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