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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/coredump.h>
28#include <linux/sched/task.h>
29#include <linux/swap.h>
30#include <linux/timex.h>
31#include <linux/jiffies.h>
32#include <linux/cpuset.h>
33#include <linux/export.h>
34#include <linux/notifier.h>
35#include <linux/memcontrol.h>
36#include <linux/mempolicy.h>
37#include <linux/security.h>
38#include <linux/ptrace.h>
39#include <linux/freezer.h>
40#include <linux/ftrace.h>
41#include <linux/ratelimit.h>
42#include <linux/kthread.h>
43#include <linux/init.h>
44#include <linux/mmu_notifier.h>
45
46#include <asm/tlb.h>
47#include "internal.h"
48#include "slab.h"
49
50#define CREATE_TRACE_POINTS
51#include <trace/events/oom.h>
52
53int sysctl_panic_on_oom;
54int sysctl_oom_kill_allocating_task;
55int sysctl_oom_dump_tasks = 1;
56
57/*
58 * Serializes oom killer invocations (out_of_memory()) from all contexts to
59 * prevent from over eager oom killing (e.g. when the oom killer is invoked
60 * from different domains).
61 *
62 * oom_killer_disable() relies on this lock to stabilize oom_killer_disabled
63 * and mark_oom_victim
64 */
65DEFINE_MUTEX(oom_lock);
66
67static inline bool is_memcg_oom(struct oom_control *oc)
68{
69 return oc->memcg != NULL;
70}
71
72#ifdef CONFIG_NUMA
73/**
74 * oom_cpuset_eligible() - check task eligiblity for kill
75 * @start: task struct of which task to consider
76 * @oc: pointer to struct oom_control
77 *
78 * Task eligibility is determined by whether or not a candidate task, @tsk,
79 * shares the same mempolicy nodes as current if it is bound by such a policy
80 * and whether or not it has the same set of allowed cpuset nodes.
81 *
82 * This function is assuming oom-killer context and 'current' has triggered
83 * the oom-killer.
84 */
85static bool oom_cpuset_eligible(struct task_struct *start,
86 struct oom_control *oc)
87{
88 struct task_struct *tsk;
89 bool ret = false;
90 const nodemask_t *mask = oc->nodemask;
91
92 if (is_memcg_oom(oc))
93 return true;
94
95 rcu_read_lock();
96 for_each_thread(start, tsk) {
97 if (mask) {
98 /*
99 * If this is a mempolicy constrained oom, tsk's
100 * cpuset is irrelevant. Only return true if its
101 * mempolicy intersects current, otherwise it may be
102 * needlessly killed.
103 */
104 ret = mempolicy_nodemask_intersects(tsk, mask);
105 } else {
106 /*
107 * This is not a mempolicy constrained oom, so only
108 * check the mems of tsk's cpuset.
109 */
110 ret = cpuset_mems_allowed_intersects(current, tsk);
111 }
112 if (ret)
113 break;
114 }
115 rcu_read_unlock();
116
117 return ret;
118}
119#else
120static bool oom_cpuset_eligible(struct task_struct *tsk, struct oom_control *oc)
121{
122 return true;
123}
124#endif /* CONFIG_NUMA */
125
126/*
127 * The process p may have detached its own ->mm while exiting or through
128 * use_mm(), but one or more of its subthreads may still have a valid
129 * pointer. Return p, or any of its subthreads with a valid ->mm, with
130 * task_lock() held.
131 */
132struct task_struct *find_lock_task_mm(struct task_struct *p)
133{
134 struct task_struct *t;
135
136 rcu_read_lock();
137
138 for_each_thread(p, t) {
139 task_lock(t);
140 if (likely(t->mm))
141 goto found;
142 task_unlock(t);
143 }
144 t = NULL;
145found:
146 rcu_read_unlock();
147
148 return t;
149}
150
151/*
152 * order == -1 means the oom kill is required by sysrq, otherwise only
153 * for display purposes.
154 */
155static inline bool is_sysrq_oom(struct oom_control *oc)
156{
157 return oc->order == -1;
158}
159
160/* return true if the task is not adequate as candidate victim task. */
161static bool oom_unkillable_task(struct task_struct *p)
162{
163 if (is_global_init(p))
164 return true;
165 if (p->flags & PF_KTHREAD)
166 return true;
167 return false;
168}
169
170/*
171 * Print out unreclaimble slabs info when unreclaimable slabs amount is greater
172 * than all user memory (LRU pages)
173 */
174static bool is_dump_unreclaim_slabs(void)
175{
176 unsigned long nr_lru;
177
178 nr_lru = global_node_page_state(NR_ACTIVE_ANON) +
179 global_node_page_state(NR_INACTIVE_ANON) +
180 global_node_page_state(NR_ACTIVE_FILE) +
181 global_node_page_state(NR_INACTIVE_FILE) +
182 global_node_page_state(NR_ISOLATED_ANON) +
183 global_node_page_state(NR_ISOLATED_FILE) +
184 global_node_page_state(NR_UNEVICTABLE);
185
186 return (global_node_page_state(NR_SLAB_UNRECLAIMABLE) > nr_lru);
187}
188
189/**
190 * oom_badness - heuristic function to determine which candidate task to kill
191 * @p: task struct of which task we should calculate
192 * @totalpages: total present RAM allowed for page allocation
193 *
194 * The heuristic for determining which task to kill is made to be as simple and
195 * predictable as possible. The goal is to return the highest value for the
196 * task consuming the most memory to avoid subsequent oom failures.
197 */
198unsigned long oom_badness(struct task_struct *p, unsigned long totalpages)
199{
200 long points;
201 long adj;
202
203 if (oom_unkillable_task(p))
204 return 0;
205
206 p = find_lock_task_mm(p);
207 if (!p)
208 return 0;
209
210 /*
211 * Do not even consider tasks which are explicitly marked oom
212 * unkillable or have been already oom reaped or the are in
213 * the middle of vfork
214 */
215 adj = (long)p->signal->oom_score_adj;
216 if (adj == OOM_SCORE_ADJ_MIN ||
217 test_bit(MMF_OOM_SKIP, &p->mm->flags) ||
218 in_vfork(p)) {
219 task_unlock(p);
220 return 0;
221 }
222
223 /*
224 * The baseline for the badness score is the proportion of RAM that each
225 * task's rss, pagetable and swap space use.
226 */
227 points = get_mm_rss(p->mm) + get_mm_counter(p->mm, MM_SWAPENTS) +
228 mm_pgtables_bytes(p->mm) / PAGE_SIZE;
229 task_unlock(p);
230
231 /* Normalize to oom_score_adj units */
232 adj *= totalpages / 1000;
233 points += adj;
234
235 /*
236 * Never return 0 for an eligible task regardless of the root bonus and
237 * oom_score_adj (oom_score_adj can't be OOM_SCORE_ADJ_MIN here).
238 */
239 return points > 0 ? points : 1;
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 high_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 high_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 unsigned 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 = ULONG_MAX;
339 goto select;
340 }
341
342 points = oom_badness(task, oc->totalpages);
343 if (!points || 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 if (is_memcg_oom(oc))
368 mem_cgroup_scan_tasks(oc->memcg, oom_evaluate_task, oc);
369 else {
370 struct task_struct *p;
371
372 rcu_read_lock();
373 for_each_process(p)
374 if (oom_evaluate_task(p, oc))
375 break;
376 rcu_read_unlock();
377 }
378}
379
380static int dump_task(struct task_struct *p, void *arg)
381{
382 struct oom_control *oc = arg;
383 struct task_struct *task;
384
385 if (oom_unkillable_task(p))
386 return 0;
387
388 /* p may not have freeable memory in nodemask */
389 if (!is_memcg_oom(oc) && !oom_cpuset_eligible(p, oc))
390 return 0;
391
392 task = find_lock_task_mm(p);
393 if (!task) {
394 /*
395 * This is a kthread or all of p's threads have already
396 * detached their mm's. There's no need to report
397 * them; they can't be oom killed anyway.
398 */
399 return 0;
400 }
401
402 pr_info("[%7d] %5d %5d %8lu %8lu %8ld %8lu %5hd %s\n",
403 task->pid, from_kuid(&init_user_ns, task_uid(task)),
404 task->tgid, task->mm->total_vm, get_mm_rss(task->mm),
405 mm_pgtables_bytes(task->mm),
406 get_mm_counter(task->mm, MM_SWAPENTS),
407 task->signal->oom_score_adj, task->comm);
408 task_unlock(task);
409
410 return 0;
411}
412
413/**
414 * dump_tasks - dump current memory state of all system tasks
415 * @oc: pointer to struct oom_control
416 *
417 * Dumps the current memory state of all eligible tasks. Tasks not in the same
418 * memcg, not in the same cpuset, or bound to a disjoint set of mempolicy nodes
419 * are not shown.
420 * State information includes task's pid, uid, tgid, vm size, rss,
421 * pgtables_bytes, swapents, oom_score_adj value, and name.
422 */
423static void dump_tasks(struct oom_control *oc)
424{
425 pr_info("Tasks state (memory values in pages):\n");
426 pr_info("[ pid ] uid tgid total_vm rss pgtables_bytes swapents oom_score_adj name\n");
427
428 if (is_memcg_oom(oc))
429 mem_cgroup_scan_tasks(oc->memcg, dump_task, oc);
430 else {
431 struct task_struct *p;
432
433 rcu_read_lock();
434 for_each_process(p)
435 dump_task(p, oc);
436 rcu_read_unlock();
437 }
438}
439
440static void dump_oom_summary(struct oom_control *oc, struct task_struct *victim)
441{
442 /* one line summary of the oom killer context. */
443 pr_info("oom-kill:constraint=%s,nodemask=%*pbl",
444 oom_constraint_text[oc->constraint],
445 nodemask_pr_args(oc->nodemask));
446 cpuset_print_current_mems_allowed();
447 mem_cgroup_print_oom_context(oc->memcg, victim);
448 pr_cont(",task=%s,pid=%d,uid=%d\n", victim->comm, victim->pid,
449 from_kuid(&init_user_ns, task_uid(victim)));
450}
451
452static void dump_header(struct oom_control *oc, struct task_struct *p)
453{
454 pr_warn("%s invoked oom-killer: gfp_mask=%#x(%pGg), order=%d, oom_score_adj=%hd\n",
455 current->comm, oc->gfp_mask, &oc->gfp_mask, oc->order,
456 current->signal->oom_score_adj);
457 if (!IS_ENABLED(CONFIG_COMPACTION) && oc->order)
458 pr_warn("COMPACTION is disabled!!!\n");
459
460 dump_stack();
461 if (is_memcg_oom(oc))
462 mem_cgroup_print_oom_meminfo(oc->memcg);
463 else {
464 show_mem(SHOW_MEM_FILTER_NODES, oc->nodemask);
465 if (is_dump_unreclaim_slabs())
466 dump_unreclaimable_slab();
467 }
468 if (sysctl_oom_dump_tasks)
469 dump_tasks(oc);
470 if (p)
471 dump_oom_summary(oc, p);
472}
473
474/*
475 * Number of OOM victims in flight
476 */
477static atomic_t oom_victims = ATOMIC_INIT(0);
478static DECLARE_WAIT_QUEUE_HEAD(oom_victims_wait);
479
480static bool oom_killer_disabled __read_mostly;
481
482#define K(x) ((x) << (PAGE_SHIFT-10))
483
484/*
485 * task->mm can be NULL if the task is the exited group leader. So to
486 * determine whether the task is using a particular mm, we examine all the
487 * task's threads: if one of those is using this mm then this task was also
488 * using it.
489 */
490bool process_shares_mm(struct task_struct *p, struct mm_struct *mm)
491{
492 struct task_struct *t;
493
494 for_each_thread(p, t) {
495 struct mm_struct *t_mm = READ_ONCE(t->mm);
496 if (t_mm)
497 return t_mm == mm;
498 }
499 return false;
500}
501
502#ifdef CONFIG_MMU
503/*
504 * OOM Reaper kernel thread which tries to reap the memory used by the OOM
505 * victim (if that is possible) to help the OOM killer to move on.
506 */
507static struct task_struct *oom_reaper_th;
508static DECLARE_WAIT_QUEUE_HEAD(oom_reaper_wait);
509static struct task_struct *oom_reaper_list;
510static DEFINE_SPINLOCK(oom_reaper_lock);
511
512bool __oom_reap_task_mm(struct mm_struct *mm)
513{
514 struct vm_area_struct *vma;
515 bool ret = true;
516
517 /*
518 * Tell all users of get_user/copy_from_user etc... that the content
519 * is no longer stable. No barriers really needed because unmapping
520 * should imply barriers already and the reader would hit a page fault
521 * if it stumbled over a reaped memory.
522 */
523 set_bit(MMF_UNSTABLE, &mm->flags);
524
525 for (vma = mm->mmap ; vma; vma = vma->vm_next) {
526 if (!can_madv_lru_vma(vma))
527 continue;
528
529 /*
530 * Only anonymous pages have a good chance to be dropped
531 * without additional steps which we cannot afford as we
532 * are OOM already.
533 *
534 * We do not even care about fs backed pages because all
535 * which are reclaimable have already been reclaimed and
536 * we do not want to block exit_mmap by keeping mm ref
537 * count elevated without a good reason.
538 */
539 if (vma_is_anonymous(vma) || !(vma->vm_flags & VM_SHARED)) {
540 struct mmu_notifier_range range;
541 struct mmu_gather tlb;
542
543 mmu_notifier_range_init(&range, MMU_NOTIFY_UNMAP, 0,
544 vma, mm, vma->vm_start,
545 vma->vm_end);
546 tlb_gather_mmu(&tlb, mm, range.start, range.end);
547 if (mmu_notifier_invalidate_range_start_nonblock(&range)) {
548 tlb_finish_mmu(&tlb, range.start, range.end);
549 ret = false;
550 continue;
551 }
552 unmap_page_range(&tlb, vma, range.start, range.end, NULL);
553 mmu_notifier_invalidate_range_end(&range);
554 tlb_finish_mmu(&tlb, range.start, range.end);
555 }
556 }
557
558 return ret;
559}
560
561/*
562 * Reaps the address space of the give task.
563 *
564 * Returns true on success and false if none or part of the address space
565 * has been reclaimed and the caller should retry later.
566 */
567static bool oom_reap_task_mm(struct task_struct *tsk, struct mm_struct *mm)
568{
569 bool ret = true;
570
571 if (!down_read_trylock(&mm->mmap_sem)) {
572 trace_skip_task_reaping(tsk->pid);
573 return false;
574 }
575
576 /*
577 * MMF_OOM_SKIP is set by exit_mmap when the OOM reaper can't
578 * work on the mm anymore. The check for MMF_OOM_SKIP must run
579 * under mmap_sem for reading because it serializes against the
580 * down_write();up_write() cycle in exit_mmap().
581 */
582 if (test_bit(MMF_OOM_SKIP, &mm->flags)) {
583 trace_skip_task_reaping(tsk->pid);
584 goto out_unlock;
585 }
586
587 trace_start_task_reaping(tsk->pid);
588
589 /* failed to reap part of the address space. Try again later */
590 ret = __oom_reap_task_mm(mm);
591 if (!ret)
592 goto out_finish;
593
594 pr_info("oom_reaper: reaped process %d (%s), now anon-rss:%lukB, file-rss:%lukB, shmem-rss:%lukB\n",
595 task_pid_nr(tsk), tsk->comm,
596 K(get_mm_counter(mm, MM_ANONPAGES)),
597 K(get_mm_counter(mm, MM_FILEPAGES)),
598 K(get_mm_counter(mm, MM_SHMEMPAGES)));
599out_finish:
600 trace_finish_task_reaping(tsk->pid);
601out_unlock:
602 up_read(&mm->mmap_sem);
603
604 return ret;
605}
606
607#define MAX_OOM_REAP_RETRIES 10
608static void oom_reap_task(struct task_struct *tsk)
609{
610 int attempts = 0;
611 struct mm_struct *mm = tsk->signal->oom_mm;
612
613 /* Retry the down_read_trylock(mmap_sem) a few times */
614 while (attempts++ < MAX_OOM_REAP_RETRIES && !oom_reap_task_mm(tsk, mm))
615 schedule_timeout_idle(HZ/10);
616
617 if (attempts <= MAX_OOM_REAP_RETRIES ||
618 test_bit(MMF_OOM_SKIP, &mm->flags))
619 goto done;
620
621 pr_info("oom_reaper: unable to reap pid:%d (%s)\n",
622 task_pid_nr(tsk), tsk->comm);
623 debug_show_all_locks();
624
625done:
626 tsk->oom_reaper_list = NULL;
627
628 /*
629 * Hide this mm from OOM killer because it has been either reaped or
630 * somebody can't call up_write(mmap_sem).
631 */
632 set_bit(MMF_OOM_SKIP, &mm->flags);
633
634 /* Drop a reference taken by wake_oom_reaper */
635 put_task_struct(tsk);
636}
637
638static int oom_reaper(void *unused)
639{
640 while (true) {
641 struct task_struct *tsk = NULL;
642
643 wait_event_freezable(oom_reaper_wait, oom_reaper_list != NULL);
644 spin_lock(&oom_reaper_lock);
645 if (oom_reaper_list != NULL) {
646 tsk = oom_reaper_list;
647 oom_reaper_list = tsk->oom_reaper_list;
648 }
649 spin_unlock(&oom_reaper_lock);
650
651 if (tsk)
652 oom_reap_task(tsk);
653 }
654
655 return 0;
656}
657
658static void wake_oom_reaper(struct task_struct *tsk)
659{
660 /* mm is already queued? */
661 if (test_and_set_bit(MMF_OOM_REAP_QUEUED, &tsk->signal->oom_mm->flags))
662 return;
663
664 get_task_struct(tsk);
665
666 spin_lock(&oom_reaper_lock);
667 tsk->oom_reaper_list = oom_reaper_list;
668 oom_reaper_list = tsk;
669 spin_unlock(&oom_reaper_lock);
670 trace_wake_reaper(tsk->pid);
671 wake_up(&oom_reaper_wait);
672}
673
674static int __init oom_init(void)
675{
676 oom_reaper_th = kthread_run(oom_reaper, NULL, "oom_reaper");
677 return 0;
678}
679subsys_initcall(oom_init)
680#else
681static inline void wake_oom_reaper(struct task_struct *tsk)
682{
683}
684#endif /* CONFIG_MMU */
685
686/**
687 * mark_oom_victim - mark the given task as OOM victim
688 * @tsk: task to mark
689 *
690 * Has to be called with oom_lock held and never after
691 * oom has been disabled already.
692 *
693 * tsk->mm has to be non NULL and caller has to guarantee it is stable (either
694 * under task_lock or operate on the current).
695 */
696static void mark_oom_victim(struct task_struct *tsk)
697{
698 struct mm_struct *mm = tsk->mm;
699
700 WARN_ON(oom_killer_disabled);
701 /* OOM killer might race with memcg OOM */
702 if (test_and_set_tsk_thread_flag(tsk, TIF_MEMDIE))
703 return;
704
705 /* oom_mm is bound to the signal struct life time. */
706 if (!cmpxchg(&tsk->signal->oom_mm, NULL, mm)) {
707 mmgrab(tsk->signal->oom_mm);
708 set_bit(MMF_OOM_VICTIM, &mm->flags);
709 }
710
711 /*
712 * Make sure that the task is woken up from uninterruptible sleep
713 * if it is frozen because OOM killer wouldn't be able to free
714 * any memory and livelock. freezing_slow_path will tell the freezer
715 * that TIF_MEMDIE tasks should be ignored.
716 */
717 __thaw_task(tsk);
718 atomic_inc(&oom_victims);
719 trace_mark_victim(tsk->pid);
720}
721
722/**
723 * exit_oom_victim - note the exit of an OOM victim
724 */
725void exit_oom_victim(void)
726{
727 clear_thread_flag(TIF_MEMDIE);
728
729 if (!atomic_dec_return(&oom_victims))
730 wake_up_all(&oom_victims_wait);
731}
732
733/**
734 * oom_killer_enable - enable OOM killer
735 */
736void oom_killer_enable(void)
737{
738 oom_killer_disabled = false;
739 pr_info("OOM killer enabled.\n");
740}
741
742/**
743 * oom_killer_disable - disable OOM killer
744 * @timeout: maximum timeout to wait for oom victims in jiffies
745 *
746 * Forces all page allocations to fail rather than trigger OOM killer.
747 * Will block and wait until all OOM victims are killed or the given
748 * timeout expires.
749 *
750 * The function cannot be called when there are runnable user tasks because
751 * the userspace would see unexpected allocation failures as a result. Any
752 * new usage of this function should be consulted with MM people.
753 *
754 * Returns true if successful and false if the OOM killer cannot be
755 * disabled.
756 */
757bool oom_killer_disable(signed long timeout)
758{
759 signed long ret;
760
761 /*
762 * Make sure to not race with an ongoing OOM killer. Check that the
763 * current is not killed (possibly due to sharing the victim's memory).
764 */
765 if (mutex_lock_killable(&oom_lock))
766 return false;
767 oom_killer_disabled = true;
768 mutex_unlock(&oom_lock);
769
770 ret = wait_event_interruptible_timeout(oom_victims_wait,
771 !atomic_read(&oom_victims), timeout);
772 if (ret <= 0) {
773 oom_killer_enable();
774 return false;
775 }
776 pr_info("OOM killer disabled.\n");
777
778 return true;
779}
780
781static inline bool __task_will_free_mem(struct task_struct *task)
782{
783 struct signal_struct *sig = task->signal;
784
785 /*
786 * A coredumping process may sleep for an extended period in exit_mm(),
787 * so the oom killer cannot assume that the process will promptly exit
788 * and release memory.
789 */
790 if (sig->flags & SIGNAL_GROUP_COREDUMP)
791 return false;
792
793 if (sig->flags & SIGNAL_GROUP_EXIT)
794 return true;
795
796 if (thread_group_empty(task) && (task->flags & PF_EXITING))
797 return true;
798
799 return false;
800}
801
802/*
803 * Checks whether the given task is dying or exiting and likely to
804 * release its address space. This means that all threads and processes
805 * sharing the same mm have to be killed or exiting.
806 * Caller has to make sure that task->mm is stable (hold task_lock or
807 * it operates on the current).
808 */
809static bool task_will_free_mem(struct task_struct *task)
810{
811 struct mm_struct *mm = task->mm;
812 struct task_struct *p;
813 bool ret = true;
814
815 /*
816 * Skip tasks without mm because it might have passed its exit_mm and
817 * exit_oom_victim. oom_reaper could have rescued that but do not rely
818 * on that for now. We can consider find_lock_task_mm in future.
819 */
820 if (!mm)
821 return false;
822
823 if (!__task_will_free_mem(task))
824 return false;
825
826 /*
827 * This task has already been drained by the oom reaper so there are
828 * only small chances it will free some more
829 */
830 if (test_bit(MMF_OOM_SKIP, &mm->flags))
831 return false;
832
833 if (atomic_read(&mm->mm_users) <= 1)
834 return true;
835
836 /*
837 * Make sure that all tasks which share the mm with the given tasks
838 * are dying as well to make sure that a) nobody pins its mm and
839 * b) the task is also reapable by the oom reaper.
840 */
841 rcu_read_lock();
842 for_each_process(p) {
843 if (!process_shares_mm(p, mm))
844 continue;
845 if (same_thread_group(task, p))
846 continue;
847 ret = __task_will_free_mem(p);
848 if (!ret)
849 break;
850 }
851 rcu_read_unlock();
852
853 return ret;
854}
855
856static void __oom_kill_process(struct task_struct *victim, const char *message)
857{
858 struct task_struct *p;
859 struct mm_struct *mm;
860 bool can_oom_reap = true;
861
862 p = find_lock_task_mm(victim);
863 if (!p) {
864 put_task_struct(victim);
865 return;
866 } else if (victim != p) {
867 get_task_struct(p);
868 put_task_struct(victim);
869 victim = p;
870 }
871
872 /* Get a reference to safely compare mm after task_unlock(victim) */
873 mm = victim->mm;
874 mmgrab(mm);
875
876 /* Raise event before sending signal: task reaper must see this */
877 count_vm_event(OOM_KILL);
878 memcg_memory_event_mm(mm, MEMCG_OOM_KILL);
879
880 /*
881 * We should send SIGKILL before granting access to memory reserves
882 * in order to prevent the OOM victim from depleting the memory
883 * reserves from the user space under its control.
884 */
885 do_send_sig_info(SIGKILL, SEND_SIG_PRIV, victim, PIDTYPE_TGID);
886 mark_oom_victim(victim);
887 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",
888 message, task_pid_nr(victim), victim->comm, K(mm->total_vm),
889 K(get_mm_counter(mm, MM_ANONPAGES)),
890 K(get_mm_counter(mm, MM_FILEPAGES)),
891 K(get_mm_counter(mm, MM_SHMEMPAGES)),
892 from_kuid(&init_user_ns, task_uid(victim)),
893 mm_pgtables_bytes(mm), victim->signal->oom_score_adj);
894 task_unlock(victim);
895
896 /*
897 * Kill all user processes sharing victim->mm in other thread groups, if
898 * any. They don't get access to memory reserves, though, to avoid
899 * depletion of all memory. This prevents mm->mmap_sem livelock when an
900 * oom killed thread cannot exit because it requires the semaphore and
901 * its contended by another thread trying to allocate memory itself.
902 * That thread will now get access to memory reserves since it has a
903 * pending fatal signal.
904 */
905 rcu_read_lock();
906 for_each_process(p) {
907 if (!process_shares_mm(p, mm))
908 continue;
909 if (same_thread_group(p, victim))
910 continue;
911 if (is_global_init(p)) {
912 can_oom_reap = false;
913 set_bit(MMF_OOM_SKIP, &mm->flags);
914 pr_info("oom killer %d (%s) has mm pinned by %d (%s)\n",
915 task_pid_nr(victim), victim->comm,
916 task_pid_nr(p), p->comm);
917 continue;
918 }
919 /*
920 * No use_mm() user needs to read from the userspace so we are
921 * ok to reap it.
922 */
923 if (unlikely(p->flags & PF_KTHREAD))
924 continue;
925 do_send_sig_info(SIGKILL, SEND_SIG_PRIV, p, PIDTYPE_TGID);
926 }
927 rcu_read_unlock();
928
929 if (can_oom_reap)
930 wake_oom_reaper(victim);
931
932 mmdrop(mm);
933 put_task_struct(victim);
934}
935#undef K
936
937/*
938 * Kill provided task unless it's secured by setting
939 * oom_score_adj to OOM_SCORE_ADJ_MIN.
940 */
941static int oom_kill_memcg_member(struct task_struct *task, void *message)
942{
943 if (task->signal->oom_score_adj != OOM_SCORE_ADJ_MIN &&
944 !is_global_init(task)) {
945 get_task_struct(task);
946 __oom_kill_process(task, message);
947 }
948 return 0;
949}
950
951static void oom_kill_process(struct oom_control *oc, const char *message)
952{
953 struct task_struct *victim = oc->chosen;
954 struct mem_cgroup *oom_group;
955 static DEFINE_RATELIMIT_STATE(oom_rs, DEFAULT_RATELIMIT_INTERVAL,
956 DEFAULT_RATELIMIT_BURST);
957
958 /*
959 * If the task is already exiting, don't alarm the sysadmin or kill
960 * its children or threads, just give it access to memory reserves
961 * so it can die quickly
962 */
963 task_lock(victim);
964 if (task_will_free_mem(victim)) {
965 mark_oom_victim(victim);
966 wake_oom_reaper(victim);
967 task_unlock(victim);
968 put_task_struct(victim);
969 return;
970 }
971 task_unlock(victim);
972
973 if (__ratelimit(&oom_rs))
974 dump_header(oc, victim);
975
976 /*
977 * Do we need to kill the entire memory cgroup?
978 * Or even one of the ancestor memory cgroups?
979 * Check this out before killing the victim task.
980 */
981 oom_group = mem_cgroup_get_oom_group(victim, oc->memcg);
982
983 __oom_kill_process(victim, message);
984
985 /*
986 * If necessary, kill all tasks in the selected memory cgroup.
987 */
988 if (oom_group) {
989 mem_cgroup_print_oom_group(oom_group);
990 mem_cgroup_scan_tasks(oom_group, oom_kill_memcg_member,
991 (void*)message);
992 mem_cgroup_put(oom_group);
993 }
994}
995
996/*
997 * Determines whether the kernel must panic because of the panic_on_oom sysctl.
998 */
999static void check_panic_on_oom(struct oom_control *oc)
1000{
1001 if (likely(!sysctl_panic_on_oom))
1002 return;
1003 if (sysctl_panic_on_oom != 2) {
1004 /*
1005 * panic_on_oom == 1 only affects CONSTRAINT_NONE, the kernel
1006 * does not panic for cpuset, mempolicy, or memcg allocation
1007 * failures.
1008 */
1009 if (oc->constraint != CONSTRAINT_NONE)
1010 return;
1011 }
1012 /* Do not panic for oom kills triggered by sysrq */
1013 if (is_sysrq_oom(oc))
1014 return;
1015 dump_header(oc, NULL);
1016 panic("Out of memory: %s panic_on_oom is enabled\n",
1017 sysctl_panic_on_oom == 2 ? "compulsory" : "system-wide");
1018}
1019
1020static BLOCKING_NOTIFIER_HEAD(oom_notify_list);
1021
1022int register_oom_notifier(struct notifier_block *nb)
1023{
1024 return blocking_notifier_chain_register(&oom_notify_list, nb);
1025}
1026EXPORT_SYMBOL_GPL(register_oom_notifier);
1027
1028int unregister_oom_notifier(struct notifier_block *nb)
1029{
1030 return blocking_notifier_chain_unregister(&oom_notify_list, nb);
1031}
1032EXPORT_SYMBOL_GPL(unregister_oom_notifier);
1033
1034/**
1035 * out_of_memory - kill the "best" process when we run out of memory
1036 * @oc: pointer to struct oom_control
1037 *
1038 * If we run out of memory, we have the choice between either
1039 * killing a random task (bad), letting the system crash (worse)
1040 * OR try to be smart about which process to kill. Note that we
1041 * don't have to be perfect here, we just have to be good.
1042 */
1043bool out_of_memory(struct oom_control *oc)
1044{
1045 unsigned long freed = 0;
1046
1047 if (oom_killer_disabled)
1048 return false;
1049
1050 if (!is_memcg_oom(oc)) {
1051 blocking_notifier_call_chain(&oom_notify_list, 0, &freed);
1052 if (freed > 0)
1053 /* Got some memory back in the last second. */
1054 return true;
1055 }
1056
1057 /*
1058 * If current has a pending SIGKILL or is exiting, then automatically
1059 * select it. The goal is to allow it to allocate so that it may
1060 * quickly exit and free its memory.
1061 */
1062 if (task_will_free_mem(current)) {
1063 mark_oom_victim(current);
1064 wake_oom_reaper(current);
1065 return true;
1066 }
1067
1068 /*
1069 * The OOM killer does not compensate for IO-less reclaim.
1070 * pagefault_out_of_memory lost its gfp context so we have to
1071 * make sure exclude 0 mask - all other users should have at least
1072 * ___GFP_DIRECT_RECLAIM to get here. But mem_cgroup_oom() has to
1073 * invoke the OOM killer even if it is a GFP_NOFS allocation.
1074 */
1075 if (oc->gfp_mask && !(oc->gfp_mask & __GFP_FS) && !is_memcg_oom(oc))
1076 return true;
1077
1078 /*
1079 * Check if there were limitations on the allocation (only relevant for
1080 * NUMA and memcg) that may require different handling.
1081 */
1082 oc->constraint = constrained_alloc(oc);
1083 if (oc->constraint != CONSTRAINT_MEMORY_POLICY)
1084 oc->nodemask = NULL;
1085 check_panic_on_oom(oc);
1086
1087 if (!is_memcg_oom(oc) && sysctl_oom_kill_allocating_task &&
1088 current->mm && !oom_unkillable_task(current) &&
1089 oom_cpuset_eligible(current, oc) &&
1090 current->signal->oom_score_adj != OOM_SCORE_ADJ_MIN) {
1091 get_task_struct(current);
1092 oc->chosen = current;
1093 oom_kill_process(oc, "Out of memory (oom_kill_allocating_task)");
1094 return true;
1095 }
1096
1097 select_bad_process(oc);
1098 /* Found nothing?!?! */
1099 if (!oc->chosen) {
1100 dump_header(oc, NULL);
1101 pr_warn("Out of memory and no killable processes...\n");
1102 /*
1103 * If we got here due to an actual allocation at the
1104 * system level, we cannot survive this and will enter
1105 * an endless loop in the allocator. Bail out now.
1106 */
1107 if (!is_sysrq_oom(oc) && !is_memcg_oom(oc))
1108 panic("System is deadlocked on memory\n");
1109 }
1110 if (oc->chosen && oc->chosen != (void *)-1UL)
1111 oom_kill_process(oc, !is_memcg_oom(oc) ? "Out of memory" :
1112 "Memory cgroup out of memory");
1113 return !!oc->chosen;
1114}
1115
1116/*
1117 * The pagefault handler calls here because it is out of memory, so kill a
1118 * memory-hogging task. If oom_lock is held by somebody else, a parallel oom
1119 * killing is already in progress so do nothing.
1120 */
1121void pagefault_out_of_memory(void)
1122{
1123 struct oom_control oc = {
1124 .zonelist = NULL,
1125 .nodemask = NULL,
1126 .memcg = NULL,
1127 .gfp_mask = 0,
1128 .order = 0,
1129 };
1130
1131 if (mem_cgroup_oom_synchronize(true))
1132 return;
1133
1134 if (!mutex_trylock(&oom_lock))
1135 return;
1136 out_of_memory(&oc);
1137 mutex_unlock(&oom_lock);
1138}
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/coredump.h>
28#include <linux/sched/task.h>
29#include <linux/sched/debug.h>
30#include <linux/swap.h>
31#include <linux/syscalls.h>
32#include <linux/timex.h>
33#include <linux/jiffies.h>
34#include <linux/cpuset.h>
35#include <linux/export.h>
36#include <linux/notifier.h>
37#include <linux/memcontrol.h>
38#include <linux/mempolicy.h>
39#include <linux/security.h>
40#include <linux/ptrace.h>
41#include <linux/freezer.h>
42#include <linux/ftrace.h>
43#include <linux/ratelimit.h>
44#include <linux/kthread.h>
45#include <linux/init.h>
46#include <linux/mmu_notifier.h>
47
48#include <asm/tlb.h>
49#include "internal.h"
50#include "slab.h"
51
52#define CREATE_TRACE_POINTS
53#include <trace/events/oom.h>
54
55static int sysctl_panic_on_oom;
56static int sysctl_oom_kill_allocating_task;
57static int sysctl_oom_dump_tasks = 1;
58
59/*
60 * Serializes oom killer invocations (out_of_memory()) from all contexts to
61 * prevent from over eager oom killing (e.g. when the oom killer is invoked
62 * from different domains).
63 *
64 * oom_killer_disable() relies on this lock to stabilize oom_killer_disabled
65 * and mark_oom_victim
66 */
67DEFINE_MUTEX(oom_lock);
68/* Serializes oom_score_adj and oom_score_adj_min updates */
69DEFINE_MUTEX(oom_adj_mutex);
70
71static inline bool is_memcg_oom(struct oom_control *oc)
72{
73 return oc->memcg != NULL;
74}
75
76#ifdef CONFIG_NUMA
77/**
78 * oom_cpuset_eligible() - check task eligibility for kill
79 * @start: task struct of which task to consider
80 * @oc: pointer to struct oom_control
81 *
82 * Task eligibility is determined by whether or not a candidate task, @tsk,
83 * shares the same mempolicy nodes as current if it is bound by such a policy
84 * and whether or not it has the same set of allowed cpuset nodes.
85 *
86 * This function is assuming oom-killer context and 'current' has triggered
87 * the oom-killer.
88 */
89static bool oom_cpuset_eligible(struct task_struct *start,
90 struct oom_control *oc)
91{
92 struct task_struct *tsk;
93 bool ret = false;
94 const nodemask_t *mask = oc->nodemask;
95
96 rcu_read_lock();
97 for_each_thread(start, tsk) {
98 if (mask) {
99 /*
100 * If this is a mempolicy constrained oom, tsk's
101 * cpuset is irrelevant. Only return true if its
102 * mempolicy intersects current, otherwise it may be
103 * needlessly killed.
104 */
105 ret = mempolicy_in_oom_domain(tsk, mask);
106 } else {
107 /*
108 * This is not a mempolicy constrained oom, so only
109 * check the mems of tsk's cpuset.
110 */
111 ret = cpuset_mems_allowed_intersects(current, tsk);
112 }
113 if (ret)
114 break;
115 }
116 rcu_read_unlock();
117
118 return ret;
119}
120#else
121static bool oom_cpuset_eligible(struct task_struct *tsk, struct oom_control *oc)
122{
123 return true;
124}
125#endif /* CONFIG_NUMA */
126
127/*
128 * The process p may have detached its own ->mm while exiting or through
129 * kthread_use_mm(), but one or more of its subthreads may still have a valid
130 * pointer. Return p, or any of its subthreads with a valid ->mm, with
131 * task_lock() held.
132 */
133struct task_struct *find_lock_task_mm(struct task_struct *p)
134{
135 struct task_struct *t;
136
137 rcu_read_lock();
138
139 for_each_thread(p, t) {
140 task_lock(t);
141 if (likely(t->mm))
142 goto found;
143 task_unlock(t);
144 }
145 t = NULL;
146found:
147 rcu_read_unlock();
148
149 return t;
150}
151
152/*
153 * order == -1 means the oom kill is required by sysrq, otherwise only
154 * for display purposes.
155 */
156static inline bool is_sysrq_oom(struct oom_control *oc)
157{
158 return oc->order == -1;
159}
160
161/* return true if the task is not adequate as candidate victim task. */
162static bool oom_unkillable_task(struct task_struct *p)
163{
164 if (is_global_init(p))
165 return true;
166 if (p->flags & PF_KTHREAD)
167 return true;
168 return false;
169}
170
171/*
172 * Check whether unreclaimable slab amount is greater than
173 * all user memory(LRU pages).
174 * dump_unreclaimable_slab() could help in the case that
175 * oom due to too much unreclaimable slab used by kernel.
176*/
177static bool should_dump_unreclaim_slab(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_pages(NR_SLAB_UNRECLAIMABLE_B) > 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 *
197 * The heuristic for determining which task to kill is made to be as simple and
198 * predictable as possible. The goal is to return the highest value for the
199 * task consuming the most memory to avoid subsequent oom failures.
200 */
201long oom_badness(struct task_struct *p, unsigned long totalpages)
202{
203 long points;
204 long adj;
205
206 if (oom_unkillable_task(p))
207 return LONG_MIN;
208
209 p = find_lock_task_mm(p);
210 if (!p)
211 return LONG_MIN;
212
213 /*
214 * Do not even consider tasks which are explicitly marked oom
215 * unkillable or have been already oom reaped or the are in
216 * the middle of vfork
217 */
218 adj = (long)p->signal->oom_score_adj;
219 if (adj == OOM_SCORE_ADJ_MIN ||
220 test_bit(MMF_OOM_SKIP, &p->mm->flags) ||
221 in_vfork(p)) {
222 task_unlock(p);
223 return LONG_MIN;
224 }
225
226 /*
227 * The baseline for the badness score is the proportion of RAM that each
228 * task's rss, pagetable and swap space use.
229 */
230 points = get_mm_rss(p->mm) + get_mm_counter(p->mm, MM_SWAPENTS) +
231 mm_pgtables_bytes(p->mm) / PAGE_SIZE;
232 task_unlock(p);
233
234 /* Normalize to oom_score_adj units */
235 adj *= totalpages / 1000;
236 points += adj;
237
238 return points;
239}
240
241static const char * const oom_constraint_text[] = {
242 [CONSTRAINT_NONE] = "CONSTRAINT_NONE",
243 [CONSTRAINT_CPUSET] = "CONSTRAINT_CPUSET",
244 [CONSTRAINT_MEMORY_POLICY] = "CONSTRAINT_MEMORY_POLICY",
245 [CONSTRAINT_MEMCG] = "CONSTRAINT_MEMCG",
246};
247
248/*
249 * Determine the type of allocation constraint.
250 */
251static enum oom_constraint constrained_alloc(struct oom_control *oc)
252{
253 struct zone *zone;
254 struct zoneref *z;
255 enum zone_type highest_zoneidx = gfp_zone(oc->gfp_mask);
256 bool cpuset_limited = false;
257 int nid;
258
259 if (is_memcg_oom(oc)) {
260 oc->totalpages = mem_cgroup_get_max(oc->memcg) ?: 1;
261 return CONSTRAINT_MEMCG;
262 }
263
264 /* Default to all available memory */
265 oc->totalpages = totalram_pages() + total_swap_pages;
266
267 if (!IS_ENABLED(CONFIG_NUMA))
268 return CONSTRAINT_NONE;
269
270 if (!oc->zonelist)
271 return CONSTRAINT_NONE;
272 /*
273 * Reach here only when __GFP_NOFAIL is used. So, we should avoid
274 * to kill current.We have to random task kill in this case.
275 * Hopefully, CONSTRAINT_THISNODE...but no way to handle it, now.
276 */
277 if (oc->gfp_mask & __GFP_THISNODE)
278 return CONSTRAINT_NONE;
279
280 /*
281 * This is not a __GFP_THISNODE allocation, so a truncated nodemask in
282 * the page allocator means a mempolicy is in effect. Cpuset policy
283 * is enforced in get_page_from_freelist().
284 */
285 if (oc->nodemask &&
286 !nodes_subset(node_states[N_MEMORY], *oc->nodemask)) {
287 oc->totalpages = total_swap_pages;
288 for_each_node_mask(nid, *oc->nodemask)
289 oc->totalpages += node_present_pages(nid);
290 return CONSTRAINT_MEMORY_POLICY;
291 }
292
293 /* Check this allocation failure is caused by cpuset's wall function */
294 for_each_zone_zonelist_nodemask(zone, z, oc->zonelist,
295 highest_zoneidx, oc->nodemask)
296 if (!cpuset_zone_allowed(zone, oc->gfp_mask))
297 cpuset_limited = true;
298
299 if (cpuset_limited) {
300 oc->totalpages = total_swap_pages;
301 for_each_node_mask(nid, cpuset_current_mems_allowed)
302 oc->totalpages += node_present_pages(nid);
303 return CONSTRAINT_CPUSET;
304 }
305 return CONSTRAINT_NONE;
306}
307
308static int oom_evaluate_task(struct task_struct *task, void *arg)
309{
310 struct oom_control *oc = arg;
311 long points;
312
313 if (oom_unkillable_task(task))
314 goto next;
315
316 /* p may not have freeable memory in nodemask */
317 if (!is_memcg_oom(oc) && !oom_cpuset_eligible(task, oc))
318 goto next;
319
320 /*
321 * This task already has access to memory reserves and is being killed.
322 * Don't allow any other task to have access to the reserves unless
323 * the task has MMF_OOM_SKIP because chances that it would release
324 * any memory is quite low.
325 */
326 if (!is_sysrq_oom(oc) && tsk_is_oom_victim(task)) {
327 if (test_bit(MMF_OOM_SKIP, &task->signal->oom_mm->flags))
328 goto next;
329 goto abort;
330 }
331
332 /*
333 * If task is allocating a lot of memory and has been marked to be
334 * killed first if it triggers an oom, then select it.
335 */
336 if (oom_task_origin(task)) {
337 points = LONG_MAX;
338 goto select;
339 }
340
341 points = oom_badness(task, oc->totalpages);
342 if (points == LONG_MIN || points < oc->chosen_points)
343 goto next;
344
345select:
346 if (oc->chosen)
347 put_task_struct(oc->chosen);
348 get_task_struct(task);
349 oc->chosen = task;
350 oc->chosen_points = points;
351next:
352 return 0;
353abort:
354 if (oc->chosen)
355 put_task_struct(oc->chosen);
356 oc->chosen = (void *)-1UL;
357 return 1;
358}
359
360/*
361 * Simple selection loop. We choose the process with the highest number of
362 * 'points'. In case scan was aborted, oc->chosen is set to -1.
363 */
364static void select_bad_process(struct oom_control *oc)
365{
366 oc->chosen_points = LONG_MIN;
367
368 if (is_memcg_oom(oc))
369 mem_cgroup_scan_tasks(oc->memcg, oom_evaluate_task, oc);
370 else {
371 struct task_struct *p;
372
373 rcu_read_lock();
374 for_each_process(p)
375 if (oom_evaluate_task(p, oc))
376 break;
377 rcu_read_unlock();
378 }
379}
380
381static int dump_task(struct task_struct *p, void *arg)
382{
383 struct oom_control *oc = arg;
384 struct task_struct *task;
385
386 if (oom_unkillable_task(p))
387 return 0;
388
389 /* p may not have freeable memory in nodemask */
390 if (!is_memcg_oom(oc) && !oom_cpuset_eligible(p, oc))
391 return 0;
392
393 task = find_lock_task_mm(p);
394 if (!task) {
395 /*
396 * All of p's threads have already detached their mm's. There's
397 * no need to report them; they can't be oom killed anyway.
398 */
399 return 0;
400 }
401
402 pr_info("[%7d] %5d %5d %8lu %8lu %8lu %8lu %9lu %8ld %8lu %5hd %s\n",
403 task->pid, from_kuid(&init_user_ns, task_uid(task)),
404 task->tgid, task->mm->total_vm, get_mm_rss(task->mm),
405 get_mm_counter(task->mm, MM_ANONPAGES), get_mm_counter(task->mm, MM_FILEPAGES),
406 get_mm_counter(task->mm, MM_SHMEMPAGES), mm_pgtables_bytes(task->mm),
407 get_mm_counter(task->mm, MM_SWAPENTS),
408 task->signal->oom_score_adj, task->comm);
409 task_unlock(task);
410
411 return 0;
412}
413
414/**
415 * dump_tasks - dump current memory state of all system tasks
416 * @oc: pointer to struct oom_control
417 *
418 * Dumps the current memory state of all eligible tasks. Tasks not in the same
419 * memcg, not in the same cpuset, or bound to a disjoint set of mempolicy nodes
420 * are not shown.
421 * State information includes task's pid, uid, tgid, vm size, rss,
422 * pgtables_bytes, swapents, oom_score_adj value, and name.
423 */
424static void dump_tasks(struct oom_control *oc)
425{
426 pr_info("Tasks state (memory values in pages):\n");
427 pr_info("[ pid ] uid tgid total_vm rss rss_anon rss_file rss_shmem pgtables_bytes swapents oom_score_adj name\n");
428
429 if (is_memcg_oom(oc))
430 mem_cgroup_scan_tasks(oc->memcg, dump_task, oc);
431 else {
432 struct task_struct *p;
433
434 rcu_read_lock();
435 for_each_process(p)
436 dump_task(p, oc);
437 rcu_read_unlock();
438 }
439}
440
441static void dump_oom_victim(struct oom_control *oc, struct task_struct *victim)
442{
443 /* one line summary of the oom killer context. */
444 pr_info("oom-kill:constraint=%s,nodemask=%*pbl",
445 oom_constraint_text[oc->constraint],
446 nodemask_pr_args(oc->nodemask));
447 cpuset_print_current_mems_allowed();
448 mem_cgroup_print_oom_context(oc->memcg, victim);
449 pr_cont(",task=%s,pid=%d,uid=%d\n", victim->comm, victim->pid,
450 from_kuid(&init_user_ns, task_uid(victim)));
451}
452
453static void dump_header(struct oom_control *oc)
454{
455 pr_warn("%s invoked oom-killer: gfp_mask=%#x(%pGg), order=%d, oom_score_adj=%hd\n",
456 current->comm, oc->gfp_mask, &oc->gfp_mask, oc->order,
457 current->signal->oom_score_adj);
458 if (!IS_ENABLED(CONFIG_COMPACTION) && oc->order)
459 pr_warn("COMPACTION is disabled!!!\n");
460
461 dump_stack();
462 if (is_memcg_oom(oc))
463 mem_cgroup_print_oom_meminfo(oc->memcg);
464 else {
465 __show_mem(SHOW_MEM_FILTER_NODES, oc->nodemask, gfp_zone(oc->gfp_mask));
466 if (should_dump_unreclaim_slab())
467 dump_unreclaimable_slab();
468 }
469 if (sysctl_oom_dump_tasks)
470 dump_tasks(oc);
471}
472
473/*
474 * Number of OOM victims in flight
475 */
476static atomic_t oom_victims = ATOMIC_INIT(0);
477static DECLARE_WAIT_QUEUE_HEAD(oom_victims_wait);
478
479static bool oom_killer_disabled __read_mostly;
480
481/*
482 * task->mm can be NULL if the task is the exited group leader. So to
483 * determine whether the task is using a particular mm, we examine all the
484 * task's threads: if one of those is using this mm then this task was also
485 * using it.
486 */
487bool process_shares_mm(struct task_struct *p, struct mm_struct *mm)
488{
489 struct task_struct *t;
490
491 for_each_thread(p, t) {
492 struct mm_struct *t_mm = READ_ONCE(t->mm);
493 if (t_mm)
494 return t_mm == mm;
495 }
496 return false;
497}
498
499#ifdef CONFIG_MMU
500/*
501 * OOM Reaper kernel thread which tries to reap the memory used by the OOM
502 * victim (if that is possible) to help the OOM killer to move on.
503 */
504static struct task_struct *oom_reaper_th;
505static DECLARE_WAIT_QUEUE_HEAD(oom_reaper_wait);
506static struct task_struct *oom_reaper_list;
507static DEFINE_SPINLOCK(oom_reaper_lock);
508
509static bool __oom_reap_task_mm(struct mm_struct *mm)
510{
511 struct vm_area_struct *vma;
512 bool ret = true;
513 VMA_ITERATOR(vmi, mm, 0);
514
515 /*
516 * Tell all users of get_user/copy_from_user etc... that the content
517 * is no longer stable. No barriers really needed because unmapping
518 * should imply barriers already and the reader would hit a page fault
519 * if it stumbled over a reaped memory.
520 */
521 set_bit(MMF_UNSTABLE, &mm->flags);
522
523 for_each_vma(vmi, vma) {
524 if (vma->vm_flags & (VM_HUGETLB|VM_PFNMAP))
525 continue;
526
527 /*
528 * Only anonymous pages have a good chance to be dropped
529 * without additional steps which we cannot afford as we
530 * are OOM already.
531 *
532 * We do not even care about fs backed pages because all
533 * which are reclaimable have already been reclaimed and
534 * we do not want to block exit_mmap by keeping mm ref
535 * count elevated without a good reason.
536 */
537 if (vma_is_anonymous(vma) || !(vma->vm_flags & VM_SHARED)) {
538 struct mmu_notifier_range range;
539 struct mmu_gather tlb;
540
541 mmu_notifier_range_init(&range, MMU_NOTIFY_UNMAP, 0,
542 mm, vma->vm_start,
543 vma->vm_end);
544 tlb_gather_mmu(&tlb, mm);
545 if (mmu_notifier_invalidate_range_start_nonblock(&range)) {
546 tlb_finish_mmu(&tlb);
547 ret = false;
548 continue;
549 }
550 unmap_page_range(&tlb, vma, range.start, range.end, NULL);
551 mmu_notifier_invalidate_range_end(&range);
552 tlb_finish_mmu(&tlb);
553 }
554 }
555
556 return ret;
557}
558
559/*
560 * Reaps the address space of the give task.
561 *
562 * Returns true on success and false if none or part of the address space
563 * has been reclaimed and the caller should retry later.
564 */
565static bool oom_reap_task_mm(struct task_struct *tsk, struct mm_struct *mm)
566{
567 bool ret = true;
568
569 if (!mmap_read_trylock(mm)) {
570 trace_skip_task_reaping(tsk->pid);
571 return false;
572 }
573
574 /*
575 * MMF_OOM_SKIP is set by exit_mmap when the OOM reaper can't
576 * work on the mm anymore. The check for MMF_OOM_SKIP must run
577 * under mmap_lock for reading because it serializes against the
578 * mmap_write_lock();mmap_write_unlock() cycle in exit_mmap().
579 */
580 if (test_bit(MMF_OOM_SKIP, &mm->flags)) {
581 trace_skip_task_reaping(tsk->pid);
582 goto out_unlock;
583 }
584
585 trace_start_task_reaping(tsk->pid);
586
587 /* failed to reap part of the address space. Try again later */
588 ret = __oom_reap_task_mm(mm);
589 if (!ret)
590 goto out_finish;
591
592 pr_info("oom_reaper: reaped process %d (%s), now anon-rss:%lukB, file-rss:%lukB, shmem-rss:%lukB\n",
593 task_pid_nr(tsk), tsk->comm,
594 K(get_mm_counter(mm, MM_ANONPAGES)),
595 K(get_mm_counter(mm, MM_FILEPAGES)),
596 K(get_mm_counter(mm, MM_SHMEMPAGES)));
597out_finish:
598 trace_finish_task_reaping(tsk->pid);
599out_unlock:
600 mmap_read_unlock(mm);
601
602 return ret;
603}
604
605#define MAX_OOM_REAP_RETRIES 10
606static void oom_reap_task(struct task_struct *tsk)
607{
608 int attempts = 0;
609 struct mm_struct *mm = tsk->signal->oom_mm;
610
611 /* Retry the mmap_read_trylock(mm) a few times */
612 while (attempts++ < MAX_OOM_REAP_RETRIES && !oom_reap_task_mm(tsk, mm))
613 schedule_timeout_idle(HZ/10);
614
615 if (attempts <= MAX_OOM_REAP_RETRIES ||
616 test_bit(MMF_OOM_SKIP, &mm->flags))
617 goto done;
618
619 pr_info("oom_reaper: unable to reap pid:%d (%s)\n",
620 task_pid_nr(tsk), tsk->comm);
621 sched_show_task(tsk);
622 debug_show_all_locks();
623
624done:
625 tsk->oom_reaper_list = NULL;
626
627 /*
628 * Hide this mm from OOM killer because it has been either reaped or
629 * somebody can't call mmap_write_unlock(mm).
630 */
631 set_bit(MMF_OOM_SKIP, &mm->flags);
632
633 /* Drop a reference taken by queue_oom_reaper */
634 put_task_struct(tsk);
635}
636
637static int oom_reaper(void *unused)
638{
639 set_freezable();
640
641 while (true) {
642 struct task_struct *tsk = NULL;
643
644 wait_event_freezable(oom_reaper_wait, oom_reaper_list != NULL);
645 spin_lock_irq(&oom_reaper_lock);
646 if (oom_reaper_list != NULL) {
647 tsk = oom_reaper_list;
648 oom_reaper_list = tsk->oom_reaper_list;
649 }
650 spin_unlock_irq(&oom_reaper_lock);
651
652 if (tsk)
653 oom_reap_task(tsk);
654 }
655
656 return 0;
657}
658
659static void wake_oom_reaper(struct timer_list *timer)
660{
661 struct task_struct *tsk = container_of(timer, struct task_struct,
662 oom_reaper_timer);
663 struct mm_struct *mm = tsk->signal->oom_mm;
664 unsigned long flags;
665
666 /* The victim managed to terminate on its own - see exit_mmap */
667 if (test_bit(MMF_OOM_SKIP, &mm->flags)) {
668 put_task_struct(tsk);
669 return;
670 }
671
672 spin_lock_irqsave(&oom_reaper_lock, flags);
673 tsk->oom_reaper_list = oom_reaper_list;
674 oom_reaper_list = tsk;
675 spin_unlock_irqrestore(&oom_reaper_lock, flags);
676 trace_wake_reaper(tsk->pid);
677 wake_up(&oom_reaper_wait);
678}
679
680/*
681 * Give the OOM victim time to exit naturally before invoking the oom_reaping.
682 * The timers timeout is arbitrary... the longer it is, the longer the worst
683 * case scenario for the OOM can take. If it is too small, the oom_reaper can
684 * get in the way and release resources needed by the process exit path.
685 * e.g. The futex robust list can sit in Anon|Private memory that gets reaped
686 * before the exit path is able to wake the futex waiters.
687 */
688#define OOM_REAPER_DELAY (2*HZ)
689static void queue_oom_reaper(struct task_struct *tsk)
690{
691 /* mm is already queued? */
692 if (test_and_set_bit(MMF_OOM_REAP_QUEUED, &tsk->signal->oom_mm->flags))
693 return;
694
695 get_task_struct(tsk);
696 timer_setup(&tsk->oom_reaper_timer, wake_oom_reaper, 0);
697 tsk->oom_reaper_timer.expires = jiffies + OOM_REAPER_DELAY;
698 add_timer(&tsk->oom_reaper_timer);
699}
700
701#ifdef CONFIG_SYSCTL
702static struct ctl_table vm_oom_kill_table[] = {
703 {
704 .procname = "panic_on_oom",
705 .data = &sysctl_panic_on_oom,
706 .maxlen = sizeof(sysctl_panic_on_oom),
707 .mode = 0644,
708 .proc_handler = proc_dointvec_minmax,
709 .extra1 = SYSCTL_ZERO,
710 .extra2 = SYSCTL_TWO,
711 },
712 {
713 .procname = "oom_kill_allocating_task",
714 .data = &sysctl_oom_kill_allocating_task,
715 .maxlen = sizeof(sysctl_oom_kill_allocating_task),
716 .mode = 0644,
717 .proc_handler = proc_dointvec,
718 },
719 {
720 .procname = "oom_dump_tasks",
721 .data = &sysctl_oom_dump_tasks,
722 .maxlen = sizeof(sysctl_oom_dump_tasks),
723 .mode = 0644,
724 .proc_handler = proc_dointvec,
725 },
726 {}
727};
728#endif
729
730static int __init oom_init(void)
731{
732 oom_reaper_th = kthread_run(oom_reaper, NULL, "oom_reaper");
733#ifdef CONFIG_SYSCTL
734 register_sysctl_init("vm", vm_oom_kill_table);
735#endif
736 return 0;
737}
738subsys_initcall(oom_init)
739#else
740static inline void queue_oom_reaper(struct task_struct *tsk)
741{
742}
743#endif /* CONFIG_MMU */
744
745/**
746 * mark_oom_victim - mark the given task as OOM victim
747 * @tsk: task to mark
748 *
749 * Has to be called with oom_lock held and never after
750 * oom has been disabled already.
751 *
752 * tsk->mm has to be non NULL and caller has to guarantee it is stable (either
753 * under task_lock or operate on the current).
754 */
755static void mark_oom_victim(struct task_struct *tsk)
756{
757 struct mm_struct *mm = tsk->mm;
758
759 WARN_ON(oom_killer_disabled);
760 /* OOM killer might race with memcg OOM */
761 if (test_and_set_tsk_thread_flag(tsk, TIF_MEMDIE))
762 return;
763
764 /* oom_mm is bound to the signal struct life time. */
765 if (!cmpxchg(&tsk->signal->oom_mm, NULL, mm))
766 mmgrab(tsk->signal->oom_mm);
767
768 /*
769 * Make sure that the task is woken up from uninterruptible sleep
770 * if it is frozen because OOM killer wouldn't be able to free
771 * any memory and livelock. freezing_slow_path will tell the freezer
772 * that TIF_MEMDIE tasks should be ignored.
773 */
774 __thaw_task(tsk);
775 atomic_inc(&oom_victims);
776 trace_mark_victim(tsk->pid);
777}
778
779/**
780 * exit_oom_victim - note the exit of an OOM victim
781 */
782void exit_oom_victim(void)
783{
784 clear_thread_flag(TIF_MEMDIE);
785
786 if (!atomic_dec_return(&oom_victims))
787 wake_up_all(&oom_victims_wait);
788}
789
790/**
791 * oom_killer_enable - enable OOM killer
792 */
793void oom_killer_enable(void)
794{
795 oom_killer_disabled = false;
796 pr_info("OOM killer enabled.\n");
797}
798
799/**
800 * oom_killer_disable - disable OOM killer
801 * @timeout: maximum timeout to wait for oom victims in jiffies
802 *
803 * Forces all page allocations to fail rather than trigger OOM killer.
804 * Will block and wait until all OOM victims are killed or the given
805 * timeout expires.
806 *
807 * The function cannot be called when there are runnable user tasks because
808 * the userspace would see unexpected allocation failures as a result. Any
809 * new usage of this function should be consulted with MM people.
810 *
811 * Returns true if successful and false if the OOM killer cannot be
812 * disabled.
813 */
814bool oom_killer_disable(signed long timeout)
815{
816 signed long ret;
817
818 /*
819 * Make sure to not race with an ongoing OOM killer. Check that the
820 * current is not killed (possibly due to sharing the victim's memory).
821 */
822 if (mutex_lock_killable(&oom_lock))
823 return false;
824 oom_killer_disabled = true;
825 mutex_unlock(&oom_lock);
826
827 ret = wait_event_interruptible_timeout(oom_victims_wait,
828 !atomic_read(&oom_victims), timeout);
829 if (ret <= 0) {
830 oom_killer_enable();
831 return false;
832 }
833 pr_info("OOM killer disabled.\n");
834
835 return true;
836}
837
838static inline bool __task_will_free_mem(struct task_struct *task)
839{
840 struct signal_struct *sig = task->signal;
841
842 /*
843 * A coredumping process may sleep for an extended period in
844 * coredump_task_exit(), so the oom killer cannot assume that
845 * the process will promptly exit and release memory.
846 */
847 if (sig->core_state)
848 return false;
849
850 if (sig->flags & SIGNAL_GROUP_EXIT)
851 return true;
852
853 if (thread_group_empty(task) && (task->flags & PF_EXITING))
854 return true;
855
856 return false;
857}
858
859/*
860 * Checks whether the given task is dying or exiting and likely to
861 * release its address space. This means that all threads and processes
862 * sharing the same mm have to be killed or exiting.
863 * Caller has to make sure that task->mm is stable (hold task_lock or
864 * it operates on the current).
865 */
866static bool task_will_free_mem(struct task_struct *task)
867{
868 struct mm_struct *mm = task->mm;
869 struct task_struct *p;
870 bool ret = true;
871
872 /*
873 * Skip tasks without mm because it might have passed its exit_mm and
874 * exit_oom_victim. oom_reaper could have rescued that but do not rely
875 * on that for now. We can consider find_lock_task_mm in future.
876 */
877 if (!mm)
878 return false;
879
880 if (!__task_will_free_mem(task))
881 return false;
882
883 /*
884 * This task has already been drained by the oom reaper so there are
885 * only small chances it will free some more
886 */
887 if (test_bit(MMF_OOM_SKIP, &mm->flags))
888 return false;
889
890 if (atomic_read(&mm->mm_users) <= 1)
891 return true;
892
893 /*
894 * Make sure that all tasks which share the mm with the given tasks
895 * are dying as well to make sure that a) nobody pins its mm and
896 * b) the task is also reapable by the oom reaper.
897 */
898 rcu_read_lock();
899 for_each_process(p) {
900 if (!process_shares_mm(p, mm))
901 continue;
902 if (same_thread_group(task, p))
903 continue;
904 ret = __task_will_free_mem(p);
905 if (!ret)
906 break;
907 }
908 rcu_read_unlock();
909
910 return ret;
911}
912
913static void __oom_kill_process(struct task_struct *victim, const char *message)
914{
915 struct task_struct *p;
916 struct mm_struct *mm;
917 bool can_oom_reap = true;
918
919 p = find_lock_task_mm(victim);
920 if (!p) {
921 pr_info("%s: OOM victim %d (%s) is already exiting. Skip killing the task\n",
922 message, task_pid_nr(victim), victim->comm);
923 put_task_struct(victim);
924 return;
925 } else if (victim != p) {
926 get_task_struct(p);
927 put_task_struct(victim);
928 victim = p;
929 }
930
931 /* Get a reference to safely compare mm after task_unlock(victim) */
932 mm = victim->mm;
933 mmgrab(mm);
934
935 /* Raise event before sending signal: task reaper must see this */
936 count_vm_event(OOM_KILL);
937 memcg_memory_event_mm(mm, MEMCG_OOM_KILL);
938
939 /*
940 * We should send SIGKILL before granting access to memory reserves
941 * in order to prevent the OOM victim from depleting the memory
942 * reserves from the user space under its control.
943 */
944 do_send_sig_info(SIGKILL, SEND_SIG_PRIV, victim, PIDTYPE_TGID);
945 mark_oom_victim(victim);
946 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",
947 message, task_pid_nr(victim), victim->comm, K(mm->total_vm),
948 K(get_mm_counter(mm, MM_ANONPAGES)),
949 K(get_mm_counter(mm, MM_FILEPAGES)),
950 K(get_mm_counter(mm, MM_SHMEMPAGES)),
951 from_kuid(&init_user_ns, task_uid(victim)),
952 mm_pgtables_bytes(mm) >> 10, victim->signal->oom_score_adj);
953 task_unlock(victim);
954
955 /*
956 * Kill all user processes sharing victim->mm in other thread groups, if
957 * any. They don't get access to memory reserves, though, to avoid
958 * depletion of all memory. This prevents mm->mmap_lock livelock when an
959 * oom killed thread cannot exit because it requires the semaphore and
960 * its contended by another thread trying to allocate memory itself.
961 * That thread will now get access to memory reserves since it has a
962 * pending fatal signal.
963 */
964 rcu_read_lock();
965 for_each_process(p) {
966 if (!process_shares_mm(p, mm))
967 continue;
968 if (same_thread_group(p, victim))
969 continue;
970 if (is_global_init(p)) {
971 can_oom_reap = false;
972 set_bit(MMF_OOM_SKIP, &mm->flags);
973 pr_info("oom killer %d (%s) has mm pinned by %d (%s)\n",
974 task_pid_nr(victim), victim->comm,
975 task_pid_nr(p), p->comm);
976 continue;
977 }
978 /*
979 * No kthread_use_mm() user needs to read from the userspace so
980 * we are ok to reap it.
981 */
982 if (unlikely(p->flags & PF_KTHREAD))
983 continue;
984 do_send_sig_info(SIGKILL, SEND_SIG_PRIV, p, PIDTYPE_TGID);
985 }
986 rcu_read_unlock();
987
988 if (can_oom_reap)
989 queue_oom_reaper(victim);
990
991 mmdrop(mm);
992 put_task_struct(victim);
993}
994
995/*
996 * Kill provided task unless it's secured by setting
997 * oom_score_adj to OOM_SCORE_ADJ_MIN.
998 */
999static int oom_kill_memcg_member(struct task_struct *task, void *message)
1000{
1001 if (task->signal->oom_score_adj != OOM_SCORE_ADJ_MIN &&
1002 !is_global_init(task)) {
1003 get_task_struct(task);
1004 __oom_kill_process(task, message);
1005 }
1006 return 0;
1007}
1008
1009static void oom_kill_process(struct oom_control *oc, const char *message)
1010{
1011 struct task_struct *victim = oc->chosen;
1012 struct mem_cgroup *oom_group;
1013 static DEFINE_RATELIMIT_STATE(oom_rs, DEFAULT_RATELIMIT_INTERVAL,
1014 DEFAULT_RATELIMIT_BURST);
1015
1016 /*
1017 * If the task is already exiting, don't alarm the sysadmin or kill
1018 * its children or threads, just give it access to memory reserves
1019 * so it can die quickly
1020 */
1021 task_lock(victim);
1022 if (task_will_free_mem(victim)) {
1023 mark_oom_victim(victim);
1024 queue_oom_reaper(victim);
1025 task_unlock(victim);
1026 put_task_struct(victim);
1027 return;
1028 }
1029 task_unlock(victim);
1030
1031 if (__ratelimit(&oom_rs)) {
1032 dump_header(oc);
1033 dump_oom_victim(oc, victim);
1034 }
1035
1036 /*
1037 * Do we need to kill the entire memory cgroup?
1038 * Or even one of the ancestor memory cgroups?
1039 * Check this out before killing the victim task.
1040 */
1041 oom_group = mem_cgroup_get_oom_group(victim, oc->memcg);
1042
1043 __oom_kill_process(victim, message);
1044
1045 /*
1046 * If necessary, kill all tasks in the selected memory cgroup.
1047 */
1048 if (oom_group) {
1049 memcg_memory_event(oom_group, MEMCG_OOM_GROUP_KILL);
1050 mem_cgroup_print_oom_group(oom_group);
1051 mem_cgroup_scan_tasks(oom_group, oom_kill_memcg_member,
1052 (void *)message);
1053 mem_cgroup_put(oom_group);
1054 }
1055}
1056
1057/*
1058 * Determines whether the kernel must panic because of the panic_on_oom sysctl.
1059 */
1060static void check_panic_on_oom(struct oom_control *oc)
1061{
1062 if (likely(!sysctl_panic_on_oom))
1063 return;
1064 if (sysctl_panic_on_oom != 2) {
1065 /*
1066 * panic_on_oom == 1 only affects CONSTRAINT_NONE, the kernel
1067 * does not panic for cpuset, mempolicy, or memcg allocation
1068 * failures.
1069 */
1070 if (oc->constraint != CONSTRAINT_NONE)
1071 return;
1072 }
1073 /* Do not panic for oom kills triggered by sysrq */
1074 if (is_sysrq_oom(oc))
1075 return;
1076 dump_header(oc);
1077 panic("Out of memory: %s panic_on_oom is enabled\n",
1078 sysctl_panic_on_oom == 2 ? "compulsory" : "system-wide");
1079}
1080
1081static BLOCKING_NOTIFIER_HEAD(oom_notify_list);
1082
1083int register_oom_notifier(struct notifier_block *nb)
1084{
1085 return blocking_notifier_chain_register(&oom_notify_list, nb);
1086}
1087EXPORT_SYMBOL_GPL(register_oom_notifier);
1088
1089int unregister_oom_notifier(struct notifier_block *nb)
1090{
1091 return blocking_notifier_chain_unregister(&oom_notify_list, nb);
1092}
1093EXPORT_SYMBOL_GPL(unregister_oom_notifier);
1094
1095/**
1096 * out_of_memory - kill the "best" process when we run out of memory
1097 * @oc: pointer to struct oom_control
1098 *
1099 * If we run out of memory, we have the choice between either
1100 * killing a random task (bad), letting the system crash (worse)
1101 * OR try to be smart about which process to kill. Note that we
1102 * don't have to be perfect here, we just have to be good.
1103 */
1104bool out_of_memory(struct oom_control *oc)
1105{
1106 unsigned long freed = 0;
1107
1108 if (oom_killer_disabled)
1109 return false;
1110
1111 if (!is_memcg_oom(oc)) {
1112 blocking_notifier_call_chain(&oom_notify_list, 0, &freed);
1113 if (freed > 0 && !is_sysrq_oom(oc))
1114 /* Got some memory back in the last second. */
1115 return true;
1116 }
1117
1118 /*
1119 * If current has a pending SIGKILL or is exiting, then automatically
1120 * select it. The goal is to allow it to allocate so that it may
1121 * quickly exit and free its memory.
1122 */
1123 if (task_will_free_mem(current)) {
1124 mark_oom_victim(current);
1125 queue_oom_reaper(current);
1126 return true;
1127 }
1128
1129 /*
1130 * The OOM killer does not compensate for IO-less reclaim.
1131 * But mem_cgroup_oom() has to invoke the OOM killer even
1132 * if it is a GFP_NOFS allocation.
1133 */
1134 if (!(oc->gfp_mask & __GFP_FS) && !is_memcg_oom(oc))
1135 return true;
1136
1137 /*
1138 * Check if there were limitations on the allocation (only relevant for
1139 * NUMA and memcg) that may require different handling.
1140 */
1141 oc->constraint = constrained_alloc(oc);
1142 if (oc->constraint != CONSTRAINT_MEMORY_POLICY)
1143 oc->nodemask = NULL;
1144 check_panic_on_oom(oc);
1145
1146 if (!is_memcg_oom(oc) && sysctl_oom_kill_allocating_task &&
1147 current->mm && !oom_unkillable_task(current) &&
1148 oom_cpuset_eligible(current, oc) &&
1149 current->signal->oom_score_adj != OOM_SCORE_ADJ_MIN) {
1150 get_task_struct(current);
1151 oc->chosen = current;
1152 oom_kill_process(oc, "Out of memory (oom_kill_allocating_task)");
1153 return true;
1154 }
1155
1156 select_bad_process(oc);
1157 /* Found nothing?!?! */
1158 if (!oc->chosen) {
1159 dump_header(oc);
1160 pr_warn("Out of memory and no killable processes...\n");
1161 /*
1162 * If we got here due to an actual allocation at the
1163 * system level, we cannot survive this and will enter
1164 * an endless loop in the allocator. Bail out now.
1165 */
1166 if (!is_sysrq_oom(oc) && !is_memcg_oom(oc))
1167 panic("System is deadlocked on memory\n");
1168 }
1169 if (oc->chosen && oc->chosen != (void *)-1UL)
1170 oom_kill_process(oc, !is_memcg_oom(oc) ? "Out of memory" :
1171 "Memory cgroup out of memory");
1172 return !!oc->chosen;
1173}
1174
1175/*
1176 * The pagefault handler calls here because some allocation has failed. We have
1177 * to take care of the memcg OOM here because this is the only safe context without
1178 * any locks held but let the oom killer triggered from the allocation context care
1179 * about the global OOM.
1180 */
1181void pagefault_out_of_memory(void)
1182{
1183 static DEFINE_RATELIMIT_STATE(pfoom_rs, DEFAULT_RATELIMIT_INTERVAL,
1184 DEFAULT_RATELIMIT_BURST);
1185
1186 if (mem_cgroup_oom_synchronize(true))
1187 return;
1188
1189 if (fatal_signal_pending(current))
1190 return;
1191
1192 if (__ratelimit(&pfoom_rs))
1193 pr_warn("Huh VM_FAULT_OOM leaked out to the #PF handler. Retrying PF\n");
1194}
1195
1196SYSCALL_DEFINE2(process_mrelease, int, pidfd, unsigned int, flags)
1197{
1198#ifdef CONFIG_MMU
1199 struct mm_struct *mm = NULL;
1200 struct task_struct *task;
1201 struct task_struct *p;
1202 unsigned int f_flags;
1203 bool reap = false;
1204 long ret = 0;
1205
1206 if (flags)
1207 return -EINVAL;
1208
1209 task = pidfd_get_task(pidfd, &f_flags);
1210 if (IS_ERR(task))
1211 return PTR_ERR(task);
1212
1213 /*
1214 * Make sure to choose a thread which still has a reference to mm
1215 * during the group exit
1216 */
1217 p = find_lock_task_mm(task);
1218 if (!p) {
1219 ret = -ESRCH;
1220 goto put_task;
1221 }
1222
1223 mm = p->mm;
1224 mmgrab(mm);
1225
1226 if (task_will_free_mem(p))
1227 reap = true;
1228 else {
1229 /* Error only if the work has not been done already */
1230 if (!test_bit(MMF_OOM_SKIP, &mm->flags))
1231 ret = -EINVAL;
1232 }
1233 task_unlock(p);
1234
1235 if (!reap)
1236 goto drop_mm;
1237
1238 if (mmap_read_lock_killable(mm)) {
1239 ret = -EINTR;
1240 goto drop_mm;
1241 }
1242 /*
1243 * Check MMF_OOM_SKIP again under mmap_read_lock protection to ensure
1244 * possible change in exit_mmap is seen
1245 */
1246 if (!test_bit(MMF_OOM_SKIP, &mm->flags) && !__oom_reap_task_mm(mm))
1247 ret = -EAGAIN;
1248 mmap_read_unlock(mm);
1249
1250drop_mm:
1251 mmdrop(mm);
1252put_task:
1253 put_task_struct(task);
1254 return ret;
1255#else
1256 return -ENOSYS;
1257#endif /* CONFIG_MMU */
1258}