Root/mm/oom_kill.c

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
35int sysctl_panic_on_oom;
36int sysctl_oom_kill_allocating_task;
37int sysctl_oom_dump_tasks = 1;
38static DEFINE_SPINLOCK(zone_scan_lock);
39
40#ifdef CONFIG_NUMA
41/**
42 * has_intersects_mems_allowed() - check task eligiblity for kill
43 * @tsk: task struct of which task to consider
44 * @mask: nodemask passed to page allocator for mempolicy ooms
45 *
46 * Task eligibility is determined by whether or not a candidate task, @tsk,
47 * shares the same mempolicy nodes as current if it is bound by such a policy
48 * and whether or not it has the same set of allowed cpuset nodes.
49 */
50static bool has_intersects_mems_allowed(struct task_struct *tsk,
51                    const nodemask_t *mask)
52{
53    struct task_struct *start = tsk;
54
55    do {
56        if (mask) {
57            /*
58             * If this is a mempolicy constrained oom, tsk's
59             * cpuset is irrelevant. Only return true if its
60             * mempolicy intersects current, otherwise it may be
61             * needlessly killed.
62             */
63            if (mempolicy_nodemask_intersects(tsk, mask))
64                return true;
65        } else {
66            /*
67             * This is not a mempolicy constrained oom, so only
68             * check the mems of tsk's cpuset.
69             */
70            if (cpuset_mems_allowed_intersects(current, tsk))
71                return true;
72        }
73    } while_each_thread(start, tsk);
74
75    return false;
76}
77#else
78static bool has_intersects_mems_allowed(struct task_struct *tsk,
79                    const nodemask_t *mask)
80{
81    return true;
82}
83#endif /* CONFIG_NUMA */
84
85/*
86 * If this is a system OOM (not a memcg OOM) and the task selected to be
87 * killed is not already running at high (RT) priorities, speed up the
88 * recovery by boosting the dying task to the lowest FIFO priority.
89 * That helps with the recovery and avoids interfering with RT tasks.
90 */
91static void boost_dying_task_prio(struct task_struct *p,
92                  struct mem_cgroup *mem)
93{
94    struct sched_param param = { .sched_priority = 1 };
95
96    if (mem)
97        return;
98
99    if (!rt_task(p))
100        sched_setscheduler_nocheck(p, SCHED_FIFO, &param);
101}
102
103/*
104 * The process p may have detached its own ->mm while exiting or through
105 * use_mm(), but one or more of its subthreads may still have a valid
106 * pointer. Return p, or any of its subthreads with a valid ->mm, with
107 * task_lock() held.
108 */
109struct task_struct *find_lock_task_mm(struct task_struct *p)
110{
111    struct task_struct *t = p;
112
113    do {
114        task_lock(t);
115        if (likely(t->mm))
116            return t;
117        task_unlock(t);
118    } while_each_thread(p, t);
119
120    return NULL;
121}
122
123/* return true if the task is not adequate as candidate victim task. */
124static bool oom_unkillable_task(struct task_struct *p,
125        const struct mem_cgroup *mem, const nodemask_t *nodemask)
126{
127    if (is_global_init(p))
128        return true;
129    if (p->flags & PF_KTHREAD)
130        return true;
131
132    /* When mem_cgroup_out_of_memory() and p is not member of the group */
133    if (mem && !task_in_mem_cgroup(p, mem))
134        return true;
135
136    /* p may not have freeable memory in nodemask */
137    if (!has_intersects_mems_allowed(p, nodemask))
138        return true;
139
140    return false;
141}
142
143/**
144 * oom_badness - heuristic function to determine which candidate task to kill
145 * @p: task struct of which task we should calculate
146 * @totalpages: total present RAM allowed for page allocation
147 *
148 * The heuristic for determining which task to kill is made to be as simple and
149 * predictable as possible. The goal is to return the highest value for the
150 * task consuming the most memory to avoid subsequent oom failures.
151 */
152unsigned int oom_badness(struct task_struct *p, struct mem_cgroup *mem,
153              const nodemask_t *nodemask, unsigned long totalpages)
154{
155    int points;
156
157    if (oom_unkillable_task(p, mem, nodemask))
158        return 0;
159
160    p = find_lock_task_mm(p);
161    if (!p)
162        return 0;
163
164    /*
165     * Shortcut check for OOM_SCORE_ADJ_MIN so the entire heuristic doesn't
166     * need to be executed for something that cannot be killed.
167     */
168    if (p->signal->oom_score_adj == OOM_SCORE_ADJ_MIN) {
169        task_unlock(p);
170        return 0;
171    }
172
173    /*
174     * When the PF_OOM_ORIGIN bit is set, it indicates the task should have
175     * priority for oom killing.
176     */
177    if (p->flags & PF_OOM_ORIGIN) {
178        task_unlock(p);
179        return 1000;
180    }
181
182    /*
183     * The memory controller may have a limit of 0 bytes, so avoid a divide
184     * by zero, if necessary.
185     */
186    if (!totalpages)
187        totalpages = 1;
188
189    /*
190     * The baseline for the badness score is the proportion of RAM that each
191     * task's rss and swap space use.
192     */
193    points = (get_mm_rss(p->mm) + get_mm_counter(p->mm, MM_SWAPENTS)) * 1000 /
194            totalpages;
195    task_unlock(p);
196
197    /*
198     * Root processes get 3% bonus, just like the __vm_enough_memory()
199     * implementation used by LSMs.
200     */
201    if (has_capability_noaudit(p, CAP_SYS_ADMIN))
202        points -= 30;
203
204    /*
205     * /proc/pid/oom_score_adj ranges from -1000 to +1000 such that it may
206     * either completely disable oom killing or always prefer a certain
207     * task.
208     */
209    points += p->signal->oom_score_adj;
210
211    /*
212     * Never return 0 for an eligible task that may be killed since it's
213     * possible that no single user task uses more than 0.1% of memory and
214     * no single admin tasks uses more than 3.0%.
215     */
216    if (points <= 0)
217        return 1;
218    return (points < 1000) ? points : 1000;
219}
220
221/*
222 * Determine the type of allocation constraint.
223 */
224#ifdef CONFIG_NUMA
225static enum oom_constraint constrained_alloc(struct zonelist *zonelist,
226                gfp_t gfp_mask, nodemask_t *nodemask,
227                unsigned long *totalpages)
228{
229    struct zone *zone;
230    struct zoneref *z;
231    enum zone_type high_zoneidx = gfp_zone(gfp_mask);
232    bool cpuset_limited = false;
233    int nid;
234
235    /* Default to all available memory */
236    *totalpages = totalram_pages + total_swap_pages;
237
238    if (!zonelist)
239        return CONSTRAINT_NONE;
240    /*
241     * Reach here only when __GFP_NOFAIL is used. So, we should avoid
242     * to kill current.We have to random task kill in this case.
243     * Hopefully, CONSTRAINT_THISNODE...but no way to handle it, now.
244     */
245    if (gfp_mask & __GFP_THISNODE)
246        return CONSTRAINT_NONE;
247
248    /*
249     * This is not a __GFP_THISNODE allocation, so a truncated nodemask in
250     * the page allocator means a mempolicy is in effect. Cpuset policy
251     * is enforced in get_page_from_freelist().
252     */
253    if (nodemask && !nodes_subset(node_states[N_HIGH_MEMORY], *nodemask)) {
254        *totalpages = total_swap_pages;
255        for_each_node_mask(nid, *nodemask)
256            *totalpages += node_spanned_pages(nid);
257        return CONSTRAINT_MEMORY_POLICY;
258    }
259
260    /* Check this allocation failure is caused by cpuset's wall function */
261    for_each_zone_zonelist_nodemask(zone, z, zonelist,
262            high_zoneidx, nodemask)
263        if (!cpuset_zone_allowed_softwall(zone, gfp_mask))
264            cpuset_limited = true;
265
266    if (cpuset_limited) {
267        *totalpages = total_swap_pages;
268        for_each_node_mask(nid, cpuset_current_mems_allowed)
269            *totalpages += node_spanned_pages(nid);
270        return CONSTRAINT_CPUSET;
271    }
272    return CONSTRAINT_NONE;
273}
274#else
275static enum oom_constraint constrained_alloc(struct zonelist *zonelist,
276                gfp_t gfp_mask, nodemask_t *nodemask,
277                unsigned long *totalpages)
278{
279    *totalpages = totalram_pages + total_swap_pages;
280    return CONSTRAINT_NONE;
281}
282#endif
283
284/*
285 * Simple selection loop. We chose the process with the highest
286 * number of 'points'. We expect the caller will lock the tasklist.
287 *
288 * (not docbooked, we don't want this one cluttering up the manual)
289 */
290static struct task_struct *select_bad_process(unsigned int *ppoints,
291        unsigned long totalpages, struct mem_cgroup *mem,
292        const nodemask_t *nodemask)
293{
294    struct task_struct *p;
295    struct task_struct *chosen = NULL;
296    *ppoints = 0;
297
298    for_each_process(p) {
299        unsigned int points;
300
301        if (oom_unkillable_task(p, mem, nodemask))
302            continue;
303
304        /*
305         * This task already has access to memory reserves and is
306         * being killed. Don't allow any other task access to the
307         * memory reserve.
308         *
309         * Note: this may have a chance of deadlock if it gets
310         * blocked waiting for another task which itself is waiting
311         * for memory. Is there a better alternative?
312         */
313        if (test_tsk_thread_flag(p, TIF_MEMDIE))
314            return ERR_PTR(-1UL);
315
316        /*
317         * This is in the process of releasing memory so wait for it
318         * to finish before killing some other task by mistake.
319         *
320         * However, if p is the current task, we allow the 'kill' to
321         * go ahead if it is exiting: this will simply set TIF_MEMDIE,
322         * which will allow it to gain access to memory reserves in
323         * the process of exiting and releasing its resources.
324         * Otherwise we could get an easy OOM deadlock.
325         */
326        if (thread_group_empty(p) && (p->flags & PF_EXITING) && p->mm) {
327            if (p != current)
328                return ERR_PTR(-1UL);
329
330            chosen = p;
331            *ppoints = 1000;
332        }
333
334        points = oom_badness(p, mem, nodemask, totalpages);
335        if (points > *ppoints) {
336            chosen = p;
337            *ppoints = points;
338        }
339    }
340
341    return chosen;
342}
343
344/**
345 * dump_tasks - dump current memory state of all system tasks
346 * @mem: current's memory controller, if constrained
347 * @nodemask: nodemask passed to page allocator for mempolicy ooms
348 *
349 * Dumps the current memory state of all eligible tasks. Tasks not in the same
350 * memcg, not in the same cpuset, or bound to a disjoint set of mempolicy nodes
351 * are not shown.
352 * State information includes task's pid, uid, tgid, vm size, rss, cpu, oom_adj
353 * value, oom_score_adj value, and name.
354 *
355 * Call with tasklist_lock read-locked.
356 */
357static void dump_tasks(const struct mem_cgroup *mem, const nodemask_t *nodemask)
358{
359    struct task_struct *p;
360    struct task_struct *task;
361
362    pr_info("[ pid ] uid tgid total_vm rss cpu oom_adj oom_score_adj name\n");
363    for_each_process(p) {
364        if (oom_unkillable_task(p, mem, nodemask))
365            continue;
366
367        task = find_lock_task_mm(p);
368        if (!task) {
369            /*
370             * This is a kthread or all of p's threads have already
371             * detached their mm's. There's no need to report
372             * them; they can't be oom killed anyway.
373             */
374            continue;
375        }
376
377        pr_info("[%5d] %5d %5d %8lu %8lu %3u %3d %5d %s\n",
378            task->pid, task_uid(task), task->tgid,
379            task->mm->total_vm, get_mm_rss(task->mm),
380            task_cpu(task), task->signal->oom_adj,
381            task->signal->oom_score_adj, task->comm);
382        task_unlock(task);
383    }
384}
385
386static void dump_header(struct task_struct *p, gfp_t gfp_mask, int order,
387            struct mem_cgroup *mem, const nodemask_t *nodemask)
388{
389    task_lock(current);
390    pr_warning("%s invoked oom-killer: gfp_mask=0x%x, order=%d, "
391        "oom_adj=%d, oom_score_adj=%d\n",
392        current->comm, gfp_mask, order, current->signal->oom_adj,
393        current->signal->oom_score_adj);
394    cpuset_print_task_mems_allowed(current);
395    task_unlock(current);
396    dump_stack();
397    mem_cgroup_print_oom_info(mem, p);
398    show_mem();
399    if (sysctl_oom_dump_tasks)
400        dump_tasks(mem, nodemask);
401}
402
403#define K(x) ((x) << (PAGE_SHIFT-10))
404static int oom_kill_task(struct task_struct *p, struct mem_cgroup *mem)
405{
406    p = find_lock_task_mm(p);
407    if (!p)
408        return 1;
409
410    pr_err("Killed process %d (%s) total-vm:%lukB, anon-rss:%lukB, file-rss:%lukB\n",
411        task_pid_nr(p), p->comm, K(p->mm->total_vm),
412        K(get_mm_counter(p->mm, MM_ANONPAGES)),
413        K(get_mm_counter(p->mm, MM_FILEPAGES)));
414    task_unlock(p);
415
416
417    set_tsk_thread_flag(p, TIF_MEMDIE);
418    force_sig(SIGKILL, p);
419
420    /*
421     * We give our sacrificial lamb high priority and access to
422     * all the memory it needs. That way it should be able to
423     * exit() and clear out its resources quickly...
424     */
425    boost_dying_task_prio(p, mem);
426
427    return 0;
428}
429#undef K
430
431static int oom_kill_process(struct task_struct *p, gfp_t gfp_mask, int order,
432                unsigned int points, unsigned long totalpages,
433                struct mem_cgroup *mem, nodemask_t *nodemask,
434                const char *message)
435{
436    struct task_struct *victim = p;
437    struct task_struct *child;
438    struct task_struct *t = p;
439    unsigned int victim_points = 0;
440
441    if (printk_ratelimit())
442        dump_header(p, gfp_mask, order, mem, nodemask);
443
444    /*
445     * If the task is already exiting, don't alarm the sysadmin or kill
446     * its children or threads, just set TIF_MEMDIE so it can die quickly
447     */
448    if (p->flags & PF_EXITING) {
449        set_tsk_thread_flag(p, TIF_MEMDIE);
450        boost_dying_task_prio(p, mem);
451        return 0;
452    }
453
454    task_lock(p);
455    pr_err("%s: Kill process %d (%s) score %d or sacrifice child\n",
456        message, task_pid_nr(p), p->comm, points);
457    task_unlock(p);
458
459    /*
460     * If any of p's children has a different mm and is eligible for kill,
461     * the one with the highest badness() score is sacrificed for its
462     * parent. This attempts to lose the minimal amount of work done while
463     * still freeing memory.
464     */
465    do {
466        list_for_each_entry(child, &t->children, sibling) {
467            unsigned int child_points;
468
469            /*
470             * oom_badness() returns 0 if the thread is unkillable
471             */
472            child_points = oom_badness(child, mem, nodemask,
473                                totalpages);
474            if (child_points > victim_points) {
475                victim = child;
476                victim_points = child_points;
477            }
478        }
479    } while_each_thread(p, t);
480
481    return oom_kill_task(victim, mem);
482}
483
484/*
485 * Determines whether the kernel must panic because of the panic_on_oom sysctl.
486 */
487static void check_panic_on_oom(enum oom_constraint constraint, gfp_t gfp_mask,
488                int order, const nodemask_t *nodemask)
489{
490    if (likely(!sysctl_panic_on_oom))
491        return;
492    if (sysctl_panic_on_oom != 2) {
493        /*
494         * panic_on_oom == 1 only affects CONSTRAINT_NONE, the kernel
495         * does not panic for cpuset, mempolicy, or memcg allocation
496         * failures.
497         */
498        if (constraint != CONSTRAINT_NONE)
499            return;
500    }
501    read_lock(&tasklist_lock);
502    dump_header(NULL, gfp_mask, order, NULL, nodemask);
503    read_unlock(&tasklist_lock);
504    panic("Out of memory: %s panic_on_oom is enabled\n",
505        sysctl_panic_on_oom == 2 ? "compulsory" : "system-wide");
506}
507
508#ifdef CONFIG_CGROUP_MEM_RES_CTLR
509void mem_cgroup_out_of_memory(struct mem_cgroup *mem, gfp_t gfp_mask)
510{
511    unsigned long limit;
512    unsigned int points = 0;
513    struct task_struct *p;
514
515    check_panic_on_oom(CONSTRAINT_MEMCG, gfp_mask, 0, NULL);
516    limit = mem_cgroup_get_limit(mem) >> PAGE_SHIFT;
517    read_lock(&tasklist_lock);
518retry:
519    p = select_bad_process(&points, limit, mem, NULL);
520    if (!p || PTR_ERR(p) == -1UL)
521        goto out;
522
523    if (oom_kill_process(p, gfp_mask, 0, points, limit, mem, NULL,
524                "Memory cgroup out of memory"))
525        goto retry;
526out:
527    read_unlock(&tasklist_lock);
528}
529#endif
530
531static BLOCKING_NOTIFIER_HEAD(oom_notify_list);
532
533int register_oom_notifier(struct notifier_block *nb)
534{
535    return blocking_notifier_chain_register(&oom_notify_list, nb);
536}
537EXPORT_SYMBOL_GPL(register_oom_notifier);
538
539int unregister_oom_notifier(struct notifier_block *nb)
540{
541    return blocking_notifier_chain_unregister(&oom_notify_list, nb);
542}
543EXPORT_SYMBOL_GPL(unregister_oom_notifier);
544
545/*
546 * Try to acquire the OOM killer lock for the zones in zonelist. Returns zero
547 * if a parallel OOM killing is already taking place that includes a zone in
548 * the zonelist. Otherwise, locks all zones in the zonelist and returns 1.
549 */
550int try_set_zonelist_oom(struct zonelist *zonelist, gfp_t gfp_mask)
551{
552    struct zoneref *z;
553    struct zone *zone;
554    int ret = 1;
555
556    spin_lock(&zone_scan_lock);
557    for_each_zone_zonelist(zone, z, zonelist, gfp_zone(gfp_mask)) {
558        if (zone_is_oom_locked(zone)) {
559            ret = 0;
560            goto out;
561        }
562    }
563
564    for_each_zone_zonelist(zone, z, zonelist, gfp_zone(gfp_mask)) {
565        /*
566         * Lock each zone in the zonelist under zone_scan_lock so a
567         * parallel invocation of try_set_zonelist_oom() doesn't succeed
568         * when it shouldn't.
569         */
570        zone_set_flag(zone, ZONE_OOM_LOCKED);
571    }
572
573out:
574    spin_unlock(&zone_scan_lock);
575    return ret;
576}
577
578/*
579 * Clears the ZONE_OOM_LOCKED flag for all zones in the zonelist so that failed
580 * allocation attempts with zonelists containing them may now recall the OOM
581 * killer, if necessary.
582 */
583void clear_zonelist_oom(struct zonelist *zonelist, gfp_t gfp_mask)
584{
585    struct zoneref *z;
586    struct zone *zone;
587
588    spin_lock(&zone_scan_lock);
589    for_each_zone_zonelist(zone, z, zonelist, gfp_zone(gfp_mask)) {
590        zone_clear_flag(zone, ZONE_OOM_LOCKED);
591    }
592    spin_unlock(&zone_scan_lock);
593}
594
595/*
596 * Try to acquire the oom killer lock for all system zones. Returns zero if a
597 * parallel oom killing is taking place, otherwise locks all zones and returns
598 * non-zero.
599 */
600static int try_set_system_oom(void)
601{
602    struct zone *zone;
603    int ret = 1;
604
605    spin_lock(&zone_scan_lock);
606    for_each_populated_zone(zone)
607        if (zone_is_oom_locked(zone)) {
608            ret = 0;
609            goto out;
610        }
611    for_each_populated_zone(zone)
612        zone_set_flag(zone, ZONE_OOM_LOCKED);
613out:
614    spin_unlock(&zone_scan_lock);
615    return ret;
616}
617
618/*
619 * Clears ZONE_OOM_LOCKED for all system zones so that failed allocation
620 * attempts or page faults may now recall the oom killer, if necessary.
621 */
622static void clear_system_oom(void)
623{
624    struct zone *zone;
625
626    spin_lock(&zone_scan_lock);
627    for_each_populated_zone(zone)
628        zone_clear_flag(zone, ZONE_OOM_LOCKED);
629    spin_unlock(&zone_scan_lock);
630}
631
632/**
633 * out_of_memory - kill the "best" process when we run out of memory
634 * @zonelist: zonelist pointer
635 * @gfp_mask: memory allocation flags
636 * @order: amount of memory being requested as a power of 2
637 * @nodemask: nodemask passed to page allocator
638 *
639 * If we run out of memory, we have the choice between either
640 * killing a random task (bad), letting the system crash (worse)
641 * OR try to be smart about which process to kill. Note that we
642 * don't have to be perfect here, we just have to be good.
643 */
644void out_of_memory(struct zonelist *zonelist, gfp_t gfp_mask,
645        int order, nodemask_t *nodemask)
646{
647    const nodemask_t *mpol_mask;
648    struct task_struct *p;
649    unsigned long totalpages;
650    unsigned long freed = 0;
651    unsigned int points;
652    enum oom_constraint constraint = CONSTRAINT_NONE;
653    int killed = 0;
654
655    blocking_notifier_call_chain(&oom_notify_list, 0, &freed);
656    if (freed > 0)
657        /* Got some memory back in the last second. */
658        return;
659
660    /*
661     * If current has a pending SIGKILL, then automatically select it. The
662     * goal is to allow it to allocate so that it may quickly exit and free
663     * its memory.
664     */
665    if (fatal_signal_pending(current)) {
666        set_thread_flag(TIF_MEMDIE);
667        boost_dying_task_prio(current, NULL);
668        return;
669    }
670
671    /*
672     * Check if there were limitations on the allocation (only relevant for
673     * NUMA) that may require different handling.
674     */
675    constraint = constrained_alloc(zonelist, gfp_mask, nodemask,
676                        &totalpages);
677    mpol_mask = (constraint == CONSTRAINT_MEMORY_POLICY) ? nodemask : NULL;
678    check_panic_on_oom(constraint, gfp_mask, order, mpol_mask);
679
680    read_lock(&tasklist_lock);
681    if (sysctl_oom_kill_allocating_task &&
682        !oom_unkillable_task(current, NULL, nodemask) &&
683        (current->signal->oom_adj != OOM_DISABLE)) {
684        /*
685         * oom_kill_process() needs tasklist_lock held. If it returns
686         * non-zero, current could not be killed so we must fallback to
687         * the tasklist scan.
688         */
689        if (!oom_kill_process(current, gfp_mask, order, 0, totalpages,
690                NULL, nodemask,
691                "Out of memory (oom_kill_allocating_task)"))
692            goto out;
693    }
694
695retry:
696    p = select_bad_process(&points, totalpages, NULL, mpol_mask);
697    if (PTR_ERR(p) == -1UL)
698        goto out;
699
700    /* Found nothing?!?! Either we hang forever, or we panic. */
701    if (!p) {
702        dump_header(NULL, gfp_mask, order, NULL, mpol_mask);
703        read_unlock(&tasklist_lock);
704        panic("Out of memory and no killable processes...\n");
705    }
706
707    if (oom_kill_process(p, gfp_mask, order, points, totalpages, NULL,
708                nodemask, "Out of memory"))
709        goto retry;
710    killed = 1;
711out:
712    read_unlock(&tasklist_lock);
713
714    /*
715     * Give "p" a good chance of killing itself before we
716     * retry to allocate memory unless "p" is current
717     */
718    if (killed && !test_thread_flag(TIF_MEMDIE))
719        schedule_timeout_uninterruptible(1);
720}
721
722/*
723 * The pagefault handler calls here because it is out of memory, so kill a
724 * memory-hogging task. If a populated zone has ZONE_OOM_LOCKED set, a parallel
725 * oom killing is already in progress so do nothing. If a task is found with
726 * TIF_MEMDIE set, it has been killed so do nothing and allow it to exit.
727 */
728void pagefault_out_of_memory(void)
729{
730    if (try_set_system_oom()) {
731        out_of_memory(NULL, 0, 0, NULL);
732        clear_system_oom();
733    }
734    if (!test_thread_flag(TIF_MEMDIE))
735        schedule_timeout_uninterruptible(1);
736}
737

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