc->chosen_points && thread_group_leader(oc->chosen))
342 goto next;
343select:
344 if (oc->chosen)
345 put_task_struct(oc->chosen);
346 get_task_struct(task);
347 oc->chosen = task;
348 oc->chosen_points = points;
349next:
350 return 0;
351abort:
352 if (oc->chosen)
353 put_task_struct(oc->chosen);
354 oc->chosen = (void *)-1UL;
355 return 1;
356}
357
358/*
359 * Simple selection loop. We choose the process with the highest number of
360 * 'points'. In case scan was aborted, oc->chosen is set to -1.
361 */
362static void select_bad_process(struct oom_control *oc)
363{
364 if (is_memcg_oom(oc))
365 mem_cgroup_scan_tasks(oc->memcg, oom_evaluate_task, oc);
366 else {
367 struct task_struct *p;
368
369 rcu_read_lock();
370 for_each_process(p)
371 if (oom_evaluate_task(p, oc))
372 break;
373 rcu_read_unlock();
374 }
375
376 oc->chosen_points = oc->chosen_points * 1000 / oc->totalpages;
377}
378
379/**
380 * dump_tasks - dump current memory state of all system tasks
381 * @memcg: current's memory controller, if constrained
382 * @nodemask: nodemask passed to page allocator for mempolicy ooms
383 *
384 * Dumps the current memory state of all eligible tasks. Tasks not in the same
385 * memcg, not in the same cpuset, or bound to a disjoint set of mempolicy nodes
386 * are not shown.
387 * State information includes task's pid, uid, tgid, vm size, rss,
388 * pgtables_bytes, swapents, oom_score_adj value, and name.
389 */
390static void dump_tasks(struct mem_cgroup *memcg, const nodemask_t *nodemask)
391{
392 struct task_struct *p;
393 struct task_struct *task;
394
395 pr_info("[ pid ] uid tgid total_vm rss pgtables_bytes swapents oom_score_adj name\n");
396 rcu_read_lock();
397 for_each_process(p) {
398 if (oom_unkillable_task(p, memcg, nodemask))
399 continue;
400
401 task = find_lock_task_mm(p);
402 if (!task) {
403 /*
404 * This is a kthread or all of p's threads have already
405 * detached their mm's. There's no need to report
406 * them; they can't be oom killed anyway.
407 */
408 continue;
409 }
410
411 pr_info("[%5d] %5d %5d %8lu %8lu %8ld %8lu %5hd %s\n",
412 task->pid, from_kuid(&init_user_ns, task_uid(task)),
413 task->tgid, task->mm->total_vm, get_mm_rss(task->mm),
414 mm_pgtables_bytes(task->mm),
415 get_mm_counter(task->mm, MM_SWAPENTS),
416 task->signal->oom_score_adj, task->comm);
417 task_unlock(task);
418 }
419 rcu_read_unlock();
420}
421
422static void dump_header(struct oom_control *oc, struct task_struct *p)
423{
424 pr_warn("%s invoked oom-killer: gfp_mask=%#x(%pGg), nodemask=%*pbl, order=%d, oom_score_adj=%hd\n",
425 current->comm, oc->gfp_mask, &oc->gfp_mask,
426 nodemask_pr_args(oc->nodemask), oc->order,
427 current->signal->oom_score_adj);
428 if (!IS_ENABLED(CONFIG_COMPACTION) && oc->order)
429 pr_warn("COMPACTION is disabled!!!\n");
430
431 cpuset_print_current_mems_allowed();
432 dump_stack();
433 if (is_memcg_oom(oc))
434 mem_cgroup_print_oom_info(oc->memcg, p);
435 else {
436 show_mem(SHOW_MEM_FILTER_NODES, oc->nodemask);
437 if (is_dump_unreclaim_slabs())
438 dump_unreclaimable_slab();
439 }
440 if (sysctl_oom_dump_tasks)
441 dump_tasks(oc->memcg, oc->nodemask);
442}
443
444/*
445 * Number of OOM victims in flight
446 */
447static atomic_t oom_victims = ATOMIC_INIT(0);
448static DECLARE_WAIT_QUEUE_HEAD(oom_victims_wait);
449
450static bool oom_killer_disabled __read_mostly;
451
452#define K(x) ((x) << (PAGE_SHIFT-10))
453
454/*
455 * task->mm can be NULL if the task is the exited group leader. So to
456 * determine whether the task is using a particular mm, we examine all the
457 * task's threads: if one of those is using this mm then this task was also
458 * using it.
459 */
460bool process_shares_mm(struct task_struct *p, struct mm_struct *mm)
461{
462 struct task_struct *t;
463
464 for_each_thread(p, t) {
465 struct mm_struct *t_mm = READ_ONCE(t->mm);
466 if (t_mm)
467 return t_mm == mm;
468 }
469 return false;
470}
471
472#ifdef CONFIG_MMU
473/*
474 * OOM Reaper kernel thread which tries to reap the memory used by the OOM
475 * victim (if that is possible) to help the OOM killer to move on.
476 */
477static struct task_struct *oom_reaper_th;
478static DECLARE_WAIT_QUEUE_HEAD(oom_reaper_wait);
479static struct task_struct *oom_reaper_list;
480static DEFINE_SPINLOCK(oom_reaper_lock);
481
482void __oom_reap_task_mm(struct mm_struct *mm)
483{
484 struct vm_area_struct *vma;
485
486 /*
487 * Tell all users of get_user/copy_from_user etc... that the content
488 * is no longer stable. No barriers really needed because unmapping
489 * should imply barriers already and the reader would hit a page fault
490 * if it stumbled over a reaped memory.
491 */
492 set_bit(MMF_UNSTABLE, &mm->flags);
493
494 for (vma = mm->mmap ; vma; vma = vma->vm_next) {
495 if (!can_madv_dontneed_vma(vma))
496 continue;
497
498 /*
499 * Only anonymous pages have a good chance to be dropped
500 * without additional steps which we cannot afford as we
501 * are OOM already.
502 *
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.
507 */
508 if (vma_is_anonymous(vma) || !(vma->vm_flags & VM_SHARED)) {
509 const unsigned long start = vma->vm_start;
510 const unsigned long end = vma->vm_end;
511 struct mmu_gather tlb;
512
513 tlb_gather_mmu(&tlb, mm, start, end);
514 mmu_notifier_invalidate_range_start(mm, start, end);
515 unmap_page_range(&tlb, vma, start, end, NULL);
516 mmu_notifier_invalidate_range_end(mm, start, end);
517 tlb_finish_mmu(&tlb, start, end);
518 }
519 }
520}
521
522static bool oom_reap_task_mm(struct task_struct *tsk, struct mm_struct *mm)
523{
524 bool ret = true;
525
526 /*
527 * We have to make sure to not race with the victim exit path
528 * and cause premature new oom victim selection:
529 * oom_reap_task_mm exit_mm
530 * mmget_not_zero
531 * mmput
532 * atomic_dec_and_test
533 * exit_oom_victim
534 * [...]
535 * out_of_memory
536 * select_bad_process
537 * # no TIF_MEMDIE task selects new victim
538 * unmap_page_range # frees some memory
539 */
540 mutex_lock(&oom_lock);
541
542 if (!down_read_trylock(&mm->mmap_sem)) {
543 ret = false;
544 trace_skip_task_reaping(tsk->pid);
545 goto unlock_oom;
546 }
547
548 /*
549 * If the mm has invalidate_{start,end}() notifiers that could block,
550 * sleep to give the oom victim some more time.
551 * TODO: we really want to get rid of this ugly hack and make sure that
552 * notifiers cannot block for unbounded amount of time
553 */
554 if (mm_has_blockable_invalidate_notifiers(mm)) {
555 up_read(&mm->mmap_sem);
556 schedule_timeout_idle(HZ);
557 goto unlock_oom;
558 }
559
560 /*
561 * MMF_OOM_SKIP is set by exit_mmap when the OOM reaper can't
562 * work on the mm anymore. The check for MMF_OOM_SKIP must run
563 * under mmap_sem for reading because it serializes against the
564 * down_write();up_write() cycle in exit_mmap().
565 */
566 if (test_bit(MMF_OOM_SKIP, &mm->flags)) {
567 up_read(&mm->mmap_sem);
568 trace_skip_task_reaping(tsk->pid);
569 goto unlock_oom;
570 }
571
572 trace_start_task_reaping(tsk->pid);
573
574 __oom_reap_task_mm(mm);
575
576 pr_info("oom_reaper: reaped process %d (%s), now anon-rss:%lukB, file-rss:%lukB, shmem-rss:%lukB\n",
577 task_pid_nr(tsk), tsk->comm,
578 K(get_mm_counter(mm, MM_ANONPAGES)),
579 K(get_mm_counter(mm, MM_FILEPAGES)),
580 K(get_mm_counter(mm, MM_SHMEMPAGES)));
581 up_read(&mm->mmap_sem);
582
583 trace_finish_task_reaping(tsk->pid);
584unlock_oom:
585 mutex_unlock(&oom_lock);
586 return ret;
587}
588
589#define MAX_OOM_REAP_RETRIES 10
590static void oom_reap_task(struct task_struct *tsk)
591{
592 int attempts = 0;
593 struct mm_struct *mm = tsk->signal->oom_mm;
594
595 /* Retry the down_read_trylock(mmap_sem) a few times */
596 while (attempts++ < MAX_OOM_REAP_RETRIES && !oom_reap_task_mm(tsk, mm))
597 schedule_timeout_idle(HZ/10);
598
599 if (attempts <= MAX_OOM_REAP_RETRIES ||
600 test_bit(MMF_OOM_SKIP, &mm->flags))
601 goto done;
602
603 pr_info("oom_reaper: unable to reap pid:%d (%s)\n",
604 task_pid_nr(tsk), tsk->comm);
605 debug_show_all_locks();
606
607done:
608 tsk->oom_reaper_list = NULL;
609
610 /*
611 * Hide this mm from OOM killer because it has been either reaped or
612 * somebody can't call up_write(mmap_sem).
613 */
614 set_bit(MMF_OOM_SKIP, &mm->flags);
615
616 /* Drop a reference taken by wake_oom_reaper */
617 put_task_struct(tsk);
618}
619
620static int oom_reaper(void *unused)
621{
622 while (true) {
623 struct task_struct *tsk = NULL;
624
625 wait_event_freezable(oom_reaper_wait, oom_reaper_list != NULL);
626 spin_lock(&oom_reaper_lock);
627 if (oom_reaper_list != NULL) {
628 tsk = oom_reaper_list;
629 oom_reaper_list = tsk->oom_reaper_list;
630 }
631 spin_unlock(&oom_reaper_lock);
632
633 if (tsk)
634 oom_reap_task(tsk);
635 }
636
637 return 0;
638}
639
640static void wake_oom_reaper(struct task_struct *tsk)
641{
642 /* tsk is already queued? */
643 if (tsk == oom_reaper_list || tsk->oom_reaper_list)
644 return;
645
646 get_task_struct(tsk);
647
648 spin_lock(&oom_reaper_lock);
649 tsk->oom_reaper_list = oom_reaper_list;
650 oom_reaper_list = tsk;
651 spin_unlock(&oom_reaper_lock);
652 trace_wake_reaper(tsk->pid);
653 wake_up(&oom_reaper_wait);
654}
655
656static int __init oom_init(void)
657{
658 oom_reaper_th = kthread_run(oom_reaper, NULL, "oom_reaper");
659 return 0;
660}
661subsys_initcall(oom_init)
662#else
663static inline void wake_oom_reaper(struct task_struct *tsk)
664{
665}
666#endif /* CONFIG_MMU */
667
668/**
669 * mark_oom_victim - mark the given task as OOM victim
670 * @tsk: task to mark
671 *
672 * Has to be called with oom_lock held and never after
673 * oom has been disabled already.
674 *
675 * tsk->mm has to be non NULL and caller has to guarantee it is stable (either
676 * under task_lock or operate on the current).
677 */
678static void mark_oom_victim(struct task_struct *tsk)
679{
680 struct mm_struct *mm = tsk->mm;
681
682 WARN_ON(oom_killer_disabled);
683 /* OOM killer might race with memcg OOM */
684 if (test_and_set_tsk_thread_flag(tsk, TIF_MEMDIE))
685 return;
686
687 /* oom_mm is bound to the signal struct life time. */
688 if (!cmpxchg(&tsk->signal->oom_mm, NULL, mm)) {
689 mmgrab(tsk->signal->oom_mm);
690 set_bit(MMF_OOM_VICTIM, &mm->flags);
691 }
692
693 /*
694 * Make sure that the task is woken up from uninterruptible sleep
695 * if it is frozen because OOM killer wouldn't be able to free
696 * any memory and livelock. freezing_slow_path will tell the freezer
697 * that TIF_MEMDIE tasks should be ignored.
698 */
699 __thaw_task(tsk);
700 atomic_inc(&oom_victims);
701 trace_mark_victim(tsk->pid);
702}
703
704/**
705 * exit_oom_victim - note the exit of an OOM victim
706 */
707void exit_oom_victim(void)
708{
709 clear_thread_flag(TIF_MEMDIE);
710
711 if (!atomic_dec_return(&oom_victims))
712 wake_up_all(&oom_victims_wait);
713}
714
715/**
716 * oom_killer_enable - enable OOM killer
717 */
718void oom_killer_enable(void)
719{
720 oom_killer_disabled = false;
721 pr_info("OOM killer enabled.\n");
722}
723
724/**
725 * oom_killer_disable - disable OOM killer
726 * @timeout: maximum timeout to wait for oom victims in jiffies
727 *
728 * Forces all page allocations to fail rather than trigger OOM killer.
729 * Will block and wait until all OOM victims are killed or the given
730 * timeout expires.
731 *
732 * The function cannot be called when there are runnable user tasks because
733 * the userspace would see unexpected allocation failures as a result. Any
734 * new usage of this function should be consulted with MM people.
735 *
736 * Returns true if successful and false if the OOM killer cannot be
737 * disabled.
738 */
739bool oom_killer_disable(signed long timeout)
740{
741 signed long ret;
742
743 /*
744 * Make sure to not race with an ongoing OOM killer. Check that the
745 * current is not killed (possibly due to sharing the victim's memory).
746 */
747 if (mutex_lock_killable(&oom_lock))
748 return false;
749 oom_killer_disabled = true;
750 mutex_unlock(&oom_lock);
751
752 ret = wait_event_interruptible_timeout(oom_victims_wait,
753 !atomic_read(&oom_victims), timeout);
754 if (ret <= 0) {
755 oom_killer_enable();
756 return false;
757 }
758 pr_info("OOM killer disabled.\n");
759
760 return true;
761}
762
763static inline bool __task_will_free_mem(struct task_struct *task)
764{
765 struct signal_struct *sig = task->signal;
766
767 /*
768 * A coredumping process may sleep for an extended period in exit_mm(),
769 * so the oom killer cannot assume that the process will promptly exit
770 * and release memory.
771 */
772 if (sig->flags & SIGNAL_GROUP_COREDUMP)
773 return false;
774
775 if (sig->flags & SIGNAL_GROUP_EXIT)
776 return true;
777
778 if (thread_group_empty(task) && (task->flags & PF_EXITING))
779 return true;
780
781 return false;
782}
783
784/*
785 * Checks whether the given task is dying or exiting and likely to
786 * release its address space. This means that all threads and processes
787 * sharing the same mm have to be killed or exiting.
788 * Caller has to make sure that task->mm is stable (hold task_lock or
789 * it operates on the current).
790 */
791static bool task_will_free_mem(struct task_struct *task)
792{
793 struct mm_struct *mm = task->mm;
794 struct task_struct *p;
795 bool ret = true;
796
797 /*
798 * Skip tasks without mm because it might have passed its exit_mm and
799 * exit_oom_victim. oom_reaper could have rescued that but do not rely
800 * on that for now. We can consider find_lock_task_mm in future.
801 */
802 if (!mm)
803 return false;
804
805 if (!__task_will_free_mem(task))
806 return false;
807
808 /*
809 * This task has already been drained by the oom reaper so there are
810 * only small chances it will free some more
811 */
812 if (test_bit(MMF_OOM_SKIP, &mm->flags))
813 return false;
814
815 if (atomic_read(&mm->mm_users) <= 1)
816 return true;
817
818 /*
819 * Make sure that all tasks which share the mm with the given tasks
820 * are dying as well to make sure that a) nobody pins its mm and
821 * b) the task is also reapable by the oom reaper.
822 */
823 rcu_read_lock();
824 for_each_process(p) {
825 if (!process_shares_mm(p, mm))
826 continue;
827 if (same_thread_group(task, p))
828 continue;
829 ret = __task_will_free_mem(p);
830 if (!ret)
831 break;
832 }
833 rcu_read_unlock();
834
835 return ret;
836}
837
838static void oom_kill_process(struct oom_control *oc, const char *message)
839{
840 struct task_struct *p = oc->chosen;
841 unsigned int points = oc->chosen_points;
842 struct task_struct *victim = p;
843 struct task_struct *child;
844 struct task_struct *t;
845 struct mm_struct *mm;
846 unsigned int victim_points = 0;
847 static DEFINE_RATELIMIT_STATE(oom_rs, DEFAULT_RATELIMIT_INTERVAL,
848 DEFAULT_RATELIMIT_BURST);
849 bool can_oom_reap = true;
850
851 /*
852 * If the task is already exiting, don't alarm the sysadmin or kill
853 * its children or threads, just give it access to memory reserves
854 * so it can die quickly
855 */
856 task_lock(p);
857 if (task_will_free_mem(p)) {
858 mark_oom_victim(p);
859 wake_oom_reaper(p);
860 task_unlock(p);
861 put_task_struct(p);
862 return;
863 }
864 task_unlock(p);
865
866 if (__ratelimit(&oom_rs))
867 dump_header(oc, p);
868
869 pr_err("%s: Kill process %d (%s) score %u or sacrifice child\n",
870 message, task_pid_nr(p), p->comm, points);
871
872 /*
873 * If any of p's children has a different mm and is eligible for kill,
874 * the one with the highest oom_badness() score is sacrificed for its
875 * parent. This attempts to lose the minimal amount of work done while
876 * still freeing memory.
877 */
878 read_lock(&tasklist_lock);
879 for_each_thread(p, t) {
880 list_for_each_entry(child, &t->children, sibling) {
881 unsigned int child_points;
882
883 if (process_shares_mm(child, p->mm))
884 continue;
885 /*
886 * oom_badness() returns 0 if the thread is unkillable
887 */
888 child_points = oom_badness(child,
889 oc->memcg, oc->nodemask, oc->totalpages);
890 if (child_points > victim_points) {
891 put_task_struct(victim);
892 victim = child;
893 victim_points = child_points;
894 get_task_struct(victim);
895 }
896 }
897 }
898 read_unlock(&tasklist_lock);
899
900 p = find_lock_task_mm(victim);
901 if (!p) {
902 put_task_struct(victim);
903 return;
904 } else if (victim != p) {
905 get_task_struct(p);
906 put_task_struct(victim);
907 victim = p;
908 }
909
910 /* Get a reference to safely compare mm after task_unlock(victim) */
911 mm = victim->mm;
912 mmgrab(mm);
913
914 /* Raise event before sending signal: task reaper must see this */
915 count_vm_event(OOM_KILL);
916 count_memcg_event_mm(mm, OOM_KILL);
917
918 /*
919 * We should send SIGKILL before granting access to memory reserves
920 * in order to prevent the OOM victim from depleting the memory
921 * reserves from the user space under its control.
922 */
923 do_send_sig_info(SIGKILL, SEND_SIG_FORCED, victim, true);
924 mark_oom_victim(victim);
925 pr_err("Killed process %d (%s) total-vm:%lukB, anon-rss:%lukB, file-rss:%lukB, shmem-rss:%lukB\n",
926 task_pid_nr(victim), victim->comm, K(victim->mm->total_vm),
927 K(get_mm_counter(victim->mm, MM_ANONPAGES)),
928 K(get_mm_counter(victim->mm, MM_FILEPAGES)),
929 K(get_mm_counter(victim->mm, MM_SHMEMPAGES)));
930 task_unlock(victim);
931
932 /*
933 * Kill all user processes sharing victim->mm in other thread groups, if
934 * any. They don't get access to memory reserves, though, to avoid
935 * depletion of all memory. This prevents mm->mmap_sem livelock when an
936 * oom killed thread cannot exit because it requires the semaphore and
937 * its contended by another thread trying to allocate memory itself.
938 * That thread will now get access to memory reserves since it has a
939 * pending fatal signal.
940 */
941 rcu_read_lock();
942 for_each_process(p) {
943 if (!process_shares_mm(p, mm))
944 continue;
945 if (same_thread_group(p, victim))
946 continue;
947 if (is_global_init(p)) {
948 can_oom_reap = false;
949 set_bit(MMF_OOM_SKIP, &mm->flags);
950 pr_info("oom killer %d (%s) has mm pinned by %d (%s)\n",
951 task_pid_nr(victim), victim->comm,
952 task_pid_nr(p), p->comm);
953 continue;
954 }
955 /*
956 * No use_mm() user needs to read from the userspace so we are
957 * ok to reap it.
958 */
959 if (unlikely(p->flags & PF_KTHREAD))
960 continue;
961 do_send_sig_info(SIGKILL, SEND_SIG_FORCED, p, true);
962 }
963 rcu_read_unlock();
964
965 if (can_oom_reap)
966 wake_oom_reaper(victim);
967
968 mmdrop(mm);
969 put_task_struct(victim);
970}
971#undef K
972
973/*
974 * Determines whether the kernel must panic because of the panic_on_oom sysctl.
975 */
976static void check_panic_on_oom(struct oom_control *oc,
977 enum oom_constraint constraint)
978{
979 if (likely(!sysctl_panic_on_oom))
980 return;
981 if (sysctl_panic_on_oom != 2) {
982 /*
983 * panic_on_oom == 1 only affects CONSTRAINT_NONE, the kernel
984 * does not panic for cpuset, mempolicy, or memcg allocation
985 * failures.
986 */
987 if (constraint != CONSTRAINT_NONE)
988 return;
989 }
990 /* Do not panic for oom kills triggered by sysrq */
991 if (is_sysrq_oom(oc))
992 return;
993 dump_header(oc, NULL);
994 panic("Out of memory: %s panic_on_oom is enabled\n",
995 sysctl_panic_on_oom == 2 ? "compulsory" : "system-wide");
996}
997
998static BLOCKING_NOTIFIER_HEAD(oom_notify_list);
999
1000int register_oom_notifier(struct notifier_block *nb)
1001{
1002 return blocking_notifier_chain_register(&oom_notify_list, nb);
1003}
1004EXPORT_SYMBOL_GPL(register_oom_notifier);
1005
1006int unregister_oom_notifier(struct notifier_block *nb)
1007{
1008 return blocking_notifier_chain_unregister(&oom_notify_list, nb);
1009}
1010EXPORT_SYMBOL_GPL(unregister_oom_notifier);
1011
1012/**
1013 * out_of_memory - kill the "best" process when we run out of memory
1014 * @oc: pointer to struct oom_control
1015 *
1016 * If we run out of memory, we have the choice between either
1017 * killing a random task (bad), letting the system crash (worse)
1018 * OR try to be smart about which process to kill. Note that we
1019 * don't have to be perfect here, we just have to be good.
1020 */
1021bool out_of_memory(struct oom_control *oc)
1022{
1023 unsigned long freed = 0;
1024 enum oom_constraint constraint = CONSTRAINT_NONE;
1025
1026 if (oom_killer_disabled)
1027 return false;
1028
1029 if (!is_memcg_oom(oc)) {
1030 blocking_notifier_call_chain(&oom_notify_list, 0, &freed);
1031 if (freed > 0)
1032 /* Got some memory back in the last second. */
1033 return true;
1034 }
1035
1036 /*
1037 * If current has a pending SIGKILL or is exiting, then automatically
1038 * select it. The goal is to allow it to allocate so that it may
1039 * quickly exit and free its memory.
1040 */
1041 if (task_will_free_mem(current)) {
1042 mark_oom_victim(current);
1043 wake_oom_reaper(current);
1044 return true;
1045 }
1046
1047 /*
1048 * The OOM killer does not compensate for IO-less reclaim.
1049 * pagefault_out_of_memory lost its gfp context so we have to
1050 * make sure exclude 0 mask - all other users should have at least
1051 * ___GFP_DIRECT_RECLAIM to get here.
1052 */
1053 if (oc->gfp_mask && !(oc->gfp_mask & __GFP_FS))
1054 return true;
1055
1056 /*
1057 * Check if there were limitations on the allocation (only relevant for
1058 * NUMA and memcg) that may require different handling.
1059 */
1060 constraint = constrained_alloc(oc);
1061 if (constraint != CONSTRAINT_MEMORY_POLICY)
1062 oc->nodemask = NULL;
1063 check_panic_on_oom(oc, constraint);
1064
1065 if (!is_memcg_oom(oc) && sysctl_oom_kill_allocating_task &&
1066 current->mm && !oom_unkillable_task(current, NULL, oc->nodemask) &&
1067 current->signal->oom_score_adj != OOM_SCORE_ADJ_MIN) {
1068 get_task_struct(current);
1069 oc->chosen = current;
1070 oom_kill_process(oc, "Out of memory (oom_kill_allocating_task)");
1071 return true;
1072 }
1073
1074 select_bad_process(oc);
1075 /* Found nothing?!?! Either we hang forever, or we panic. */
1076 if (!oc->chosen && !is_sysrq_oom(oc) && !is_memcg_oom(oc)) {
1077 dump_header(oc, NULL);
1078 panic("Out of memory and no killable processes...\n");
1079 }
1080 if (oc->chosen && oc->chosen != (void *)-1UL) {
1081 oom_kill_process(oc, !is_memcg_oom(oc) ? "Out of memory" :
1082 "Memory cgroup out of memory");
1083 /*
1084 * Give the killed process a good chance to exit before trying
1085 * to allocate memory again.
1086 */
1087 schedule_timeout_killable(1);
1088 }
1089 return !!oc->chosen;
1090}
1091
1092/*
1093 * The pagefault handler calls here because it is out of memory, so kill a
1094 * memory-hogging task. If oom_lock is held by somebody else, a parallel oom
1095 * killing is already in progress so do nothing.
1096 */
1097void pagefault_out_of_memory(void)
1098{
1099 struct oom_control oc = {
1100 .zonelist = NULL,
1101 .nodemask = NULL,
1102 .memcg = NULL,
1103 .gfp_mask = 0,
1104 .order = 0,
1105 };
1106
1107 if (mem_cgroup_oom_synchronize(true))
1108 return;
1109
1110 if (!mutex_trylock(&oom_lock))
1111 return;
1112 out_of_memory(&oc);
1113 mutex_unlock(&oom_lock);
1114}
1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * linux/mm/oom_kill.c
4 *
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
10 *
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.
14 *
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.
19 */
20
21#include <linux/oom.h>
22#include <linux/mm.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/task.h>
28#include <linux/sched/debug.h>
29#include <linux/swap.h>
30#include <linux/syscalls.h>
31#include <linux/timex.h>
32#include <linux/jiffies.h>
33#include <linux/cpuset.h>
34#include <linux/export.h>
35#include <linux/notifier.h>
36#include <linux/memcontrol.h>
37#include <linux/mempolicy.h>
38#include <linux/security.h>
39#include <linux/ptrace.h>
40#include <linux/freezer.h>
41#include <linux/ftrace.h>
42#include <linux/ratelimit.h>
43#include <linux/kthread.h>
44#include <linux/init.h>
45#include <linux/mmu_notifier.h>
46#include <linux/cred.h>
47#include <linux/nmi.h>
48
49#include <asm/tlb.h>
50#include "internal.h"
51#include "slab.h"
52
53#define CREATE_TRACE_POINTS
54#include <trace/events/oom.h>
55
56static int sysctl_panic_on_oom;
57static int sysctl_oom_kill_allocating_task;
58static int sysctl_oom_dump_tasks = 1;
59
60/*
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).
64 *
65 * oom_killer_disable() relies on this lock to stabilize oom_killer_disabled
66 * and mark_oom_victim
67 */
68DEFINE_MUTEX(oom_lock);
69/* Serializes oom_score_adj and oom_score_adj_min updates */
70DEFINE_MUTEX(oom_adj_mutex);
71
72static inline bool is_memcg_oom(struct oom_control *oc)
73{
74 return oc->memcg != NULL;
75}
76
77#ifdef CONFIG_NUMA
78/**
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
82 *
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.
86 *
87 * This function is assuming oom-killer context and 'current' has triggered
88 * the oom-killer.
89 */
90static bool oom_cpuset_eligible(struct task_struct *start,
91 struct oom_control *oc)
92{
93 struct task_struct *tsk;
94 bool ret = false;
95 const nodemask_t *mask = oc->nodemask;
96
97 rcu_read_lock();
98 for_each_thread(start, tsk) {
99 if (mask) {
100 /*
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
104 * needlessly killed.
105 */
106 ret = mempolicy_in_oom_domain(tsk, mask);
107 } else {
108 /*
109 * This is not a mempolicy constrained oom, so only
110 * check the mems of tsk's cpuset.
111 */
112 ret = cpuset_mems_allowed_intersects(current, tsk);
113 }
114 if (ret)
115 break;
116 }
117 rcu_read_unlock();
118
119 return ret;
120}
121#else
122static bool oom_cpuset_eligible(struct task_struct *tsk, struct oom_control *oc)
123{
124 return true;
125}
126#endif /* CONFIG_NUMA */
127
128/*
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
132 * task_lock() held.
133 */
134struct task_struct *find_lock_task_mm(struct task_struct *p)
135{
136 struct task_struct *t;
137
138 rcu_read_lock();
139
140 for_each_thread(p, t) {
141 task_lock(t);
142 if (likely(t->mm))
143 goto found;
144 task_unlock(t);
145 }
146 t = NULL;
147found:
148 rcu_read_unlock();
149
150 return t;
151}
152
153/*
154 * order == -1 means the oom kill is required by sysrq, otherwise only
155 * for display purposes.
156 */
157static inline bool is_sysrq_oom(struct oom_control *oc)
158{
159 return oc->order == -1;
160}
161
162/* return true if the task is not adequate as candidate victim task. */
163static bool oom_unkillable_task(struct task_struct *p)
164{
165 if (is_global_init(p))
166 return true;
167 if (p->flags & PF_KTHREAD)
168 return true;
169 return false;
170}
171
172/*
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.
177*/
178static bool should_dump_unreclaim_slab(void)
179{
180 unsigned long nr_lru;
181
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);
189
190 return (global_node_page_state_pages(NR_SLAB_UNRECLAIMABLE_B) > nr_lru);
191}
192
193/**
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
197 *
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.
201 */
202long oom_badness(struct task_struct *p, unsigned long totalpages)
203{
204 long points;
205 long adj;
206
207 if (oom_unkillable_task(p))
208 return LONG_MIN;
209
210 p = find_lock_task_mm(p);
211 if (!p)
212 return LONG_MIN;
213
214 /*
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
218 */
219 adj = (long)p->signal->oom_score_adj;
220 if (adj == OOM_SCORE_ADJ_MIN ||
221 test_bit(MMF_OOM_SKIP, &p->mm->flags) ||
222 in_vfork(p)) {
223 task_unlock(p);
224 return LONG_MIN;
225 }
226
227 /*
228 * The baseline for the badness score is the proportion of RAM that each
229 * task's rss, pagetable and swap space use.
230 */
231 points = get_mm_rss(p->mm) + get_mm_counter(p->mm, MM_SWAPENTS) +
232 mm_pgtables_bytes(p->mm) / PAGE_SIZE;
233 task_unlock(p);
234
235 /* Normalize to oom_score_adj units */
236 adj *= totalpages / 1000;
237 points += adj;
238
239 return points;
240}
241
242static 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",
247};
248
249/*
250 * Determine the type of allocation constraint.
251 */
252static enum oom_constraint constrained_alloc(struct oom_control *oc)
253{
254 struct zone *zone;
255 struct zoneref *z;
256 enum zone_type highest_zoneidx = gfp_zone(oc->gfp_mask);
257 bool cpuset_limited = false;
258 int nid;
259
260 if (is_memcg_oom(oc)) {
261 oc->totalpages = mem_cgroup_get_max(oc->memcg) ?: 1;
262 return CONSTRAINT_MEMCG;
263 }
264
265 /* Default to all available memory */
266 oc->totalpages = totalram_pages() + total_swap_pages;
267
268 if (!IS_ENABLED(CONFIG_NUMA))
269 return CONSTRAINT_NONE;
270
271 if (!oc->zonelist)
272 return CONSTRAINT_NONE;
273 /*
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.
277 */
278 if (oc->gfp_mask & __GFP_THISNODE)
279 return CONSTRAINT_NONE;
280
281 /*
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().
285 */
286 if (oc->nodemask &&
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;
292 }
293
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;
299
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;
305 }
306 return CONSTRAINT_NONE;
307}
308
309static int oom_evaluate_task(struct task_struct *task, void *arg)
310{
311 struct oom_control *oc = arg;
312 long points;
313
314 if (oom_unkillable_task(task))
315 goto next;
316
317 /* p may not have freeable memory in nodemask */
318 if (!is_memcg_oom(oc) && !oom_cpuset_eligible(task, oc))
319 goto next;
320
321 /*
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.
326 */
327 if (!is_sysrq_oom(oc) && tsk_is_oom_victim(task)) {
328 if (test_bit(MMF_OOM_SKIP, &task->signal->oom_mm->flags))
329 goto next;
330 goto abort;
331 }
332
333 /*
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.
336 */
337 if (oom_task_origin(task)) {
338 points = LONG_MAX;
339 goto select;
340 }
341
342 points = oom_badness(task, oc->totalpages);
343 if (points == LONG_MIN || points < oc->chosen_points)
344 goto next;
345
346select:
347 if (oc->chosen)
348 put_task_struct(oc->chosen);
349 get_task_struct(task);
350 oc->chosen = task;
351 oc->chosen_points = points;
352next:
353 return 0;
354abort:
355 if (oc->chosen)
356 put_task_struct(oc->chosen);
357 oc->chosen = (void *)-1UL;
358 return 1;
359}
360
361/*
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.
364 */
365static void select_bad_process(struct oom_control *oc)
366{
367 oc->chosen_points = LONG_MIN;
368
369 if (is_memcg_oom(oc))
370 mem_cgroup_scan_tasks(oc->memcg, oom_evaluate_task, oc);
371 else {
372 struct task_struct *p;
373
374 rcu_read_lock();
375 for_each_process(p)
376 if (oom_evaluate_task(p, oc))
377 break;
378 rcu_read_unlock();
379 }
380}
381
382static int dump_task(struct task_struct *p, void *arg)
383{
384 struct oom_control *oc = arg;
385 struct task_struct *task;
386
387 if (oom_unkillable_task(p))
388 return 0;
389
390 /* p may not have freeable memory in nodemask */
391 if (!is_memcg_oom(oc) && !oom_cpuset_eligible(p, oc))
392 return 0;
393
394 task = find_lock_task_mm(p);
395 if (!task) {
396 /*
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.
399 */
400 return 0;
401 }
402
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);
410 task_unlock(task);
411
412 return 0;
413}
414
415/**
416 * dump_tasks - dump current memory state of all system tasks
417 * @oc: pointer to struct oom_control
418 *
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
421 * are not shown.
422 * State information includes task's pid, uid, tgid, vm size, rss,
423 * pgtables_bytes, swapents, oom_score_adj value, and name.
424 */
425static void dump_tasks(struct oom_control *oc)
426{
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");
429
430 if (is_memcg_oom(oc))
431 mem_cgroup_scan_tasks(oc->memcg, dump_task, oc);
432 else {
433 struct task_struct *p;
434 int i = 0;
435
436 rcu_read_lock();
437 for_each_process(p) {
438 /* Avoid potential softlockup warning */
439 if ((++i & 1023) == 0)
440 touch_softlockup_watchdog();
441 dump_task(p, oc);
442 }
443 rcu_read_unlock();
444 }
445}
446
447static void dump_oom_victim(struct oom_control *oc, struct task_struct *victim)
448{
449 /* one line summary of the oom killer context. */
450 pr_info("oom-kill:constraint=%s,nodemask=%*pbl",
451 oom_constraint_text[oc->constraint],
452 nodemask_pr_args(oc->nodemask));
453 cpuset_print_current_mems_allowed();
454 mem_cgroup_print_oom_context(oc->memcg, victim);
455 pr_cont(",task=%s,pid=%d,uid=%d\n", victim->comm, victim->pid,
456 from_kuid(&init_user_ns, task_uid(victim)));
457}
458
459static void dump_header(struct oom_control *oc)
460{
461 pr_warn("%s invoked oom-killer: gfp_mask=%#x(%pGg), order=%d, oom_score_adj=%hd\n",
462 current->comm, oc->gfp_mask, &oc->gfp_mask, oc->order,
463 current->signal->oom_score_adj);
464 if (!IS_ENABLED(CONFIG_COMPACTION) && oc->order)
465 pr_warn("COMPACTION is disabled!!!\n");
466
467 dump_stack();
468 if (is_memcg_oom(oc))
469 mem_cgroup_print_oom_meminfo(oc->memcg);
470 else {
471 __show_mem(SHOW_MEM_FILTER_NODES, oc->nodemask, gfp_zone(oc->gfp_mask));
472 if (should_dump_unreclaim_slab())
473 dump_unreclaimable_slab();
474 }
475 if (sysctl_oom_dump_tasks)
476 dump_tasks(oc);
477}
478
479/*
480 * Number of OOM victims in flight
481 */
482static atomic_t oom_victims = ATOMIC_INIT(0);
483static DECLARE_WAIT_QUEUE_HEAD(oom_victims_wait);
484
485static bool oom_killer_disabled __read_mostly;
486
487/*
488 * task->mm can be NULL if the task is the exited group leader. So to
489 * determine whether the task is using a particular mm, we examine all the
490 * task's threads: if one of those is using this mm then this task was also
491 * using it.
492 */
493bool process_shares_mm(struct task_struct *p, struct mm_struct *mm)
494{
495 struct task_struct *t;
496
497 for_each_thread(p, t) {
498 struct mm_struct *t_mm = READ_ONCE(t->mm);
499 if (t_mm)
500 return t_mm == mm;
501 }
502 return false;
503}
504
505#ifdef CONFIG_MMU
506/*
507 * OOM Reaper kernel thread which tries to reap the memory used by the OOM
508 * victim (if that is possible) to help the OOM killer to move on.
509 */
510static struct task_struct *oom_reaper_th;
511static DECLARE_WAIT_QUEUE_HEAD(oom_reaper_wait);
512static struct task_struct *oom_reaper_list;
513static DEFINE_SPINLOCK(oom_reaper_lock);
514
515static bool __oom_reap_task_mm(struct mm_struct *mm)
516{
517 struct vm_area_struct *vma;
518 bool ret = true;
519 VMA_ITERATOR(vmi, mm, 0);
520
521 /*
522 * Tell all users of get_user/copy_from_user etc... that the content
523 * is no longer stable. No barriers really needed because unmapping
524 * should imply barriers already and the reader would hit a page fault
525 * if it stumbled over a reaped memory.
526 */
527 set_bit(MMF_UNSTABLE, &mm->flags);
528
529 for_each_vma(vmi, vma) {
530 if (vma->vm_flags & (VM_HUGETLB|VM_PFNMAP))
531 continue;
532
533 /*
534 * Only anonymous pages have a good chance to be dropped
535 * without additional steps which we cannot afford as we
536 * are OOM already.
537 *
538 * We do not even care about fs backed pages because all
539 * which are reclaimable have already been reclaimed and
540 * we do not want to block exit_mmap by keeping mm ref
541 * count elevated without a good reason.
542 */
543 if (vma_is_anonymous(vma) || !(vma->vm_flags & VM_SHARED)) {
544 struct mmu_notifier_range range;
545 struct mmu_gather tlb;
546
547 mmu_notifier_range_init(&range, MMU_NOTIFY_UNMAP, 0,
548 mm, vma->vm_start,
549 vma->vm_end);
550 tlb_gather_mmu(&tlb, mm);
551 if (mmu_notifier_invalidate_range_start_nonblock(&range)) {
552 tlb_finish_mmu(&tlb);
553 ret = false;
554 continue;
555 }
556 unmap_page_range(&tlb, vma, range.start, range.end, NULL);
557 mmu_notifier_invalidate_range_end(&range);
558 tlb_finish_mmu(&tlb);
559 }
560 }
561
562 return ret;
563}
564
565/*
566 * Reaps the address space of the give task.
567 *
568 * Returns true on success and false if none or part of the address space
569 * has been reclaimed and the caller should retry later.
570 */
571static bool oom_reap_task_mm(struct task_struct *tsk, struct mm_struct *mm)
572{
573 bool ret = true;
574
575 if (!mmap_read_trylock(mm)) {
576 trace_skip_task_reaping(tsk->pid);
577 return false;
578 }
579
580 /*
581 * MMF_OOM_SKIP is set by exit_mmap when the OOM reaper can't
582 * work on the mm anymore. The check for MMF_OOM_SKIP must run
583 * under mmap_lock for reading because it serializes against the
584 * mmap_write_lock();mmap_write_unlock() cycle in exit_mmap().
585 */
586 if (test_bit(MMF_OOM_SKIP, &mm->flags)) {
587 trace_skip_task_reaping(tsk->pid);
588 goto out_unlock;
589 }
590
591 trace_start_task_reaping(tsk->pid);
592
593 /* failed to reap part of the address space. Try again later */
594 ret = __oom_reap_task_mm(mm);
595 if (!ret)
596 goto out_finish;
597
598 pr_info("oom_reaper: reaped process %d (%s), now anon-rss:%lukB, file-rss:%lukB, shmem-rss:%lukB\n",
599 task_pid_nr(tsk), tsk->comm,
600 K(get_mm_counter(mm, MM_ANONPAGES)),
601 K(get_mm_counter(mm, MM_FILEPAGES)),
602 K(get_mm_counter(mm, MM_SHMEMPAGES)));
603out_finish:
604 trace_finish_task_reaping(tsk->pid);
605out_unlock:
606 mmap_read_unlock(mm);
607
608 return ret;
609}
610
611#define MAX_OOM_REAP_RETRIES 10
612static void oom_reap_task(struct task_struct *tsk)
613{
614 int attempts = 0;
615 struct mm_struct *mm = tsk->signal->oom_mm;
616
617 /* Retry the mmap_read_trylock(mm) a few times */
618 while (attempts++ < MAX_OOM_REAP_RETRIES && !oom_reap_task_mm(tsk, mm))
619 schedule_timeout_idle(HZ/10);
620
621 if (attempts <= MAX_OOM_REAP_RETRIES ||
622 test_bit(MMF_OOM_SKIP, &mm->flags))
623 goto done;
624
625 pr_info("oom_reaper: unable to reap pid:%d (%s)\n",
626 task_pid_nr(tsk), tsk->comm);
627 sched_show_task(tsk);
628 debug_show_all_locks();
629
630done:
631 tsk->oom_reaper_list = NULL;
632
633 /*
634 * Hide this mm from OOM killer because it has been either reaped or
635 * somebody can't call mmap_write_unlock(mm).
636 */
637 set_bit(MMF_OOM_SKIP, &mm->flags);
638
639 /* Drop a reference taken by queue_oom_reaper */
640 put_task_struct(tsk);
641}
642
643static int oom_reaper(void *unused)
644{
645 set_freezable();
646
647 while (true) {
648 struct task_struct *tsk = NULL;
649
650 wait_event_freezable(oom_reaper_wait, oom_reaper_list != NULL);
651 spin_lock_irq(&oom_reaper_lock);
652 if (oom_reaper_list != NULL) {
653 tsk = oom_reaper_list;
654 oom_reaper_list = tsk->oom_reaper_list;
655 }
656 spin_unlock_irq(&oom_reaper_lock);
657
658 if (tsk)
659 oom_reap_task(tsk);
660 }
661
662 return 0;
663}
664
665static void wake_oom_reaper(struct timer_list *timer)
666{
667 struct task_struct *tsk = container_of(timer, struct task_struct,
668 oom_reaper_timer);
669 struct mm_struct *mm = tsk->signal->oom_mm;
670 unsigned long flags;
671
672 /* The victim managed to terminate on its own - see exit_mmap */
673 if (test_bit(MMF_OOM_SKIP, &mm->flags)) {
674 put_task_struct(tsk);
675 return;
676 }
677
678 spin_lock_irqsave(&oom_reaper_lock, flags);
679 tsk->oom_reaper_list = oom_reaper_list;
680 oom_reaper_list = tsk;
681 spin_unlock_irqrestore(&oom_reaper_lock, flags);
682 trace_wake_reaper(tsk->pid);
683 wake_up(&oom_reaper_wait);
684}
685
686/*
687 * Give the OOM victim time to exit naturally before invoking the oom_reaping.
688 * The timers timeout is arbitrary... the longer it is, the longer the worst
689 * case scenario for the OOM can take. If it is too small, the oom_reaper can
690 * get in the way and release resources needed by the process exit path.
691 * e.g. The futex robust list can sit in Anon|Private memory that gets reaped
692 * before the exit path is able to wake the futex waiters.
693 */
694#define OOM_REAPER_DELAY (2*HZ)
695static void queue_oom_reaper(struct task_struct *tsk)
696{
697 /* mm is already queued? */
698 if (test_and_set_bit(MMF_OOM_REAP_QUEUED, &tsk->signal->oom_mm->flags))
699 return;
700
701 get_task_struct(tsk);
702 timer_setup(&tsk->oom_reaper_timer, wake_oom_reaper, 0);
703 tsk->oom_reaper_timer.expires = jiffies + OOM_REAPER_DELAY;
704 add_timer(&tsk->oom_reaper_timer);
705}
706
707#ifdef CONFIG_SYSCTL
708static struct ctl_table vm_oom_kill_table[] = {
709 {
710 .procname = "panic_on_oom",
711 .data = &sysctl_panic_on_oom,
712 .maxlen = sizeof(sysctl_panic_on_oom),
713 .mode = 0644,
714 .proc_handler = proc_dointvec_minmax,
715 .extra1 = SYSCTL_ZERO,
716 .extra2 = SYSCTL_TWO,
717 },
718 {
719 .procname = "oom_kill_allocating_task",
720 .data = &sysctl_oom_kill_allocating_task,
721 .maxlen = sizeof(sysctl_oom_kill_allocating_task),
722 .mode = 0644,
723 .proc_handler = proc_dointvec,
724 },
725 {
726 .procname = "oom_dump_tasks",
727 .data = &sysctl_oom_dump_tasks,
728 .maxlen = sizeof(sysctl_oom_dump_tasks),
729 .mode = 0644,
730 .proc_handler = proc_dointvec,
731 },
732};
733#endif
734
735static int __init oom_init(void)
736{
737 oom_reaper_th = kthread_run(oom_reaper, NULL, "oom_reaper");
738#ifdef CONFIG_SYSCTL
739 register_sysctl_init("vm", vm_oom_kill_table);
740#endif
741 return 0;
742}
743subsys_initcall(oom_init)
744#else
745static inline void queue_oom_reaper(struct task_struct *tsk)
746{
747}
748#endif /* CONFIG_MMU */
749
750/**
751 * mark_oom_victim - mark the given task as OOM victim
752 * @tsk: task to mark
753 *
754 * Has to be called with oom_lock held and never after
755 * oom has been disabled already.
756 *
757 * tsk->mm has to be non NULL and caller has to guarantee it is stable (either
758 * under task_lock or operate on the current).
759 */
760static void mark_oom_victim(struct task_struct *tsk)
761{
762 const struct cred *cred;
763 struct mm_struct *mm = tsk->mm;
764
765 WARN_ON(oom_killer_disabled);
766 /* OOM killer might race with memcg OOM */
767 if (test_and_set_tsk_thread_flag(tsk, TIF_MEMDIE))
768 return;
769
770 /* oom_mm is bound to the signal struct life time. */
771 if (!cmpxchg(&tsk->signal->oom_mm, NULL, mm))
772 mmgrab(tsk->signal->oom_mm);
773
774 /*
775 * Make sure that the task is woken up from uninterruptible sleep
776 * if it is frozen because OOM killer wouldn't be able to free
777 * any memory and livelock. freezing_slow_path will tell the freezer
778 * that TIF_MEMDIE tasks should be ignored.
779 */
780 __thaw_task(tsk);
781 atomic_inc(&oom_victims);
782 cred = get_task_cred(tsk);
783 trace_mark_victim(tsk, cred->uid.val);
784 put_cred(cred);
785}
786
787/**
788 * exit_oom_victim - note the exit of an OOM victim
789 */
790void exit_oom_victim(void)
791{
792 clear_thread_flag(TIF_MEMDIE);
793
794 if (!atomic_dec_return(&oom_victims))
795 wake_up_all(&oom_victims_wait);
796}
797
798/**
799 * oom_killer_enable - enable OOM killer
800 */
801void oom_killer_enable(void)
802{
803 oom_killer_disabled = false;
804 pr_info("OOM killer enabled.\n");
805}
806
807/**
808 * oom_killer_disable - disable OOM killer
809 * @timeout: maximum timeout to wait for oom victims in jiffies
810 *
811 * Forces all page allocations to fail rather than trigger OOM killer.
812 * Will block and wait until all OOM victims are killed or the given
813 * timeout expires.
814 *
815 * The function cannot be called when there are runnable user tasks because
816 * the userspace would see unexpected allocation failures as a result. Any
817 * new usage of this function should be consulted with MM people.
818 *
819 * Returns true if successful and false if the OOM killer cannot be
820 * disabled.
821 */
822bool oom_killer_disable(signed long timeout)
823{
824 signed long ret;
825
826 /*
827 * Make sure to not race with an ongoing OOM killer. Check that the
828 * current is not killed (possibly due to sharing the victim's memory).
829 */
830 if (mutex_lock_killable(&oom_lock))
831 return false;
832 oom_killer_disabled = true;
833 mutex_unlock(&oom_lock);
834
835 ret = wait_event_interruptible_timeout(oom_victims_wait,
836 !atomic_read(&oom_victims), timeout);
837 if (ret <= 0) {
838 oom_killer_enable();
839 return false;
840 }
841 pr_info("OOM killer disabled.\n");
842
843 return true;
844}
845
846static inline bool __task_will_free_mem(struct task_struct *task)
847{
848 struct signal_struct *sig = task->signal;
849
850 /*
851 * A coredumping process may sleep for an extended period in
852 * coredump_task_exit(), so the oom killer cannot assume that
853 * the process will promptly exit and release memory.
854 */
855 if (sig->core_state)
856 return false;
857
858 if (sig->flags & SIGNAL_GROUP_EXIT)
859 return true;
860
861 if (thread_group_empty(task) && (task->flags & PF_EXITING))
862 return true;
863
864 return false;
865}
866
867/*
868 * Checks whether the given task is dying or exiting and likely to
869 * release its address space. This means that all threads and processes
870 * sharing the same mm have to be killed or exiting.
871 * Caller has to make sure that task->mm is stable (hold task_lock or
872 * it operates on the current).
873 */
874static bool task_will_free_mem(struct task_struct *task)
875{
876 struct mm_struct *mm = task->mm;
877 struct task_struct *p;
878 bool ret = true;
879
880 /*
881 * Skip tasks without mm because it might have passed its exit_mm and
882 * exit_oom_victim. oom_reaper could have rescued that but do not rely
883 * on that for now. We can consider find_lock_task_mm in future.
884 */
885 if (!mm)
886 return false;
887
888 if (!__task_will_free_mem(task))
889 return false;
890
891 /*
892 * This task has already been drained by the oom reaper so there are
893 * only small chances it will free some more
894 */
895 if (test_bit(MMF_OOM_SKIP, &mm->flags))
896 return false;
897
898 if (atomic_read(&mm->mm_users) <= 1)
899 return true;
900
901 /*
902 * Make sure that all tasks which share the mm with the given tasks
903 * are dying as well to make sure that a) nobody pins its mm and
904 * b) the task is also reapable by the oom reaper.
905 */
906 rcu_read_lock();
907 for_each_process(p) {
908 if (!process_shares_mm(p, mm))
909 continue;
910 if (same_thread_group(task, p))
911 continue;
912 ret = __task_will_free_mem(p);
913 if (!ret)
914 break;
915 }
916 rcu_read_unlock();
917
918 return ret;
919}
920
921static void __oom_kill_process(struct task_struct *victim, const char *message)
922{
923 struct task_struct *p;
924 struct mm_struct *mm;
925 bool can_oom_reap = true;
926
927 p = find_lock_task_mm(victim);
928 if (!p) {
929 pr_info("%s: OOM victim %d (%s) is already exiting. Skip killing the task\n",
930 message, task_pid_nr(victim), victim->comm);
931 put_task_struct(victim);
932 return;
933 } else if (victim != p) {
934 get_task_struct(p);
935 put_task_struct(victim);
936 victim = p;
937 }
938
939 /* Get a reference to safely compare mm after task_unlock(victim) */
940 mm = victim->mm;
941 mmgrab(mm);
942
943 /* Raise event before sending signal: task reaper must see this */
944 count_vm_event(OOM_KILL);
945 memcg_memory_event_mm(mm, MEMCG_OOM_KILL);
946
947 /*
948 * We should send SIGKILL before granting access to memory reserves
949 * in order to prevent the OOM victim from depleting the memory
950 * reserves from the user space under its control.
951 */
952 do_send_sig_info(SIGKILL, SEND_SIG_PRIV, victim, PIDTYPE_TGID);
953 mark_oom_victim(victim);
954 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",
955 message, task_pid_nr(victim), victim->comm, K(mm->total_vm),
956 K(get_mm_counter(mm, MM_ANONPAGES)),
957 K(get_mm_counter(mm, MM_FILEPAGES)),
958 K(get_mm_counter(mm, MM_SHMEMPAGES)),
959 from_kuid(&init_user_ns, task_uid(victim)),
960 mm_pgtables_bytes(mm) >> 10, victim->signal->oom_score_adj);
961 task_unlock(victim);
962
963 /*
964 * Kill all user processes sharing victim->mm in other thread groups, if
965 * any. They don't get access to memory reserves, though, to avoid
966 * depletion of all memory. This prevents mm->mmap_lock livelock when an
967 * oom killed thread cannot exit because it requires the semaphore and
968 * its contended by another thread trying to allocate memory itself.
969 * That thread will now get access to memory reserves since it has a
970 * pending fatal signal.
971 */
972 rcu_read_lock();
973 for_each_process(p) {
974 if (!process_shares_mm(p, mm))
975 continue;
976 if (same_thread_group(p, victim))
977 continue;
978 if (is_global_init(p)) {
979 can_oom_reap = false;
980 set_bit(MMF_OOM_SKIP, &mm->flags);
981 pr_info("oom killer %d (%s) has mm pinned by %d (%s)\n",
982 task_pid_nr(victim), victim->comm,
983 task_pid_nr(p), p->comm);
984 continue;
985 }
986 /*
987 * No kthread_use_mm() user needs to read from the userspace so
988 * we are ok to reap it.
989 */
990 if (unlikely(p->flags & PF_KTHREAD))
991 continue;
992 do_send_sig_info(SIGKILL, SEND_SIG_PRIV, p, PIDTYPE_TGID);
993 }
994 rcu_read_unlock();
995
996 if (can_oom_reap)
997 queue_oom_reaper(victim);
998
999 mmdrop(mm);
1000 put_task_struct(victim);
1001}
1002
1003/*
1004 * Kill provided task unless it's secured by setting
1005 * oom_score_adj to OOM_SCORE_ADJ_MIN.
1006 */
1007static int oom_kill_memcg_member(struct task_struct *task, void *message)
1008{
1009 if (task->signal->oom_score_adj != OOM_SCORE_ADJ_MIN &&
1010 !is_global_init(task)) {
1011 get_task_struct(task);
1012 __oom_kill_process(task, message);
1013 }
1014 return 0;
1015}
1016
1017static void oom_kill_process(struct oom_control *oc, const char *message)
1018{
1019 struct task_struct *victim = oc->chosen;
1020 struct mem_cgroup *oom_group;
1021 static DEFINE_RATELIMIT_STATE(oom_rs, DEFAULT_RATELIMIT_INTERVAL,
1022 DEFAULT_RATELIMIT_BURST);
1023
1024 /*
1025 * If the task is already exiting, don't alarm the sysadmin or kill
1026 * its children or threads, just give it access to memory reserves
1027 * so it can die quickly
1028 */
1029 task_lock(victim);
1030 if (task_will_free_mem(victim)) {
1031 mark_oom_victim(victim);
1032 queue_oom_reaper(victim);
1033 task_unlock(victim);
1034 put_task_struct(victim);
1035 return;
1036 }
1037 task_unlock(victim);
1038
1039 if (__ratelimit(&oom_rs)) {
1040 dump_header(oc);
1041 dump_oom_victim(oc, victim);
1042 }
1043
1044 /*
1045 * Do we need to kill the entire memory cgroup?
1046 * Or even one of the ancestor memory cgroups?
1047 * Check this out before killing the victim task.
1048 */
1049 oom_group = mem_cgroup_get_oom_group(victim, oc->memcg);
1050
1051 __oom_kill_process(victim, message);
1052
1053 /*
1054 * If necessary, kill all tasks in the selected memory cgroup.
1055 */
1056 if (oom_group) {
1057 memcg_memory_event(oom_group, MEMCG_OOM_GROUP_KILL);
1058 mem_cgroup_print_oom_group(oom_group);
1059 mem_cgroup_scan_tasks(oom_group, oom_kill_memcg_member,
1060 (void *)message);
1061 mem_cgroup_put(oom_group);
1062 }
1063}
1064
1065/*
1066 * Determines whether the kernel must panic because of the panic_on_oom sysctl.
1067 */
1068static void check_panic_on_oom(struct oom_control *oc)
1069{
1070 if (likely(!sysctl_panic_on_oom))
1071 return;
1072 if (sysctl_panic_on_oom != 2) {
1073 /*
1074 * panic_on_oom == 1 only affects CONSTRAINT_NONE, the kernel
1075 * does not panic for cpuset, mempolicy, or memcg allocation
1076 * failures.
1077 */
1078 if (oc->constraint != CONSTRAINT_NONE)
1079 return;
1080 }
1081 /* Do not panic for oom kills triggered by sysrq */
1082 if (is_sysrq_oom(oc))
1083 return;
1084 dump_header(oc);
1085 panic("Out of memory: %s panic_on_oom is enabled\n",
1086 sysctl_panic_on_oom == 2 ? "compulsory" : "system-wide");
1087}
1088
1089static BLOCKING_NOTIFIER_HEAD(oom_notify_list);
1090
1091int register_oom_notifier(struct notifier_block *nb)
1092{
1093 return blocking_notifier_chain_register(&oom_notify_list, nb);
1094}
1095EXPORT_SYMBOL_GPL(register_oom_notifier);
1096
1097int unregister_oom_notifier(struct notifier_block *nb)
1098{
1099 return blocking_notifier_chain_unregister(&oom_notify_list, nb);
1100}
1101EXPORT_SYMBOL_GPL(unregister_oom_notifier);
1102
1103/**
1104 * out_of_memory - kill the "best" process when we run out of memory
1105 * @oc: pointer to struct oom_control
1106 *
1107 * If we run out of memory, we have the choice between either
1108 * killing a random task (bad), letting the system crash (worse)
1109 * OR try to be smart about which process to kill. Note that we
1110 * don't have to be perfect here, we just have to be good.
1111 */
1112bool out_of_memory(struct oom_control *oc)
1113{
1114 unsigned long freed = 0;
1115
1116 if (oom_killer_disabled)
1117 return false;
1118
1119 if (!is_memcg_oom(oc)) {
1120 blocking_notifier_call_chain(&oom_notify_list, 0, &freed);
1121 if (freed > 0 && !is_sysrq_oom(oc))
1122 /* Got some memory back in the last second. */
1123 return true;
1124 }
1125
1126 /*
1127 * If current has a pending SIGKILL or is exiting, then automatically
1128 * select it. The goal is to allow it to allocate so that it may
1129 * quickly exit and free its memory.
1130 */
1131 if (task_will_free_mem(current)) {
1132 mark_oom_victim(current);
1133 queue_oom_reaper(current);
1134 return true;
1135 }
1136
1137 /*
1138 * The OOM killer does not compensate for IO-less reclaim.
1139 * But mem_cgroup_oom() has to invoke the OOM killer even
1140 * if it is a GFP_NOFS allocation.
1141 */
1142 if (!(oc->gfp_mask & __GFP_FS) && !is_memcg_oom(oc))
1143 return true;
1144
1145 /*
1146 * Check if there were limitations on the allocation (only relevant for
1147 * NUMA and memcg) that may require different handling.
1148 */
1149 oc->constraint = constrained_alloc(oc);
1150 if (oc->constraint != CONSTRAINT_MEMORY_POLICY)
1151 oc->nodemask = NULL;
1152 check_panic_on_oom(oc);
1153
1154 if (!is_memcg_oom(oc) && sysctl_oom_kill_allocating_task &&
1155 current->mm && !oom_unkillable_task(current) &&
1156 oom_cpuset_eligible(current, oc) &&
1157 current->signal->oom_score_adj != OOM_SCORE_ADJ_MIN) {
1158 get_task_struct(current);
1159 oc->chosen = current;
1160 oom_kill_process(oc, "Out of memory (oom_kill_allocating_task)");
1161 return true;
1162 }
1163
1164 select_bad_process(oc);
1165 /* Found nothing?!?! */
1166 if (!oc->chosen) {
1167 dump_header(oc);
1168 pr_warn("Out of memory and no killable processes...\n");
1169 /*
1170 * If we got here due to an actual allocation at the
1171 * system level, we cannot survive this and will enter
1172 * an endless loop in the allocator. Bail out now.
1173 */
1174 if (!is_sysrq_oom(oc) && !is_memcg_oom(oc))
1175 panic("System is deadlocked on memory\n");
1176 }
1177 if (oc->chosen && oc->chosen != (void *)-1UL)
1178 oom_kill_process(oc, !is_memcg_oom(oc) ? "Out of memory" :
1179 "Memory cgroup out of memory");
1180 return !!oc->chosen;
1181}
1182
1183/*
1184 * The pagefault handler calls here because some allocation has failed. We have
1185 * to take care of the memcg OOM here because this is the only safe context without
1186 * any locks held but let the oom killer triggered from the allocation context care
1187 * about the global OOM.
1188 */
1189void pagefault_out_of_memory(void)
1190{
1191 static DEFINE_RATELIMIT_STATE(pfoom_rs, DEFAULT_RATELIMIT_INTERVAL,
1192 DEFAULT_RATELIMIT_BURST);
1193
1194 if (mem_cgroup_oom_synchronize(true))
1195 return;
1196
1197 if (fatal_signal_pending(current))
1198 return;
1199
1200 if (__ratelimit(&pfoom_rs))
1201 pr_warn("Huh VM_FAULT_OOM leaked out to the #PF handler. Retrying PF\n");
1202}
1203
1204SYSCALL_DEFINE2(process_mrelease, int, pidfd, unsigned int, flags)
1205{
1206#ifdef CONFIG_MMU
1207 struct mm_struct *mm = NULL;
1208 struct task_struct *task;
1209 struct task_struct *p;
1210 unsigned int f_flags;
1211 bool reap = false;
1212 long ret = 0;
1213
1214 if (flags)
1215 return -EINVAL;
1216
1217 task = pidfd_get_task(pidfd, &f_flags);
1218 if (IS_ERR(task))
1219 return PTR_ERR(task);
1220
1221 /*
1222 * Make sure to choose a thread which still has a reference to mm
1223 * during the group exit
1224 */
1225 p = find_lock_task_mm(task);
1226 if (!p) {
1227 ret = -ESRCH;
1228 goto put_task;
1229 }
1230
1231 mm = p->mm;
1232 mmgrab(mm);
1233
1234 if (task_will_free_mem(p))
1235 reap = true;
1236 else {
1237 /* Error only if the work has not been done already */
1238 if (!test_bit(MMF_OOM_SKIP, &mm->flags))
1239 ret = -EINVAL;
1240 }
1241 task_unlock(p);
1242
1243 if (!reap)
1244 goto drop_mm;
1245
1246 if (mmap_read_lock_killable(mm)) {
1247 ret = -EINTR;
1248 goto drop_mm;
1249 }
1250 /*
1251 * Check MMF_OOM_SKIP again under mmap_read_lock protection to ensure
1252 * possible change in exit_mmap is seen
1253 */
1254 if (!test_bit(MMF_OOM_SKIP, &mm->flags) && !__oom_reap_task_mm(mm))
1255 ret = -EAGAIN;
1256 mmap_read_unlock(mm);
1257
1258drop_mm:
1259 mmdrop(mm);
1260put_task:
1261 put_task_struct(task);
1262 return ret;
1263#else
1264 return -ENOSYS;
1265#endif /* CONFIG_MMU */
1266}