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
);
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
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.
57 static bool has_intersects_mems_allowed(struct task_struct
*tsk
,
58 const nodemask_t
*mask
)
60 struct task_struct
*start
= tsk
;
62 for_each_thread(start
, tsk
) {
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
70 if (mempolicy_nodemask_intersects(tsk
, mask
))
74 * This is not a mempolicy constrained oom, so only
75 * check the mems of tsk's cpuset.
77 if (cpuset_mems_allowed_intersects(current
, tsk
))
85 static bool has_intersects_mems_allowed(struct task_struct
*tsk
,
86 const nodemask_t
*mask
)
90 #endif /* CONFIG_NUMA */
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
98 struct task_struct
*find_lock_task_mm(struct task_struct
*p
)
100 struct task_struct
*t
;
102 for_each_thread(p
, t
) {
112 /* return true if the task is not adequate as candidate victim task. */
113 static bool oom_unkillable_task(struct task_struct
*p
,
114 const struct mem_cgroup
*memcg
, const nodemask_t
*nodemask
)
116 if (is_global_init(p
))
118 if (p
->flags
& PF_KTHREAD
)
121 /* When mem_cgroup_out_of_memory() and p is not member of the group */
122 if (memcg
&& !task_in_mem_cgroup(p
, memcg
))
125 /* p may not have freeable memory in nodemask */
126 if (!has_intersects_mems_allowed(p
, nodemask
))
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
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.
141 unsigned long oom_badness(struct task_struct
*p
, struct mem_cgroup
*memcg
,
142 const nodemask_t
*nodemask
, unsigned long totalpages
)
147 if (oom_unkillable_task(p
, memcg
, nodemask
))
150 p
= find_lock_task_mm(p
);
154 adj
= (long)p
->signal
->oom_score_adj
;
155 if (adj
== OOM_SCORE_ADJ_MIN
) {
161 * The baseline for the badness score is the proportion of RAM that each
162 * task's rss, pagetable and swap space use.
164 points
= get_mm_rss(p
->mm
) + atomic_long_read(&p
->mm
->nr_ptes
) +
165 get_mm_counter(p
->mm
, MM_SWAPENTS
);
169 * Root processes get 3% bonus, just like the __vm_enough_memory()
170 * implementation used by LSMs.
172 if (has_capability_noaudit(p
, CAP_SYS_ADMIN
))
175 /* Normalize to oom_score_adj units */
176 adj
*= totalpages
/ 1000;
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).
183 return points
> 0 ? points
: 1;
187 * Determine the type of allocation constraint.
190 static enum oom_constraint
constrained_alloc(struct zonelist
*zonelist
,
191 gfp_t gfp_mask
, nodemask_t
*nodemask
,
192 unsigned long *totalpages
)
196 enum zone_type high_zoneidx
= gfp_zone(gfp_mask
);
197 bool cpuset_limited
= false;
200 /* Default to all available memory */
201 *totalpages
= totalram_pages
+ total_swap_pages
;
204 return CONSTRAINT_NONE
;
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.
210 if (gfp_mask
& __GFP_THISNODE
)
211 return CONSTRAINT_NONE
;
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().
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
;
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;
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
;
237 return CONSTRAINT_NONE
;
240 static enum oom_constraint
constrained_alloc(struct zonelist
*zonelist
,
241 gfp_t gfp_mask
, nodemask_t
*nodemask
,
242 unsigned long *totalpages
)
244 *totalpages
= totalram_pages
+ total_swap_pages
;
245 return CONSTRAINT_NONE
;
249 enum oom_scan_t
oom_scan_process_thread(struct task_struct
*task
,
250 unsigned long totalpages
, const nodemask_t
*nodemask
,
253 if (task
->exit_state
)
254 return OOM_SCAN_CONTINUE
;
255 if (oom_unkillable_task(task
, NULL
, nodemask
))
256 return OOM_SCAN_CONTINUE
;
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.
262 if (test_tsk_thread_flag(task
, TIF_MEMDIE
)) {
263 if (unlikely(frozen(task
)))
266 return OOM_SCAN_ABORT
;
269 return OOM_SCAN_CONTINUE
;
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.
275 if (oom_task_origin(task
))
276 return OOM_SCAN_SELECT
;
278 if (task
->flags
& PF_EXITING
&& !force_kill
) {
280 * If this task is not being ptraced on exit, then wait for it
281 * to finish before killing some other task unnecessarily.
283 if (!(task
->group_leader
->ptrace
& PT_TRACE_EXIT
))
284 return OOM_SCAN_ABORT
;
290 * Simple selection loop. We chose the process with the highest
291 * number of 'points'. Returns -1 on scan abort.
293 * (not docbooked, we don't want this one cluttering up the manual)
295 static struct task_struct
*select_bad_process(unsigned int *ppoints
,
296 unsigned long totalpages
, const nodemask_t
*nodemask
,
299 struct task_struct
*g
, *p
;
300 struct task_struct
*chosen
= NULL
;
301 unsigned long chosen_points
= 0;
304 for_each_process_thread(g
, p
) {
307 switch (oom_scan_process_thread(p
, totalpages
, nodemask
,
309 case OOM_SCAN_SELECT
:
311 chosen_points
= ULONG_MAX
;
313 case OOM_SCAN_CONTINUE
:
317 return (struct task_struct
*)(-1UL);
321 points
= oom_badness(p
, NULL
, nodemask
, totalpages
);
322 if (points
> chosen_points
) {
324 chosen_points
= points
;
328 get_task_struct(chosen
);
331 *ppoints
= chosen_points
* 1000 / totalpages
;
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
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
343 * State information includes task's pid, uid, tgid, vm size, rss, nr_ptes,
344 * swapents, oom_score_adj value, and name.
346 static void dump_tasks(const struct mem_cgroup
*memcg
, const nodemask_t
*nodemask
)
348 struct task_struct
*p
;
349 struct task_struct
*task
;
351 pr_info("[ pid ] uid tgid total_vm rss nr_ptes swapents oom_score_adj name\n");
353 for_each_process(p
) {
354 if (oom_unkillable_task(p
, memcg
, nodemask
))
357 task
= find_lock_task_mm(p
);
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.
367 pr_info("[%5d] %5d %5d %8lu %8lu %7ld %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 atomic_long_read(&task
->mm
->nr_ptes
),
371 get_mm_counter(task
->mm
, MM_SWAPENTS
),
372 task
->signal
->oom_score_adj
, task
->comm
);
378 static void dump_header(struct task_struct
*p
, gfp_t gfp_mask
, int order
,
379 struct mem_cgroup
*memcg
, const nodemask_t
*nodemask
)
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
);
390 mem_cgroup_print_oom_info(memcg
, p
);
392 show_mem(SHOW_MEM_FILTER_NODES
);
393 if (sysctl_oom_dump_tasks
)
394 dump_tasks(memcg
, nodemask
);
397 #define K(x) ((x) << (PAGE_SHIFT-10))
399 * Must be called while holding a reference to p, which will be released upon
402 void 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
,
407 struct task_struct
*victim
= p
;
408 struct task_struct
*child
;
409 struct task_struct
*t
;
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
);
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
419 if (p
->flags
& PF_EXITING
) {
420 set_tsk_thread_flag(p
, TIF_MEMDIE
);
425 if (__ratelimit(&oom_rs
))
426 dump_header(p
, gfp_mask
, order
, memcg
, nodemask
);
429 pr_err("%s: Kill process %d (%s) score %d or sacrifice child\n",
430 message
, task_pid_nr(p
), p
->comm
, points
);
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.
439 read_lock(&tasklist_lock
);
440 for_each_thread(p
, t
) {
441 list_for_each_entry(child
, &t
->children
, sibling
) {
442 unsigned int child_points
;
444 if (child
->mm
== p
->mm
)
447 * oom_badness() returns 0 if the thread is unkillable
449 child_points
= oom_badness(child
, memcg
, nodemask
,
451 if (child_points
> victim_points
) {
452 put_task_struct(victim
);
454 victim_points
= child_points
;
455 get_task_struct(victim
);
459 read_unlock(&tasklist_lock
);
462 p
= find_lock_task_mm(victim
);
465 put_task_struct(victim
);
467 } else if (victim
!= p
) {
469 put_task_struct(victim
);
473 /* mm cannot safely be dereferenced after task_unlock(victim) */
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
)));
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.
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
)
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
);
500 do_send_sig_info(SIGKILL
, SEND_SIG_FORCED
, p
, true);
504 set_tsk_thread_flag(victim
, TIF_MEMDIE
);
505 do_send_sig_info(SIGKILL
, SEND_SIG_FORCED
, victim
, true);
506 put_task_struct(victim
);
511 * Determines whether the kernel must panic because of the panic_on_oom sysctl.
513 void check_panic_on_oom(enum oom_constraint constraint
, gfp_t gfp_mask
,
514 int order
, const nodemask_t
*nodemask
)
516 if (likely(!sysctl_panic_on_oom
))
518 if (sysctl_panic_on_oom
!= 2) {
520 * panic_on_oom == 1 only affects CONSTRAINT_NONE, the kernel
521 * does not panic for cpuset, mempolicy, or memcg allocation
524 if (constraint
!= CONSTRAINT_NONE
)
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");
532 static BLOCKING_NOTIFIER_HEAD(oom_notify_list
);
534 int register_oom_notifier(struct notifier_block
*nb
)
536 return blocking_notifier_chain_register(&oom_notify_list
, nb
);
538 EXPORT_SYMBOL_GPL(register_oom_notifier
);
540 int unregister_oom_notifier(struct notifier_block
*nb
)
542 return blocking_notifier_chain_unregister(&oom_notify_list
, nb
);
544 EXPORT_SYMBOL_GPL(unregister_oom_notifier
);
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.
551 int try_set_zonelist_oom(struct zonelist
*zonelist
, gfp_t gfp_mask
)
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
)) {
565 for_each_zone_zonelist(zone
, z
, zonelist
, gfp_zone(gfp_mask
)) {
567 * Lock each zone in the zonelist under zone_scan_lock so a
568 * parallel invocation of try_set_zonelist_oom() doesn't succeed
571 zone_set_flag(zone
, ZONE_OOM_LOCKED
);
575 spin_unlock(&zone_scan_lock
);
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.
584 void clear_zonelist_oom(struct zonelist
*zonelist
, gfp_t gfp_mask
)
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
);
593 spin_unlock(&zone_scan_lock
);
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
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.
609 void out_of_memory(struct zonelist
*zonelist
, gfp_t gfp_mask
,
610 int order
, nodemask_t
*nodemask
, bool force_kill
)
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
;
620 blocking_notifier_call_chain(&oom_notify_list
, 0, &freed
);
622 /* Got some memory back in the last second. */
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.
630 if (fatal_signal_pending(current
) || current
->flags
& PF_EXITING
) {
631 set_thread_flag(TIF_MEMDIE
);
636 * Check if there were limitations on the allocation (only relevant for
637 * NUMA) that may require different handling.
639 constraint
= constrained_alloc(zonelist
, gfp_mask
, nodemask
,
641 mpol_mask
= (constraint
== CONSTRAINT_MEMORY_POLICY
) ? nodemask
: NULL
;
642 check_panic_on_oom(constraint
, gfp_mask
, order
, mpol_mask
);
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
,
650 "Out of memory (oom_kill_allocating_task)");
654 p
= select_bad_process(&points
, totalpages
, mpol_mask
, force_kill
);
655 /* Found nothing?!?! Either we hang forever, or we panic. */
657 dump_header(NULL
, gfp_mask
, order
, NULL
, mpol_mask
);
658 panic("Out of memory and no killable processes...\n");
660 if (p
!= (void *)-1UL) {
661 oom_kill_process(p
, gfp_mask
, order
, points
, totalpages
, NULL
,
662 nodemask
, "Out of memory");
667 * Give the killed threads a good chance of exiting before trying to
668 * allocate memory again.
671 schedule_timeout_killable(1);
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.
679 void pagefault_out_of_memory(void)
681 struct zonelist
*zonelist
;
683 if (mem_cgroup_oom_synchronize(true))
686 zonelist
= node_zonelist(first_online_node
, GFP_KERNEL
);
687 if (try_set_zonelist_oom(zonelist
, GFP_KERNEL
)) {
688 out_of_memory(NULL
, 0, 0, NULL
, false);
689 clear_zonelist_oom(zonelist
, GFP_KERNEL
);