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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/module.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
36int sysctl_panic_on_oom;
37int sysctl_oom_kill_allocating_task;
38int sysctl_oom_dump_tasks = 1;
39static DEFINE_SPINLOCK(zone_scan_lock);
40
41/**
42 * test_set_oom_score_adj() - set current's oom_score_adj and return old value
43 * @new_val: new oom_score_adj value
44 *
45 * Sets the oom_score_adj value for current to @new_val with proper
46 * synchronization and returns the old value. Usually used to temporarily
47 * set a value, save the old value in the caller, and then reinstate it later.
48 */
49int test_set_oom_score_adj(int new_val)
50{
51 struct sighand_struct *sighand = current->sighand;
52 int old_val;
53
54 spin_lock_irq(&sighand->siglock);
55 old_val = current->signal->oom_score_adj;
56 if (new_val != old_val) {
57 if (new_val == OOM_SCORE_ADJ_MIN)
58 atomic_inc(¤t->mm->oom_disable_count);
59 else if (old_val == OOM_SCORE_ADJ_MIN)
60 atomic_dec(¤t->mm->oom_disable_count);
61 current->signal->oom_score_adj = new_val;
62 }
63 spin_unlock_irq(&sighand->siglock);
64
65 return old_val;
66}
67
68#ifdef CONFIG_NUMA
69/**
70 * has_intersects_mems_allowed() - check task eligiblity for kill
71 * @tsk: task struct of which task to consider
72 * @mask: nodemask passed to page allocator for mempolicy ooms
73 *
74 * Task eligibility is determined by whether or not a candidate task, @tsk,
75 * shares the same mempolicy nodes as current if it is bound by such a policy
76 * and whether or not it has the same set of allowed cpuset nodes.
77 */
78static bool has_intersects_mems_allowed(struct task_struct *tsk,
79 const nodemask_t *mask)
80{
81 struct task_struct *start = tsk;
82
83 do {
84 if (mask) {
85 /*
86 * If this is a mempolicy constrained oom, tsk's
87 * cpuset is irrelevant. Only return true if its
88 * mempolicy intersects current, otherwise it may be
89 * needlessly killed.
90 */
91 if (mempolicy_nodemask_intersects(tsk, mask))
92 return true;
93 } else {
94 /*
95 * This is not a mempolicy constrained oom, so only
96 * check the mems of tsk's cpuset.
97 */
98 if (cpuset_mems_allowed_intersects(current, tsk))
99 return true;
100 }
101 } while_each_thread(start, tsk);
102
103 return false;
104}
105#else
106static bool has_intersects_mems_allowed(struct task_struct *tsk,
107 const nodemask_t *mask)
108{
109 return true;
110}
111#endif /* CONFIG_NUMA */
112
113/*
114 * The process p may have detached its own ->mm while exiting or through
115 * use_mm(), but one or more of its subthreads may still have a valid
116 * pointer. Return p, or any of its subthreads with a valid ->mm, with
117 * task_lock() held.
118 */
119struct task_struct *find_lock_task_mm(struct task_struct *p)
120{
121 struct task_struct *t = p;
122
123 do {
124 task_lock(t);
125 if (likely(t->mm))
126 return t;
127 task_unlock(t);
128 } while_each_thread(p, t);
129
130 return NULL;
131}
132
133/* return true if the task is not adequate as candidate victim task. */
134static bool oom_unkillable_task(struct task_struct *p,
135 const struct mem_cgroup *mem, const nodemask_t *nodemask)
136{
137 if (is_global_init(p))
138 return true;
139 if (p->flags & PF_KTHREAD)
140 return true;
141
142 /* When mem_cgroup_out_of_memory() and p is not member of the group */
143 if (mem && !task_in_mem_cgroup(p, mem))
144 return true;
145
146 /* p may not have freeable memory in nodemask */
147 if (!has_intersects_mems_allowed(p, nodemask))
148 return true;
149
150 return false;
151}
152
153/**
154 * oom_badness - heuristic function to determine which candidate task to kill
155 * @p: task struct of which task we should calculate
156 * @totalpages: total present RAM allowed for page allocation
157 *
158 * The heuristic for determining which task to kill is made to be as simple and
159 * predictable as possible. The goal is to return the highest value for the
160 * task consuming the most memory to avoid subsequent oom failures.
161 */
162unsigned int oom_badness(struct task_struct *p, struct mem_cgroup *mem,
163 const nodemask_t *nodemask, unsigned long totalpages)
164{
165 int points;
166
167 if (oom_unkillable_task(p, mem, nodemask))
168 return 0;
169
170 p = find_lock_task_mm(p);
171 if (!p)
172 return 0;
173
174 /*
175 * Shortcut check for a thread sharing p->mm that is OOM_SCORE_ADJ_MIN
176 * so the entire heuristic doesn't need to be executed for something
177 * that cannot be killed.
178 */
179 if (atomic_read(&p->mm->oom_disable_count)) {
180 task_unlock(p);
181 return 0;
182 }
183
184 /*
185 * The memory controller may have a limit of 0 bytes, so avoid a divide
186 * by zero, if necessary.
187 */
188 if (!totalpages)
189 totalpages = 1;
190
191 /*
192 * The baseline for the badness score is the proportion of RAM that each
193 * task's rss, pagetable and swap space use.
194 */
195 points = get_mm_rss(p->mm) + p->mm->nr_ptes;
196 points += get_mm_counter(p->mm, MM_SWAPENTS);
197
198 points *= 1000;
199 points /= totalpages;
200 task_unlock(p);
201
202 /*
203 * Root processes get 3% bonus, just like the __vm_enough_memory()
204 * implementation used by LSMs.
205 */
206 if (has_capability_noaudit(p, CAP_SYS_ADMIN))
207 points -= 30;
208
209 /*
210 * /proc/pid/oom_score_adj ranges from -1000 to +1000 such that it may
211 * either completely disable oom killing or always prefer a certain
212 * task.
213 */
214 points += p->signal->oom_score_adj;
215
216 /*
217 * Never return 0 for an eligible task that may be killed since it's
218 * possible that no single user task uses more than 0.1% of memory and
219 * no single admin tasks uses more than 3.0%.
220 */
221 if (points <= 0)
222 return 1;
223 return (points < 1000) ? points : 1000;
224}
225
226/*
227 * Determine the type of allocation constraint.
228 */
229#ifdef CONFIG_NUMA
230static enum oom_constraint constrained_alloc(struct zonelist *zonelist,
231 gfp_t gfp_mask, nodemask_t *nodemask,
232 unsigned long *totalpages)
233{
234 struct zone *zone;
235 struct zoneref *z;
236 enum zone_type high_zoneidx = gfp_zone(gfp_mask);
237 bool cpuset_limited = false;
238 int nid;
239
240 /* Default to all available memory */
241 *totalpages = totalram_pages + total_swap_pages;
242
243 if (!zonelist)
244 return CONSTRAINT_NONE;
245 /*
246 * Reach here only when __GFP_NOFAIL is used. So, we should avoid
247 * to kill current.We have to random task kill in this case.
248 * Hopefully, CONSTRAINT_THISNODE...but no way to handle it, now.
249 */
250 if (gfp_mask & __GFP_THISNODE)
251 return CONSTRAINT_NONE;
252
253 /*
254 * This is not a __GFP_THISNODE allocation, so a truncated nodemask in
255 * the page allocator means a mempolicy is in effect. Cpuset policy
256 * is enforced in get_page_from_freelist().
257 */
258 if (nodemask && !nodes_subset(node_states[N_HIGH_MEMORY], *nodemask)) {
259 *totalpages = total_swap_pages;
260 for_each_node_mask(nid, *nodemask)
261 *totalpages += node_spanned_pages(nid);
262 return CONSTRAINT_MEMORY_POLICY;
263 }
264
265 /* Check this allocation failure is caused by cpuset's wall function */
266 for_each_zone_zonelist_nodemask(zone, z, zonelist,
267 high_zoneidx, nodemask)
268 if (!cpuset_zone_allowed_softwall(zone, gfp_mask))
269 cpuset_limited = true;
270
271 if (cpuset_limited) {
272 *totalpages = total_swap_pages;
273 for_each_node_mask(nid, cpuset_current_mems_allowed)
274 *totalpages += node_spanned_pages(nid);
275 return CONSTRAINT_CPUSET;
276 }
277 return CONSTRAINT_NONE;
278}
279#else
280static enum oom_constraint constrained_alloc(struct zonelist *zonelist,
281 gfp_t gfp_mask, nodemask_t *nodemask,
282 unsigned long *totalpages)
283{
284 *totalpages = totalram_pages + total_swap_pages;
285 return CONSTRAINT_NONE;
286}
287#endif
288
289/*
290 * Simple selection loop. We chose the process with the highest
291 * number of 'points'. We expect the caller will lock the tasklist.
292 *
293 * (not docbooked, we don't want this one cluttering up the manual)
294 */
295static struct task_struct *select_bad_process(unsigned int *ppoints,
296 unsigned long totalpages, struct mem_cgroup *mem,
297 const nodemask_t *nodemask)
298{
299 struct task_struct *g, *p;
300 struct task_struct *chosen = NULL;
301 *ppoints = 0;
302
303 do_each_thread(g, p) {
304 unsigned int points;
305
306 if (p->exit_state)
307 continue;
308 if (oom_unkillable_task(p, mem, nodemask))
309 continue;
310
311 /*
312 * This task already has access to memory reserves and is
313 * being killed. Don't allow any other task access to the
314 * memory reserve.
315 *
316 * Note: this may have a chance of deadlock if it gets
317 * blocked waiting for another task which itself is waiting
318 * for memory. Is there a better alternative?
319 */
320 if (test_tsk_thread_flag(p, TIF_MEMDIE))
321 return ERR_PTR(-1UL);
322 if (!p->mm)
323 continue;
324
325 if (p->flags & PF_EXITING) {
326 /*
327 * If p is the current task and is in the process of
328 * releasing memory, we allow the "kill" to set
329 * TIF_MEMDIE, which will allow it to gain access to
330 * memory reserves. Otherwise, it may stall forever.
331 *
332 * The loop isn't broken here, however, in case other
333 * threads are found to have already been oom killed.
334 */
335 if (p == current) {
336 chosen = p;
337 *ppoints = 1000;
338 } else {
339 /*
340 * If this task is not being ptraced on exit,
341 * then wait for it to finish before killing
342 * some other task unnecessarily.
343 */
344 if (!(p->group_leader->ptrace & PT_TRACE_EXIT))
345 return ERR_PTR(-1UL);
346 }
347 }
348
349 points = oom_badness(p, mem, nodemask, totalpages);
350 if (points > *ppoints) {
351 chosen = p;
352 *ppoints = points;
353 }
354 } while_each_thread(g, p);
355
356 return chosen;
357}
358
359/**
360 * dump_tasks - dump current memory state of all system tasks
361 * @mem: current's memory controller, if constrained
362 * @nodemask: nodemask passed to page allocator for mempolicy ooms
363 *
364 * Dumps the current memory state of all eligible tasks. Tasks not in the same
365 * memcg, not in the same cpuset, or bound to a disjoint set of mempolicy nodes
366 * are not shown.
367 * State information includes task's pid, uid, tgid, vm size, rss, cpu, oom_adj
368 * value, oom_score_adj value, and name.
369 *
370 * Call with tasklist_lock read-locked.
371 */
372static void dump_tasks(const struct mem_cgroup *mem, const nodemask_t *nodemask)
373{
374 struct task_struct *p;
375 struct task_struct *task;
376
377 pr_info("[ pid ] uid tgid total_vm rss cpu oom_adj oom_score_adj name\n");
378 for_each_process(p) {
379 if (oom_unkillable_task(p, mem, nodemask))
380 continue;
381
382 task = find_lock_task_mm(p);
383 if (!task) {
384 /*
385 * This is a kthread or all of p's threads have already
386 * detached their mm's. There's no need to report
387 * them; they can't be oom killed anyway.
388 */
389 continue;
390 }
391
392 pr_info("[%5d] %5d %5d %8lu %8lu %3u %3d %5d %s\n",
393 task->pid, task_uid(task), task->tgid,
394 task->mm->total_vm, get_mm_rss(task->mm),
395 task_cpu(task), task->signal->oom_adj,
396 task->signal->oom_score_adj, task->comm);
397 task_unlock(task);
398 }
399}
400
401static void dump_header(struct task_struct *p, gfp_t gfp_mask, int order,
402 struct mem_cgroup *mem, const nodemask_t *nodemask)
403{
404 task_lock(current);
405 pr_warning("%s invoked oom-killer: gfp_mask=0x%x, order=%d, "
406 "oom_adj=%d, oom_score_adj=%d\n",
407 current->comm, gfp_mask, order, current->signal->oom_adj,
408 current->signal->oom_score_adj);
409 cpuset_print_task_mems_allowed(current);
410 task_unlock(current);
411 dump_stack();
412 mem_cgroup_print_oom_info(mem, p);
413 show_mem(SHOW_MEM_FILTER_NODES);
414 if (sysctl_oom_dump_tasks)
415 dump_tasks(mem, nodemask);
416}
417
418#define K(x) ((x) << (PAGE_SHIFT-10))
419static int oom_kill_task(struct task_struct *p, struct mem_cgroup *mem)
420{
421 struct task_struct *q;
422 struct mm_struct *mm;
423
424 p = find_lock_task_mm(p);
425 if (!p)
426 return 1;
427
428 /* mm cannot be safely dereferenced after task_unlock(p) */
429 mm = p->mm;
430
431 pr_err("Killed process %d (%s) total-vm:%lukB, anon-rss:%lukB, file-rss:%lukB\n",
432 task_pid_nr(p), p->comm, K(p->mm->total_vm),
433 K(get_mm_counter(p->mm, MM_ANONPAGES)),
434 K(get_mm_counter(p->mm, MM_FILEPAGES)));
435 task_unlock(p);
436
437 /*
438 * Kill all processes sharing p->mm in other thread groups, if any.
439 * They don't get access to memory reserves or a higher scheduler
440 * priority, though, to avoid depletion of all memory or task
441 * starvation. This prevents mm->mmap_sem livelock when an oom killed
442 * task cannot exit because it requires the semaphore and its contended
443 * by another thread trying to allocate memory itself. That thread will
444 * now get access to memory reserves since it has a pending fatal
445 * signal.
446 */
447 for_each_process(q)
448 if (q->mm == mm && !same_thread_group(q, p)) {
449 task_lock(q); /* Protect ->comm from prctl() */
450 pr_err("Kill process %d (%s) sharing same memory\n",
451 task_pid_nr(q), q->comm);
452 task_unlock(q);
453 force_sig(SIGKILL, q);
454 }
455
456 set_tsk_thread_flag(p, TIF_MEMDIE);
457 force_sig(SIGKILL, p);
458
459 return 0;
460}
461#undef K
462
463static int oom_kill_process(struct task_struct *p, gfp_t gfp_mask, int order,
464 unsigned int points, unsigned long totalpages,
465 struct mem_cgroup *mem, nodemask_t *nodemask,
466 const char *message)
467{
468 struct task_struct *victim = p;
469 struct task_struct *child;
470 struct task_struct *t = p;
471 unsigned int victim_points = 0;
472
473 if (printk_ratelimit())
474 dump_header(p, gfp_mask, order, mem, nodemask);
475
476 /*
477 * If the task is already exiting, don't alarm the sysadmin or kill
478 * its children or threads, just set TIF_MEMDIE so it can die quickly
479 */
480 if (p->flags & PF_EXITING) {
481 set_tsk_thread_flag(p, TIF_MEMDIE);
482 return 0;
483 }
484
485 task_lock(p);
486 pr_err("%s: Kill process %d (%s) score %d or sacrifice child\n",
487 message, task_pid_nr(p), p->comm, points);
488 task_unlock(p);
489
490 /*
491 * If any of p's children has a different mm and is eligible for kill,
492 * the one with the highest oom_badness() score is sacrificed for its
493 * parent. This attempts to lose the minimal amount of work done while
494 * still freeing memory.
495 */
496 do {
497 list_for_each_entry(child, &t->children, sibling) {
498 unsigned int child_points;
499
500 if (child->mm == p->mm)
501 continue;
502 /*
503 * oom_badness() returns 0 if the thread is unkillable
504 */
505 child_points = oom_badness(child, mem, nodemask,
506 totalpages);
507 if (child_points > victim_points) {
508 victim = child;
509 victim_points = child_points;
510 }
511 }
512 } while_each_thread(p, t);
513
514 return oom_kill_task(victim, mem);
515}
516
517/*
518 * Determines whether the kernel must panic because of the panic_on_oom sysctl.
519 */
520static void check_panic_on_oom(enum oom_constraint constraint, gfp_t gfp_mask,
521 int order, const nodemask_t *nodemask)
522{
523 if (likely(!sysctl_panic_on_oom))
524 return;
525 if (sysctl_panic_on_oom != 2) {
526 /*
527 * panic_on_oom == 1 only affects CONSTRAINT_NONE, the kernel
528 * does not panic for cpuset, mempolicy, or memcg allocation
529 * failures.
530 */
531 if (constraint != CONSTRAINT_NONE)
532 return;
533 }
534 read_lock(&tasklist_lock);
535 dump_header(NULL, gfp_mask, order, NULL, nodemask);
536 read_unlock(&tasklist_lock);
537 panic("Out of memory: %s panic_on_oom is enabled\n",
538 sysctl_panic_on_oom == 2 ? "compulsory" : "system-wide");
539}
540
541#ifdef CONFIG_CGROUP_MEM_RES_CTLR
542void mem_cgroup_out_of_memory(struct mem_cgroup *mem, gfp_t gfp_mask)
543{
544 unsigned long limit;
545 unsigned int points = 0;
546 struct task_struct *p;
547
548 /*
549 * If current has a pending SIGKILL, then automatically select it. The
550 * goal is to allow it to allocate so that it may quickly exit and free
551 * its memory.
552 */
553 if (fatal_signal_pending(current)) {
554 set_thread_flag(TIF_MEMDIE);
555 return;
556 }
557
558 check_panic_on_oom(CONSTRAINT_MEMCG, gfp_mask, 0, NULL);
559 limit = mem_cgroup_get_limit(mem) >> PAGE_SHIFT;
560 read_lock(&tasklist_lock);
561retry:
562 p = select_bad_process(&points, limit, mem, NULL);
563 if (!p || PTR_ERR(p) == -1UL)
564 goto out;
565
566 if (oom_kill_process(p, gfp_mask, 0, points, limit, mem, NULL,
567 "Memory cgroup out of memory"))
568 goto retry;
569out:
570 read_unlock(&tasklist_lock);
571}
572#endif
573
574static BLOCKING_NOTIFIER_HEAD(oom_notify_list);
575
576int register_oom_notifier(struct notifier_block *nb)
577{
578 return blocking_notifier_chain_register(&oom_notify_list, nb);
579}
580EXPORT_SYMBOL_GPL(register_oom_notifier);
581
582int unregister_oom_notifier(struct notifier_block *nb)
583{
584 return blocking_notifier_chain_unregister(&oom_notify_list, nb);
585}
586EXPORT_SYMBOL_GPL(unregister_oom_notifier);
587
588/*
589 * Try to acquire the OOM killer lock for the zones in zonelist. Returns zero
590 * if a parallel OOM killing is already taking place that includes a zone in
591 * the zonelist. Otherwise, locks all zones in the zonelist and returns 1.
592 */
593int try_set_zonelist_oom(struct zonelist *zonelist, gfp_t gfp_mask)
594{
595 struct zoneref *z;
596 struct zone *zone;
597 int ret = 1;
598
599 spin_lock(&zone_scan_lock);
600 for_each_zone_zonelist(zone, z, zonelist, gfp_zone(gfp_mask)) {
601 if (zone_is_oom_locked(zone)) {
602 ret = 0;
603 goto out;
604 }
605 }
606
607 for_each_zone_zonelist(zone, z, zonelist, gfp_zone(gfp_mask)) {
608 /*
609 * Lock each zone in the zonelist under zone_scan_lock so a
610 * parallel invocation of try_set_zonelist_oom() doesn't succeed
611 * when it shouldn't.
612 */
613 zone_set_flag(zone, ZONE_OOM_LOCKED);
614 }
615
616out:
617 spin_unlock(&zone_scan_lock);
618 return ret;
619}
620
621/*
622 * Clears the ZONE_OOM_LOCKED flag for all zones in the zonelist so that failed
623 * allocation attempts with zonelists containing them may now recall the OOM
624 * killer, if necessary.
625 */
626void clear_zonelist_oom(struct zonelist *zonelist, gfp_t gfp_mask)
627{
628 struct zoneref *z;
629 struct zone *zone;
630
631 spin_lock(&zone_scan_lock);
632 for_each_zone_zonelist(zone, z, zonelist, gfp_zone(gfp_mask)) {
633 zone_clear_flag(zone, ZONE_OOM_LOCKED);
634 }
635 spin_unlock(&zone_scan_lock);
636}
637
638/*
639 * Try to acquire the oom killer lock for all system zones. Returns zero if a
640 * parallel oom killing is taking place, otherwise locks all zones and returns
641 * non-zero.
642 */
643static int try_set_system_oom(void)
644{
645 struct zone *zone;
646 int ret = 1;
647
648 spin_lock(&zone_scan_lock);
649 for_each_populated_zone(zone)
650 if (zone_is_oom_locked(zone)) {
651 ret = 0;
652 goto out;
653 }
654 for_each_populated_zone(zone)
655 zone_set_flag(zone, ZONE_OOM_LOCKED);
656out:
657 spin_unlock(&zone_scan_lock);
658 return ret;
659}
660
661/*
662 * Clears ZONE_OOM_LOCKED for all system zones so that failed allocation
663 * attempts or page faults may now recall the oom killer, if necessary.
664 */
665static void clear_system_oom(void)
666{
667 struct zone *zone;
668
669 spin_lock(&zone_scan_lock);
670 for_each_populated_zone(zone)
671 zone_clear_flag(zone, ZONE_OOM_LOCKED);
672 spin_unlock(&zone_scan_lock);
673}
674
675/**
676 * out_of_memory - kill the "best" process when we run out of memory
677 * @zonelist: zonelist pointer
678 * @gfp_mask: memory allocation flags
679 * @order: amount of memory being requested as a power of 2
680 * @nodemask: nodemask passed to page allocator
681 *
682 * If we run out of memory, we have the choice between either
683 * killing a random task (bad), letting the system crash (worse)
684 * OR try to be smart about which process to kill. Note that we
685 * don't have to be perfect here, we just have to be good.
686 */
687void out_of_memory(struct zonelist *zonelist, gfp_t gfp_mask,
688 int order, nodemask_t *nodemask)
689{
690 const nodemask_t *mpol_mask;
691 struct task_struct *p;
692 unsigned long totalpages;
693 unsigned long freed = 0;
694 unsigned int points;
695 enum oom_constraint constraint = CONSTRAINT_NONE;
696 int killed = 0;
697
698 blocking_notifier_call_chain(&oom_notify_list, 0, &freed);
699 if (freed > 0)
700 /* Got some memory back in the last second. */
701 return;
702
703 /*
704 * If current has a pending SIGKILL, then automatically select it. The
705 * goal is to allow it to allocate so that it may quickly exit and free
706 * its memory.
707 */
708 if (fatal_signal_pending(current)) {
709 set_thread_flag(TIF_MEMDIE);
710 return;
711 }
712
713 /*
714 * Check if there were limitations on the allocation (only relevant for
715 * NUMA) that may require different handling.
716 */
717 constraint = constrained_alloc(zonelist, gfp_mask, nodemask,
718 &totalpages);
719 mpol_mask = (constraint == CONSTRAINT_MEMORY_POLICY) ? nodemask : NULL;
720 check_panic_on_oom(constraint, gfp_mask, order, mpol_mask);
721
722 read_lock(&tasklist_lock);
723 if (sysctl_oom_kill_allocating_task &&
724 !oom_unkillable_task(current, NULL, nodemask) &&
725 current->mm && !atomic_read(¤t->mm->oom_disable_count)) {
726 /*
727 * oom_kill_process() needs tasklist_lock held. If it returns
728 * non-zero, current could not be killed so we must fallback to
729 * the tasklist scan.
730 */
731 if (!oom_kill_process(current, gfp_mask, order, 0, totalpages,
732 NULL, nodemask,
733 "Out of memory (oom_kill_allocating_task)"))
734 goto out;
735 }
736
737retry:
738 p = select_bad_process(&points, totalpages, NULL, mpol_mask);
739 if (PTR_ERR(p) == -1UL)
740 goto out;
741
742 /* Found nothing?!?! Either we hang forever, or we panic. */
743 if (!p) {
744 dump_header(NULL, gfp_mask, order, NULL, mpol_mask);
745 read_unlock(&tasklist_lock);
746 panic("Out of memory and no killable processes...\n");
747 }
748
749 if (oom_kill_process(p, gfp_mask, order, points, totalpages, NULL,
750 nodemask, "Out of memory"))
751 goto retry;
752 killed = 1;
753out:
754 read_unlock(&tasklist_lock);
755
756 /*
757 * Give "p" a good chance of killing itself before we
758 * retry to allocate memory unless "p" is current
759 */
760 if (killed && !test_thread_flag(TIF_MEMDIE))
761 schedule_timeout_uninterruptible(1);
762}
763
764/*
765 * The pagefault handler calls here because it is out of memory, so kill a
766 * memory-hogging task. If a populated zone has ZONE_OOM_LOCKED set, a parallel
767 * oom killing is already in progress so do nothing. If a task is found with
768 * TIF_MEMDIE set, it has been killed so do nothing and allow it to exit.
769 */
770void pagefault_out_of_memory(void)
771{
772 if (try_set_system_oom()) {
773 out_of_memory(NULL, 0, 0, NULL);
774 clear_system_oom();
775 }
776 if (!test_thread_flag(TIF_MEMDIE))
777 schedule_timeout_uninterruptible(1);
778}
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}