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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/*
2 * linux/mm/oom_kill.c
3 *
4 * Copyright (C) 1998,2000 Rik van Riel
5 * Thanks go out to Claus Fischer for some serious inspiration and
6 * for goading me into coding this file...
7 * Copyright (C) 2010 Google, Inc.
8 * Rewritten by David Rientjes
9 *
10 * The routines in this file are used to kill a process when
11 * we're seriously out of memory. This gets called from __alloc_pages()
12 * in mm/page_alloc.c when we really run out of memory.
13 *
14 * Since we won't call these routines often (on a well-configured
15 * machine) this file will double as a 'coding guide' and a signpost
16 * for newbie kernel hackers. It features several pointers to major
17 * kernel subsystems and hints as to where to find out what things do.
18 */
19
20#include <linux/oom.h>
21#include <linux/mm.h>
22#include <linux/err.h>
23#include <linux/gfp.h>
24#include <linux/sched.h>
25#include <linux/swap.h>
26#include <linux/timex.h>
27#include <linux/jiffies.h>
28#include <linux/cpuset.h>
29#include <linux/export.h>
30#include <linux/notifier.h>
31#include <linux/memcontrol.h>
32#include <linux/mempolicy.h>
33#include <linux/security.h>
34#include <linux/ptrace.h>
35#include <linux/freezer.h>
36#include <linux/ftrace.h>
37#include <linux/ratelimit.h>
38
39#define CREATE_TRACE_POINTS
40#include <trace/events/oom.h>
41
42int sysctl_panic_on_oom;
43int sysctl_oom_kill_allocating_task;
44int sysctl_oom_dump_tasks = 1;
45static DEFINE_SPINLOCK(zone_scan_lock);
46
47/*
48 * compare_swap_oom_score_adj() - compare and swap current's oom_score_adj
49 * @old_val: old oom_score_adj for compare
50 * @new_val: new oom_score_adj for swap
51 *
52 * Sets the oom_score_adj value for current to @new_val iff its present value is
53 * @old_val. Usually used to reinstate a previous value to prevent racing with
54 * userspacing tuning the value in the interim.
55 */
56void compare_swap_oom_score_adj(int old_val, int new_val)
57{
58 struct sighand_struct *sighand = current->sighand;
59
60 spin_lock_irq(&sighand->siglock);
61 if (current->signal->oom_score_adj == old_val)
62 current->signal->oom_score_adj = new_val;
63 trace_oom_score_adj_update(current);
64 spin_unlock_irq(&sighand->siglock);
65}
66
67/**
68 * test_set_oom_score_adj() - set current's oom_score_adj and return old value
69 * @new_val: new oom_score_adj value
70 *
71 * Sets the oom_score_adj value for current to @new_val with proper
72 * synchronization and returns the old value. Usually used to temporarily
73 * set a value, save the old value in the caller, and then reinstate it later.
74 */
75int test_set_oom_score_adj(int new_val)
76{
77 struct sighand_struct *sighand = current->sighand;
78 int old_val;
79
80 spin_lock_irq(&sighand->siglock);
81 old_val = current->signal->oom_score_adj;
82 current->signal->oom_score_adj = new_val;
83 trace_oom_score_adj_update(current);
84 spin_unlock_irq(&sighand->siglock);
85
86 return old_val;
87}
88
89#ifdef CONFIG_NUMA
90/**
91 * has_intersects_mems_allowed() - check task eligiblity for kill
92 * @tsk: task struct of which task to consider
93 * @mask: nodemask passed to page allocator for mempolicy ooms
94 *
95 * Task eligibility is determined by whether or not a candidate task, @tsk,
96 * shares the same mempolicy nodes as current if it is bound by such a policy
97 * and whether or not it has the same set of allowed cpuset nodes.
98 */
99static bool has_intersects_mems_allowed(struct task_struct *tsk,
100 const nodemask_t *mask)
101{
102 struct task_struct *start = tsk;
103
104 do {
105 if (mask) {
106 /*
107 * If this is a mempolicy constrained oom, tsk's
108 * cpuset is irrelevant. Only return true if its
109 * mempolicy intersects current, otherwise it may be
110 * needlessly killed.
111 */
112 if (mempolicy_nodemask_intersects(tsk, mask))
113 return true;
114 } else {
115 /*
116 * This is not a mempolicy constrained oom, so only
117 * check the mems of tsk's cpuset.
118 */
119 if (cpuset_mems_allowed_intersects(current, tsk))
120 return true;
121 }
122 } while_each_thread(start, tsk);
123
124 return false;
125}
126#else
127static bool has_intersects_mems_allowed(struct task_struct *tsk,
128 const nodemask_t *mask)
129{
130 return true;
131}
132#endif /* CONFIG_NUMA */
133
134/*
135 * The process p may have detached its own ->mm while exiting or through
136 * use_mm(), but one or more of its subthreads may still have a valid
137 * pointer. Return p, or any of its subthreads with a valid ->mm, with
138 * task_lock() held.
139 */
140struct task_struct *find_lock_task_mm(struct task_struct *p)
141{
142 struct task_struct *t = p;
143
144 do {
145 task_lock(t);
146 if (likely(t->mm))
147 return t;
148 task_unlock(t);
149 } while_each_thread(p, t);
150
151 return NULL;
152}
153
154/* return true if the task is not adequate as candidate victim task. */
155static bool oom_unkillable_task(struct task_struct *p,
156 const struct mem_cgroup *memcg, const nodemask_t *nodemask)
157{
158 if (is_global_init(p))
159 return true;
160 if (p->flags & PF_KTHREAD)
161 return true;
162
163 /* When mem_cgroup_out_of_memory() and p is not member of the group */
164 if (memcg && !task_in_mem_cgroup(p, memcg))
165 return true;
166
167 /* p may not have freeable memory in nodemask */
168 if (!has_intersects_mems_allowed(p, nodemask))
169 return true;
170
171 return false;
172}
173
174/**
175 * oom_badness - heuristic function to determine which candidate task to kill
176 * @p: task struct of which task we should calculate
177 * @totalpages: total present RAM allowed for page allocation
178 *
179 * The heuristic for determining which task to kill is made to be as simple and
180 * predictable as possible. The goal is to return the highest value for the
181 * task consuming the most memory to avoid subsequent oom failures.
182 */
183unsigned long oom_badness(struct task_struct *p, struct mem_cgroup *memcg,
184 const nodemask_t *nodemask, unsigned long totalpages)
185{
186 long points;
187 long adj;
188
189 if (oom_unkillable_task(p, memcg, nodemask))
190 return 0;
191
192 p = find_lock_task_mm(p);
193 if (!p)
194 return 0;
195
196 adj = p->signal->oom_score_adj;
197 if (adj == OOM_SCORE_ADJ_MIN) {
198 task_unlock(p);
199 return 0;
200 }
201
202 /*
203 * The baseline for the badness score is the proportion of RAM that each
204 * task's rss, pagetable and swap space use.
205 */
206 points = get_mm_rss(p->mm) + p->mm->nr_ptes +
207 get_mm_counter(p->mm, MM_SWAPENTS);
208 task_unlock(p);
209
210 /*
211 * Root processes get 3% bonus, just like the __vm_enough_memory()
212 * implementation used by LSMs.
213 */
214 if (has_capability_noaudit(p, CAP_SYS_ADMIN))
215 adj -= 30;
216
217 /* Normalize to oom_score_adj units */
218 adj *= totalpages / 1000;
219 points += adj;
220
221 /*
222 * Never return 0 for an eligible task regardless of the root bonus and
223 * oom_score_adj (oom_score_adj can't be OOM_SCORE_ADJ_MIN here).
224 */
225 return points > 0 ? points : 1;
226}
227
228/*
229 * Determine the type of allocation constraint.
230 */
231#ifdef CONFIG_NUMA
232static enum oom_constraint constrained_alloc(struct zonelist *zonelist,
233 gfp_t gfp_mask, nodemask_t *nodemask,
234 unsigned long *totalpages)
235{
236 struct zone *zone;
237 struct zoneref *z;
238 enum zone_type high_zoneidx = gfp_zone(gfp_mask);
239 bool cpuset_limited = false;
240 int nid;
241
242 /* Default to all available memory */
243 *totalpages = totalram_pages + total_swap_pages;
244
245 if (!zonelist)
246 return CONSTRAINT_NONE;
247 /*
248 * Reach here only when __GFP_NOFAIL is used. So, we should avoid
249 * to kill current.We have to random task kill in this case.
250 * Hopefully, CONSTRAINT_THISNODE...but no way to handle it, now.
251 */
252 if (gfp_mask & __GFP_THISNODE)
253 return CONSTRAINT_NONE;
254
255 /*
256 * This is not a __GFP_THISNODE allocation, so a truncated nodemask in
257 * the page allocator means a mempolicy is in effect. Cpuset policy
258 * is enforced in get_page_from_freelist().
259 */
260 if (nodemask && !nodes_subset(node_states[N_HIGH_MEMORY], *nodemask)) {
261 *totalpages = total_swap_pages;
262 for_each_node_mask(nid, *nodemask)
263 *totalpages += node_spanned_pages(nid);
264 return CONSTRAINT_MEMORY_POLICY;
265 }
266
267 /* Check this allocation failure is caused by cpuset's wall function */
268 for_each_zone_zonelist_nodemask(zone, z, zonelist,
269 high_zoneidx, nodemask)
270 if (!cpuset_zone_allowed_softwall(zone, gfp_mask))
271 cpuset_limited = true;
272
273 if (cpuset_limited) {
274 *totalpages = total_swap_pages;
275 for_each_node_mask(nid, cpuset_current_mems_allowed)
276 *totalpages += node_spanned_pages(nid);
277 return CONSTRAINT_CPUSET;
278 }
279 return CONSTRAINT_NONE;
280}
281#else
282static enum oom_constraint constrained_alloc(struct zonelist *zonelist,
283 gfp_t gfp_mask, nodemask_t *nodemask,
284 unsigned long *totalpages)
285{
286 *totalpages = totalram_pages + total_swap_pages;
287 return CONSTRAINT_NONE;
288}
289#endif
290
291/*
292 * Simple selection loop. We chose the process with the highest
293 * number of 'points'. We expect the caller will lock the tasklist.
294 *
295 * (not docbooked, we don't want this one cluttering up the manual)
296 */
297static struct task_struct *select_bad_process(unsigned int *ppoints,
298 unsigned long totalpages, struct mem_cgroup *memcg,
299 const nodemask_t *nodemask, bool force_kill)
300{
301 struct task_struct *g, *p;
302 struct task_struct *chosen = NULL;
303 unsigned long chosen_points = 0;
304
305 do_each_thread(g, p) {
306 unsigned int points;
307
308 if (p->exit_state)
309 continue;
310 if (oom_unkillable_task(p, memcg, nodemask))
311 continue;
312
313 /*
314 * This task already has access to memory reserves and is
315 * being killed. Don't allow any other task access to the
316 * memory reserve.
317 *
318 * Note: this may have a chance of deadlock if it gets
319 * blocked waiting for another task which itself is waiting
320 * for memory. Is there a better alternative?
321 */
322 if (test_tsk_thread_flag(p, TIF_MEMDIE)) {
323 if (unlikely(frozen(p)))
324 __thaw_task(p);
325 if (!force_kill)
326 return ERR_PTR(-1UL);
327 }
328 if (!p->mm)
329 continue;
330
331 if (p->flags & PF_EXITING) {
332 /*
333 * If p is the current task and is in the process of
334 * releasing memory, we allow the "kill" to set
335 * TIF_MEMDIE, which will allow it to gain access to
336 * memory reserves. Otherwise, it may stall forever.
337 *
338 * The loop isn't broken here, however, in case other
339 * threads are found to have already been oom killed.
340 */
341 if (p == current) {
342 chosen = p;
343 chosen_points = ULONG_MAX;
344 } else if (!force_kill) {
345 /*
346 * If this task is not being ptraced on exit,
347 * then wait for it to finish before killing
348 * some other task unnecessarily.
349 */
350 if (!(p->group_leader->ptrace & PT_TRACE_EXIT))
351 return ERR_PTR(-1UL);
352 }
353 }
354
355 points = oom_badness(p, memcg, nodemask, totalpages);
356 if (points > chosen_points) {
357 chosen = p;
358 chosen_points = points;
359 }
360 } while_each_thread(g, p);
361
362 *ppoints = chosen_points * 1000 / totalpages;
363 return chosen;
364}
365
366/**
367 * dump_tasks - dump current memory state of all system tasks
368 * @memcg: current's memory controller, if constrained
369 * @nodemask: nodemask passed to page allocator for mempolicy ooms
370 *
371 * Dumps the current memory state of all eligible tasks. Tasks not in the same
372 * memcg, not in the same cpuset, or bound to a disjoint set of mempolicy nodes
373 * are not shown.
374 * State information includes task's pid, uid, tgid, vm size, rss, cpu, oom_adj
375 * value, oom_score_adj value, and name.
376 *
377 * Call with tasklist_lock read-locked.
378 */
379static void dump_tasks(const struct mem_cgroup *memcg, const nodemask_t *nodemask)
380{
381 struct task_struct *p;
382 struct task_struct *task;
383
384 pr_info("[ pid ] uid tgid total_vm rss cpu oom_adj oom_score_adj name\n");
385 for_each_process(p) {
386 if (oom_unkillable_task(p, memcg, nodemask))
387 continue;
388
389 task = find_lock_task_mm(p);
390 if (!task) {
391 /*
392 * This is a kthread or all of p's threads have already
393 * detached their mm's. There's no need to report
394 * them; they can't be oom killed anyway.
395 */
396 continue;
397 }
398
399 pr_info("[%5d] %5d %5d %8lu %8lu %3u %3d %5d %s\n",
400 task->pid, from_kuid(&init_user_ns, task_uid(task)),
401 task->tgid, task->mm->total_vm, get_mm_rss(task->mm),
402 task_cpu(task), task->signal->oom_adj,
403 task->signal->oom_score_adj, task->comm);
404 task_unlock(task);
405 }
406}
407
408static void dump_header(struct task_struct *p, gfp_t gfp_mask, int order,
409 struct mem_cgroup *memcg, const nodemask_t *nodemask)
410{
411 task_lock(current);
412 pr_warning("%s invoked oom-killer: gfp_mask=0x%x, order=%d, "
413 "oom_adj=%d, oom_score_adj=%d\n",
414 current->comm, gfp_mask, order, current->signal->oom_adj,
415 current->signal->oom_score_adj);
416 cpuset_print_task_mems_allowed(current);
417 task_unlock(current);
418 dump_stack();
419 mem_cgroup_print_oom_info(memcg, p);
420 show_mem(SHOW_MEM_FILTER_NODES);
421 if (sysctl_oom_dump_tasks)
422 dump_tasks(memcg, nodemask);
423}
424
425#define K(x) ((x) << (PAGE_SHIFT-10))
426static void oom_kill_process(struct task_struct *p, gfp_t gfp_mask, int order,
427 unsigned int points, unsigned long totalpages,
428 struct mem_cgroup *memcg, nodemask_t *nodemask,
429 const char *message)
430{
431 struct task_struct *victim = p;
432 struct task_struct *child;
433 struct task_struct *t = p;
434 struct mm_struct *mm;
435 unsigned int victim_points = 0;
436 static DEFINE_RATELIMIT_STATE(oom_rs, DEFAULT_RATELIMIT_INTERVAL,
437 DEFAULT_RATELIMIT_BURST);
438
439 /*
440 * If the task is already exiting, don't alarm the sysadmin or kill
441 * its children or threads, just set TIF_MEMDIE so it can die quickly
442 */
443 if (p->flags & PF_EXITING) {
444 set_tsk_thread_flag(p, TIF_MEMDIE);
445 return;
446 }
447
448 if (__ratelimit(&oom_rs))
449 dump_header(p, gfp_mask, order, memcg, nodemask);
450
451 task_lock(p);
452 pr_err("%s: Kill process %d (%s) score %d or sacrifice child\n",
453 message, task_pid_nr(p), p->comm, points);
454 task_unlock(p);
455
456 /*
457 * If any of p's children has a different mm and is eligible for kill,
458 * the one with the highest oom_badness() score is sacrificed for its
459 * parent. This attempts to lose the minimal amount of work done while
460 * still freeing memory.
461 */
462 do {
463 list_for_each_entry(child, &t->children, sibling) {
464 unsigned int child_points;
465
466 if (child->mm == p->mm)
467 continue;
468 /*
469 * oom_badness() returns 0 if the thread is unkillable
470 */
471 child_points = oom_badness(child, memcg, nodemask,
472 totalpages);
473 if (child_points > victim_points) {
474 victim = child;
475 victim_points = child_points;
476 }
477 }
478 } while_each_thread(p, t);
479
480 victim = find_lock_task_mm(victim);
481 if (!victim)
482 return;
483
484 /* mm cannot safely be dereferenced after task_unlock(victim) */
485 mm = victim->mm;
486 pr_err("Killed process %d (%s) total-vm:%lukB, anon-rss:%lukB, file-rss:%lukB\n",
487 task_pid_nr(victim), victim->comm, K(victim->mm->total_vm),
488 K(get_mm_counter(victim->mm, MM_ANONPAGES)),
489 K(get_mm_counter(victim->mm, MM_FILEPAGES)));
490 task_unlock(victim);
491
492 /*
493 * Kill all user processes sharing victim->mm in other thread groups, if
494 * any. They don't get access to memory reserves, though, to avoid
495 * depletion of all memory. This prevents mm->mmap_sem livelock when an
496 * oom killed thread cannot exit because it requires the semaphore and
497 * its contended by another thread trying to allocate memory itself.
498 * That thread will now get access to memory reserves since it has a
499 * pending fatal signal.
500 */
501 for_each_process(p)
502 if (p->mm == mm && !same_thread_group(p, victim) &&
503 !(p->flags & PF_KTHREAD)) {
504 if (p->signal->oom_score_adj == OOM_SCORE_ADJ_MIN)
505 continue;
506
507 task_lock(p); /* Protect ->comm from prctl() */
508 pr_err("Kill process %d (%s) sharing same memory\n",
509 task_pid_nr(p), p->comm);
510 task_unlock(p);
511 do_send_sig_info(SIGKILL, SEND_SIG_FORCED, p, true);
512 }
513
514 set_tsk_thread_flag(victim, TIF_MEMDIE);
515 do_send_sig_info(SIGKILL, SEND_SIG_FORCED, victim, true);
516}
517#undef K
518
519/*
520 * Determines whether the kernel must panic because of the panic_on_oom sysctl.
521 */
522static void check_panic_on_oom(enum oom_constraint constraint, gfp_t gfp_mask,
523 int order, const nodemask_t *nodemask)
524{
525 if (likely(!sysctl_panic_on_oom))
526 return;
527 if (sysctl_panic_on_oom != 2) {
528 /*
529 * panic_on_oom == 1 only affects CONSTRAINT_NONE, the kernel
530 * does not panic for cpuset, mempolicy, or memcg allocation
531 * failures.
532 */
533 if (constraint != CONSTRAINT_NONE)
534 return;
535 }
536 read_lock(&tasklist_lock);
537 dump_header(NULL, gfp_mask, order, NULL, nodemask);
538 read_unlock(&tasklist_lock);
539 panic("Out of memory: %s panic_on_oom is enabled\n",
540 sysctl_panic_on_oom == 2 ? "compulsory" : "system-wide");
541}
542
543#ifdef CONFIG_CGROUP_MEM_RES_CTLR
544void mem_cgroup_out_of_memory(struct mem_cgroup *memcg, gfp_t gfp_mask,
545 int order)
546{
547 unsigned long limit;
548 unsigned int points = 0;
549 struct task_struct *p;
550
551 /*
552 * If current has a pending SIGKILL, then automatically select it. The
553 * goal is to allow it to allocate so that it may quickly exit and free
554 * its memory.
555 */
556 if (fatal_signal_pending(current)) {
557 set_thread_flag(TIF_MEMDIE);
558 return;
559 }
560
561 check_panic_on_oom(CONSTRAINT_MEMCG, gfp_mask, order, NULL);
562 limit = mem_cgroup_get_limit(memcg) >> PAGE_SHIFT ? : 1;
563 read_lock(&tasklist_lock);
564 p = select_bad_process(&points, limit, memcg, NULL, false);
565 if (p && PTR_ERR(p) != -1UL)
566 oom_kill_process(p, gfp_mask, order, points, limit, memcg, NULL,
567 "Memory cgroup out of memory");
568 read_unlock(&tasklist_lock);
569}
570#endif
571
572static BLOCKING_NOTIFIER_HEAD(oom_notify_list);
573
574int register_oom_notifier(struct notifier_block *nb)
575{
576 return blocking_notifier_chain_register(&oom_notify_list, nb);
577}
578EXPORT_SYMBOL_GPL(register_oom_notifier);
579
580int unregister_oom_notifier(struct notifier_block *nb)
581{
582 return blocking_notifier_chain_unregister(&oom_notify_list, nb);
583}
584EXPORT_SYMBOL_GPL(unregister_oom_notifier);
585
586/*
587 * Try to acquire the OOM killer lock for the zones in zonelist. Returns zero
588 * if a parallel OOM killing is already taking place that includes a zone in
589 * the zonelist. Otherwise, locks all zones in the zonelist and returns 1.
590 */
591int try_set_zonelist_oom(struct zonelist *zonelist, gfp_t gfp_mask)
592{
593 struct zoneref *z;
594 struct zone *zone;
595 int ret = 1;
596
597 spin_lock(&zone_scan_lock);
598 for_each_zone_zonelist(zone, z, zonelist, gfp_zone(gfp_mask)) {
599 if (zone_is_oom_locked(zone)) {
600 ret = 0;
601 goto out;
602 }
603 }
604
605 for_each_zone_zonelist(zone, z, zonelist, gfp_zone(gfp_mask)) {
606 /*
607 * Lock each zone in the zonelist under zone_scan_lock so a
608 * parallel invocation of try_set_zonelist_oom() doesn't succeed
609 * when it shouldn't.
610 */
611 zone_set_flag(zone, ZONE_OOM_LOCKED);
612 }
613
614out:
615 spin_unlock(&zone_scan_lock);
616 return ret;
617}
618
619/*
620 * Clears the ZONE_OOM_LOCKED flag for all zones in the zonelist so that failed
621 * allocation attempts with zonelists containing them may now recall the OOM
622 * killer, if necessary.
623 */
624void clear_zonelist_oom(struct zonelist *zonelist, gfp_t gfp_mask)
625{
626 struct zoneref *z;
627 struct zone *zone;
628
629 spin_lock(&zone_scan_lock);
630 for_each_zone_zonelist(zone, z, zonelist, gfp_zone(gfp_mask)) {
631 zone_clear_flag(zone, ZONE_OOM_LOCKED);
632 }
633 spin_unlock(&zone_scan_lock);
634}
635
636/*
637 * Try to acquire the oom killer lock for all system zones. Returns zero if a
638 * parallel oom killing is taking place, otherwise locks all zones and returns
639 * non-zero.
640 */
641static int try_set_system_oom(void)
642{
643 struct zone *zone;
644 int ret = 1;
645
646 spin_lock(&zone_scan_lock);
647 for_each_populated_zone(zone)
648 if (zone_is_oom_locked(zone)) {
649 ret = 0;
650 goto out;
651 }
652 for_each_populated_zone(zone)
653 zone_set_flag(zone, ZONE_OOM_LOCKED);
654out:
655 spin_unlock(&zone_scan_lock);
656 return ret;
657}
658
659/*
660 * Clears ZONE_OOM_LOCKED for all system zones so that failed allocation
661 * attempts or page faults may now recall the oom killer, if necessary.
662 */
663static void clear_system_oom(void)
664{
665 struct zone *zone;
666
667 spin_lock(&zone_scan_lock);
668 for_each_populated_zone(zone)
669 zone_clear_flag(zone, ZONE_OOM_LOCKED);
670 spin_unlock(&zone_scan_lock);
671}
672
673/**
674 * out_of_memory - kill the "best" process when we run out of memory
675 * @zonelist: zonelist pointer
676 * @gfp_mask: memory allocation flags
677 * @order: amount of memory being requested as a power of 2
678 * @nodemask: nodemask passed to page allocator
679 * @force_kill: true if a task must be killed, even if others are exiting
680 *
681 * If we run out of memory, we have the choice between either
682 * killing a random task (bad), letting the system crash (worse)
683 * OR try to be smart about which process to kill. Note that we
684 * don't have to be perfect here, we just have to be good.
685 */
686void out_of_memory(struct zonelist *zonelist, gfp_t gfp_mask,
687 int order, nodemask_t *nodemask, bool force_kill)
688{
689 const nodemask_t *mpol_mask;
690 struct task_struct *p;
691 unsigned long totalpages;
692 unsigned long freed = 0;
693 unsigned int points;
694 enum oom_constraint constraint = CONSTRAINT_NONE;
695 int killed = 0;
696
697 blocking_notifier_call_chain(&oom_notify_list, 0, &freed);
698 if (freed > 0)
699 /* Got some memory back in the last second. */
700 return;
701
702 /*
703 * If current has a pending SIGKILL, then automatically select it. The
704 * goal is to allow it to allocate so that it may quickly exit and free
705 * its memory.
706 */
707 if (fatal_signal_pending(current)) {
708 set_thread_flag(TIF_MEMDIE);
709 return;
710 }
711
712 /*
713 * Check if there were limitations on the allocation (only relevant for
714 * NUMA) that may require different handling.
715 */
716 constraint = constrained_alloc(zonelist, gfp_mask, nodemask,
717 &totalpages);
718 mpol_mask = (constraint == CONSTRAINT_MEMORY_POLICY) ? nodemask : NULL;
719 check_panic_on_oom(constraint, gfp_mask, order, mpol_mask);
720
721 read_lock(&tasklist_lock);
722 if (sysctl_oom_kill_allocating_task &&
723 !oom_unkillable_task(current, NULL, nodemask) &&
724 current->mm) {
725 oom_kill_process(current, gfp_mask, order, 0, totalpages, NULL,
726 nodemask,
727 "Out of memory (oom_kill_allocating_task)");
728 goto out;
729 }
730
731 p = select_bad_process(&points, totalpages, NULL, mpol_mask,
732 force_kill);
733 /* Found nothing?!?! Either we hang forever, or we panic. */
734 if (!p) {
735 dump_header(NULL, gfp_mask, order, NULL, mpol_mask);
736 read_unlock(&tasklist_lock);
737 panic("Out of memory and no killable processes...\n");
738 }
739 if (PTR_ERR(p) != -1UL) {
740 oom_kill_process(p, gfp_mask, order, points, totalpages, NULL,
741 nodemask, "Out of memory");
742 killed = 1;
743 }
744out:
745 read_unlock(&tasklist_lock);
746
747 /*
748 * Give "p" a good chance of killing itself before we
749 * retry to allocate memory unless "p" is current
750 */
751 if (killed && !test_thread_flag(TIF_MEMDIE))
752 schedule_timeout_uninterruptible(1);
753}
754
755/*
756 * The pagefault handler calls here because it is out of memory, so kill a
757 * memory-hogging task. If a populated zone has ZONE_OOM_LOCKED set, a parallel
758 * oom killing is already in progress so do nothing. If a task is found with
759 * TIF_MEMDIE set, it has been killed so do nothing and allow it to exit.
760 */
761void pagefault_out_of_memory(void)
762{
763 if (try_set_system_oom()) {
764 out_of_memory(NULL, 0, 0, NULL, false);
765 clear_system_oom();
766 }
767 if (!test_thread_flag(TIF_MEMDIE))
768 schedule_timeout_uninterruptible(1);
769}