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
56/*
57 * Serializes oom killer invocations (out_of_memory()) from all contexts to
58 * prevent from over eager oom killing (e.g. when the oom killer is invoked
59 * from different domains).
60 *
61 * oom_killer_disable() relies on this lock to stabilize oom_killer_disabled
62 * and mark_oom_victim
63 */
64DEFINE_MUTEX(oom_lock);
65
66#ifdef CONFIG_NUMA
67/**
68 * has_intersects_mems_allowed() - check task eligiblity for kill
69 * @start: task struct of which task to consider
70 * @mask: nodemask passed to page allocator for mempolicy ooms
71 *
72 * Task eligibility is determined by whether or not a candidate task, @tsk,
73 * shares the same mempolicy nodes as current if it is bound by such a policy
74 * and whether or not it has the same set of allowed cpuset nodes.
75 */
76static bool has_intersects_mems_allowed(struct task_struct *start,
77 const nodemask_t *mask)
78{
79 struct task_struct *tsk;
80 bool ret = false;
81
82 rcu_read_lock();
83 for_each_thread(start, tsk) {
84 if (mask) {
85 /*
86 * If this is a mempolicy constrained oom, tsk's
87 * cpuset is irrelevant. Only return true if its
88 * mempolicy intersects current, otherwise it may be
89 * needlessly killed.
90 */
91 ret = mempolicy_nodemask_intersects(tsk, mask);
92 } else {
93 /*
94 * This is not a mempolicy constrained oom, so only
95 * check the mems of tsk's cpuset.
96 */
97 ret = cpuset_mems_allowed_intersects(current, tsk);
98 }
99 if (ret)
100 break;
101 }
102 rcu_read_unlock();
103
104 return ret;
105}
106#else
107static bool has_intersects_mems_allowed(struct task_struct *tsk,
108 const nodemask_t *mask)
109{
110 return true;
111}
112#endif /* CONFIG_NUMA */
113
114/*
115 * The process p may have detached its own ->mm while exiting or through
116 * use_mm(), but one or more of its subthreads may still have a valid
117 * pointer. Return p, or any of its subthreads with a valid ->mm, with
118 * task_lock() held.
119 */
120struct task_struct *find_lock_task_mm(struct task_struct *p)
121{
122 struct task_struct *t;
123
124 rcu_read_lock();
125
126 for_each_thread(p, t) {
127 task_lock(t);
128 if (likely(t->mm))
129 goto found;
130 task_unlock(t);
131 }
132 t = NULL;
133found:
134 rcu_read_unlock();
135
136 return t;
137}
138
139/*
140 * order == -1 means the oom kill is required by sysrq, otherwise only
141 * for display purposes.
142 */
143static inline bool is_sysrq_oom(struct oom_control *oc)
144{
145 return oc->order == -1;
146}
147
148static inline bool is_memcg_oom(struct oom_control *oc)
149{
150 return oc->memcg != NULL;
151}
152
153/* return true if the task is not adequate as candidate victim task. */
154static bool oom_unkillable_task(struct task_struct *p,
155 struct mem_cgroup *memcg, const nodemask_t *nodemask)
156{
157 if (is_global_init(p))
158 return true;
159 if (p->flags & PF_KTHREAD)
160 return true;
161
162 /* When mem_cgroup_out_of_memory() and p is not member of the group */
163 if (memcg && !task_in_mem_cgroup(p, memcg))
164 return true;
165
166 /* p may not have freeable memory in nodemask */
167 if (!has_intersects_mems_allowed(p, nodemask))
168 return true;
169
170 return false;
171}
172
173/*
174 * Print out unreclaimble slabs info when unreclaimable slabs amount is greater
175 * than all user memory (LRU pages)
176 */
177static bool is_dump_unreclaim_slabs(void)
178{
179 unsigned long nr_lru;
180
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);
188
189 return (global_node_page_state(NR_SLAB_UNRECLAIMABLE) > nr_lru);
190}
191
192/**
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
196 * @memcg: task's memory controller, if constrained
197 * @nodemask: nodemask passed to page allocator for mempolicy ooms
198 *
199 * The heuristic for determining which task to kill is made to be as simple and
200 * predictable as possible. The goal is to return the highest value for the
201 * task consuming the most memory to avoid subsequent oom failures.
202 */
203unsigned long oom_badness(struct task_struct *p, struct mem_cgroup *memcg,
204 const nodemask_t *nodemask, unsigned long totalpages)
205{
206 long points;
207 long adj;
208
209 if (oom_unkillable_task(p, memcg, nodemask))
210 return 0;
211
212 p = find_lock_task_mm(p);
213 if (!p)
214 return 0;
215
216 /*
217 * Do not even consider tasks which are explicitly marked oom
218 * unkillable or have been already oom reaped or the are in
219 * the middle of vfork
220 */
221 adj = (long)p->signal->oom_score_adj;
222 if (adj == OOM_SCORE_ADJ_MIN ||
223 test_bit(MMF_OOM_SKIP, &p->mm->flags) ||
224 in_vfork(p)) {
225 task_unlock(p);
226 return 0;
227 }
228
229 /*
230 * The baseline for the badness score is the proportion of RAM that each
231 * task's rss, pagetable and swap space use.
232 */
233 points = get_mm_rss(p->mm) + get_mm_counter(p->mm, MM_SWAPENTS) +
234 mm_pgtables_bytes(p->mm) / PAGE_SIZE;
235 task_unlock(p);
236
237 /* Normalize to oom_score_adj units */
238 adj *= totalpages / 1000;
239 points += adj;
240
241 /*
242 * Never return 0 for an eligible task regardless of the root bonus and
243 * oom_score_adj (oom_score_adj can't be OOM_SCORE_ADJ_MIN here).
244 */
245 return points > 0 ? points : 1;
246}
247
248static const char * const oom_constraint_text[] = {
249 [CONSTRAINT_NONE] = "CONSTRAINT_NONE",
250 [CONSTRAINT_CPUSET] = "CONSTRAINT_CPUSET",
251 [CONSTRAINT_MEMORY_POLICY] = "CONSTRAINT_MEMORY_POLICY",
252 [CONSTRAINT_MEMCG] = "CONSTRAINT_MEMCG",
253};
254
255/*
256 * Determine the type of allocation constraint.
257 */
258static enum oom_constraint constrained_alloc(struct oom_control *oc)
259{
260 struct zone *zone;
261 struct zoneref *z;
262 enum zone_type high_zoneidx = gfp_zone(oc->gfp_mask);
263 bool cpuset_limited = false;
264 int nid;
265
266 if (is_memcg_oom(oc)) {
267 oc->totalpages = mem_cgroup_get_max(oc->memcg) ?: 1;
268 return CONSTRAINT_MEMCG;
269 }
270
271 /* Default to all available memory */
272 oc->totalpages = totalram_pages() + total_swap_pages;
273
274 if (!IS_ENABLED(CONFIG_NUMA))
275 return CONSTRAINT_NONE;
276
277 if (!oc->zonelist)
278 return CONSTRAINT_NONE;
279 /*
280 * Reach here only when __GFP_NOFAIL is used. So, we should avoid
281 * to kill current.We have to random task kill in this case.
282 * Hopefully, CONSTRAINT_THISNODE...but no way to handle it, now.
283 */
284 if (oc->gfp_mask & __GFP_THISNODE)
285 return CONSTRAINT_NONE;
286
287 /*
288 * This is not a __GFP_THISNODE allocation, so a truncated nodemask in
289 * the page allocator means a mempolicy is in effect. Cpuset policy
290 * is enforced in get_page_from_freelist().
291 */
292 if (oc->nodemask &&
293 !nodes_subset(node_states[N_MEMORY], *oc->nodemask)) {
294 oc->totalpages = total_swap_pages;
295 for_each_node_mask(nid, *oc->nodemask)
296 oc->totalpages += node_spanned_pages(nid);
297 return CONSTRAINT_MEMORY_POLICY;
298 }
299
300 /* Check this allocation failure is caused by cpuset's wall function */
301 for_each_zone_zonelist_nodemask(zone, z, oc->zonelist,
302 high_zoneidx, oc->nodemask)
303 if (!cpuset_zone_allowed(zone, oc->gfp_mask))
304 cpuset_limited = true;
305
306 if (cpuset_limited) {
307 oc->totalpages = total_swap_pages;
308 for_each_node_mask(nid, cpuset_current_mems_allowed)
309 oc->totalpages += node_spanned_pages(nid);
310 return CONSTRAINT_CPUSET;
311 }
312 return CONSTRAINT_NONE;
313}
314
315static int oom_evaluate_task(struct task_struct *task, void *arg)
316{
317 struct oom_control *oc = arg;
318 unsigned long points;
319
320 if (oom_unkillable_task(task, NULL, oc->nodemask))
321 goto next;
322
323 /*
324 * This task already has access to memory reserves and is being killed.
325 * Don't allow any other task to have access to the reserves unless
326 * the task has MMF_OOM_SKIP because chances that it would release
327 * any memory is quite low.
328 */
329 if (!is_sysrq_oom(oc) && tsk_is_oom_victim(task)) {
330 if (test_bit(MMF_OOM_SKIP, &task->signal->oom_mm->flags))
331 goto next;
332 goto abort;
333 }
334
335 /*
336 * If task is allocating a lot of memory and has been marked to be
337 * killed first if it triggers an oom, then select it.
338 */
339 if (oom_task_origin(task)) {
340 points = ULONG_MAX;
341 goto select;
342 }
343
344 points = oom_badness(task, NULL, oc->nodemask, oc->totalpages);
345 if (!points || points < oc->chosen_points)
346 goto next;
347
348 /* Prefer thread group leaders for display purposes */
349 if (points == oc->chosen_points && thread_group_leader(oc->chosen))
350 goto next;
351select:
352 if (oc->chosen)
353 put_task_struct(oc->chosen);
354 get_task_struct(task);
355 oc->chosen = task;
356 oc->chosen_points = points;
357next:
358 return 0;
359abort:
360 if (oc->chosen)
361 put_task_struct(oc->chosen);
362 oc->chosen = (void *)-1UL;
363 return 1;
364}
365
366/*
367 * Simple selection loop. We choose the process with the highest number of
368 * 'points'. In case scan was aborted, oc->chosen is set to -1.
369 */
370static void select_bad_process(struct oom_control *oc)
371{
372 if (is_memcg_oom(oc))
373 mem_cgroup_scan_tasks(oc->memcg, oom_evaluate_task, oc);
374 else {
375 struct task_struct *p;
376
377 rcu_read_lock();
378 for_each_process(p)
379 if (oom_evaluate_task(p, oc))
380 break;
381 rcu_read_unlock();
382 }
383
384 oc->chosen_points = oc->chosen_points * 1000 / oc->totalpages;
385}
386
387/**
388 * dump_tasks - dump current memory state of all system tasks
389 * @memcg: current's memory controller, if constrained
390 * @nodemask: nodemask passed to page allocator for mempolicy ooms
391 *
392 * Dumps the current memory state of all eligible tasks. Tasks not in the same
393 * memcg, not in the same cpuset, or bound to a disjoint set of mempolicy nodes
394 * are not shown.
395 * State information includes task's pid, uid, tgid, vm size, rss,
396 * pgtables_bytes, swapents, oom_score_adj value, and name.
397 */
398static void dump_tasks(struct mem_cgroup *memcg, const nodemask_t *nodemask)
399{
400 struct task_struct *p;
401 struct task_struct *task;
402
403 pr_info("Tasks state (memory values in pages):\n");
404 pr_info("[ pid ] uid tgid total_vm rss pgtables_bytes swapents oom_score_adj name\n");
405 rcu_read_lock();
406 for_each_process(p) {
407 if (oom_unkillable_task(p, memcg, nodemask))
408 continue;
409
410 task = find_lock_task_mm(p);
411 if (!task) {
412 /*
413 * This is a kthread or all of p's threads have already
414 * detached their mm's. There's no need to report
415 * them; they can't be oom killed anyway.
416 */
417 continue;
418 }
419
420 pr_info("[%7d] %5d %5d %8lu %8lu %8ld %8lu %5hd %s\n",
421 task->pid, from_kuid(&init_user_ns, task_uid(task)),
422 task->tgid, task->mm->total_vm, get_mm_rss(task->mm),
423 mm_pgtables_bytes(task->mm),
424 get_mm_counter(task->mm, MM_SWAPENTS),
425 task->signal->oom_score_adj, task->comm);
426 task_unlock(task);
427 }
428 rcu_read_unlock();
429}
430
431static void dump_oom_summary(struct oom_control *oc, struct task_struct *victim)
432{
433 /* one line summary of the oom killer context. */
434 pr_info("oom-kill:constraint=%s,nodemask=%*pbl",
435 oom_constraint_text[oc->constraint],
436 nodemask_pr_args(oc->nodemask));
437 cpuset_print_current_mems_allowed();
438 mem_cgroup_print_oom_context(oc->memcg, victim);
439 pr_cont(",task=%s,pid=%d,uid=%d\n", victim->comm, victim->pid,
440 from_kuid(&init_user_ns, task_uid(victim)));
441}
442
443static void dump_header(struct oom_control *oc, struct task_struct *p)
444{
445 pr_warn("%s invoked oom-killer: gfp_mask=%#x(%pGg), order=%d, oom_score_adj=%hd\n",
446 current->comm, oc->gfp_mask, &oc->gfp_mask, oc->order,
447 current->signal->oom_score_adj);
448 if (!IS_ENABLED(CONFIG_COMPACTION) && oc->order)
449 pr_warn("COMPACTION is disabled!!!\n");
450
451 dump_stack();
452 if (is_memcg_oom(oc))
453 mem_cgroup_print_oom_meminfo(oc->memcg);
454 else {
455 show_mem(SHOW_MEM_FILTER_NODES, oc->nodemask);
456 if (is_dump_unreclaim_slabs())
457 dump_unreclaimable_slab();
458 }
459 if (sysctl_oom_dump_tasks)
460 dump_tasks(oc->memcg, oc->nodemask);
461 if (p)
462 dump_oom_summary(oc, p);
463}
464
465/*
466 * Number of OOM victims in flight
467 */
468static atomic_t oom_victims = ATOMIC_INIT(0);
469static DECLARE_WAIT_QUEUE_HEAD(oom_victims_wait);
470
471static bool oom_killer_disabled __read_mostly;
472
473#define K(x) ((x) << (PAGE_SHIFT-10))
474
475/*
476 * task->mm can be NULL if the task is the exited group leader. So to
477 * determine whether the task is using a particular mm, we examine all the
478 * task's threads: if one of those is using this mm then this task was also
479 * using it.
480 */
481bool process_shares_mm(struct task_struct *p, struct mm_struct *mm)
482{
483 struct task_struct *t;
484
485 for_each_thread(p, t) {
486 struct mm_struct *t_mm = READ_ONCE(t->mm);
487 if (t_mm)
488 return t_mm == mm;
489 }
490 return false;
491}
492
493#ifdef CONFIG_MMU
494/*
495 * OOM Reaper kernel thread which tries to reap the memory used by the OOM
496 * victim (if that is possible) to help the OOM killer to move on.
497 */
498static struct task_struct *oom_reaper_th;
499static DECLARE_WAIT_QUEUE_HEAD(oom_reaper_wait);
500static struct task_struct *oom_reaper_list;
501static DEFINE_SPINLOCK(oom_reaper_lock);
502
503bool __oom_reap_task_mm(struct mm_struct *mm)
504{
505 struct vm_area_struct *vma;
506 bool ret = true;
507
508 /*
509 * Tell all users of get_user/copy_from_user etc... that the content
510 * is no longer stable. No barriers really needed because unmapping
511 * should imply barriers already and the reader would hit a page fault
512 * if it stumbled over a reaped memory.
513 */
514 set_bit(MMF_UNSTABLE, &mm->flags);
515
516 for (vma = mm->mmap ; vma; vma = vma->vm_next) {
517 if (!can_madv_dontneed_vma(vma))
518 continue;
519
520 /*
521 * Only anonymous pages have a good chance to be dropped
522 * without additional steps which we cannot afford as we
523 * are OOM already.
524 *
525 * We do not even care about fs backed pages because all
526 * which are reclaimable have already been reclaimed and
527 * we do not want to block exit_mmap by keeping mm ref
528 * count elevated without a good reason.
529 */
530 if (vma_is_anonymous(vma) || !(vma->vm_flags & VM_SHARED)) {
531 struct mmu_notifier_range range;
532 struct mmu_gather tlb;
533
534 mmu_notifier_range_init(&range, mm, vma->vm_start,
535 vma->vm_end);
536 tlb_gather_mmu(&tlb, mm, range.start, range.end);
537 if (mmu_notifier_invalidate_range_start_nonblock(&range)) {
538 tlb_finish_mmu(&tlb, range.start, range.end);
539 ret = false;
540 continue;
541 }
542 unmap_page_range(&tlb, vma, range.start, range.end, NULL);
543 mmu_notifier_invalidate_range_end(&range);
544 tlb_finish_mmu(&tlb, range.start, range.end);
545 }
546 }
547
548 return ret;
549}
550
551/*
552 * Reaps the address space of the give task.
553 *
554 * Returns true on success and false if none or part of the address space
555 * has been reclaimed and the caller should retry later.
556 */
557static bool oom_reap_task_mm(struct task_struct *tsk, struct mm_struct *mm)
558{
559 bool ret = true;
560
561 if (!down_read_trylock(&mm->mmap_sem)) {
562 trace_skip_task_reaping(tsk->pid);
563 return false;
564 }
565
566 /*
567 * MMF_OOM_SKIP is set by exit_mmap when the OOM reaper can't
568 * work on the mm anymore. The check for MMF_OOM_SKIP must run
569 * under mmap_sem for reading because it serializes against the
570 * down_write();up_write() cycle in exit_mmap().
571 */
572 if (test_bit(MMF_OOM_SKIP, &mm->flags)) {
573 trace_skip_task_reaping(tsk->pid);
574 goto out_unlock;
575 }
576
577 trace_start_task_reaping(tsk->pid);
578
579 /* failed to reap part of the address space. Try again later */
580 ret = __oom_reap_task_mm(mm);
581 if (!ret)
582 goto out_finish;
583
584 pr_info("oom_reaper: reaped process %d (%s), now anon-rss:%lukB, file-rss:%lukB, shmem-rss:%lukB\n",
585 task_pid_nr(tsk), tsk->comm,
586 K(get_mm_counter(mm, MM_ANONPAGES)),
587 K(get_mm_counter(mm, MM_FILEPAGES)),
588 K(get_mm_counter(mm, MM_SHMEMPAGES)));
589out_finish:
590 trace_finish_task_reaping(tsk->pid);
591out_unlock:
592 up_read(&mm->mmap_sem);
593
594 return ret;
595}
596
597#define MAX_OOM_REAP_RETRIES 10
598static void oom_reap_task(struct task_struct *tsk)
599{
600 int attempts = 0;
601 struct mm_struct *mm = tsk->signal->oom_mm;
602
603 /* Retry the down_read_trylock(mmap_sem) a few times */
604 while (attempts++ < MAX_OOM_REAP_RETRIES && !oom_reap_task_mm(tsk, mm))
605 schedule_timeout_idle(HZ/10);
606
607 if (attempts <= MAX_OOM_REAP_RETRIES ||
608 test_bit(MMF_OOM_SKIP, &mm->flags))
609 goto done;
610
611 pr_info("oom_reaper: unable to reap pid:%d (%s)\n",
612 task_pid_nr(tsk), tsk->comm);
613 debug_show_all_locks();
614
615done:
616 tsk->oom_reaper_list = NULL;
617
618 /*
619 * Hide this mm from OOM killer because it has been either reaped or
620 * somebody can't call up_write(mmap_sem).
621 */
622 set_bit(MMF_OOM_SKIP, &mm->flags);
623
624 /* Drop a reference taken by wake_oom_reaper */
625 put_task_struct(tsk);
626}
627
628static int oom_reaper(void *unused)
629{
630 while (true) {
631 struct task_struct *tsk = NULL;
632
633 wait_event_freezable(oom_reaper_wait, oom_reaper_list != NULL);
634 spin_lock(&oom_reaper_lock);
635 if (oom_reaper_list != NULL) {
636 tsk = oom_reaper_list;
637 oom_reaper_list = tsk->oom_reaper_list;
638 }
639 spin_unlock(&oom_reaper_lock);
640
641 if (tsk)
642 oom_reap_task(tsk);
643 }
644
645 return 0;
646}
647
648static void wake_oom_reaper(struct task_struct *tsk)
649{
650 /* mm is already queued? */
651 if (test_and_set_bit(MMF_OOM_REAP_QUEUED, &tsk->signal->oom_mm->flags))
652 return;
653
654 get_task_struct(tsk);
655
656 spin_lock(&oom_reaper_lock);
657 tsk->oom_reaper_list = oom_reaper_list;
658 oom_reaper_list = tsk;
659 spin_unlock(&oom_reaper_lock);
660 trace_wake_reaper(tsk->pid);
661 wake_up(&oom_reaper_wait);
662}
663
664static int __init oom_init(void)
665{
666 oom_reaper_th = kthread_run(oom_reaper, NULL, "oom_reaper");
667 return 0;
668}
669subsys_initcall(oom_init)
670#else
671static inline void wake_oom_reaper(struct task_struct *tsk)
672{
673}
674#endif /* CONFIG_MMU */
675
676/**
677 * mark_oom_victim - mark the given task as OOM victim
678 * @tsk: task to mark
679 *
680 * Has to be called with oom_lock held and never after
681 * oom has been disabled already.
682 *
683 * tsk->mm has to be non NULL and caller has to guarantee it is stable (either
684 * under task_lock or operate on the current).
685 */
686static void mark_oom_victim(struct task_struct *tsk)
687{
688 struct mm_struct *mm = tsk->mm;
689
690 WARN_ON(oom_killer_disabled);
691 /* OOM killer might race with memcg OOM */
692 if (test_and_set_tsk_thread_flag(tsk, TIF_MEMDIE))
693 return;
694
695 /* oom_mm is bound to the signal struct life time. */
696 if (!cmpxchg(&tsk->signal->oom_mm, NULL, mm)) {
697 mmgrab(tsk->signal->oom_mm);
698 set_bit(MMF_OOM_VICTIM, &mm->flags);
699 }
700
701 /*
702 * Make sure that the task is woken up from uninterruptible sleep
703 * if it is frozen because OOM killer wouldn't be able to free
704 * any memory and livelock. freezing_slow_path will tell the freezer
705 * that TIF_MEMDIE tasks should be ignored.
706 */
707 __thaw_task(tsk);
708 atomic_inc(&oom_victims);
709 trace_mark_victim(tsk->pid);
710}
711
712/**
713 * exit_oom_victim - note the exit of an OOM victim
714 */
715void exit_oom_victim(void)
716{
717 clear_thread_flag(TIF_MEMDIE);
718
719 if (!atomic_dec_return(&oom_victims))
720 wake_up_all(&oom_victims_wait);
721}
722
723/**
724 * oom_killer_enable - enable OOM killer
725 */
726void oom_killer_enable(void)
727{
728 oom_killer_disabled = false;
729 pr_info("OOM killer enabled.\n");
730}
731
732/**
733 * oom_killer_disable - disable OOM killer
734 * @timeout: maximum timeout to wait for oom victims in jiffies
735 *
736 * Forces all page allocations to fail rather than trigger OOM killer.
737 * Will block and wait until all OOM victims are killed or the given
738 * timeout expires.
739 *
740 * The function cannot be called when there are runnable user tasks because
741 * the userspace would see unexpected allocation failures as a result. Any
742 * new usage of this function should be consulted with MM people.
743 *
744 * Returns true if successful and false if the OOM killer cannot be
745 * disabled.
746 */
747bool oom_killer_disable(signed long timeout)
748{
749 signed long ret;
750
751 /*
752 * Make sure to not race with an ongoing OOM killer. Check that the
753 * current is not killed (possibly due to sharing the victim's memory).
754 */
755 if (mutex_lock_killable(&oom_lock))
756 return false;
757 oom_killer_disabled = true;
758 mutex_unlock(&oom_lock);
759
760 ret = wait_event_interruptible_timeout(oom_victims_wait,
761 !atomic_read(&oom_victims), timeout);
762 if (ret <= 0) {
763 oom_killer_enable();
764 return false;
765 }
766 pr_info("OOM killer disabled.\n");
767
768 return true;
769}
770
771static inline bool __task_will_free_mem(struct task_struct *task)
772{
773 struct signal_struct *sig = task->signal;
774
775 /*
776 * A coredumping process may sleep for an extended period in exit_mm(),
777 * so the oom killer cannot assume that the process will promptly exit
778 * and release memory.
779 */
780 if (sig->flags & SIGNAL_GROUP_COREDUMP)
781 return false;
782
783 if (sig->flags & SIGNAL_GROUP_EXIT)
784 return true;
785
786 if (thread_group_empty(task) && (task->flags & PF_EXITING))
787 return true;
788
789 return false;
790}
791
792/*
793 * Checks whether the given task is dying or exiting and likely to
794 * release its address space. This means that all threads and processes
795 * sharing the same mm have to be killed or exiting.
796 * Caller has to make sure that task->mm is stable (hold task_lock or
797 * it operates on the current).
798 */
799static bool task_will_free_mem(struct task_struct *task)
800{
801 struct mm_struct *mm = task->mm;
802 struct task_struct *p;
803 bool ret = true;
804
805 /*
806 * Skip tasks without mm because it might have passed its exit_mm and
807 * exit_oom_victim. oom_reaper could have rescued that but do not rely
808 * on that for now. We can consider find_lock_task_mm in future.
809 */
810 if (!mm)
811 return false;
812
813 if (!__task_will_free_mem(task))
814 return false;
815
816 /*
817 * This task has already been drained by the oom reaper so there are
818 * only small chances it will free some more
819 */
820 if (test_bit(MMF_OOM_SKIP, &mm->flags))
821 return false;
822
823 if (atomic_read(&mm->mm_users) <= 1)
824 return true;
825
826 /*
827 * Make sure that all tasks which share the mm with the given tasks
828 * are dying as well to make sure that a) nobody pins its mm and
829 * b) the task is also reapable by the oom reaper.
830 */
831 rcu_read_lock();
832 for_each_process(p) {
833 if (!process_shares_mm(p, mm))
834 continue;
835 if (same_thread_group(task, p))
836 continue;
837 ret = __task_will_free_mem(p);
838 if (!ret)
839 break;
840 }
841 rcu_read_unlock();
842
843 return ret;
844}
845
846static void __oom_kill_process(struct task_struct *victim, const char *message)
847{
848 struct task_struct *p;
849 struct mm_struct *mm;
850 bool can_oom_reap = true;
851
852 p = find_lock_task_mm(victim);
853 if (!p) {
854 put_task_struct(victim);
855 return;
856 } else if (victim != p) {
857 get_task_struct(p);
858 put_task_struct(victim);
859 victim = p;
860 }
861
862 /* Get a reference to safely compare mm after task_unlock(victim) */
863 mm = victim->mm;
864 mmgrab(mm);
865
866 /* Raise event before sending signal: task reaper must see this */
867 count_vm_event(OOM_KILL);
868 memcg_memory_event_mm(mm, MEMCG_OOM_KILL);
869
870 /*
871 * We should send SIGKILL before granting access to memory reserves
872 * in order to prevent the OOM victim from depleting the memory
873 * reserves from the user space under its control.
874 */
875 do_send_sig_info(SIGKILL, SEND_SIG_PRIV, victim, PIDTYPE_TGID);
876 mark_oom_victim(victim);
877 pr_err("%s: Killed process %d (%s) total-vm:%lukB, anon-rss:%lukB, file-rss:%lukB, shmem-rss:%lukB\n",
878 message, task_pid_nr(victim), victim->comm,
879 K(victim->mm->total_vm),
880 K(get_mm_counter(victim->mm, MM_ANONPAGES)),
881 K(get_mm_counter(victim->mm, MM_FILEPAGES)),
882 K(get_mm_counter(victim->mm, MM_SHMEMPAGES)));
883 task_unlock(victim);
884
885 /*
886 * Kill all user processes sharing victim->mm in other thread groups, if
887 * any. They don't get access to memory reserves, though, to avoid
888 * depletion of all memory. This prevents mm->mmap_sem livelock when an
889 * oom killed thread cannot exit because it requires the semaphore and
890 * its contended by another thread trying to allocate memory itself.
891 * That thread will now get access to memory reserves since it has a
892 * pending fatal signal.
893 */
894 rcu_read_lock();
895 for_each_process(p) {
896 if (!process_shares_mm(p, mm))
897 continue;
898 if (same_thread_group(p, victim))
899 continue;
900 if (is_global_init(p)) {
901 can_oom_reap = false;
902 set_bit(MMF_OOM_SKIP, &mm->flags);
903 pr_info("oom killer %d (%s) has mm pinned by %d (%s)\n",
904 task_pid_nr(victim), victim->comm,
905 task_pid_nr(p), p->comm);
906 continue;
907 }
908 /*
909 * No use_mm() user needs to read from the userspace so we are
910 * ok to reap it.
911 */
912 if (unlikely(p->flags & PF_KTHREAD))
913 continue;
914 do_send_sig_info(SIGKILL, SEND_SIG_PRIV, p, PIDTYPE_TGID);
915 }
916 rcu_read_unlock();
917
918 if (can_oom_reap)
919 wake_oom_reaper(victim);
920
921 mmdrop(mm);
922 put_task_struct(victim);
923}
924#undef K
925
926/*
927 * Kill provided task unless it's secured by setting
928 * oom_score_adj to OOM_SCORE_ADJ_MIN.
929 */
930static int oom_kill_memcg_member(struct task_struct *task, void *message)
931{
932 if (task->signal->oom_score_adj != OOM_SCORE_ADJ_MIN &&
933 !is_global_init(task)) {
934 get_task_struct(task);
935 __oom_kill_process(task, message);
936 }
937 return 0;
938}
939
940static void oom_kill_process(struct oom_control *oc, const char *message)
941{
942 struct task_struct *victim = oc->chosen;
943 struct mem_cgroup *oom_group;
944 static DEFINE_RATELIMIT_STATE(oom_rs, DEFAULT_RATELIMIT_INTERVAL,
945 DEFAULT_RATELIMIT_BURST);
946
947 /*
948 * If the task is already exiting, don't alarm the sysadmin or kill
949 * its children or threads, just give it access to memory reserves
950 * so it can die quickly
951 */
952 task_lock(victim);
953 if (task_will_free_mem(victim)) {
954 mark_oom_victim(victim);
955 wake_oom_reaper(victim);
956 task_unlock(victim);
957 put_task_struct(victim);
958 return;
959 }
960 task_unlock(victim);
961
962 if (__ratelimit(&oom_rs))
963 dump_header(oc, victim);
964
965 /*
966 * Do we need to kill the entire memory cgroup?
967 * Or even one of the ancestor memory cgroups?
968 * Check this out before killing the victim task.
969 */
970 oom_group = mem_cgroup_get_oom_group(victim, oc->memcg);
971
972 __oom_kill_process(victim, message);
973
974 /*
975 * If necessary, kill all tasks in the selected memory cgroup.
976 */
977 if (oom_group) {
978 mem_cgroup_print_oom_group(oom_group);
979 mem_cgroup_scan_tasks(oom_group, oom_kill_memcg_member,
980 (void*)message);
981 mem_cgroup_put(oom_group);
982 }
983}
984
985/*
986 * Determines whether the kernel must panic because of the panic_on_oom sysctl.
987 */
988static void check_panic_on_oom(struct oom_control *oc,
989 enum oom_constraint constraint)
990{
991 if (likely(!sysctl_panic_on_oom))
992 return;
993 if (sysctl_panic_on_oom != 2) {
994 /*
995 * panic_on_oom == 1 only affects CONSTRAINT_NONE, the kernel
996 * does not panic for cpuset, mempolicy, or memcg allocation
997 * failures.
998 */
999 if (constraint != CONSTRAINT_NONE)
1000 return;
1001 }
1002 /* Do not panic for oom kills triggered by sysrq */
1003 if (is_sysrq_oom(oc))
1004 return;
1005 dump_header(oc, NULL);
1006 panic("Out of memory: %s panic_on_oom is enabled\n",
1007 sysctl_panic_on_oom == 2 ? "compulsory" : "system-wide");
1008}
1009
1010static BLOCKING_NOTIFIER_HEAD(oom_notify_list);
1011
1012int register_oom_notifier(struct notifier_block *nb)
1013{
1014 return blocking_notifier_chain_register(&oom_notify_list, nb);
1015}
1016EXPORT_SYMBOL_GPL(register_oom_notifier);
1017
1018int unregister_oom_notifier(struct notifier_block *nb)
1019{
1020 return blocking_notifier_chain_unregister(&oom_notify_list, nb);
1021}
1022EXPORT_SYMBOL_GPL(unregister_oom_notifier);
1023
1024/**
1025 * out_of_memory - kill the "best" process when we run out of memory
1026 * @oc: pointer to struct oom_control
1027 *
1028 * If we run out of memory, we have the choice between either
1029 * killing a random task (bad), letting the system crash (worse)
1030 * OR try to be smart about which process to kill. Note that we
1031 * don't have to be perfect here, we just have to be good.
1032 */
1033bool out_of_memory(struct oom_control *oc)
1034{
1035 unsigned long freed = 0;
1036 enum oom_constraint constraint = CONSTRAINT_NONE;
1037
1038 if (oom_killer_disabled)
1039 return false;
1040
1041 if (!is_memcg_oom(oc)) {
1042 blocking_notifier_call_chain(&oom_notify_list, 0, &freed);
1043 if (freed > 0)
1044 /* Got some memory back in the last second. */
1045 return true;
1046 }
1047
1048 /*
1049 * If current has a pending SIGKILL or is exiting, then automatically
1050 * select it. The goal is to allow it to allocate so that it may
1051 * quickly exit and free its memory.
1052 */
1053 if (task_will_free_mem(current)) {
1054 mark_oom_victim(current);
1055 wake_oom_reaper(current);
1056 return true;
1057 }
1058
1059 /*
1060 * The OOM killer does not compensate for IO-less reclaim.
1061 * pagefault_out_of_memory lost its gfp context so we have to
1062 * make sure exclude 0 mask - all other users should have at least
1063 * ___GFP_DIRECT_RECLAIM to get here.
1064 */
1065 if (oc->gfp_mask && !(oc->gfp_mask & __GFP_FS))
1066 return true;
1067
1068 /*
1069 * Check if there were limitations on the allocation (only relevant for
1070 * NUMA and memcg) that may require different handling.
1071 */
1072 constraint = constrained_alloc(oc);
1073 if (constraint != CONSTRAINT_MEMORY_POLICY)
1074 oc->nodemask = NULL;
1075 check_panic_on_oom(oc, constraint);
1076
1077 if (!is_memcg_oom(oc) && sysctl_oom_kill_allocating_task &&
1078 current->mm && !oom_unkillable_task(current, NULL, oc->nodemask) &&
1079 current->signal->oom_score_adj != OOM_SCORE_ADJ_MIN) {
1080 get_task_struct(current);
1081 oc->chosen = current;
1082 oom_kill_process(oc, "Out of memory (oom_kill_allocating_task)");
1083 return true;
1084 }
1085
1086 select_bad_process(oc);
1087 /* Found nothing?!?! */
1088 if (!oc->chosen) {
1089 dump_header(oc, NULL);
1090 pr_warn("Out of memory and no killable processes...\n");
1091 /*
1092 * If we got here due to an actual allocation at the
1093 * system level, we cannot survive this and will enter
1094 * an endless loop in the allocator. Bail out now.
1095 */
1096 if (!is_sysrq_oom(oc) && !is_memcg_oom(oc))
1097 panic("System is deadlocked on memory\n");
1098 }
1099 if (oc->chosen && oc->chosen != (void *)-1UL)
1100 oom_kill_process(oc, !is_memcg_oom(oc) ? "Out of memory" :
1101 "Memory cgroup out of memory");
1102 return !!oc->chosen;
1103}
1104
1105/*
1106 * The pagefault handler calls here because it is out of memory, so kill a
1107 * memory-hogging task. If oom_lock is held by somebody else, a parallel oom
1108 * killing is already in progress so do nothing.
1109 */
1110void pagefault_out_of_memory(void)
1111{
1112 struct oom_control oc = {
1113 .zonelist = NULL,
1114 .nodemask = NULL,
1115 .memcg = NULL,
1116 .gfp_mask = 0,
1117 .order = 0,
1118 };
1119
1120 if (mem_cgroup_oom_synchronize(true))
1121 return;
1122
1123 if (!mutex_trylock(&oom_lock))
1124 return;
1125 out_of_memory(&oc);
1126 mutex_unlock(&oom_lock);
1127}
1128