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/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#ifdef CONFIG_NUMA
48/**
49 * has_intersects_mems_allowed() - check task eligiblity for kill
50 * @tsk: task struct of which task to consider
51 * @mask: nodemask passed to page allocator for mempolicy ooms
52 *
53 * Task eligibility is determined by whether or not a candidate task, @tsk,
54 * shares the same mempolicy nodes as current if it is bound by such a policy
55 * and whether or not it has the same set of allowed cpuset nodes.
56 */
57static bool has_intersects_mems_allowed(struct task_struct *tsk,
58                    const nodemask_t *mask)
59{
60    struct task_struct *start = tsk;
61
62    do {
63        if (mask) {
64            /*
65             * If this is a mempolicy constrained oom, tsk's
66             * cpuset is irrelevant. Only return true if its
67             * mempolicy intersects current, otherwise it may be
68             * needlessly killed.
69             */
70            if (mempolicy_nodemask_intersects(tsk, mask))
71                return true;
72        } else {
73            /*
74             * This is not a mempolicy constrained oom, so only
75             * check the mems of tsk's cpuset.
76             */
77            if (cpuset_mems_allowed_intersects(current, tsk))
78                return true;
79        }
80    } while_each_thread(start, tsk);
81
82    return false;
83}
84#else
85static bool has_intersects_mems_allowed(struct task_struct *tsk,
86                    const nodemask_t *mask)
87{
88    return true;
89}
90#endif /* CONFIG_NUMA */
91
92/*
93 * The process p may have detached its own ->mm while exiting or through
94 * use_mm(), but one or more of its subthreads may still have a valid
95 * pointer. Return p, or any of its subthreads with a valid ->mm, with
96 * task_lock() held.
97 */
98struct task_struct *find_lock_task_mm(struct task_struct *p)
99{
100    struct task_struct *t = p;
101
102    do {
103        task_lock(t);
104        if (likely(t->mm))
105            return t;
106        task_unlock(t);
107    } while_each_thread(p, t);
108
109    return NULL;
110}
111
112/* return true if the task is not adequate as candidate victim task. */
113static bool oom_unkillable_task(struct task_struct *p,
114        const struct mem_cgroup *memcg, const nodemask_t *nodemask)
115{
116    if (is_global_init(p))
117        return true;
118    if (p->flags & PF_KTHREAD)
119        return true;
120
121    /* When mem_cgroup_out_of_memory() and p is not member of the group */
122    if (memcg && !task_in_mem_cgroup(p, memcg))
123        return true;
124
125    /* p may not have freeable memory in nodemask */
126    if (!has_intersects_mems_allowed(p, nodemask))
127        return true;
128
129    return false;
130}
131
132/**
133 * oom_badness - heuristic function to determine which candidate task to kill
134 * @p: task struct of which task we should calculate
135 * @totalpages: total present RAM allowed for page allocation
136 *
137 * The heuristic for determining which task to kill is made to be as simple and
138 * predictable as possible. The goal is to return the highest value for the
139 * task consuming the most memory to avoid subsequent oom failures.
140 */
141unsigned long oom_badness(struct task_struct *p, struct mem_cgroup *memcg,
142              const nodemask_t *nodemask, unsigned long totalpages)
143{
144    long points;
145    long adj;
146
147    if (oom_unkillable_task(p, memcg, nodemask))
148        return 0;
149
150    p = find_lock_task_mm(p);
151    if (!p)
152        return 0;
153
154    adj = (long)p->signal->oom_score_adj;
155    if (adj == OOM_SCORE_ADJ_MIN) {
156        task_unlock(p);
157        return 0;
158    }
159
160    /*
161     * The baseline for the badness score is the proportion of RAM that each
162     * task's rss, pagetable and swap space use.
163     */
164    points = get_mm_rss(p->mm) + p->mm->nr_ptes +
165         get_mm_counter(p->mm, MM_SWAPENTS);
166    task_unlock(p);
167
168    /*
169     * Root processes get 3% bonus, just like the __vm_enough_memory()
170     * implementation used by LSMs.
171     */
172    if (has_capability_noaudit(p, CAP_SYS_ADMIN))
173        adj -= 30;
174
175    /* Normalize to oom_score_adj units */
176    adj *= totalpages / 1000;
177    points += adj;
178
179    /*
180     * Never return 0 for an eligible task regardless of the root bonus and
181     * oom_score_adj (oom_score_adj can't be OOM_SCORE_ADJ_MIN here).
182     */
183    return points > 0 ? points : 1;
184}
185
186/*
187 * Determine the type of allocation constraint.
188 */
189#ifdef CONFIG_NUMA
190static enum oom_constraint constrained_alloc(struct zonelist *zonelist,
191                gfp_t gfp_mask, nodemask_t *nodemask,
192                unsigned long *totalpages)
193{
194    struct zone *zone;
195    struct zoneref *z;
196    enum zone_type high_zoneidx = gfp_zone(gfp_mask);
197    bool cpuset_limited = false;
198    int nid;
199
200    /* Default to all available memory */
201    *totalpages = totalram_pages + total_swap_pages;
202
203    if (!zonelist)
204        return CONSTRAINT_NONE;
205    /*
206     * Reach here only when __GFP_NOFAIL is used. So, we should avoid
207     * to kill current.We have to random task kill in this case.
208     * Hopefully, CONSTRAINT_THISNODE...but no way to handle it, now.
209     */
210    if (gfp_mask & __GFP_THISNODE)
211        return CONSTRAINT_NONE;
212
213    /*
214     * This is not a __GFP_THISNODE allocation, so a truncated nodemask in
215     * the page allocator means a mempolicy is in effect. Cpuset policy
216     * is enforced in get_page_from_freelist().
217     */
218    if (nodemask && !nodes_subset(node_states[N_MEMORY], *nodemask)) {
219        *totalpages = total_swap_pages;
220        for_each_node_mask(nid, *nodemask)
221            *totalpages += node_spanned_pages(nid);
222        return CONSTRAINT_MEMORY_POLICY;
223    }
224
225    /* Check this allocation failure is caused by cpuset's wall function */
226    for_each_zone_zonelist_nodemask(zone, z, zonelist,
227            high_zoneidx, nodemask)
228        if (!cpuset_zone_allowed_softwall(zone, gfp_mask))
229            cpuset_limited = true;
230
231    if (cpuset_limited) {
232        *totalpages = total_swap_pages;
233        for_each_node_mask(nid, cpuset_current_mems_allowed)
234            *totalpages += node_spanned_pages(nid);
235        return CONSTRAINT_CPUSET;
236    }
237    return CONSTRAINT_NONE;
238}
239#else
240static enum oom_constraint constrained_alloc(struct zonelist *zonelist,
241                gfp_t gfp_mask, nodemask_t *nodemask,
242                unsigned long *totalpages)
243{
244    *totalpages = totalram_pages + total_swap_pages;
245    return CONSTRAINT_NONE;
246}
247#endif
248
249enum oom_scan_t oom_scan_process_thread(struct task_struct *task,
250        unsigned long totalpages, const nodemask_t *nodemask,
251        bool force_kill)
252{
253    if (task->exit_state)
254        return OOM_SCAN_CONTINUE;
255    if (oom_unkillable_task(task, NULL, nodemask))
256        return OOM_SCAN_CONTINUE;
257
258    /*
259     * This task already has access to memory reserves and is being killed.
260     * Don't allow any other task to have access to the reserves.
261     */
262    if (test_tsk_thread_flag(task, TIF_MEMDIE)) {
263        if (unlikely(frozen(task)))
264            __thaw_task(task);
265        if (!force_kill)
266            return OOM_SCAN_ABORT;
267    }
268    if (!task->mm)
269        return OOM_SCAN_CONTINUE;
270
271    /*
272     * If task is allocating a lot of memory and has been marked to be
273     * killed first if it triggers an oom, then select it.
274     */
275    if (oom_task_origin(task))
276        return OOM_SCAN_SELECT;
277
278    if (task->flags & PF_EXITING && !force_kill) {
279        /*
280         * If this task is not being ptraced on exit, then wait for it
281         * to finish before killing some other task unnecessarily.
282         */
283        if (!(task->group_leader->ptrace & PT_TRACE_EXIT))
284            return OOM_SCAN_ABORT;
285    }
286    return OOM_SCAN_OK;
287}
288
289/*
290 * Simple selection loop. We chose the process with the highest
291 * number of 'points'.
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, const nodemask_t *nodemask,
297        bool force_kill)
298{
299    struct task_struct *g, *p;
300    struct task_struct *chosen = NULL;
301    unsigned long chosen_points = 0;
302
303    rcu_read_lock();
304    do_each_thread(g, p) {
305        unsigned int points;
306
307        switch (oom_scan_process_thread(p, totalpages, nodemask,
308                        force_kill)) {
309        case OOM_SCAN_SELECT:
310            chosen = p;
311            chosen_points = ULONG_MAX;
312            /* fall through */
313        case OOM_SCAN_CONTINUE:
314            continue;
315        case OOM_SCAN_ABORT:
316            rcu_read_unlock();
317            return ERR_PTR(-1UL);
318        case OOM_SCAN_OK:
319            break;
320        };
321        points = oom_badness(p, NULL, nodemask, totalpages);
322        if (points > chosen_points) {
323            chosen = p;
324            chosen_points = points;
325        }
326    } while_each_thread(g, p);
327    if (chosen)
328        get_task_struct(chosen);
329    rcu_read_unlock();
330
331    *ppoints = chosen_points * 1000 / totalpages;
332    return chosen;
333}
334
335/**
336 * dump_tasks - dump current memory state of all system tasks
337 * @memcg: current's memory controller, if constrained
338 * @nodemask: nodemask passed to page allocator for mempolicy ooms
339 *
340 * Dumps the current memory state of all eligible tasks. Tasks not in the same
341 * memcg, not in the same cpuset, or bound to a disjoint set of mempolicy nodes
342 * are not shown.
343 * State information includes task's pid, uid, tgid, vm size, rss, nr_ptes,
344 * swapents, oom_score_adj value, and name.
345 */
346static void dump_tasks(const struct mem_cgroup *memcg, const nodemask_t *nodemask)
347{
348    struct task_struct *p;
349    struct task_struct *task;
350
351    pr_info("[ pid ] uid tgid total_vm rss nr_ptes swapents oom_score_adj name\n");
352    rcu_read_lock();
353    for_each_process(p) {
354        if (oom_unkillable_task(p, memcg, nodemask))
355            continue;
356
357        task = find_lock_task_mm(p);
358        if (!task) {
359            /*
360             * This is a kthread or all of p's threads have already
361             * detached their mm's. There's no need to report
362             * them; they can't be oom killed anyway.
363             */
364            continue;
365        }
366
367        pr_info("[%5d] %5d %5d %8lu %8lu %7lu %8lu %5hd %s\n",
368            task->pid, from_kuid(&init_user_ns, task_uid(task)),
369            task->tgid, task->mm->total_vm, get_mm_rss(task->mm),
370            task->mm->nr_ptes,
371            get_mm_counter(task->mm, MM_SWAPENTS),
372            task->signal->oom_score_adj, task->comm);
373        task_unlock(task);
374    }
375    rcu_read_unlock();
376}
377
378static void dump_header(struct task_struct *p, gfp_t gfp_mask, int order,
379            struct mem_cgroup *memcg, const nodemask_t *nodemask)
380{
381    task_lock(current);
382    pr_warning("%s invoked oom-killer: gfp_mask=0x%x, order=%d, "
383        "oom_score_adj=%hd\n",
384        current->comm, gfp_mask, order,
385        current->signal->oom_score_adj);
386    cpuset_print_task_mems_allowed(current);
387    task_unlock(current);
388    dump_stack();
389    if (memcg)
390        mem_cgroup_print_oom_info(memcg, p);
391    else
392        show_mem(SHOW_MEM_FILTER_NODES);
393    if (sysctl_oom_dump_tasks)
394        dump_tasks(memcg, nodemask);
395}
396
397#define K(x) ((x) << (PAGE_SHIFT-10))
398/*
399 * Must be called while holding a reference to p, which will be released upon
400 * returning.
401 */
402void oom_kill_process(struct task_struct *p, gfp_t gfp_mask, int order,
403              unsigned int points, unsigned long totalpages,
404              struct mem_cgroup *memcg, nodemask_t *nodemask,
405              const char *message)
406{
407    struct task_struct *victim = p;
408    struct task_struct *child;
409    struct task_struct *t = p;
410    struct mm_struct *mm;
411    unsigned int victim_points = 0;
412    static DEFINE_RATELIMIT_STATE(oom_rs, DEFAULT_RATELIMIT_INTERVAL,
413                          DEFAULT_RATELIMIT_BURST);
414
415    /*
416     * If the task is already exiting, don't alarm the sysadmin or kill
417     * its children or threads, just set TIF_MEMDIE so it can die quickly
418     */
419    if (p->flags & PF_EXITING) {
420        set_tsk_thread_flag(p, TIF_MEMDIE);
421        put_task_struct(p);
422        return;
423    }
424
425    if (__ratelimit(&oom_rs))
426        dump_header(p, gfp_mask, order, memcg, nodemask);
427
428    task_lock(p);
429    pr_err("%s: Kill process %d (%s) score %d or sacrifice child\n",
430        message, task_pid_nr(p), p->comm, points);
431    task_unlock(p);
432
433    /*
434     * If any of p's children has a different mm and is eligible for kill,
435     * the one with the highest oom_badness() score is sacrificed for its
436     * parent. This attempts to lose the minimal amount of work done while
437     * still freeing memory.
438     */
439    read_lock(&tasklist_lock);
440    do {
441        list_for_each_entry(child, &t->children, sibling) {
442            unsigned int child_points;
443
444            if (child->mm == p->mm)
445                continue;
446            /*
447             * oom_badness() returns 0 if the thread is unkillable
448             */
449            child_points = oom_badness(child, memcg, nodemask,
450                                totalpages);
451            if (child_points > victim_points) {
452                put_task_struct(victim);
453                victim = child;
454                victim_points = child_points;
455                get_task_struct(victim);
456            }
457        }
458    } while_each_thread(p, t);
459    read_unlock(&tasklist_lock);
460
461    rcu_read_lock();
462    p = find_lock_task_mm(victim);
463    if (!p) {
464        rcu_read_unlock();
465        put_task_struct(victim);
466        return;
467    } else if (victim != p) {
468        get_task_struct(p);
469        put_task_struct(victim);
470        victim = p;
471    }
472
473    /* mm cannot safely be dereferenced after task_unlock(victim) */
474    mm = victim->mm;
475    pr_err("Killed process %d (%s) total-vm:%lukB, anon-rss:%lukB, file-rss:%lukB\n",
476        task_pid_nr(victim), victim->comm, K(victim->mm->total_vm),
477        K(get_mm_counter(victim->mm, MM_ANONPAGES)),
478        K(get_mm_counter(victim->mm, MM_FILEPAGES)));
479    task_unlock(victim);
480
481    /*
482     * Kill all user processes sharing victim->mm in other thread groups, if
483     * any. They don't get access to memory reserves, though, to avoid
484     * depletion of all memory. This prevents mm->mmap_sem livelock when an
485     * oom killed thread cannot exit because it requires the semaphore and
486     * its contended by another thread trying to allocate memory itself.
487     * That thread will now get access to memory reserves since it has a
488     * pending fatal signal.
489     */
490    for_each_process(p)
491        if (p->mm == mm && !same_thread_group(p, victim) &&
492            !(p->flags & PF_KTHREAD)) {
493            if (p->signal->oom_score_adj == OOM_SCORE_ADJ_MIN)
494                continue;
495
496            task_lock(p); /* Protect ->comm from prctl() */
497            pr_err("Kill process %d (%s) sharing same memory\n",
498                task_pid_nr(p), p->comm);
499            task_unlock(p);
500            do_send_sig_info(SIGKILL, SEND_SIG_FORCED, p, true);
501        }
502    rcu_read_unlock();
503
504    set_tsk_thread_flag(victim, TIF_MEMDIE);
505    do_send_sig_info(SIGKILL, SEND_SIG_FORCED, victim, true);
506    put_task_struct(victim);
507}
508#undef K
509
510/*
511 * Determines whether the kernel must panic because of the panic_on_oom sysctl.
512 */
513void check_panic_on_oom(enum oom_constraint constraint, gfp_t gfp_mask,
514            int order, const nodemask_t *nodemask)
515{
516    if (likely(!sysctl_panic_on_oom))
517        return;
518    if (sysctl_panic_on_oom != 2) {
519        /*
520         * panic_on_oom == 1 only affects CONSTRAINT_NONE, the kernel
521         * does not panic for cpuset, mempolicy, or memcg allocation
522         * failures.
523         */
524        if (constraint != CONSTRAINT_NONE)
525            return;
526    }
527    dump_header(NULL, gfp_mask, order, NULL, nodemask);
528    panic("Out of memory: %s panic_on_oom is enabled\n",
529        sysctl_panic_on_oom == 2 ? "compulsory" : "system-wide");
530}
531
532static BLOCKING_NOTIFIER_HEAD(oom_notify_list);
533
534int register_oom_notifier(struct notifier_block *nb)
535{
536    return blocking_notifier_chain_register(&oom_notify_list, nb);
537}
538EXPORT_SYMBOL_GPL(register_oom_notifier);
539
540int unregister_oom_notifier(struct notifier_block *nb)
541{
542    return blocking_notifier_chain_unregister(&oom_notify_list, nb);
543}
544EXPORT_SYMBOL_GPL(unregister_oom_notifier);
545
546/*
547 * Try to acquire the OOM killer lock for the zones in zonelist. Returns zero
548 * if a parallel OOM killing is already taking place that includes a zone in
549 * the zonelist. Otherwise, locks all zones in the zonelist and returns 1.
550 */
551int try_set_zonelist_oom(struct zonelist *zonelist, gfp_t gfp_mask)
552{
553    struct zoneref *z;
554    struct zone *zone;
555    int ret = 1;
556
557    spin_lock(&zone_scan_lock);
558    for_each_zone_zonelist(zone, z, zonelist, gfp_zone(gfp_mask)) {
559        if (zone_is_oom_locked(zone)) {
560            ret = 0;
561            goto out;
562        }
563    }
564
565    for_each_zone_zonelist(zone, z, zonelist, gfp_zone(gfp_mask)) {
566        /*
567         * Lock each zone in the zonelist under zone_scan_lock so a
568         * parallel invocation of try_set_zonelist_oom() doesn't succeed
569         * when it shouldn't.
570         */
571        zone_set_flag(zone, ZONE_OOM_LOCKED);
572    }
573
574out:
575    spin_unlock(&zone_scan_lock);
576    return ret;
577}
578
579/*
580 * Clears the ZONE_OOM_LOCKED flag for all zones in the zonelist so that failed
581 * allocation attempts with zonelists containing them may now recall the OOM
582 * killer, if necessary.
583 */
584void clear_zonelist_oom(struct zonelist *zonelist, gfp_t gfp_mask)
585{
586    struct zoneref *z;
587    struct zone *zone;
588
589    spin_lock(&zone_scan_lock);
590    for_each_zone_zonelist(zone, z, zonelist, gfp_zone(gfp_mask)) {
591        zone_clear_flag(zone, ZONE_OOM_LOCKED);
592    }
593    spin_unlock(&zone_scan_lock);
594}
595
596/**
597 * out_of_memory - kill the "best" process when we run out of memory
598 * @zonelist: zonelist pointer
599 * @gfp_mask: memory allocation flags
600 * @order: amount of memory being requested as a power of 2
601 * @nodemask: nodemask passed to page allocator
602 * @force_kill: true if a task must be killed, even if others are exiting
603 *
604 * If we run out of memory, we have the choice between either
605 * killing a random task (bad), letting the system crash (worse)
606 * OR try to be smart about which process to kill. Note that we
607 * don't have to be perfect here, we just have to be good.
608 */
609void out_of_memory(struct zonelist *zonelist, gfp_t gfp_mask,
610        int order, nodemask_t *nodemask, bool force_kill)
611{
612    const nodemask_t *mpol_mask;
613    struct task_struct *p;
614    unsigned long totalpages;
615    unsigned long freed = 0;
616    unsigned int uninitialized_var(points);
617    enum oom_constraint constraint = CONSTRAINT_NONE;
618    int killed = 0;
619
620    blocking_notifier_call_chain(&oom_notify_list, 0, &freed);
621    if (freed > 0)
622        /* Got some memory back in the last second. */
623        return;
624
625    /*
626     * If current has a pending SIGKILL or is exiting, then automatically
627     * select it. The goal is to allow it to allocate so that it may
628     * quickly exit and free its memory.
629     */
630    if (fatal_signal_pending(current) || current->flags & PF_EXITING) {
631        set_thread_flag(TIF_MEMDIE);
632        return;
633    }
634
635    /*
636     * Check if there were limitations on the allocation (only relevant for
637     * NUMA) that may require different handling.
638     */
639    constraint = constrained_alloc(zonelist, gfp_mask, nodemask,
640                        &totalpages);
641    mpol_mask = (constraint == CONSTRAINT_MEMORY_POLICY) ? nodemask : NULL;
642    check_panic_on_oom(constraint, gfp_mask, order, mpol_mask);
643
644    if (sysctl_oom_kill_allocating_task && current->mm &&
645        !oom_unkillable_task(current, NULL, nodemask) &&
646        current->signal->oom_score_adj != OOM_SCORE_ADJ_MIN) {
647        get_task_struct(current);
648        oom_kill_process(current, gfp_mask, order, 0, totalpages, NULL,
649                 nodemask,
650                 "Out of memory (oom_kill_allocating_task)");
651        goto out;
652    }
653
654    p = select_bad_process(&points, totalpages, mpol_mask, force_kill);
655    /* Found nothing?!?! Either we hang forever, or we panic. */
656    if (!p) {
657        dump_header(NULL, gfp_mask, order, NULL, mpol_mask);
658        panic("Out of memory and no killable processes...\n");
659    }
660    if (PTR_ERR(p) != -1UL) {
661        oom_kill_process(p, gfp_mask, order, points, totalpages, NULL,
662                 nodemask, "Out of memory");
663        killed = 1;
664    }
665out:
666    /*
667     * Give the killed threads a good chance of exiting before trying to
668     * allocate memory again.
669     */
670    if (killed)
671        schedule_timeout_killable(1);
672}
673
674/*
675 * The pagefault handler calls here because it is out of memory, so kill a
676 * memory-hogging task. If any populated zone has ZONE_OOM_LOCKED set, a
677 * parallel oom killing is already in progress so do nothing.
678 */
679void pagefault_out_of_memory(void)
680{
681    struct zonelist *zonelist = node_zonelist(first_online_node,
682                          GFP_KERNEL);
683
684    if (try_set_zonelist_oom(zonelist, GFP_KERNEL)) {
685        out_of_memory(NULL, 0, 0, NULL, false);
686        clear_zonelist_oom(zonelist, GFP_KERNEL);
687    }
688}
689

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