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
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.
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.
20 #include <linux/oom.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>
39 #define CREATE_TRACE_POINTS
40 #include <trace/events/oom.h>
42 int sysctl_panic_on_oom
;
43 int sysctl_oom_kill_allocating_task
;
44 int sysctl_oom_dump_tasks
= 1;
45 static DEFINE_SPINLOCK(zone_scan_lock
);
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
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.
56 void compare_swap_oom_score_adj(int old_val
, int new_val
)
58 struct sighand_struct
*sighand
= current
->sighand
;
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
);
68 * test_set_oom_score_adj() - set current's oom_score_adj and return old value
69 * @new_val: new oom_score_adj value
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.
75 int test_set_oom_score_adj(int new_val
)
77 struct sighand_struct
*sighand
= current
->sighand
;
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
);
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
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.
99 static bool has_intersects_mems_allowed(struct task_struct
*tsk
,
100 const nodemask_t
*mask
)
102 struct task_struct
*start
= tsk
;
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
112 if (mempolicy_nodemask_intersects(tsk
, mask
))
116 * This is not a mempolicy constrained oom, so only
117 * check the mems of tsk's cpuset.
119 if (cpuset_mems_allowed_intersects(current
, tsk
))
122 } while_each_thread(start
, tsk
);
127 static bool has_intersects_mems_allowed(struct task_struct
*tsk
,
128 const nodemask_t
*mask
)
132 #endif /* CONFIG_NUMA */
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
140 struct task_struct
*find_lock_task_mm(struct task_struct
*p
)
142 struct task_struct
*t
= p
;
149 } while_each_thread(p
, t
);
154 /* return true if the task is not adequate as candidate victim task. */
155 static bool oom_unkillable_task(struct task_struct
*p
,
156 const struct mem_cgroup
*memcg
, const nodemask_t
*nodemask
)
158 if (is_global_init(p
))
160 if (p
->flags
& PF_KTHREAD
)
163 /* When mem_cgroup_out_of_memory() and p is not member of the group */
164 if (memcg
&& !task_in_mem_cgroup(p
, memcg
))
167 /* p may not have freeable memory in nodemask */
168 if (!has_intersects_mems_allowed(p
, nodemask
))
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
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.
183 unsigned long oom_badness(struct task_struct
*p
, struct mem_cgroup
*memcg
,
184 const nodemask_t
*nodemask
, unsigned long totalpages
)
189 if (oom_unkillable_task(p
, memcg
, nodemask
))
192 p
= find_lock_task_mm(p
);
196 adj
= p
->signal
->oom_score_adj
;
197 if (adj
== OOM_SCORE_ADJ_MIN
) {
203 * The baseline for the badness score is the proportion of RAM that each
204 * task's rss, pagetable and swap space use.
206 points
= get_mm_rss(p
->mm
) + p
->mm
->nr_ptes
+
207 get_mm_counter(p
->mm
, MM_SWAPENTS
);
211 * Root processes get 3% bonus, just like the __vm_enough_memory()
212 * implementation used by LSMs.
214 if (has_capability_noaudit(p
, CAP_SYS_ADMIN
))
217 /* Normalize to oom_score_adj units */
218 adj
*= totalpages
/ 1000;
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).
225 return points
> 0 ? points
: 1;
229 * Determine the type of allocation constraint.
232 static enum oom_constraint
constrained_alloc(struct zonelist
*zonelist
,
233 gfp_t gfp_mask
, nodemask_t
*nodemask
,
234 unsigned long *totalpages
)
238 enum zone_type high_zoneidx
= gfp_zone(gfp_mask
);
239 bool cpuset_limited
= false;
242 /* Default to all available memory */
243 *totalpages
= totalram_pages
+ total_swap_pages
;
246 return CONSTRAINT_NONE
;
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.
252 if (gfp_mask
& __GFP_THISNODE
)
253 return CONSTRAINT_NONE
;
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().
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
;
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;
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
;
279 return CONSTRAINT_NONE
;
282 static enum oom_constraint
constrained_alloc(struct zonelist
*zonelist
,
283 gfp_t gfp_mask
, nodemask_t
*nodemask
,
284 unsigned long *totalpages
)
286 *totalpages
= totalram_pages
+ total_swap_pages
;
287 return CONSTRAINT_NONE
;
291 enum oom_scan_t
oom_scan_process_thread(struct task_struct
*task
,
292 unsigned long totalpages
, const nodemask_t
*nodemask
,
295 if (task
->exit_state
)
296 return OOM_SCAN_CONTINUE
;
297 if (oom_unkillable_task(task
, NULL
, nodemask
))
298 return OOM_SCAN_CONTINUE
;
301 * This task already has access to memory reserves and is being killed.
302 * Don't allow any other task to have access to the reserves.
304 if (test_tsk_thread_flag(task
, TIF_MEMDIE
)) {
305 if (unlikely(frozen(task
)))
308 return OOM_SCAN_ABORT
;
311 return OOM_SCAN_CONTINUE
;
313 if (task
->flags
& PF_EXITING
) {
315 * If task is current and is in the process of releasing memory,
316 * allow the "kill" to set TIF_MEMDIE, which will allow it to
317 * access memory reserves. Otherwise, it may stall forever.
319 * The iteration isn't broken here, however, in case other
320 * threads are found to have already been oom killed.
323 return OOM_SCAN_SELECT
;
324 else if (!force_kill
) {
326 * If this task is not being ptraced on exit, then wait
327 * for it to finish before killing some other task
330 if (!(task
->group_leader
->ptrace
& PT_TRACE_EXIT
))
331 return OOM_SCAN_ABORT
;
338 * Simple selection loop. We chose the process with the highest
339 * number of 'points'. We expect the caller will lock the tasklist.
341 * (not docbooked, we don't want this one cluttering up the manual)
343 static struct task_struct
*select_bad_process(unsigned int *ppoints
,
344 unsigned long totalpages
, const nodemask_t
*nodemask
,
347 struct task_struct
*g
, *p
;
348 struct task_struct
*chosen
= NULL
;
349 unsigned long chosen_points
= 0;
351 do_each_thread(g
, p
) {
354 switch (oom_scan_process_thread(p
, totalpages
, nodemask
,
356 case OOM_SCAN_SELECT
:
358 chosen_points
= ULONG_MAX
;
360 case OOM_SCAN_CONTINUE
:
363 return ERR_PTR(-1UL);
367 points
= oom_badness(p
, NULL
, nodemask
, totalpages
);
368 if (points
> chosen_points
) {
370 chosen_points
= points
;
372 } while_each_thread(g
, p
);
374 *ppoints
= chosen_points
* 1000 / totalpages
;
379 * dump_tasks - dump current memory state of all system tasks
380 * @memcg: current's memory controller, if constrained
381 * @nodemask: nodemask passed to page allocator for mempolicy ooms
383 * Dumps the current memory state of all eligible tasks. Tasks not in the same
384 * memcg, not in the same cpuset, or bound to a disjoint set of mempolicy nodes
386 * State information includes task's pid, uid, tgid, vm size, rss, nr_ptes,
387 * swapents, oom_score_adj value, and name.
389 * Call with tasklist_lock read-locked.
391 static void dump_tasks(const struct mem_cgroup
*memcg
, const nodemask_t
*nodemask
)
393 struct task_struct
*p
;
394 struct task_struct
*task
;
396 pr_info("[ pid ] uid tgid total_vm rss nr_ptes swapents oom_score_adj name\n");
397 for_each_process(p
) {
398 if (oom_unkillable_task(p
, memcg
, nodemask
))
401 task
= find_lock_task_mm(p
);
404 * This is a kthread or all of p's threads have already
405 * detached their mm's. There's no need to report
406 * them; they can't be oom killed anyway.
411 pr_info("[%5d] %5d %5d %8lu %8lu %7lu %8lu %5d %s\n",
412 task
->pid
, from_kuid(&init_user_ns
, task_uid(task
)),
413 task
->tgid
, task
->mm
->total_vm
, get_mm_rss(task
->mm
),
415 get_mm_counter(task
->mm
, MM_SWAPENTS
),
416 task
->signal
->oom_score_adj
, task
->comm
);
421 static void dump_header(struct task_struct
*p
, gfp_t gfp_mask
, int order
,
422 struct mem_cgroup
*memcg
, const nodemask_t
*nodemask
)
425 pr_warning("%s invoked oom-killer: gfp_mask=0x%x, order=%d, "
426 "oom_adj=%d, oom_score_adj=%d\n",
427 current
->comm
, gfp_mask
, order
, current
->signal
->oom_adj
,
428 current
->signal
->oom_score_adj
);
429 cpuset_print_task_mems_allowed(current
);
430 task_unlock(current
);
432 mem_cgroup_print_oom_info(memcg
, p
);
433 show_mem(SHOW_MEM_FILTER_NODES
);
434 if (sysctl_oom_dump_tasks
)
435 dump_tasks(memcg
, nodemask
);
438 #define K(x) ((x) << (PAGE_SHIFT-10))
439 void oom_kill_process(struct task_struct
*p
, gfp_t gfp_mask
, int order
,
440 unsigned int points
, unsigned long totalpages
,
441 struct mem_cgroup
*memcg
, nodemask_t
*nodemask
,
444 struct task_struct
*victim
= p
;
445 struct task_struct
*child
;
446 struct task_struct
*t
= p
;
447 struct mm_struct
*mm
;
448 unsigned int victim_points
= 0;
449 static DEFINE_RATELIMIT_STATE(oom_rs
, DEFAULT_RATELIMIT_INTERVAL
,
450 DEFAULT_RATELIMIT_BURST
);
453 * If the task is already exiting, don't alarm the sysadmin or kill
454 * its children or threads, just set TIF_MEMDIE so it can die quickly
456 if (p
->flags
& PF_EXITING
) {
457 set_tsk_thread_flag(p
, TIF_MEMDIE
);
461 if (__ratelimit(&oom_rs
))
462 dump_header(p
, gfp_mask
, order
, memcg
, nodemask
);
465 pr_err("%s: Kill process %d (%s) score %d or sacrifice child\n",
466 message
, task_pid_nr(p
), p
->comm
, points
);
470 * If any of p's children has a different mm and is eligible for kill,
471 * the one with the highest oom_badness() score is sacrificed for its
472 * parent. This attempts to lose the minimal amount of work done while
473 * still freeing memory.
476 list_for_each_entry(child
, &t
->children
, sibling
) {
477 unsigned int child_points
;
479 if (child
->mm
== p
->mm
)
482 * oom_badness() returns 0 if the thread is unkillable
484 child_points
= oom_badness(child
, memcg
, nodemask
,
486 if (child_points
> victim_points
) {
488 victim_points
= child_points
;
491 } while_each_thread(p
, t
);
493 victim
= find_lock_task_mm(victim
);
497 /* mm cannot safely be dereferenced after task_unlock(victim) */
499 pr_err("Killed process %d (%s) total-vm:%lukB, anon-rss:%lukB, file-rss:%lukB\n",
500 task_pid_nr(victim
), victim
->comm
, K(victim
->mm
->total_vm
),
501 K(get_mm_counter(victim
->mm
, MM_ANONPAGES
)),
502 K(get_mm_counter(victim
->mm
, MM_FILEPAGES
)));
506 * Kill all user processes sharing victim->mm in other thread groups, if
507 * any. They don't get access to memory reserves, though, to avoid
508 * depletion of all memory. This prevents mm->mmap_sem livelock when an
509 * oom killed thread cannot exit because it requires the semaphore and
510 * its contended by another thread trying to allocate memory itself.
511 * That thread will now get access to memory reserves since it has a
512 * pending fatal signal.
515 if (p
->mm
== mm
&& !same_thread_group(p
, victim
) &&
516 !(p
->flags
& PF_KTHREAD
)) {
517 if (p
->signal
->oom_score_adj
== OOM_SCORE_ADJ_MIN
)
520 task_lock(p
); /* Protect ->comm from prctl() */
521 pr_err("Kill process %d (%s) sharing same memory\n",
522 task_pid_nr(p
), p
->comm
);
524 do_send_sig_info(SIGKILL
, SEND_SIG_FORCED
, p
, true);
527 set_tsk_thread_flag(victim
, TIF_MEMDIE
);
528 do_send_sig_info(SIGKILL
, SEND_SIG_FORCED
, victim
, true);
533 * Determines whether the kernel must panic because of the panic_on_oom sysctl.
535 static void check_panic_on_oom(enum oom_constraint constraint
, gfp_t gfp_mask
,
536 int order
, const nodemask_t
*nodemask
)
538 if (likely(!sysctl_panic_on_oom
))
540 if (sysctl_panic_on_oom
!= 2) {
542 * panic_on_oom == 1 only affects CONSTRAINT_NONE, the kernel
543 * does not panic for cpuset, mempolicy, or memcg allocation
546 if (constraint
!= CONSTRAINT_NONE
)
549 read_lock(&tasklist_lock
);
550 dump_header(NULL
, gfp_mask
, order
, NULL
, nodemask
);
551 read_unlock(&tasklist_lock
);
552 panic("Out of memory: %s panic_on_oom is enabled\n",
553 sysctl_panic_on_oom
== 2 ? "compulsory" : "system-wide");
557 void mem_cgroup_out_of_memory(struct mem_cgroup
*memcg
, gfp_t gfp_mask
,
561 * If current has a pending SIGKILL, then automatically select it. The
562 * goal is to allow it to allocate so that it may quickly exit and free
565 if (fatal_signal_pending(current
)) {
566 set_thread_flag(TIF_MEMDIE
);
570 check_panic_on_oom(CONSTRAINT_MEMCG
, gfp_mask
, order
, NULL
);
571 __mem_cgroup_out_of_memory(memcg
, gfp_mask
, order
);
575 static BLOCKING_NOTIFIER_HEAD(oom_notify_list
);
577 int register_oom_notifier(struct notifier_block
*nb
)
579 return blocking_notifier_chain_register(&oom_notify_list
, nb
);
581 EXPORT_SYMBOL_GPL(register_oom_notifier
);
583 int unregister_oom_notifier(struct notifier_block
*nb
)
585 return blocking_notifier_chain_unregister(&oom_notify_list
, nb
);
587 EXPORT_SYMBOL_GPL(unregister_oom_notifier
);
590 * Try to acquire the OOM killer lock for the zones in zonelist. Returns zero
591 * if a parallel OOM killing is already taking place that includes a zone in
592 * the zonelist. Otherwise, locks all zones in the zonelist and returns 1.
594 int try_set_zonelist_oom(struct zonelist
*zonelist
, gfp_t gfp_mask
)
600 spin_lock(&zone_scan_lock
);
601 for_each_zone_zonelist(zone
, z
, zonelist
, gfp_zone(gfp_mask
)) {
602 if (zone_is_oom_locked(zone
)) {
608 for_each_zone_zonelist(zone
, z
, zonelist
, gfp_zone(gfp_mask
)) {
610 * Lock each zone in the zonelist under zone_scan_lock so a
611 * parallel invocation of try_set_zonelist_oom() doesn't succeed
614 zone_set_flag(zone
, ZONE_OOM_LOCKED
);
618 spin_unlock(&zone_scan_lock
);
623 * Clears the ZONE_OOM_LOCKED flag for all zones in the zonelist so that failed
624 * allocation attempts with zonelists containing them may now recall the OOM
625 * killer, if necessary.
627 void clear_zonelist_oom(struct zonelist
*zonelist
, gfp_t gfp_mask
)
632 spin_lock(&zone_scan_lock
);
633 for_each_zone_zonelist(zone
, z
, zonelist
, gfp_zone(gfp_mask
)) {
634 zone_clear_flag(zone
, ZONE_OOM_LOCKED
);
636 spin_unlock(&zone_scan_lock
);
640 * Try to acquire the oom killer lock for all system zones. Returns zero if a
641 * parallel oom killing is taking place, otherwise locks all zones and returns
644 static int try_set_system_oom(void)
649 spin_lock(&zone_scan_lock
);
650 for_each_populated_zone(zone
)
651 if (zone_is_oom_locked(zone
)) {
655 for_each_populated_zone(zone
)
656 zone_set_flag(zone
, ZONE_OOM_LOCKED
);
658 spin_unlock(&zone_scan_lock
);
663 * Clears ZONE_OOM_LOCKED for all system zones so that failed allocation
664 * attempts or page faults may now recall the oom killer, if necessary.
666 static void clear_system_oom(void)
670 spin_lock(&zone_scan_lock
);
671 for_each_populated_zone(zone
)
672 zone_clear_flag(zone
, ZONE_OOM_LOCKED
);
673 spin_unlock(&zone_scan_lock
);
677 * out_of_memory - kill the "best" process when we run out of memory
678 * @zonelist: zonelist pointer
679 * @gfp_mask: memory allocation flags
680 * @order: amount of memory being requested as a power of 2
681 * @nodemask: nodemask passed to page allocator
682 * @force_kill: true if a task must be killed, even if others are exiting
684 * If we run out of memory, we have the choice between either
685 * killing a random task (bad), letting the system crash (worse)
686 * OR try to be smart about which process to kill. Note that we
687 * don't have to be perfect here, we just have to be good.
689 void out_of_memory(struct zonelist
*zonelist
, gfp_t gfp_mask
,
690 int order
, nodemask_t
*nodemask
, bool force_kill
)
692 const nodemask_t
*mpol_mask
;
693 struct task_struct
*p
;
694 unsigned long totalpages
;
695 unsigned long freed
= 0;
696 unsigned int uninitialized_var(points
);
697 enum oom_constraint constraint
= CONSTRAINT_NONE
;
700 blocking_notifier_call_chain(&oom_notify_list
, 0, &freed
);
702 /* Got some memory back in the last second. */
706 * If current has a pending SIGKILL, then automatically select it. The
707 * goal is to allow it to allocate so that it may quickly exit and free
710 if (fatal_signal_pending(current
)) {
711 set_thread_flag(TIF_MEMDIE
);
716 * Check if there were limitations on the allocation (only relevant for
717 * NUMA) that may require different handling.
719 constraint
= constrained_alloc(zonelist
, gfp_mask
, nodemask
,
721 mpol_mask
= (constraint
== CONSTRAINT_MEMORY_POLICY
) ? nodemask
: NULL
;
722 check_panic_on_oom(constraint
, gfp_mask
, order
, mpol_mask
);
724 read_lock(&tasklist_lock
);
725 if (sysctl_oom_kill_allocating_task
&& current
->mm
&&
726 !oom_unkillable_task(current
, NULL
, nodemask
) &&
727 current
->signal
->oom_score_adj
!= OOM_SCORE_ADJ_MIN
) {
728 oom_kill_process(current
, gfp_mask
, order
, 0, totalpages
, NULL
,
730 "Out of memory (oom_kill_allocating_task)");
734 p
= select_bad_process(&points
, totalpages
, mpol_mask
, force_kill
);
735 /* Found nothing?!?! Either we hang forever, or we panic. */
737 dump_header(NULL
, gfp_mask
, order
, NULL
, mpol_mask
);
738 read_unlock(&tasklist_lock
);
739 panic("Out of memory and no killable processes...\n");
741 if (PTR_ERR(p
) != -1UL) {
742 oom_kill_process(p
, gfp_mask
, order
, points
, totalpages
, NULL
,
743 nodemask
, "Out of memory");
747 read_unlock(&tasklist_lock
);
750 * Give the killed threads a good chance of exiting before trying to
751 * allocate memory again.
754 schedule_timeout_killable(1);
758 * The pagefault handler calls here because it is out of memory, so kill a
759 * memory-hogging task. If a populated zone has ZONE_OOM_LOCKED set, a parallel
760 * oom killing is already in progress so do nothing. If a task is found with
761 * TIF_MEMDIE set, it has been killed so do nothing and allow it to exit.
763 void pagefault_out_of_memory(void)
765 if (try_set_system_oom()) {
766 out_of_memory(NULL
, 0, 0, NULL
, false);
769 schedule_timeout_killable(1);