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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/sched/debug.h>
30#include <linux/swap.h>
31#include <linux/timex.h>
32#include <linux/jiffies.h>
33#include <linux/cpuset.h>
34#include <linux/export.h>
35#include <linux/notifier.h>
36#include <linux/memcontrol.h>
37#include <linux/mempolicy.h>
38#include <linux/security.h>
39#include <linux/ptrace.h>
40#include <linux/freezer.h>
41#include <linux/ftrace.h>
42#include <linux/ratelimit.h>
43#include <linux/kthread.h>
44#include <linux/init.h>
45#include <linux/mmu_notifier.h>
46
47#include <asm/tlb.h>
48#include "internal.h"
49#include "slab.h"
50
51#define CREATE_TRACE_POINTS
52#include <trace/events/oom.h>
53
54int sysctl_panic_on_oom;
55int sysctl_oom_kill_allocating_task;
56int sysctl_oom_dump_tasks = 1;
57
58/*
59 * Serializes oom killer invocations (out_of_memory()) from all contexts to
60 * prevent from over eager oom killing (e.g. when the oom killer is invoked
61 * from different domains).
62 *
63 * oom_killer_disable() relies on this lock to stabilize oom_killer_disabled
64 * and mark_oom_victim
65 */
66DEFINE_MUTEX(oom_lock);
67
68static inline bool is_memcg_oom(struct oom_control *oc)
69{
70 return oc->memcg != NULL;
71}
72
73#ifdef CONFIG_NUMA
74/**
75 * oom_cpuset_eligible() - check task eligiblity for kill
76 * @start: task struct of which task to consider
77 * @oc: pointer to struct oom_control
78 *
79 * Task eligibility is determined by whether or not a candidate task, @tsk,
80 * shares the same mempolicy nodes as current if it is bound by such a policy
81 * and whether or not it has the same set of allowed cpuset nodes.
82 *
83 * This function is assuming oom-killer context and 'current' has triggered
84 * the oom-killer.
85 */
86static bool oom_cpuset_eligible(struct task_struct *start,
87 struct oom_control *oc)
88{
89 struct task_struct *tsk;
90 bool ret = false;
91 const nodemask_t *mask = oc->nodemask;
92
93 if (is_memcg_oom(oc))
94 return true;
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_nodemask_intersects(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 * Print out unreclaimble slabs info when unreclaimable slabs amount is greater
173 * than all user memory (LRU pages)
174 */
175static bool is_dump_unreclaim_slabs(void)
176{
177 unsigned long nr_lru;
178
179 nr_lru = global_node_page_state(NR_ACTIVE_ANON) +
180 global_node_page_state(NR_INACTIVE_ANON) +
181 global_node_page_state(NR_ACTIVE_FILE) +
182 global_node_page_state(NR_INACTIVE_FILE) +
183 global_node_page_state(NR_ISOLATED_ANON) +
184 global_node_page_state(NR_ISOLATED_FILE) +
185 global_node_page_state(NR_UNEVICTABLE);
186
187 return (global_node_page_state_pages(NR_SLAB_UNRECLAIMABLE_B) > nr_lru);
188}
189
190/**
191 * oom_badness - heuristic function to determine which candidate task to kill
192 * @p: task struct of which task we should calculate
193 * @totalpages: total present RAM allowed for page allocation
194 *
195 * The heuristic for determining which task to kill is made to be as simple and
196 * predictable as possible. The goal is to return the highest value for the
197 * task consuming the most memory to avoid subsequent oom failures.
198 */
199long oom_badness(struct task_struct *p, unsigned long totalpages)
200{
201 long points;
202 long adj;
203
204 if (oom_unkillable_task(p))
205 return LONG_MIN;
206
207 p = find_lock_task_mm(p);
208 if (!p)
209 return LONG_MIN;
210
211 /*
212 * Do not even consider tasks which are explicitly marked oom
213 * unkillable or have been already oom reaped or the are in
214 * the middle of vfork
215 */
216 adj = (long)p->signal->oom_score_adj;
217 if (adj == OOM_SCORE_ADJ_MIN ||
218 test_bit(MMF_OOM_SKIP, &p->mm->flags) ||
219 in_vfork(p)) {
220 task_unlock(p);
221 return LONG_MIN;
222 }
223
224 /*
225 * The baseline for the badness score is the proportion of RAM that each
226 * task's rss, pagetable and swap space use.
227 */
228 points = get_mm_rss(p->mm) + get_mm_counter(p->mm, MM_SWAPENTS) +
229 mm_pgtables_bytes(p->mm) / PAGE_SIZE;
230 task_unlock(p);
231
232 /* Normalize to oom_score_adj units */
233 adj *= totalpages / 1000;
234 points += adj;
235
236 return points;
237}
238
239static const char * const oom_constraint_text[] = {
240 [CONSTRAINT_NONE] = "CONSTRAINT_NONE",
241 [CONSTRAINT_CPUSET] = "CONSTRAINT_CPUSET",
242 [CONSTRAINT_MEMORY_POLICY] = "CONSTRAINT_MEMORY_POLICY",
243 [CONSTRAINT_MEMCG] = "CONSTRAINT_MEMCG",
244};
245
246/*
247 * Determine the type of allocation constraint.
248 */
249static enum oom_constraint constrained_alloc(struct oom_control *oc)
250{
251 struct zone *zone;
252 struct zoneref *z;
253 enum zone_type highest_zoneidx = gfp_zone(oc->gfp_mask);
254 bool cpuset_limited = false;
255 int nid;
256
257 if (is_memcg_oom(oc)) {
258 oc->totalpages = mem_cgroup_get_max(oc->memcg) ?: 1;
259 return CONSTRAINT_MEMCG;
260 }
261
262 /* Default to all available memory */
263 oc->totalpages = totalram_pages() + total_swap_pages;
264
265 if (!IS_ENABLED(CONFIG_NUMA))
266 return CONSTRAINT_NONE;
267
268 if (!oc->zonelist)
269 return CONSTRAINT_NONE;
270 /*
271 * Reach here only when __GFP_NOFAIL is used. So, we should avoid
272 * to kill current.We have to random task kill in this case.
273 * Hopefully, CONSTRAINT_THISNODE...but no way to handle it, now.
274 */
275 if (oc->gfp_mask & __GFP_THISNODE)
276 return CONSTRAINT_NONE;
277
278 /*
279 * This is not a __GFP_THISNODE allocation, so a truncated nodemask in
280 * the page allocator means a mempolicy is in effect. Cpuset policy
281 * is enforced in get_page_from_freelist().
282 */
283 if (oc->nodemask &&
284 !nodes_subset(node_states[N_MEMORY], *oc->nodemask)) {
285 oc->totalpages = total_swap_pages;
286 for_each_node_mask(nid, *oc->nodemask)
287 oc->totalpages += node_present_pages(nid);
288 return CONSTRAINT_MEMORY_POLICY;
289 }
290
291 /* Check this allocation failure is caused by cpuset's wall function */
292 for_each_zone_zonelist_nodemask(zone, z, oc->zonelist,
293 highest_zoneidx, oc->nodemask)
294 if (!cpuset_zone_allowed(zone, oc->gfp_mask))
295 cpuset_limited = true;
296
297 if (cpuset_limited) {
298 oc->totalpages = total_swap_pages;
299 for_each_node_mask(nid, cpuset_current_mems_allowed)
300 oc->totalpages += node_present_pages(nid);
301 return CONSTRAINT_CPUSET;
302 }
303 return CONSTRAINT_NONE;
304}
305
306static int oom_evaluate_task(struct task_struct *task, void *arg)
307{
308 struct oom_control *oc = arg;
309 long points;
310
311 if (oom_unkillable_task(task))
312 goto next;
313
314 /* p may not have freeable memory in nodemask */
315 if (!is_memcg_oom(oc) && !oom_cpuset_eligible(task, oc))
316 goto next;
317
318 /*
319 * This task already has access to memory reserves and is being killed.
320 * Don't allow any other task to have access to the reserves unless
321 * the task has MMF_OOM_SKIP because chances that it would release
322 * any memory is quite low.
323 */
324 if (!is_sysrq_oom(oc) && tsk_is_oom_victim(task)) {
325 if (test_bit(MMF_OOM_SKIP, &task->signal->oom_mm->flags))
326 goto next;
327 goto abort;
328 }
329
330 /*
331 * If task is allocating a lot of memory and has been marked to be
332 * killed first if it triggers an oom, then select it.
333 */
334 if (oom_task_origin(task)) {
335 points = LONG_MAX;
336 goto select;
337 }
338
339 points = oom_badness(task, oc->totalpages);
340 if (points == LONG_MIN || points < oc->chosen_points)
341 goto next;
342
343select:
344 if (oc->chosen)
345 put_task_struct(oc->chosen);
346 get_task_struct(task);
347 oc->chosen = task;
348 oc->chosen_points = points;
349next:
350 return 0;
351abort:
352 if (oc->chosen)
353 put_task_struct(oc->chosen);
354 oc->chosen = (void *)-1UL;
355 return 1;
356}
357
358/*
359 * Simple selection loop. We choose the process with the highest number of
360 * 'points'. In case scan was aborted, oc->chosen is set to -1.
361 */
362static void select_bad_process(struct oom_control *oc)
363{
364 oc->chosen_points = LONG_MIN;
365
366 if (is_memcg_oom(oc))
367 mem_cgroup_scan_tasks(oc->memcg, oom_evaluate_task, oc);
368 else {
369 struct task_struct *p;
370
371 rcu_read_lock();
372 for_each_process(p)
373 if (oom_evaluate_task(p, oc))
374 break;
375 rcu_read_unlock();
376 }
377}
378
379static int dump_task(struct task_struct *p, void *arg)
380{
381 struct oom_control *oc = arg;
382 struct task_struct *task;
383
384 if (oom_unkillable_task(p))
385 return 0;
386
387 /* p may not have freeable memory in nodemask */
388 if (!is_memcg_oom(oc) && !oom_cpuset_eligible(p, oc))
389 return 0;
390
391 task = find_lock_task_mm(p);
392 if (!task) {
393 /*
394 * This is a kthread or all of p's threads have already
395 * detached their mm's. There's no need to report
396 * them; they can't be oom killed anyway.
397 */
398 return 0;
399 }
400
401 pr_info("[%7d] %5d %5d %8lu %8lu %8ld %8lu %5hd %s\n",
402 task->pid, from_kuid(&init_user_ns, task_uid(task)),
403 task->tgid, task->mm->total_vm, get_mm_rss(task->mm),
404 mm_pgtables_bytes(task->mm),
405 get_mm_counter(task->mm, MM_SWAPENTS),
406 task->signal->oom_score_adj, task->comm);
407 task_unlock(task);
408
409 return 0;
410}
411
412/**
413 * dump_tasks - dump current memory state of all system tasks
414 * @oc: pointer to struct oom_control
415 *
416 * Dumps the current memory state of all eligible tasks. Tasks not in the same
417 * memcg, not in the same cpuset, or bound to a disjoint set of mempolicy nodes
418 * are not shown.
419 * State information includes task's pid, uid, tgid, vm size, rss,
420 * pgtables_bytes, swapents, oom_score_adj value, and name.
421 */
422static void dump_tasks(struct oom_control *oc)
423{
424 pr_info("Tasks state (memory values in pages):\n");
425 pr_info("[ pid ] uid tgid total_vm rss pgtables_bytes swapents oom_score_adj name\n");
426
427 if (is_memcg_oom(oc))
428 mem_cgroup_scan_tasks(oc->memcg, dump_task, oc);
429 else {
430 struct task_struct *p;
431
432 rcu_read_lock();
433 for_each_process(p)
434 dump_task(p, oc);
435 rcu_read_unlock();
436 }
437}
438
439static void dump_oom_summary(struct oom_control *oc, struct task_struct *victim)
440{
441 /* one line summary of the oom killer context. */
442 pr_info("oom-kill:constraint=%s,nodemask=%*pbl",
443 oom_constraint_text[oc->constraint],
444 nodemask_pr_args(oc->nodemask));
445 cpuset_print_current_mems_allowed();
446 mem_cgroup_print_oom_context(oc->memcg, victim);
447 pr_cont(",task=%s,pid=%d,uid=%d\n", victim->comm, victim->pid,
448 from_kuid(&init_user_ns, task_uid(victim)));
449}
450
451static void dump_header(struct oom_control *oc, struct task_struct *p)
452{
453 pr_warn("%s invoked oom-killer: gfp_mask=%#x(%pGg), order=%d, oom_score_adj=%hd\n",
454 current->comm, oc->gfp_mask, &oc->gfp_mask, oc->order,
455 current->signal->oom_score_adj);
456 if (!IS_ENABLED(CONFIG_COMPACTION) && oc->order)
457 pr_warn("COMPACTION is disabled!!!\n");
458
459 dump_stack();
460 if (is_memcg_oom(oc))
461 mem_cgroup_print_oom_meminfo(oc->memcg);
462 else {
463 show_mem(SHOW_MEM_FILTER_NODES, oc->nodemask);
464 if (is_dump_unreclaim_slabs())
465 dump_unreclaimable_slab();
466 }
467 if (sysctl_oom_dump_tasks)
468 dump_tasks(oc);
469 if (p)
470 dump_oom_summary(oc, p);
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#define K(x) ((x) << (PAGE_SHIFT-10))
482
483/*
484 * task->mm can be NULL if the task is the exited group leader. So to
485 * determine whether the task is using a particular mm, we examine all the
486 * task's threads: if one of those is using this mm then this task was also
487 * using it.
488 */
489bool process_shares_mm(struct task_struct *p, struct mm_struct *mm)
490{
491 struct task_struct *t;
492
493 for_each_thread(p, t) {
494 struct mm_struct *t_mm = READ_ONCE(t->mm);
495 if (t_mm)
496 return t_mm == mm;
497 }
498 return false;
499}
500
501#ifdef CONFIG_MMU
502/*
503 * OOM Reaper kernel thread which tries to reap the memory used by the OOM
504 * victim (if that is possible) to help the OOM killer to move on.
505 */
506static struct task_struct *oom_reaper_th;
507static DECLARE_WAIT_QUEUE_HEAD(oom_reaper_wait);
508static struct task_struct *oom_reaper_list;
509static DEFINE_SPINLOCK(oom_reaper_lock);
510
511bool __oom_reap_task_mm(struct mm_struct *mm)
512{
513 struct vm_area_struct *vma;
514 bool ret = true;
515
516 /*
517 * Tell all users of get_user/copy_from_user etc... that the content
518 * is no longer stable. No barriers really needed because unmapping
519 * should imply barriers already and the reader would hit a page fault
520 * if it stumbled over a reaped memory.
521 */
522 set_bit(MMF_UNSTABLE, &mm->flags);
523
524 for (vma = mm->mmap ; vma; vma = vma->vm_next) {
525 if (!can_madv_lru_vma(vma))
526 continue;
527
528 /*
529 * Only anonymous pages have a good chance to be dropped
530 * without additional steps which we cannot afford as we
531 * are OOM already.
532 *
533 * We do not even care about fs backed pages because all
534 * which are reclaimable have already been reclaimed and
535 * we do not want to block exit_mmap by keeping mm ref
536 * count elevated without a good reason.
537 */
538 if (vma_is_anonymous(vma) || !(vma->vm_flags & VM_SHARED)) {
539 struct mmu_notifier_range range;
540 struct mmu_gather tlb;
541
542 mmu_notifier_range_init(&range, MMU_NOTIFY_UNMAP, 0,
543 vma, mm, vma->vm_start,
544 vma->vm_end);
545 tlb_gather_mmu(&tlb, mm, range.start, range.end);
546 if (mmu_notifier_invalidate_range_start_nonblock(&range)) {
547 tlb_finish_mmu(&tlb, range.start, range.end);
548 ret = false;
549 continue;
550 }
551 unmap_page_range(&tlb, vma, range.start, range.end, NULL);
552 mmu_notifier_invalidate_range_end(&range);
553 tlb_finish_mmu(&tlb, range.start, range.end);
554 }
555 }
556
557 return ret;
558}
559
560/*
561 * Reaps the address space of the give task.
562 *
563 * Returns true on success and false if none or part of the address space
564 * has been reclaimed and the caller should retry later.
565 */
566static bool oom_reap_task_mm(struct task_struct *tsk, struct mm_struct *mm)
567{
568 bool ret = true;
569
570 if (!mmap_read_trylock(mm)) {
571 trace_skip_task_reaping(tsk->pid);
572 return false;
573 }
574
575 /*
576 * MMF_OOM_SKIP is set by exit_mmap when the OOM reaper can't
577 * work on the mm anymore. The check for MMF_OOM_SKIP must run
578 * under mmap_lock for reading because it serializes against the
579 * mmap_write_lock();mmap_write_unlock() cycle in exit_mmap().
580 */
581 if (test_bit(MMF_OOM_SKIP, &mm->flags)) {
582 trace_skip_task_reaping(tsk->pid);
583 goto out_unlock;
584 }
585
586 trace_start_task_reaping(tsk->pid);
587
588 /* failed to reap part of the address space. Try again later */
589 ret = __oom_reap_task_mm(mm);
590 if (!ret)
591 goto out_finish;
592
593 pr_info("oom_reaper: reaped process %d (%s), now anon-rss:%lukB, file-rss:%lukB, shmem-rss:%lukB\n",
594 task_pid_nr(tsk), tsk->comm,
595 K(get_mm_counter(mm, MM_ANONPAGES)),
596 K(get_mm_counter(mm, MM_FILEPAGES)),
597 K(get_mm_counter(mm, MM_SHMEMPAGES)));
598out_finish:
599 trace_finish_task_reaping(tsk->pid);
600out_unlock:
601 mmap_read_unlock(mm);
602
603 return ret;
604}
605
606#define MAX_OOM_REAP_RETRIES 10
607static void oom_reap_task(struct task_struct *tsk)
608{
609 int attempts = 0;
610 struct mm_struct *mm = tsk->signal->oom_mm;
611
612 /* Retry the mmap_read_trylock(mm) a few times */
613 while (attempts++ < MAX_OOM_REAP_RETRIES && !oom_reap_task_mm(tsk, mm))
614 schedule_timeout_idle(HZ/10);
615
616 if (attempts <= MAX_OOM_REAP_RETRIES ||
617 test_bit(MMF_OOM_SKIP, &mm->flags))
618 goto done;
619
620 pr_info("oom_reaper: unable to reap pid:%d (%s)\n",
621 task_pid_nr(tsk), tsk->comm);
622 sched_show_task(tsk);
623 debug_show_all_locks();
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 mmap_write_unlock(mm).
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 pr_info("%s: OOM victim %d (%s) is already exiting. Skip killing the task\n",
865 message, task_pid_nr(victim), victim->comm);
866 put_task_struct(victim);
867 return;
868 } else if (victim != p) {
869 get_task_struct(p);
870 put_task_struct(victim);
871 victim = p;
872 }
873
874 /* Get a reference to safely compare mm after task_unlock(victim) */
875 mm = victim->mm;
876 mmgrab(mm);
877
878 /* Raise event before sending signal: task reaper must see this */
879 count_vm_event(OOM_KILL);
880 memcg_memory_event_mm(mm, MEMCG_OOM_KILL);
881
882 /*
883 * We should send SIGKILL before granting access to memory reserves
884 * in order to prevent the OOM victim from depleting the memory
885 * reserves from the user space under its control.
886 */
887 do_send_sig_info(SIGKILL, SEND_SIG_PRIV, victim, PIDTYPE_TGID);
888 mark_oom_victim(victim);
889 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",
890 message, task_pid_nr(victim), victim->comm, K(mm->total_vm),
891 K(get_mm_counter(mm, MM_ANONPAGES)),
892 K(get_mm_counter(mm, MM_FILEPAGES)),
893 K(get_mm_counter(mm, MM_SHMEMPAGES)),
894 from_kuid(&init_user_ns, task_uid(victim)),
895 mm_pgtables_bytes(mm) >> 10, victim->signal->oom_score_adj);
896 task_unlock(victim);
897
898 /*
899 * Kill all user processes sharing victim->mm in other thread groups, if
900 * any. They don't get access to memory reserves, though, to avoid
901 * depletion of all memory. This prevents mm->mmap_lock livelock when an
902 * oom killed thread cannot exit because it requires the semaphore and
903 * its contended by another thread trying to allocate memory itself.
904 * That thread will now get access to memory reserves since it has a
905 * pending fatal signal.
906 */
907 rcu_read_lock();
908 for_each_process(p) {
909 if (!process_shares_mm(p, mm))
910 continue;
911 if (same_thread_group(p, victim))
912 continue;
913 if (is_global_init(p)) {
914 can_oom_reap = false;
915 set_bit(MMF_OOM_SKIP, &mm->flags);
916 pr_info("oom killer %d (%s) has mm pinned by %d (%s)\n",
917 task_pid_nr(victim), victim->comm,
918 task_pid_nr(p), p->comm);
919 continue;
920 }
921 /*
922 * No kthead_use_mm() user needs to read from the userspace so
923 * we are ok to reap it.
924 */
925 if (unlikely(p->flags & PF_KTHREAD))
926 continue;
927 do_send_sig_info(SIGKILL, SEND_SIG_PRIV, p, PIDTYPE_TGID);
928 }
929 rcu_read_unlock();
930
931 if (can_oom_reap)
932 wake_oom_reaper(victim);
933
934 mmdrop(mm);
935 put_task_struct(victim);
936}
937#undef K
938
939/*
940 * Kill provided task unless it's secured by setting
941 * oom_score_adj to OOM_SCORE_ADJ_MIN.
942 */
943static int oom_kill_memcg_member(struct task_struct *task, void *message)
944{
945 if (task->signal->oom_score_adj != OOM_SCORE_ADJ_MIN &&
946 !is_global_init(task)) {
947 get_task_struct(task);
948 __oom_kill_process(task, message);
949 }
950 return 0;
951}
952
953static void oom_kill_process(struct oom_control *oc, const char *message)
954{
955 struct task_struct *victim = oc->chosen;
956 struct mem_cgroup *oom_group;
957 static DEFINE_RATELIMIT_STATE(oom_rs, DEFAULT_RATELIMIT_INTERVAL,
958 DEFAULT_RATELIMIT_BURST);
959
960 /*
961 * If the task is already exiting, don't alarm the sysadmin or kill
962 * its children or threads, just give it access to memory reserves
963 * so it can die quickly
964 */
965 task_lock(victim);
966 if (task_will_free_mem(victim)) {
967 mark_oom_victim(victim);
968 wake_oom_reaper(victim);
969 task_unlock(victim);
970 put_task_struct(victim);
971 return;
972 }
973 task_unlock(victim);
974
975 if (__ratelimit(&oom_rs))
976 dump_header(oc, victim);
977
978 /*
979 * Do we need to kill the entire memory cgroup?
980 * Or even one of the ancestor memory cgroups?
981 * Check this out before killing the victim task.
982 */
983 oom_group = mem_cgroup_get_oom_group(victim, oc->memcg);
984
985 __oom_kill_process(victim, message);
986
987 /*
988 * If necessary, kill all tasks in the selected memory cgroup.
989 */
990 if (oom_group) {
991 mem_cgroup_print_oom_group(oom_group);
992 mem_cgroup_scan_tasks(oom_group, oom_kill_memcg_member,
993 (void*)message);
994 mem_cgroup_put(oom_group);
995 }
996}
997
998/*
999 * Determines whether the kernel must panic because of the panic_on_oom sysctl.
1000 */
1001static void check_panic_on_oom(struct oom_control *oc)
1002{
1003 if (likely(!sysctl_panic_on_oom))
1004 return;
1005 if (sysctl_panic_on_oom != 2) {
1006 /*
1007 * panic_on_oom == 1 only affects CONSTRAINT_NONE, the kernel
1008 * does not panic for cpuset, mempolicy, or memcg allocation
1009 * failures.
1010 */
1011 if (oc->constraint != CONSTRAINT_NONE)
1012 return;
1013 }
1014 /* Do not panic for oom kills triggered by sysrq */
1015 if (is_sysrq_oom(oc))
1016 return;
1017 dump_header(oc, NULL);
1018 panic("Out of memory: %s panic_on_oom is enabled\n",
1019 sysctl_panic_on_oom == 2 ? "compulsory" : "system-wide");
1020}
1021
1022static BLOCKING_NOTIFIER_HEAD(oom_notify_list);
1023
1024int register_oom_notifier(struct notifier_block *nb)
1025{
1026 return blocking_notifier_chain_register(&oom_notify_list, nb);
1027}
1028EXPORT_SYMBOL_GPL(register_oom_notifier);
1029
1030int unregister_oom_notifier(struct notifier_block *nb)
1031{
1032 return blocking_notifier_chain_unregister(&oom_notify_list, nb);
1033}
1034EXPORT_SYMBOL_GPL(unregister_oom_notifier);
1035
1036/**
1037 * out_of_memory - kill the "best" process when we run out of memory
1038 * @oc: pointer to struct oom_control
1039 *
1040 * If we run out of memory, we have the choice between either
1041 * killing a random task (bad), letting the system crash (worse)
1042 * OR try to be smart about which process to kill. Note that we
1043 * don't have to be perfect here, we just have to be good.
1044 */
1045bool out_of_memory(struct oom_control *oc)
1046{
1047 unsigned long freed = 0;
1048
1049 if (oom_killer_disabled)
1050 return false;
1051
1052 if (!is_memcg_oom(oc)) {
1053 blocking_notifier_call_chain(&oom_notify_list, 0, &freed);
1054 if (freed > 0)
1055 /* Got some memory back in the last second. */
1056 return true;
1057 }
1058
1059 /*
1060 * If current has a pending SIGKILL or is exiting, then automatically
1061 * select it. The goal is to allow it to allocate so that it may
1062 * quickly exit and free its memory.
1063 */
1064 if (task_will_free_mem(current)) {
1065 mark_oom_victim(current);
1066 wake_oom_reaper(current);
1067 return true;
1068 }
1069
1070 /*
1071 * The OOM killer does not compensate for IO-less reclaim.
1072 * pagefault_out_of_memory lost its gfp context so we have to
1073 * make sure exclude 0 mask - all other users should have at least
1074 * ___GFP_DIRECT_RECLAIM to get here. But mem_cgroup_oom() has to
1075 * invoke the OOM killer even if it is a GFP_NOFS allocation.
1076 */
1077 if (oc->gfp_mask && !(oc->gfp_mask & __GFP_FS) && !is_memcg_oom(oc))
1078 return true;
1079
1080 /*
1081 * Check if there were limitations on the allocation (only relevant for
1082 * NUMA and memcg) that may require different handling.
1083 */
1084 oc->constraint = constrained_alloc(oc);
1085 if (oc->constraint != CONSTRAINT_MEMORY_POLICY)
1086 oc->nodemask = NULL;
1087 check_panic_on_oom(oc);
1088
1089 if (!is_memcg_oom(oc) && sysctl_oom_kill_allocating_task &&
1090 current->mm && !oom_unkillable_task(current) &&
1091 oom_cpuset_eligible(current, oc) &&
1092 current->signal->oom_score_adj != OOM_SCORE_ADJ_MIN) {
1093 get_task_struct(current);
1094 oc->chosen = current;
1095 oom_kill_process(oc, "Out of memory (oom_kill_allocating_task)");
1096 return true;
1097 }
1098
1099 select_bad_process(oc);
1100 /* Found nothing?!?! */
1101 if (!oc->chosen) {
1102 dump_header(oc, NULL);
1103 pr_warn("Out of memory and no killable processes...\n");
1104 /*
1105 * If we got here due to an actual allocation at the
1106 * system level, we cannot survive this and will enter
1107 * an endless loop in the allocator. Bail out now.
1108 */
1109 if (!is_sysrq_oom(oc) && !is_memcg_oom(oc))
1110 panic("System is deadlocked on memory\n");
1111 }
1112 if (oc->chosen && oc->chosen != (void *)-1UL)
1113 oom_kill_process(oc, !is_memcg_oom(oc) ? "Out of memory" :
1114 "Memory cgroup out of memory");
1115 return !!oc->chosen;
1116}
1117
1118/*
1119 * The pagefault handler calls here because it is out of memory, so kill a
1120 * memory-hogging task. If oom_lock is held by somebody else, a parallel oom
1121 * killing is already in progress so do nothing.
1122 */
1123void pagefault_out_of_memory(void)
1124{
1125 struct oom_control oc = {
1126 .zonelist = NULL,
1127 .nodemask = NULL,
1128 .memcg = NULL,
1129 .gfp_mask = 0,
1130 .order = 0,
1131 };
1132
1133 if (mem_cgroup_oom_synchronize(true))
1134 return;
1135
1136 if (!mutex_trylock(&oom_lock))
1137 return;
1138 out_of_memory(&oc);
1139 mutex_unlock(&oom_lock);
1140}
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#include <linux/cred.h>
48
49#include <asm/tlb.h>
50#include "internal.h"
51#include "slab.h"
52
53#define CREATE_TRACE_POINTS
54#include <trace/events/oom.h>
55
56static int sysctl_panic_on_oom;
57static int sysctl_oom_kill_allocating_task;
58static int sysctl_oom_dump_tasks = 1;
59
60/*
61 * Serializes oom killer invocations (out_of_memory()) from all contexts to
62 * prevent from over eager oom killing (e.g. when the oom killer is invoked
63 * from different domains).
64 *
65 * oom_killer_disable() relies on this lock to stabilize oom_killer_disabled
66 * and mark_oom_victim
67 */
68DEFINE_MUTEX(oom_lock);
69/* Serializes oom_score_adj and oom_score_adj_min updates */
70DEFINE_MUTEX(oom_adj_mutex);
71
72static inline bool is_memcg_oom(struct oom_control *oc)
73{
74 return oc->memcg != NULL;
75}
76
77#ifdef CONFIG_NUMA
78/**
79 * oom_cpuset_eligible() - check task eligibility for kill
80 * @start: task struct of which task to consider
81 * @oc: pointer to struct oom_control
82 *
83 * Task eligibility is determined by whether or not a candidate task, @tsk,
84 * shares the same mempolicy nodes as current if it is bound by such a policy
85 * and whether or not it has the same set of allowed cpuset nodes.
86 *
87 * This function is assuming oom-killer context and 'current' has triggered
88 * the oom-killer.
89 */
90static bool oom_cpuset_eligible(struct task_struct *start,
91 struct oom_control *oc)
92{
93 struct task_struct *tsk;
94 bool ret = false;
95 const nodemask_t *mask = oc->nodemask;
96
97 rcu_read_lock();
98 for_each_thread(start, tsk) {
99 if (mask) {
100 /*
101 * If this is a mempolicy constrained oom, tsk's
102 * cpuset is irrelevant. Only return true if its
103 * mempolicy intersects current, otherwise it may be
104 * needlessly killed.
105 */
106 ret = mempolicy_in_oom_domain(tsk, mask);
107 } else {
108 /*
109 * This is not a mempolicy constrained oom, so only
110 * check the mems of tsk's cpuset.
111 */
112 ret = cpuset_mems_allowed_intersects(current, tsk);
113 }
114 if (ret)
115 break;
116 }
117 rcu_read_unlock();
118
119 return ret;
120}
121#else
122static bool oom_cpuset_eligible(struct task_struct *tsk, struct oom_control *oc)
123{
124 return true;
125}
126#endif /* CONFIG_NUMA */
127
128/*
129 * The process p may have detached its own ->mm while exiting or through
130 * kthread_use_mm(), but one or more of its subthreads may still have a valid
131 * pointer. Return p, or any of its subthreads with a valid ->mm, with
132 * task_lock() held.
133 */
134struct task_struct *find_lock_task_mm(struct task_struct *p)
135{
136 struct task_struct *t;
137
138 rcu_read_lock();
139
140 for_each_thread(p, t) {
141 task_lock(t);
142 if (likely(t->mm))
143 goto found;
144 task_unlock(t);
145 }
146 t = NULL;
147found:
148 rcu_read_unlock();
149
150 return t;
151}
152
153/*
154 * order == -1 means the oom kill is required by sysrq, otherwise only
155 * for display purposes.
156 */
157static inline bool is_sysrq_oom(struct oom_control *oc)
158{
159 return oc->order == -1;
160}
161
162/* return true if the task is not adequate as candidate victim task. */
163static bool oom_unkillable_task(struct task_struct *p)
164{
165 if (is_global_init(p))
166 return true;
167 if (p->flags & PF_KTHREAD)
168 return true;
169 return false;
170}
171
172/*
173 * Check whether unreclaimable slab amount is greater than
174 * all user memory(LRU pages).
175 * dump_unreclaimable_slab() could help in the case that
176 * oom due to too much unreclaimable slab used by kernel.
177*/
178static bool should_dump_unreclaim_slab(void)
179{
180 unsigned long nr_lru;
181
182 nr_lru = global_node_page_state(NR_ACTIVE_ANON) +
183 global_node_page_state(NR_INACTIVE_ANON) +
184 global_node_page_state(NR_ACTIVE_FILE) +
185 global_node_page_state(NR_INACTIVE_FILE) +
186 global_node_page_state(NR_ISOLATED_ANON) +
187 global_node_page_state(NR_ISOLATED_FILE) +
188 global_node_page_state(NR_UNEVICTABLE);
189
190 return (global_node_page_state_pages(NR_SLAB_UNRECLAIMABLE_B) > nr_lru);
191}
192
193/**
194 * oom_badness - heuristic function to determine which candidate task to kill
195 * @p: task struct of which task we should calculate
196 * @totalpages: total present RAM allowed for page allocation
197 *
198 * The heuristic for determining which task to kill is made to be as simple and
199 * predictable as possible. The goal is to return the highest value for the
200 * task consuming the most memory to avoid subsequent oom failures.
201 */
202long oom_badness(struct task_struct *p, unsigned long totalpages)
203{
204 long points;
205 long adj;
206
207 if (oom_unkillable_task(p))
208 return LONG_MIN;
209
210 p = find_lock_task_mm(p);
211 if (!p)
212 return LONG_MIN;
213
214 /*
215 * Do not even consider tasks which are explicitly marked oom
216 * unkillable or have been already oom reaped or the are in
217 * the middle of vfork
218 */
219 adj = (long)p->signal->oom_score_adj;
220 if (adj == OOM_SCORE_ADJ_MIN ||
221 test_bit(MMF_OOM_SKIP, &p->mm->flags) ||
222 in_vfork(p)) {
223 task_unlock(p);
224 return LONG_MIN;
225 }
226
227 /*
228 * The baseline for the badness score is the proportion of RAM that each
229 * task's rss, pagetable and swap space use.
230 */
231 points = get_mm_rss(p->mm) + get_mm_counter(p->mm, MM_SWAPENTS) +
232 mm_pgtables_bytes(p->mm) / PAGE_SIZE;
233 task_unlock(p);
234
235 /* Normalize to oom_score_adj units */
236 adj *= totalpages / 1000;
237 points += adj;
238
239 return points;
240}
241
242static const char * const oom_constraint_text[] = {
243 [CONSTRAINT_NONE] = "CONSTRAINT_NONE",
244 [CONSTRAINT_CPUSET] = "CONSTRAINT_CPUSET",
245 [CONSTRAINT_MEMORY_POLICY] = "CONSTRAINT_MEMORY_POLICY",
246 [CONSTRAINT_MEMCG] = "CONSTRAINT_MEMCG",
247};
248
249/*
250 * Determine the type of allocation constraint.
251 */
252static enum oom_constraint constrained_alloc(struct oom_control *oc)
253{
254 struct zone *zone;
255 struct zoneref *z;
256 enum zone_type highest_zoneidx = gfp_zone(oc->gfp_mask);
257 bool cpuset_limited = false;
258 int nid;
259
260 if (is_memcg_oom(oc)) {
261 oc->totalpages = mem_cgroup_get_max(oc->memcg) ?: 1;
262 return CONSTRAINT_MEMCG;
263 }
264
265 /* Default to all available memory */
266 oc->totalpages = totalram_pages() + total_swap_pages;
267
268 if (!IS_ENABLED(CONFIG_NUMA))
269 return CONSTRAINT_NONE;
270
271 if (!oc->zonelist)
272 return CONSTRAINT_NONE;
273 /*
274 * Reach here only when __GFP_NOFAIL is used. So, we should avoid
275 * to kill current.We have to random task kill in this case.
276 * Hopefully, CONSTRAINT_THISNODE...but no way to handle it, now.
277 */
278 if (oc->gfp_mask & __GFP_THISNODE)
279 return CONSTRAINT_NONE;
280
281 /*
282 * This is not a __GFP_THISNODE allocation, so a truncated nodemask in
283 * the page allocator means a mempolicy is in effect. Cpuset policy
284 * is enforced in get_page_from_freelist().
285 */
286 if (oc->nodemask &&
287 !nodes_subset(node_states[N_MEMORY], *oc->nodemask)) {
288 oc->totalpages = total_swap_pages;
289 for_each_node_mask(nid, *oc->nodemask)
290 oc->totalpages += node_present_pages(nid);
291 return CONSTRAINT_MEMORY_POLICY;
292 }
293
294 /* Check this allocation failure is caused by cpuset's wall function */
295 for_each_zone_zonelist_nodemask(zone, z, oc->zonelist,
296 highest_zoneidx, oc->nodemask)
297 if (!cpuset_zone_allowed(zone, oc->gfp_mask))
298 cpuset_limited = true;
299
300 if (cpuset_limited) {
301 oc->totalpages = total_swap_pages;
302 for_each_node_mask(nid, cpuset_current_mems_allowed)
303 oc->totalpages += node_present_pages(nid);
304 return CONSTRAINT_CPUSET;
305 }
306 return CONSTRAINT_NONE;
307}
308
309static int oom_evaluate_task(struct task_struct *task, void *arg)
310{
311 struct oom_control *oc = arg;
312 long points;
313
314 if (oom_unkillable_task(task))
315 goto next;
316
317 /* p may not have freeable memory in nodemask */
318 if (!is_memcg_oom(oc) && !oom_cpuset_eligible(task, oc))
319 goto next;
320
321 /*
322 * This task already has access to memory reserves and is being killed.
323 * Don't allow any other task to have access to the reserves unless
324 * the task has MMF_OOM_SKIP because chances that it would release
325 * any memory is quite low.
326 */
327 if (!is_sysrq_oom(oc) && tsk_is_oom_victim(task)) {
328 if (test_bit(MMF_OOM_SKIP, &task->signal->oom_mm->flags))
329 goto next;
330 goto abort;
331 }
332
333 /*
334 * If task is allocating a lot of memory and has been marked to be
335 * killed first if it triggers an oom, then select it.
336 */
337 if (oom_task_origin(task)) {
338 points = LONG_MAX;
339 goto select;
340 }
341
342 points = oom_badness(task, oc->totalpages);
343 if (points == LONG_MIN || points < oc->chosen_points)
344 goto next;
345
346select:
347 if (oc->chosen)
348 put_task_struct(oc->chosen);
349 get_task_struct(task);
350 oc->chosen = task;
351 oc->chosen_points = points;
352next:
353 return 0;
354abort:
355 if (oc->chosen)
356 put_task_struct(oc->chosen);
357 oc->chosen = (void *)-1UL;
358 return 1;
359}
360
361/*
362 * Simple selection loop. We choose the process with the highest number of
363 * 'points'. In case scan was aborted, oc->chosen is set to -1.
364 */
365static void select_bad_process(struct oom_control *oc)
366{
367 oc->chosen_points = LONG_MIN;
368
369 if (is_memcg_oom(oc))
370 mem_cgroup_scan_tasks(oc->memcg, oom_evaluate_task, oc);
371 else {
372 struct task_struct *p;
373
374 rcu_read_lock();
375 for_each_process(p)
376 if (oom_evaluate_task(p, oc))
377 break;
378 rcu_read_unlock();
379 }
380}
381
382static int dump_task(struct task_struct *p, void *arg)
383{
384 struct oom_control *oc = arg;
385 struct task_struct *task;
386
387 if (oom_unkillable_task(p))
388 return 0;
389
390 /* p may not have freeable memory in nodemask */
391 if (!is_memcg_oom(oc) && !oom_cpuset_eligible(p, oc))
392 return 0;
393
394 task = find_lock_task_mm(p);
395 if (!task) {
396 /*
397 * All of p's threads have already detached their mm's. There's
398 * no need to report them; they can't be oom killed anyway.
399 */
400 return 0;
401 }
402
403 pr_info("[%7d] %5d %5d %8lu %8lu %8lu %8lu %9lu %8ld %8lu %5hd %s\n",
404 task->pid, from_kuid(&init_user_ns, task_uid(task)),
405 task->tgid, task->mm->total_vm, get_mm_rss(task->mm),
406 get_mm_counter(task->mm, MM_ANONPAGES), get_mm_counter(task->mm, MM_FILEPAGES),
407 get_mm_counter(task->mm, MM_SHMEMPAGES), mm_pgtables_bytes(task->mm),
408 get_mm_counter(task->mm, MM_SWAPENTS),
409 task->signal->oom_score_adj, task->comm);
410 task_unlock(task);
411
412 return 0;
413}
414
415/**
416 * dump_tasks - dump current memory state of all system tasks
417 * @oc: pointer to struct oom_control
418 *
419 * Dumps the current memory state of all eligible tasks. Tasks not in the same
420 * memcg, not in the same cpuset, or bound to a disjoint set of mempolicy nodes
421 * are not shown.
422 * State information includes task's pid, uid, tgid, vm size, rss,
423 * pgtables_bytes, swapents, oom_score_adj value, and name.
424 */
425static void dump_tasks(struct oom_control *oc)
426{
427 pr_info("Tasks state (memory values in pages):\n");
428 pr_info("[ pid ] uid tgid total_vm rss rss_anon rss_file rss_shmem pgtables_bytes swapents oom_score_adj name\n");
429
430 if (is_memcg_oom(oc))
431 mem_cgroup_scan_tasks(oc->memcg, dump_task, oc);
432 else {
433 struct task_struct *p;
434
435 rcu_read_lock();
436 for_each_process(p)
437 dump_task(p, oc);
438 rcu_read_unlock();
439 }
440}
441
442static void dump_oom_victim(struct oom_control *oc, struct task_struct *victim)
443{
444 /* one line summary of the oom killer context. */
445 pr_info("oom-kill:constraint=%s,nodemask=%*pbl",
446 oom_constraint_text[oc->constraint],
447 nodemask_pr_args(oc->nodemask));
448 cpuset_print_current_mems_allowed();
449 mem_cgroup_print_oom_context(oc->memcg, victim);
450 pr_cont(",task=%s,pid=%d,uid=%d\n", victim->comm, victim->pid,
451 from_kuid(&init_user_ns, task_uid(victim)));
452}
453
454static void dump_header(struct oom_control *oc)
455{
456 pr_warn("%s invoked oom-killer: gfp_mask=%#x(%pGg), order=%d, oom_score_adj=%hd\n",
457 current->comm, oc->gfp_mask, &oc->gfp_mask, oc->order,
458 current->signal->oom_score_adj);
459 if (!IS_ENABLED(CONFIG_COMPACTION) && oc->order)
460 pr_warn("COMPACTION is disabled!!!\n");
461
462 dump_stack();
463 if (is_memcg_oom(oc))
464 mem_cgroup_print_oom_meminfo(oc->memcg);
465 else {
466 __show_mem(SHOW_MEM_FILTER_NODES, oc->nodemask, gfp_zone(oc->gfp_mask));
467 if (should_dump_unreclaim_slab())
468 dump_unreclaimable_slab();
469 }
470 if (sysctl_oom_dump_tasks)
471 dump_tasks(oc);
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/*
483 * task->mm can be NULL if the task is the exited group leader. So to
484 * determine whether the task is using a particular mm, we examine all the
485 * task's threads: if one of those is using this mm then this task was also
486 * using it.
487 */
488bool process_shares_mm(struct task_struct *p, struct mm_struct *mm)
489{
490 struct task_struct *t;
491
492 for_each_thread(p, t) {
493 struct mm_struct *t_mm = READ_ONCE(t->mm);
494 if (t_mm)
495 return t_mm == mm;
496 }
497 return false;
498}
499
500#ifdef CONFIG_MMU
501/*
502 * OOM Reaper kernel thread which tries to reap the memory used by the OOM
503 * victim (if that is possible) to help the OOM killer to move on.
504 */
505static struct task_struct *oom_reaper_th;
506static DECLARE_WAIT_QUEUE_HEAD(oom_reaper_wait);
507static struct task_struct *oom_reaper_list;
508static DEFINE_SPINLOCK(oom_reaper_lock);
509
510static bool __oom_reap_task_mm(struct mm_struct *mm)
511{
512 struct vm_area_struct *vma;
513 bool ret = true;
514 VMA_ITERATOR(vmi, mm, 0);
515
516 /*
517 * Tell all users of get_user/copy_from_user etc... that the content
518 * is no longer stable. No barriers really needed because unmapping
519 * should imply barriers already and the reader would hit a page fault
520 * if it stumbled over a reaped memory.
521 */
522 set_bit(MMF_UNSTABLE, &mm->flags);
523
524 for_each_vma(vmi, vma) {
525 if (vma->vm_flags & (VM_HUGETLB|VM_PFNMAP))
526 continue;
527
528 /*
529 * Only anonymous pages have a good chance to be dropped
530 * without additional steps which we cannot afford as we
531 * are OOM already.
532 *
533 * We do not even care about fs backed pages because all
534 * which are reclaimable have already been reclaimed and
535 * we do not want to block exit_mmap by keeping mm ref
536 * count elevated without a good reason.
537 */
538 if (vma_is_anonymous(vma) || !(vma->vm_flags & VM_SHARED)) {
539 struct mmu_notifier_range range;
540 struct mmu_gather tlb;
541
542 mmu_notifier_range_init(&range, MMU_NOTIFY_UNMAP, 0,
543 mm, vma->vm_start,
544 vma->vm_end);
545 tlb_gather_mmu(&tlb, mm);
546 if (mmu_notifier_invalidate_range_start_nonblock(&range)) {
547 tlb_finish_mmu(&tlb);
548 ret = false;
549 continue;
550 }
551 unmap_page_range(&tlb, vma, range.start, range.end, NULL);
552 mmu_notifier_invalidate_range_end(&range);
553 tlb_finish_mmu(&tlb);
554 }
555 }
556
557 return ret;
558}
559
560/*
561 * Reaps the address space of the give task.
562 *
563 * Returns true on success and false if none or part of the address space
564 * has been reclaimed and the caller should retry later.
565 */
566static bool oom_reap_task_mm(struct task_struct *tsk, struct mm_struct *mm)
567{
568 bool ret = true;
569
570 if (!mmap_read_trylock(mm)) {
571 trace_skip_task_reaping(tsk->pid);
572 return false;
573 }
574
575 /*
576 * MMF_OOM_SKIP is set by exit_mmap when the OOM reaper can't
577 * work on the mm anymore. The check for MMF_OOM_SKIP must run
578 * under mmap_lock for reading because it serializes against the
579 * mmap_write_lock();mmap_write_unlock() cycle in exit_mmap().
580 */
581 if (test_bit(MMF_OOM_SKIP, &mm->flags)) {
582 trace_skip_task_reaping(tsk->pid);
583 goto out_unlock;
584 }
585
586 trace_start_task_reaping(tsk->pid);
587
588 /* failed to reap part of the address space. Try again later */
589 ret = __oom_reap_task_mm(mm);
590 if (!ret)
591 goto out_finish;
592
593 pr_info("oom_reaper: reaped process %d (%s), now anon-rss:%lukB, file-rss:%lukB, shmem-rss:%lukB\n",
594 task_pid_nr(tsk), tsk->comm,
595 K(get_mm_counter(mm, MM_ANONPAGES)),
596 K(get_mm_counter(mm, MM_FILEPAGES)),
597 K(get_mm_counter(mm, MM_SHMEMPAGES)));
598out_finish:
599 trace_finish_task_reaping(tsk->pid);
600out_unlock:
601 mmap_read_unlock(mm);
602
603 return ret;
604}
605
606#define MAX_OOM_REAP_RETRIES 10
607static void oom_reap_task(struct task_struct *tsk)
608{
609 int attempts = 0;
610 struct mm_struct *mm = tsk->signal->oom_mm;
611
612 /* Retry the mmap_read_trylock(mm) a few times */
613 while (attempts++ < MAX_OOM_REAP_RETRIES && !oom_reap_task_mm(tsk, mm))
614 schedule_timeout_idle(HZ/10);
615
616 if (attempts <= MAX_OOM_REAP_RETRIES ||
617 test_bit(MMF_OOM_SKIP, &mm->flags))
618 goto done;
619
620 pr_info("oom_reaper: unable to reap pid:%d (%s)\n",
621 task_pid_nr(tsk), tsk->comm);
622 sched_show_task(tsk);
623 debug_show_all_locks();
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 mmap_write_unlock(mm).
631 */
632 set_bit(MMF_OOM_SKIP, &mm->flags);
633
634 /* Drop a reference taken by queue_oom_reaper */
635 put_task_struct(tsk);
636}
637
638static int oom_reaper(void *unused)
639{
640 set_freezable();
641
642 while (true) {
643 struct task_struct *tsk = NULL;
644
645 wait_event_freezable(oom_reaper_wait, oom_reaper_list != NULL);
646 spin_lock_irq(&oom_reaper_lock);
647 if (oom_reaper_list != NULL) {
648 tsk = oom_reaper_list;
649 oom_reaper_list = tsk->oom_reaper_list;
650 }
651 spin_unlock_irq(&oom_reaper_lock);
652
653 if (tsk)
654 oom_reap_task(tsk);
655 }
656
657 return 0;
658}
659
660static void wake_oom_reaper(struct timer_list *timer)
661{
662 struct task_struct *tsk = container_of(timer, struct task_struct,
663 oom_reaper_timer);
664 struct mm_struct *mm = tsk->signal->oom_mm;
665 unsigned long flags;
666
667 /* The victim managed to terminate on its own - see exit_mmap */
668 if (test_bit(MMF_OOM_SKIP, &mm->flags)) {
669 put_task_struct(tsk);
670 return;
671 }
672
673 spin_lock_irqsave(&oom_reaper_lock, flags);
674 tsk->oom_reaper_list = oom_reaper_list;
675 oom_reaper_list = tsk;
676 spin_unlock_irqrestore(&oom_reaper_lock, flags);
677 trace_wake_reaper(tsk->pid);
678 wake_up(&oom_reaper_wait);
679}
680
681/*
682 * Give the OOM victim time to exit naturally before invoking the oom_reaping.
683 * The timers timeout is arbitrary... the longer it is, the longer the worst
684 * case scenario for the OOM can take. If it is too small, the oom_reaper can
685 * get in the way and release resources needed by the process exit path.
686 * e.g. The futex robust list can sit in Anon|Private memory that gets reaped
687 * before the exit path is able to wake the futex waiters.
688 */
689#define OOM_REAPER_DELAY (2*HZ)
690static void queue_oom_reaper(struct task_struct *tsk)
691{
692 /* mm is already queued? */
693 if (test_and_set_bit(MMF_OOM_REAP_QUEUED, &tsk->signal->oom_mm->flags))
694 return;
695
696 get_task_struct(tsk);
697 timer_setup(&tsk->oom_reaper_timer, wake_oom_reaper, 0);
698 tsk->oom_reaper_timer.expires = jiffies + OOM_REAPER_DELAY;
699 add_timer(&tsk->oom_reaper_timer);
700}
701
702#ifdef CONFIG_SYSCTL
703static struct ctl_table vm_oom_kill_table[] = {
704 {
705 .procname = "panic_on_oom",
706 .data = &sysctl_panic_on_oom,
707 .maxlen = sizeof(sysctl_panic_on_oom),
708 .mode = 0644,
709 .proc_handler = proc_dointvec_minmax,
710 .extra1 = SYSCTL_ZERO,
711 .extra2 = SYSCTL_TWO,
712 },
713 {
714 .procname = "oom_kill_allocating_task",
715 .data = &sysctl_oom_kill_allocating_task,
716 .maxlen = sizeof(sysctl_oom_kill_allocating_task),
717 .mode = 0644,
718 .proc_handler = proc_dointvec,
719 },
720 {
721 .procname = "oom_dump_tasks",
722 .data = &sysctl_oom_dump_tasks,
723 .maxlen = sizeof(sysctl_oom_dump_tasks),
724 .mode = 0644,
725 .proc_handler = proc_dointvec,
726 },
727 {}
728};
729#endif
730
731static int __init oom_init(void)
732{
733 oom_reaper_th = kthread_run(oom_reaper, NULL, "oom_reaper");
734#ifdef CONFIG_SYSCTL
735 register_sysctl_init("vm", vm_oom_kill_table);
736#endif
737 return 0;
738}
739subsys_initcall(oom_init)
740#else
741static inline void queue_oom_reaper(struct task_struct *tsk)
742{
743}
744#endif /* CONFIG_MMU */
745
746/**
747 * mark_oom_victim - mark the given task as OOM victim
748 * @tsk: task to mark
749 *
750 * Has to be called with oom_lock held and never after
751 * oom has been disabled already.
752 *
753 * tsk->mm has to be non NULL and caller has to guarantee it is stable (either
754 * under task_lock or operate on the current).
755 */
756static void mark_oom_victim(struct task_struct *tsk)
757{
758 const struct cred *cred;
759 struct mm_struct *mm = tsk->mm;
760
761 WARN_ON(oom_killer_disabled);
762 /* OOM killer might race with memcg OOM */
763 if (test_and_set_tsk_thread_flag(tsk, TIF_MEMDIE))
764 return;
765
766 /* oom_mm is bound to the signal struct life time. */
767 if (!cmpxchg(&tsk->signal->oom_mm, NULL, mm))
768 mmgrab(tsk->signal->oom_mm);
769
770 /*
771 * Make sure that the task is woken up from uninterruptible sleep
772 * if it is frozen because OOM killer wouldn't be able to free
773 * any memory and livelock. freezing_slow_path will tell the freezer
774 * that TIF_MEMDIE tasks should be ignored.
775 */
776 __thaw_task(tsk);
777 atomic_inc(&oom_victims);
778 cred = get_task_cred(tsk);
779 trace_mark_victim(tsk, cred->uid.val);
780 put_cred(cred);
781}
782
783/**
784 * exit_oom_victim - note the exit of an OOM victim
785 */
786void exit_oom_victim(void)
787{
788 clear_thread_flag(TIF_MEMDIE);
789
790 if (!atomic_dec_return(&oom_victims))
791 wake_up_all(&oom_victims_wait);
792}
793
794/**
795 * oom_killer_enable - enable OOM killer
796 */
797void oom_killer_enable(void)
798{
799 oom_killer_disabled = false;
800 pr_info("OOM killer enabled.\n");
801}
802
803/**
804 * oom_killer_disable - disable OOM killer
805 * @timeout: maximum timeout to wait for oom victims in jiffies
806 *
807 * Forces all page allocations to fail rather than trigger OOM killer.
808 * Will block and wait until all OOM victims are killed or the given
809 * timeout expires.
810 *
811 * The function cannot be called when there are runnable user tasks because
812 * the userspace would see unexpected allocation failures as a result. Any
813 * new usage of this function should be consulted with MM people.
814 *
815 * Returns true if successful and false if the OOM killer cannot be
816 * disabled.
817 */
818bool oom_killer_disable(signed long timeout)
819{
820 signed long ret;
821
822 /*
823 * Make sure to not race with an ongoing OOM killer. Check that the
824 * current is not killed (possibly due to sharing the victim's memory).
825 */
826 if (mutex_lock_killable(&oom_lock))
827 return false;
828 oom_killer_disabled = true;
829 mutex_unlock(&oom_lock);
830
831 ret = wait_event_interruptible_timeout(oom_victims_wait,
832 !atomic_read(&oom_victims), timeout);
833 if (ret <= 0) {
834 oom_killer_enable();
835 return false;
836 }
837 pr_info("OOM killer disabled.\n");
838
839 return true;
840}
841
842static inline bool __task_will_free_mem(struct task_struct *task)
843{
844 struct signal_struct *sig = task->signal;
845
846 /*
847 * A coredumping process may sleep for an extended period in
848 * coredump_task_exit(), so the oom killer cannot assume that
849 * the process will promptly exit and release memory.
850 */
851 if (sig->core_state)
852 return false;
853
854 if (sig->flags & SIGNAL_GROUP_EXIT)
855 return true;
856
857 if (thread_group_empty(task) && (task->flags & PF_EXITING))
858 return true;
859
860 return false;
861}
862
863/*
864 * Checks whether the given task is dying or exiting and likely to
865 * release its address space. This means that all threads and processes
866 * sharing the same mm have to be killed or exiting.
867 * Caller has to make sure that task->mm is stable (hold task_lock or
868 * it operates on the current).
869 */
870static bool task_will_free_mem(struct task_struct *task)
871{
872 struct mm_struct *mm = task->mm;
873 struct task_struct *p;
874 bool ret = true;
875
876 /*
877 * Skip tasks without mm because it might have passed its exit_mm and
878 * exit_oom_victim. oom_reaper could have rescued that but do not rely
879 * on that for now. We can consider find_lock_task_mm in future.
880 */
881 if (!mm)
882 return false;
883
884 if (!__task_will_free_mem(task))
885 return false;
886
887 /*
888 * This task has already been drained by the oom reaper so there are
889 * only small chances it will free some more
890 */
891 if (test_bit(MMF_OOM_SKIP, &mm->flags))
892 return false;
893
894 if (atomic_read(&mm->mm_users) <= 1)
895 return true;
896
897 /*
898 * Make sure that all tasks which share the mm with the given tasks
899 * are dying as well to make sure that a) nobody pins its mm and
900 * b) the task is also reapable by the oom reaper.
901 */
902 rcu_read_lock();
903 for_each_process(p) {
904 if (!process_shares_mm(p, mm))
905 continue;
906 if (same_thread_group(task, p))
907 continue;
908 ret = __task_will_free_mem(p);
909 if (!ret)
910 break;
911 }
912 rcu_read_unlock();
913
914 return ret;
915}
916
917static void __oom_kill_process(struct task_struct *victim, const char *message)
918{
919 struct task_struct *p;
920 struct mm_struct *mm;
921 bool can_oom_reap = true;
922
923 p = find_lock_task_mm(victim);
924 if (!p) {
925 pr_info("%s: OOM victim %d (%s) is already exiting. Skip killing the task\n",
926 message, task_pid_nr(victim), victim->comm);
927 put_task_struct(victim);
928 return;
929 } else if (victim != p) {
930 get_task_struct(p);
931 put_task_struct(victim);
932 victim = p;
933 }
934
935 /* Get a reference to safely compare mm after task_unlock(victim) */
936 mm = victim->mm;
937 mmgrab(mm);
938
939 /* Raise event before sending signal: task reaper must see this */
940 count_vm_event(OOM_KILL);
941 memcg_memory_event_mm(mm, MEMCG_OOM_KILL);
942
943 /*
944 * We should send SIGKILL before granting access to memory reserves
945 * in order to prevent the OOM victim from depleting the memory
946 * reserves from the user space under its control.
947 */
948 do_send_sig_info(SIGKILL, SEND_SIG_PRIV, victim, PIDTYPE_TGID);
949 mark_oom_victim(victim);
950 pr_err("%s: Killed process %d (%s) total-vm:%lukB, anon-rss:%lukB, file-rss:%lukB, shmem-rss:%lukB, UID:%u pgtables:%lukB oom_score_adj:%hd\n",
951 message, task_pid_nr(victim), victim->comm, K(mm->total_vm),
952 K(get_mm_counter(mm, MM_ANONPAGES)),
953 K(get_mm_counter(mm, MM_FILEPAGES)),
954 K(get_mm_counter(mm, MM_SHMEMPAGES)),
955 from_kuid(&init_user_ns, task_uid(victim)),
956 mm_pgtables_bytes(mm) >> 10, victim->signal->oom_score_adj);
957 task_unlock(victim);
958
959 /*
960 * Kill all user processes sharing victim->mm in other thread groups, if
961 * any. They don't get access to memory reserves, though, to avoid
962 * depletion of all memory. This prevents mm->mmap_lock livelock when an
963 * oom killed thread cannot exit because it requires the semaphore and
964 * its contended by another thread trying to allocate memory itself.
965 * That thread will now get access to memory reserves since it has a
966 * pending fatal signal.
967 */
968 rcu_read_lock();
969 for_each_process(p) {
970 if (!process_shares_mm(p, mm))
971 continue;
972 if (same_thread_group(p, victim))
973 continue;
974 if (is_global_init(p)) {
975 can_oom_reap = false;
976 set_bit(MMF_OOM_SKIP, &mm->flags);
977 pr_info("oom killer %d (%s) has mm pinned by %d (%s)\n",
978 task_pid_nr(victim), victim->comm,
979 task_pid_nr(p), p->comm);
980 continue;
981 }
982 /*
983 * No kthread_use_mm() user needs to read from the userspace so
984 * we are ok to reap it.
985 */
986 if (unlikely(p->flags & PF_KTHREAD))
987 continue;
988 do_send_sig_info(SIGKILL, SEND_SIG_PRIV, p, PIDTYPE_TGID);
989 }
990 rcu_read_unlock();
991
992 if (can_oom_reap)
993 queue_oom_reaper(victim);
994
995 mmdrop(mm);
996 put_task_struct(victim);
997}
998
999/*
1000 * Kill provided task unless it's secured by setting
1001 * oom_score_adj to OOM_SCORE_ADJ_MIN.
1002 */
1003static int oom_kill_memcg_member(struct task_struct *task, void *message)
1004{
1005 if (task->signal->oom_score_adj != OOM_SCORE_ADJ_MIN &&
1006 !is_global_init(task)) {
1007 get_task_struct(task);
1008 __oom_kill_process(task, message);
1009 }
1010 return 0;
1011}
1012
1013static void oom_kill_process(struct oom_control *oc, const char *message)
1014{
1015 struct task_struct *victim = oc->chosen;
1016 struct mem_cgroup *oom_group;
1017 static DEFINE_RATELIMIT_STATE(oom_rs, DEFAULT_RATELIMIT_INTERVAL,
1018 DEFAULT_RATELIMIT_BURST);
1019
1020 /*
1021 * If the task is already exiting, don't alarm the sysadmin or kill
1022 * its children or threads, just give it access to memory reserves
1023 * so it can die quickly
1024 */
1025 task_lock(victim);
1026 if (task_will_free_mem(victim)) {
1027 mark_oom_victim(victim);
1028 queue_oom_reaper(victim);
1029 task_unlock(victim);
1030 put_task_struct(victim);
1031 return;
1032 }
1033 task_unlock(victim);
1034
1035 if (__ratelimit(&oom_rs)) {
1036 dump_header(oc);
1037 dump_oom_victim(oc, victim);
1038 }
1039
1040 /*
1041 * Do we need to kill the entire memory cgroup?
1042 * Or even one of the ancestor memory cgroups?
1043 * Check this out before killing the victim task.
1044 */
1045 oom_group = mem_cgroup_get_oom_group(victim, oc->memcg);
1046
1047 __oom_kill_process(victim, message);
1048
1049 /*
1050 * If necessary, kill all tasks in the selected memory cgroup.
1051 */
1052 if (oom_group) {
1053 memcg_memory_event(oom_group, MEMCG_OOM_GROUP_KILL);
1054 mem_cgroup_print_oom_group(oom_group);
1055 mem_cgroup_scan_tasks(oom_group, oom_kill_memcg_member,
1056 (void *)message);
1057 mem_cgroup_put(oom_group);
1058 }
1059}
1060
1061/*
1062 * Determines whether the kernel must panic because of the panic_on_oom sysctl.
1063 */
1064static void check_panic_on_oom(struct oom_control *oc)
1065{
1066 if (likely(!sysctl_panic_on_oom))
1067 return;
1068 if (sysctl_panic_on_oom != 2) {
1069 /*
1070 * panic_on_oom == 1 only affects CONSTRAINT_NONE, the kernel
1071 * does not panic for cpuset, mempolicy, or memcg allocation
1072 * failures.
1073 */
1074 if (oc->constraint != CONSTRAINT_NONE)
1075 return;
1076 }
1077 /* Do not panic for oom kills triggered by sysrq */
1078 if (is_sysrq_oom(oc))
1079 return;
1080 dump_header(oc);
1081 panic("Out of memory: %s panic_on_oom is enabled\n",
1082 sysctl_panic_on_oom == 2 ? "compulsory" : "system-wide");
1083}
1084
1085static BLOCKING_NOTIFIER_HEAD(oom_notify_list);
1086
1087int register_oom_notifier(struct notifier_block *nb)
1088{
1089 return blocking_notifier_chain_register(&oom_notify_list, nb);
1090}
1091EXPORT_SYMBOL_GPL(register_oom_notifier);
1092
1093int unregister_oom_notifier(struct notifier_block *nb)
1094{
1095 return blocking_notifier_chain_unregister(&oom_notify_list, nb);
1096}
1097EXPORT_SYMBOL_GPL(unregister_oom_notifier);
1098
1099/**
1100 * out_of_memory - kill the "best" process when we run out of memory
1101 * @oc: pointer to struct oom_control
1102 *
1103 * If we run out of memory, we have the choice between either
1104 * killing a random task (bad), letting the system crash (worse)
1105 * OR try to be smart about which process to kill. Note that we
1106 * don't have to be perfect here, we just have to be good.
1107 */
1108bool out_of_memory(struct oom_control *oc)
1109{
1110 unsigned long freed = 0;
1111
1112 if (oom_killer_disabled)
1113 return false;
1114
1115 if (!is_memcg_oom(oc)) {
1116 blocking_notifier_call_chain(&oom_notify_list, 0, &freed);
1117 if (freed > 0 && !is_sysrq_oom(oc))
1118 /* Got some memory back in the last second. */
1119 return true;
1120 }
1121
1122 /*
1123 * If current has a pending SIGKILL or is exiting, then automatically
1124 * select it. The goal is to allow it to allocate so that it may
1125 * quickly exit and free its memory.
1126 */
1127 if (task_will_free_mem(current)) {
1128 mark_oom_victim(current);
1129 queue_oom_reaper(current);
1130 return true;
1131 }
1132
1133 /*
1134 * The OOM killer does not compensate for IO-less reclaim.
1135 * But mem_cgroup_oom() has to invoke the OOM killer even
1136 * if it is a GFP_NOFS allocation.
1137 */
1138 if (!(oc->gfp_mask & __GFP_FS) && !is_memcg_oom(oc))
1139 return true;
1140
1141 /*
1142 * Check if there were limitations on the allocation (only relevant for
1143 * NUMA and memcg) that may require different handling.
1144 */
1145 oc->constraint = constrained_alloc(oc);
1146 if (oc->constraint != CONSTRAINT_MEMORY_POLICY)
1147 oc->nodemask = NULL;
1148 check_panic_on_oom(oc);
1149
1150 if (!is_memcg_oom(oc) && sysctl_oom_kill_allocating_task &&
1151 current->mm && !oom_unkillable_task(current) &&
1152 oom_cpuset_eligible(current, oc) &&
1153 current->signal->oom_score_adj != OOM_SCORE_ADJ_MIN) {
1154 get_task_struct(current);
1155 oc->chosen = current;
1156 oom_kill_process(oc, "Out of memory (oom_kill_allocating_task)");
1157 return true;
1158 }
1159
1160 select_bad_process(oc);
1161 /* Found nothing?!?! */
1162 if (!oc->chosen) {
1163 dump_header(oc);
1164 pr_warn("Out of memory and no killable processes...\n");
1165 /*
1166 * If we got here due to an actual allocation at the
1167 * system level, we cannot survive this and will enter
1168 * an endless loop in the allocator. Bail out now.
1169 */
1170 if (!is_sysrq_oom(oc) && !is_memcg_oom(oc))
1171 panic("System is deadlocked on memory\n");
1172 }
1173 if (oc->chosen && oc->chosen != (void *)-1UL)
1174 oom_kill_process(oc, !is_memcg_oom(oc) ? "Out of memory" :
1175 "Memory cgroup out of memory");
1176 return !!oc->chosen;
1177}
1178
1179/*
1180 * The pagefault handler calls here because some allocation has failed. We have
1181 * to take care of the memcg OOM here because this is the only safe context without
1182 * any locks held but let the oom killer triggered from the allocation context care
1183 * about the global OOM.
1184 */
1185void pagefault_out_of_memory(void)
1186{
1187 static DEFINE_RATELIMIT_STATE(pfoom_rs, DEFAULT_RATELIMIT_INTERVAL,
1188 DEFAULT_RATELIMIT_BURST);
1189
1190 if (mem_cgroup_oom_synchronize(true))
1191 return;
1192
1193 if (fatal_signal_pending(current))
1194 return;
1195
1196 if (__ratelimit(&pfoom_rs))
1197 pr_warn("Huh VM_FAULT_OOM leaked out to the #PF handler. Retrying PF\n");
1198}
1199
1200SYSCALL_DEFINE2(process_mrelease, int, pidfd, unsigned int, flags)
1201{
1202#ifdef CONFIG_MMU
1203 struct mm_struct *mm = NULL;
1204 struct task_struct *task;
1205 struct task_struct *p;
1206 unsigned int f_flags;
1207 bool reap = false;
1208 long ret = 0;
1209
1210 if (flags)
1211 return -EINVAL;
1212
1213 task = pidfd_get_task(pidfd, &f_flags);
1214 if (IS_ERR(task))
1215 return PTR_ERR(task);
1216
1217 /*
1218 * Make sure to choose a thread which still has a reference to mm
1219 * during the group exit
1220 */
1221 p = find_lock_task_mm(task);
1222 if (!p) {
1223 ret = -ESRCH;
1224 goto put_task;
1225 }
1226
1227 mm = p->mm;
1228 mmgrab(mm);
1229
1230 if (task_will_free_mem(p))
1231 reap = true;
1232 else {
1233 /* Error only if the work has not been done already */
1234 if (!test_bit(MMF_OOM_SKIP, &mm->flags))
1235 ret = -EINVAL;
1236 }
1237 task_unlock(p);
1238
1239 if (!reap)
1240 goto drop_mm;
1241
1242 if (mmap_read_lock_killable(mm)) {
1243 ret = -EINTR;
1244 goto drop_mm;
1245 }
1246 /*
1247 * Check MMF_OOM_SKIP again under mmap_read_lock protection to ensure
1248 * possible change in exit_mmap is seen
1249 */
1250 if (!test_bit(MMF_OOM_SKIP, &mm->flags) && !__oom_reap_task_mm(mm))
1251 ret = -EAGAIN;
1252 mmap_read_unlock(mm);
1253
1254drop_mm:
1255 mmdrop(mm);
1256put_task:
1257 put_task_struct(task);
1258 return ret;
1259#else
1260 return -ENOSYS;
1261#endif /* CONFIG_MMU */
1262}