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TOMOYO Linux Cross Reference
Linux/mm/oom_kill.c

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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/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 
 42 int sysctl_panic_on_oom;
 43 int sysctl_oom_kill_allocating_task;
 44 int sysctl_oom_dump_tasks = 1;
 45 
 46 DEFINE_MUTEX(oom_lock);
 47 
 48 #ifdef CONFIG_NUMA
 49 /**
 50  * has_intersects_mems_allowed() - check task eligiblity for kill
 51  * @start: task struct of which task to consider
 52  * @mask: nodemask passed to page allocator for mempolicy ooms
 53  *
 54  * Task eligibility is determined by whether or not a candidate task, @tsk,
 55  * shares the same mempolicy nodes as current if it is bound by such a policy
 56  * and whether or not it has the same set of allowed cpuset nodes.
 57  */
 58 static bool has_intersects_mems_allowed(struct task_struct *start,
 59                                         const nodemask_t *mask)
 60 {
 61         struct task_struct *tsk;
 62         bool ret = false;
 63 
 64         rcu_read_lock();
 65         for_each_thread(start, tsk) {
 66                 if (mask) {
 67                         /*
 68                          * If this is a mempolicy constrained oom, tsk's
 69                          * cpuset is irrelevant.  Only return true if its
 70                          * mempolicy intersects current, otherwise it may be
 71                          * needlessly killed.
 72                          */
 73                         ret = mempolicy_nodemask_intersects(tsk, mask);
 74                 } else {
 75                         /*
 76                          * This is not a mempolicy constrained oom, so only
 77                          * check the mems of tsk's cpuset.
 78                          */
 79                         ret = cpuset_mems_allowed_intersects(current, tsk);
 80                 }
 81                 if (ret)
 82                         break;
 83         }
 84         rcu_read_unlock();
 85 
 86         return ret;
 87 }
 88 #else
 89 static bool has_intersects_mems_allowed(struct task_struct *tsk,
 90                                         const nodemask_t *mask)
 91 {
 92         return true;
 93 }
 94 #endif /* CONFIG_NUMA */
 95 
 96 /*
 97  * The process p may have detached its own ->mm while exiting or through
 98  * use_mm(), but one or more of its subthreads may still have a valid
 99  * pointer.  Return p, or any of its subthreads with a valid ->mm, with
100  * task_lock() held.
101  */
102 struct task_struct *find_lock_task_mm(struct task_struct *p)
103 {
104         struct task_struct *t;
105 
106         rcu_read_lock();
107 
108         for_each_thread(p, t) {
109                 task_lock(t);
110                 if (likely(t->mm))
111                         goto found;
112                 task_unlock(t);
113         }
114         t = NULL;
115 found:
116         rcu_read_unlock();
117 
118         return t;
119 }
120 
121 /* return true if the task is not adequate as candidate victim task. */
122 static bool oom_unkillable_task(struct task_struct *p,
123                 struct mem_cgroup *memcg, const nodemask_t *nodemask)
124 {
125         if (is_global_init(p))
126                 return true;
127         if (p->flags & PF_KTHREAD)
128                 return true;
129 
130         /* When mem_cgroup_out_of_memory() and p is not member of the group */
131         if (memcg && !task_in_mem_cgroup(p, memcg))
132                 return true;
133 
134         /* p may not have freeable memory in nodemask */
135         if (!has_intersects_mems_allowed(p, nodemask))
136                 return true;
137 
138         return false;
139 }
140 
141 /**
142  * oom_badness - heuristic function to determine which candidate task to kill
143  * @p: task struct of which task we should calculate
144  * @totalpages: total present RAM allowed for page allocation
145  *
146  * The heuristic for determining which task to kill is made to be as simple and
147  * predictable as possible.  The goal is to return the highest value for the
148  * task consuming the most memory to avoid subsequent oom failures.
149  */
150 unsigned long oom_badness(struct task_struct *p, struct mem_cgroup *memcg,
151                           const nodemask_t *nodemask, unsigned long totalpages)
152 {
153         long points;
154         long adj;
155 
156         if (oom_unkillable_task(p, memcg, nodemask))
157                 return 0;
158 
159         p = find_lock_task_mm(p);
160         if (!p)
161                 return 0;
162 
163         adj = (long)p->signal->oom_score_adj;
164         if (adj == OOM_SCORE_ADJ_MIN) {
165                 task_unlock(p);
166                 return 0;
167         }
168 
169         /*
170          * The baseline for the badness score is the proportion of RAM that each
171          * task's rss, pagetable and swap space use.
172          */
173         points = get_mm_rss(p->mm) + get_mm_counter(p->mm, MM_SWAPENTS) +
174                 atomic_long_read(&p->mm->nr_ptes) + mm_nr_pmds(p->mm);
175         task_unlock(p);
176 
177         /*
178          * Root processes get 3% bonus, just like the __vm_enough_memory()
179          * implementation used by LSMs.
180          */
181         if (has_capability_noaudit(p, CAP_SYS_ADMIN))
182                 points -= (points * 3) / 100;
183 
184         /* Normalize to oom_score_adj units */
185         adj *= totalpages / 1000;
186         points += adj;
187 
188         /*
189          * Never return 0 for an eligible task regardless of the root bonus and
190          * oom_score_adj (oom_score_adj can't be OOM_SCORE_ADJ_MIN here).
191          */
192         return points > 0 ? points : 1;
193 }
194 
195 /*
196  * Determine the type of allocation constraint.
197  */
198 #ifdef CONFIG_NUMA
199 static enum oom_constraint constrained_alloc(struct oom_control *oc,
200                                              unsigned long *totalpages)
201 {
202         struct zone *zone;
203         struct zoneref *z;
204         enum zone_type high_zoneidx = gfp_zone(oc->gfp_mask);
205         bool cpuset_limited = false;
206         int nid;
207 
208         /* Default to all available memory */
209         *totalpages = totalram_pages + total_swap_pages;
210 
211         if (!oc->zonelist)
212                 return CONSTRAINT_NONE;
213         /*
214          * Reach here only when __GFP_NOFAIL is used. So, we should avoid
215          * to kill current.We have to random task kill in this case.
216          * Hopefully, CONSTRAINT_THISNODE...but no way to handle it, now.
217          */
218         if (oc->gfp_mask & __GFP_THISNODE)
219                 return CONSTRAINT_NONE;
220 
221         /*
222          * This is not a __GFP_THISNODE allocation, so a truncated nodemask in
223          * the page allocator means a mempolicy is in effect.  Cpuset policy
224          * is enforced in get_page_from_freelist().
225          */
226         if (oc->nodemask &&
227             !nodes_subset(node_states[N_MEMORY], *oc->nodemask)) {
228                 *totalpages = total_swap_pages;
229                 for_each_node_mask(nid, *oc->nodemask)
230                         *totalpages += node_spanned_pages(nid);
231                 return CONSTRAINT_MEMORY_POLICY;
232         }
233 
234         /* Check this allocation failure is caused by cpuset's wall function */
235         for_each_zone_zonelist_nodemask(zone, z, oc->zonelist,
236                         high_zoneidx, oc->nodemask)
237                 if (!cpuset_zone_allowed(zone, oc->gfp_mask))
238                         cpuset_limited = true;
239 
240         if (cpuset_limited) {
241                 *totalpages = total_swap_pages;
242                 for_each_node_mask(nid, cpuset_current_mems_allowed)
243                         *totalpages += node_spanned_pages(nid);
244                 return CONSTRAINT_CPUSET;
245         }
246         return CONSTRAINT_NONE;
247 }
248 #else
249 static enum oom_constraint constrained_alloc(struct oom_control *oc,
250                                              unsigned long *totalpages)
251 {
252         *totalpages = totalram_pages + total_swap_pages;
253         return CONSTRAINT_NONE;
254 }
255 #endif
256 
257 enum oom_scan_t oom_scan_process_thread(struct oom_control *oc,
258                         struct task_struct *task, unsigned long totalpages)
259 {
260         if (oom_unkillable_task(task, NULL, oc->nodemask))
261                 return OOM_SCAN_CONTINUE;
262 
263         /*
264          * This task already has access to memory reserves and is being killed.
265          * Don't allow any other task to have access to the reserves.
266          */
267         if (test_tsk_thread_flag(task, TIF_MEMDIE)) {
268                 if (oc->order != -1)
269                         return OOM_SCAN_ABORT;
270         }
271         if (!task->mm)
272                 return OOM_SCAN_CONTINUE;
273 
274         /*
275          * If task is allocating a lot of memory and has been marked to be
276          * killed first if it triggers an oom, then select it.
277          */
278         if (oom_task_origin(task))
279                 return OOM_SCAN_SELECT;
280 
281         if (task_will_free_mem(task) && oc->order != -1)
282                 return OOM_SCAN_ABORT;
283 
284         return OOM_SCAN_OK;
285 }
286 
287 /*
288  * Simple selection loop. We chose the process with the highest
289  * number of 'points'.  Returns -1 on scan abort.
290  */
291 static struct task_struct *select_bad_process(struct oom_control *oc,
292                 unsigned int *ppoints, unsigned long totalpages)
293 {
294         struct task_struct *g, *p;
295         struct task_struct *chosen = NULL;
296         unsigned long chosen_points = 0;
297 
298         rcu_read_lock();
299         for_each_process_thread(g, p) {
300                 unsigned int points;
301 
302                 switch (oom_scan_process_thread(oc, p, totalpages)) {
303                 case OOM_SCAN_SELECT:
304                         chosen = p;
305                         chosen_points = ULONG_MAX;
306                         /* fall through */
307                 case OOM_SCAN_CONTINUE:
308                         continue;
309                 case OOM_SCAN_ABORT:
310                         rcu_read_unlock();
311                         return (struct task_struct *)(-1UL);
312                 case OOM_SCAN_OK:
313                         break;
314                 };
315                 points = oom_badness(p, NULL, oc->nodemask, totalpages);
316                 if (!points || points < chosen_points)
317                         continue;
318                 /* Prefer thread group leaders for display purposes */
319                 if (points == chosen_points && thread_group_leader(chosen))
320                         continue;
321 
322                 chosen = p;
323                 chosen_points = points;
324         }
325         if (chosen)
326                 get_task_struct(chosen);
327         rcu_read_unlock();
328 
329         *ppoints = chosen_points * 1000 / totalpages;
330         return chosen;
331 }
332 
333 /**
334  * dump_tasks - dump current memory state of all system tasks
335  * @memcg: current's memory controller, if constrained
336  * @nodemask: nodemask passed to page allocator for mempolicy ooms
337  *
338  * Dumps the current memory state of all eligible tasks.  Tasks not in the same
339  * memcg, not in the same cpuset, or bound to a disjoint set of mempolicy nodes
340  * are not shown.
341  * State information includes task's pid, uid, tgid, vm size, rss, nr_ptes,
342  * swapents, oom_score_adj value, and name.
343  */
344 static void dump_tasks(struct mem_cgroup *memcg, const nodemask_t *nodemask)
345 {
346         struct task_struct *p;
347         struct task_struct *task;
348 
349         pr_info("[ pid ]   uid  tgid total_vm      rss nr_ptes nr_pmds swapents oom_score_adj name\n");
350         rcu_read_lock();
351         for_each_process(p) {
352                 if (oom_unkillable_task(p, memcg, nodemask))
353                         continue;
354 
355                 task = find_lock_task_mm(p);
356                 if (!task) {
357                         /*
358                          * This is a kthread or all of p's threads have already
359                          * detached their mm's.  There's no need to report
360                          * them; they can't be oom killed anyway.
361                          */
362                         continue;
363                 }
364 
365                 pr_info("[%5d] %5d %5d %8lu %8lu %7ld %7ld %8lu         %5hd %s\n",
366                         task->pid, from_kuid(&init_user_ns, task_uid(task)),
367                         task->tgid, task->mm->total_vm, get_mm_rss(task->mm),
368                         atomic_long_read(&task->mm->nr_ptes),
369                         mm_nr_pmds(task->mm),
370                         get_mm_counter(task->mm, MM_SWAPENTS),
371                         task->signal->oom_score_adj, task->comm);
372                 task_unlock(task);
373         }
374         rcu_read_unlock();
375 }
376 
377 static void dump_header(struct oom_control *oc, struct task_struct *p,
378                         struct mem_cgroup *memcg)
379 {
380         task_lock(current);
381         pr_warning("%s invoked oom-killer: gfp_mask=0x%x, order=%d, "
382                 "oom_score_adj=%hd\n",
383                 current->comm, oc->gfp_mask, oc->order,
384                 current->signal->oom_score_adj);
385         cpuset_print_task_mems_allowed(current);
386         task_unlock(current);
387         dump_stack();
388         if (memcg)
389                 mem_cgroup_print_oom_info(memcg, p);
390         else
391                 show_mem(SHOW_MEM_FILTER_NODES);
392         if (sysctl_oom_dump_tasks)
393                 dump_tasks(memcg, oc->nodemask);
394 }
395 
396 /*
397  * Number of OOM victims in flight
398  */
399 static atomic_t oom_victims = ATOMIC_INIT(0);
400 static DECLARE_WAIT_QUEUE_HEAD(oom_victims_wait);
401 
402 bool oom_killer_disabled __read_mostly;
403 
404 /**
405  * mark_oom_victim - mark the given task as OOM victim
406  * @tsk: task to mark
407  *
408  * Has to be called with oom_lock held and never after
409  * oom has been disabled already.
410  */
411 void mark_oom_victim(struct task_struct *tsk)
412 {
413         WARN_ON(oom_killer_disabled);
414         /* OOM killer might race with memcg OOM */
415         if (test_and_set_tsk_thread_flag(tsk, TIF_MEMDIE))
416                 return;
417         /*
418          * Make sure that the task is woken up from uninterruptible sleep
419          * if it is frozen because OOM killer wouldn't be able to free
420          * any memory and livelock. freezing_slow_path will tell the freezer
421          * that TIF_MEMDIE tasks should be ignored.
422          */
423         __thaw_task(tsk);
424         atomic_inc(&oom_victims);
425 }
426 
427 /**
428  * exit_oom_victim - note the exit of an OOM victim
429  */
430 void exit_oom_victim(void)
431 {
432         clear_thread_flag(TIF_MEMDIE);
433 
434         if (!atomic_dec_return(&oom_victims))
435                 wake_up_all(&oom_victims_wait);
436 }
437 
438 /**
439  * oom_killer_disable - disable OOM killer
440  *
441  * Forces all page allocations to fail rather than trigger OOM killer.
442  * Will block and wait until all OOM victims are killed.
443  *
444  * The function cannot be called when there are runnable user tasks because
445  * the userspace would see unexpected allocation failures as a result. Any
446  * new usage of this function should be consulted with MM people.
447  *
448  * Returns true if successful and false if the OOM killer cannot be
449  * disabled.
450  */
451 bool oom_killer_disable(void)
452 {
453         /*
454          * Make sure to not race with an ongoing OOM killer
455          * and that the current is not the victim.
456          */
457         mutex_lock(&oom_lock);
458         if (test_thread_flag(TIF_MEMDIE)) {
459                 mutex_unlock(&oom_lock);
460                 return false;
461         }
462 
463         oom_killer_disabled = true;
464         mutex_unlock(&oom_lock);
465 
466         wait_event(oom_victims_wait, !atomic_read(&oom_victims));
467 
468         return true;
469 }
470 
471 /**
472  * oom_killer_enable - enable OOM killer
473  */
474 void oom_killer_enable(void)
475 {
476         oom_killer_disabled = false;
477 }
478 
479 #define K(x) ((x) << (PAGE_SHIFT-10))
480 /*
481  * Must be called while holding a reference to p, which will be released upon
482  * returning.
483  */
484 void oom_kill_process(struct oom_control *oc, struct task_struct *p,
485                       unsigned int points, unsigned long totalpages,
486                       struct mem_cgroup *memcg, const char *message)
487 {
488         struct task_struct *victim = p;
489         struct task_struct *child;
490         struct task_struct *t;
491         struct mm_struct *mm;
492         unsigned int victim_points = 0;
493         static DEFINE_RATELIMIT_STATE(oom_rs, DEFAULT_RATELIMIT_INTERVAL,
494                                               DEFAULT_RATELIMIT_BURST);
495 
496         /*
497          * If the task is already exiting, don't alarm the sysadmin or kill
498          * its children or threads, just set TIF_MEMDIE so it can die quickly
499          */
500         task_lock(p);
501         if (p->mm && task_will_free_mem(p)) {
502                 mark_oom_victim(p);
503                 task_unlock(p);
504                 put_task_struct(p);
505                 return;
506         }
507         task_unlock(p);
508 
509         if (__ratelimit(&oom_rs))
510                 dump_header(oc, p, memcg);
511 
512         task_lock(p);
513         pr_err("%s: Kill process %d (%s) score %u or sacrifice child\n",
514                 message, task_pid_nr(p), p->comm, points);
515         task_unlock(p);
516 
517         /*
518          * If any of p's children has a different mm and is eligible for kill,
519          * the one with the highest oom_badness() score is sacrificed for its
520          * parent.  This attempts to lose the minimal amount of work done while
521          * still freeing memory.
522          */
523         read_lock(&tasklist_lock);
524         for_each_thread(p, t) {
525                 list_for_each_entry(child, &t->children, sibling) {
526                         unsigned int child_points;
527 
528                         if (child->mm == p->mm)
529                                 continue;
530                         /*
531                          * oom_badness() returns 0 if the thread is unkillable
532                          */
533                         child_points = oom_badness(child, memcg, oc->nodemask,
534                                                                 totalpages);
535                         if (child_points > victim_points) {
536                                 put_task_struct(victim);
537                                 victim = child;
538                                 victim_points = child_points;
539                                 get_task_struct(victim);
540                         }
541                 }
542         }
543         read_unlock(&tasklist_lock);
544 
545         p = find_lock_task_mm(victim);
546         if (!p) {
547                 put_task_struct(victim);
548                 return;
549         } else if (victim != p) {
550                 get_task_struct(p);
551                 put_task_struct(victim);
552                 victim = p;
553         }
554 
555         /* mm cannot safely be dereferenced after task_unlock(victim) */
556         mm = victim->mm;
557         /*
558          * We should send SIGKILL before setting TIF_MEMDIE in order to prevent
559          * the OOM victim from depleting the memory reserves from the user
560          * space under its control.
561          */
562         do_send_sig_info(SIGKILL, SEND_SIG_FORCED, victim, true);
563         mark_oom_victim(victim);
564         pr_err("Killed process %d (%s) total-vm:%lukB, anon-rss:%lukB, file-rss:%lukB\n",
565                 task_pid_nr(victim), victim->comm, K(victim->mm->total_vm),
566                 K(get_mm_counter(victim->mm, MM_ANONPAGES)),
567                 K(get_mm_counter(victim->mm, MM_FILEPAGES)));
568         task_unlock(victim);
569 
570         /*
571          * Kill all user processes sharing victim->mm in other thread groups, if
572          * any.  They don't get access to memory reserves, though, to avoid
573          * depletion of all memory.  This prevents mm->mmap_sem livelock when an
574          * oom killed thread cannot exit because it requires the semaphore and
575          * its contended by another thread trying to allocate memory itself.
576          * That thread will now get access to memory reserves since it has a
577          * pending fatal signal.
578          */
579         rcu_read_lock();
580         for_each_process(p)
581                 if (p->mm == mm && !same_thread_group(p, victim) &&
582                     !(p->flags & PF_KTHREAD)) {
583                         if (p->signal->oom_score_adj == OOM_SCORE_ADJ_MIN)
584                                 continue;
585 
586                         task_lock(p);   /* Protect ->comm from prctl() */
587                         pr_err("Kill process %d (%s) sharing same memory\n",
588                                 task_pid_nr(p), p->comm);
589                         task_unlock(p);
590                         do_send_sig_info(SIGKILL, SEND_SIG_FORCED, p, true);
591                 }
592         rcu_read_unlock();
593 
594         put_task_struct(victim);
595 }
596 #undef K
597 
598 /*
599  * Determines whether the kernel must panic because of the panic_on_oom sysctl.
600  */
601 void check_panic_on_oom(struct oom_control *oc, enum oom_constraint constraint,
602                         struct mem_cgroup *memcg)
603 {
604         if (likely(!sysctl_panic_on_oom))
605                 return;
606         if (sysctl_panic_on_oom != 2) {
607                 /*
608                  * panic_on_oom == 1 only affects CONSTRAINT_NONE, the kernel
609                  * does not panic for cpuset, mempolicy, or memcg allocation
610                  * failures.
611                  */
612                 if (constraint != CONSTRAINT_NONE)
613                         return;
614         }
615         /* Do not panic for oom kills triggered by sysrq */
616         if (oc->order == -1)
617                 return;
618         dump_header(oc, NULL, memcg);
619         panic("Out of memory: %s panic_on_oom is enabled\n",
620                 sysctl_panic_on_oom == 2 ? "compulsory" : "system-wide");
621 }
622 
623 static BLOCKING_NOTIFIER_HEAD(oom_notify_list);
624 
625 int register_oom_notifier(struct notifier_block *nb)
626 {
627         return blocking_notifier_chain_register(&oom_notify_list, nb);
628 }
629 EXPORT_SYMBOL_GPL(register_oom_notifier);
630 
631 int unregister_oom_notifier(struct notifier_block *nb)
632 {
633         return blocking_notifier_chain_unregister(&oom_notify_list, nb);
634 }
635 EXPORT_SYMBOL_GPL(unregister_oom_notifier);
636 
637 /**
638  * out_of_memory - kill the "best" process when we run out of memory
639  * @oc: pointer to struct oom_control
640  *
641  * If we run out of memory, we have the choice between either
642  * killing a random task (bad), letting the system crash (worse)
643  * OR try to be smart about which process to kill. Note that we
644  * don't have to be perfect here, we just have to be good.
645  */
646 bool out_of_memory(struct oom_control *oc)
647 {
648         struct task_struct *p;
649         unsigned long totalpages;
650         unsigned long freed = 0;
651         unsigned int uninitialized_var(points);
652         enum oom_constraint constraint = CONSTRAINT_NONE;
653 
654         if (oom_killer_disabled)
655                 return false;
656 
657         blocking_notifier_call_chain(&oom_notify_list, 0, &freed);
658         if (freed > 0)
659                 /* Got some memory back in the last second. */
660                 return true;
661 
662         /*
663          * If current has a pending SIGKILL or is exiting, then automatically
664          * select it.  The goal is to allow it to allocate so that it may
665          * quickly exit and free its memory.
666          *
667          * But don't select if current has already released its mm and cleared
668          * TIF_MEMDIE flag at exit_mm(), otherwise an OOM livelock may occur.
669          */
670         if (current->mm &&
671             (fatal_signal_pending(current) || task_will_free_mem(current))) {
672                 mark_oom_victim(current);
673                 return true;
674         }
675 
676         /*
677          * Check if there were limitations on the allocation (only relevant for
678          * NUMA) that may require different handling.
679          */
680         constraint = constrained_alloc(oc, &totalpages);
681         if (constraint != CONSTRAINT_MEMORY_POLICY)
682                 oc->nodemask = NULL;
683         check_panic_on_oom(oc, constraint, NULL);
684 
685         if (sysctl_oom_kill_allocating_task && current->mm &&
686             !oom_unkillable_task(current, NULL, oc->nodemask) &&
687             current->signal->oom_score_adj != OOM_SCORE_ADJ_MIN) {
688                 get_task_struct(current);
689                 oom_kill_process(oc, current, 0, totalpages, NULL,
690                                  "Out of memory (oom_kill_allocating_task)");
691                 return true;
692         }
693 
694         p = select_bad_process(oc, &points, totalpages);
695         /* Found nothing?!?! Either we hang forever, or we panic. */
696         if (!p && oc->order != -1) {
697                 dump_header(oc, NULL, NULL);
698                 panic("Out of memory and no killable processes...\n");
699         }
700         if (p && p != (void *)-1UL) {
701                 oom_kill_process(oc, p, points, totalpages, NULL,
702                                  "Out of memory");
703                 /*
704                  * Give the killed process a good chance to exit before trying
705                  * to allocate memory again.
706                  */
707                 schedule_timeout_killable(1);
708         }
709         return true;
710 }
711 
712 /*
713  * The pagefault handler calls here because it is out of memory, so kill a
714  * memory-hogging task.  If any populated zone has ZONE_OOM_LOCKED set, a
715  * parallel oom killing is already in progress so do nothing.
716  */
717 void pagefault_out_of_memory(void)
718 {
719         struct oom_control oc = {
720                 .zonelist = NULL,
721                 .nodemask = NULL,
722                 .gfp_mask = 0,
723                 .order = 0,
724         };
725 
726         if (mem_cgroup_oom_synchronize(true))
727                 return;
728 
729         if (!mutex_trylock(&oom_lock))
730                 return;
731 
732         if (!out_of_memory(&oc)) {
733                 /*
734                  * There shouldn't be any user tasks runnable while the
735                  * OOM killer is disabled, so the current task has to
736                  * be a racing OOM victim for which oom_killer_disable()
737                  * is waiting for.
738                  */
739                 WARN_ON(test_thread_flag(TIF_MEMDIE));
740         }
741 
742         mutex_unlock(&oom_lock);
743 }
744 

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