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/module.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>
37 int sysctl_panic_on_oom;
38 int sysctl_oom_kill_allocating_task;
39 int sysctl_oom_dump_tasks = 1;
40 static DEFINE_SPINLOCK(zone_scan_lock);
43 * test_set_oom_score_adj() - set current's oom_score_adj and return old value
44 * @new_val: new oom_score_adj value
46 * Sets the oom_score_adj value for current to @new_val with proper
47 * synchronization and returns the old value. Usually used to temporarily
48 * set a value, save the old value in the caller, and then reinstate it later.
50 int test_set_oom_score_adj(int new_val)
52 struct sighand_struct *sighand = current->sighand;
55 spin_lock_irq(&sighand->siglock);
56 old_val = current->signal->oom_score_adj;
57 if (new_val != old_val) {
58 if (new_val == OOM_SCORE_ADJ_MIN)
59 atomic_inc(¤t->mm->oom_disable_count);
60 else if (old_val == OOM_SCORE_ADJ_MIN)
61 atomic_dec(¤t->mm->oom_disable_count);
62 current->signal->oom_score_adj = new_val;
64 spin_unlock_irq(&sighand->siglock);
71 * has_intersects_mems_allowed() - check task eligiblity for kill
72 * @tsk: task struct of which task to consider
73 * @mask: nodemask passed to page allocator for mempolicy ooms
75 * Task eligibility is determined by whether or not a candidate task, @tsk,
76 * shares the same mempolicy nodes as current if it is bound by such a policy
77 * and whether or not it has the same set of allowed cpuset nodes.
79 static bool has_intersects_mems_allowed(struct task_struct *tsk,
80 const nodemask_t *mask)
82 struct task_struct *start = tsk;
87 * If this is a mempolicy constrained oom, tsk's
88 * cpuset is irrelevant. Only return true if its
89 * mempolicy intersects current, otherwise it may be
92 if (mempolicy_nodemask_intersects(tsk, mask))
96 * This is not a mempolicy constrained oom, so only
97 * check the mems of tsk's cpuset.
99 if (cpuset_mems_allowed_intersects(current, tsk))
102 } while_each_thread(start, tsk);
107 static bool has_intersects_mems_allowed(struct task_struct *tsk,
108 const nodemask_t *mask)
112 #endif /* CONFIG_NUMA */
115 * The process p may have detached its own ->mm while exiting or through
116 * use_mm(), but one or more of its subthreads may still have a valid
117 * pointer. Return p, or any of its subthreads with a valid ->mm, with
120 struct task_struct *find_lock_task_mm(struct task_struct *p)
122 struct task_struct *t = p;
129 } while_each_thread(p, t);
134 /* return true if the task is not adequate as candidate victim task. */
135 static bool oom_unkillable_task(struct task_struct *p,
136 const struct mem_cgroup *mem, const nodemask_t *nodemask)
138 if (is_global_init(p))
140 if (p->flags & PF_KTHREAD)
143 /* When mem_cgroup_out_of_memory() and p is not member of the group */
144 if (mem && !task_in_mem_cgroup(p, mem))
147 /* p may not have freeable memory in nodemask */
148 if (!has_intersects_mems_allowed(p, nodemask))
155 * oom_badness - heuristic function to determine which candidate task to kill
156 * @p: task struct of which task we should calculate
157 * @totalpages: total present RAM allowed for page allocation
159 * The heuristic for determining which task to kill is made to be as simple and
160 * predictable as possible. The goal is to return the highest value for the
161 * task consuming the most memory to avoid subsequent oom failures.
163 unsigned int oom_badness(struct task_struct *p, struct mem_cgroup *mem,
164 const nodemask_t *nodemask, unsigned long totalpages)
168 if (oom_unkillable_task(p, mem, nodemask))
171 p = find_lock_task_mm(p);
176 * Shortcut check for a thread sharing p->mm that is OOM_SCORE_ADJ_MIN
177 * so the entire heuristic doesn't need to be executed for something
178 * that cannot be killed.
180 if (atomic_read(&p->mm->oom_disable_count)) {
186 * The memory controller may have a limit of 0 bytes, so avoid a divide
187 * by zero, if necessary.
193 * The baseline for the badness score is the proportion of RAM that each
194 * task's rss, pagetable and swap space use.
196 points = get_mm_rss(p->mm) + p->mm->nr_ptes;
197 points += get_mm_counter(p->mm, MM_SWAPENTS);
200 points /= totalpages;
204 * Root processes get 3% bonus, just like the __vm_enough_memory()
205 * implementation used by LSMs.
207 if (has_capability_noaudit(p, CAP_SYS_ADMIN))
211 * /proc/pid/oom_score_adj ranges from -1000 to +1000 such that it may
212 * either completely disable oom killing or always prefer a certain
215 points += p->signal->oom_score_adj;
218 * Never return 0 for an eligible task that may be killed since it's
219 * possible that no single user task uses more than 0.1% of memory and
220 * no single admin tasks uses more than 3.0%.
224 return (points < 1000) ? points : 1000;
228 * Determine the type of allocation constraint.
231 static enum oom_constraint constrained_alloc(struct zonelist *zonelist,
232 gfp_t gfp_mask, nodemask_t *nodemask,
233 unsigned long *totalpages)
237 enum zone_type high_zoneidx = gfp_zone(gfp_mask);
238 bool cpuset_limited = false;
241 /* Default to all available memory */
242 *totalpages = totalram_pages + total_swap_pages;
245 return CONSTRAINT_NONE;
247 * Reach here only when __GFP_NOFAIL is used. So, we should avoid
248 * to kill current.We have to random task kill in this case.
249 * Hopefully, CONSTRAINT_THISNODE...but no way to handle it, now.
251 if (gfp_mask & __GFP_THISNODE)
252 return CONSTRAINT_NONE;
255 * This is not a __GFP_THISNODE allocation, so a truncated nodemask in
256 * the page allocator means a mempolicy is in effect. Cpuset policy
257 * is enforced in get_page_from_freelist().
259 if (nodemask && !nodes_subset(node_states[N_HIGH_MEMORY], *nodemask)) {
260 *totalpages = total_swap_pages;
261 for_each_node_mask(nid, *nodemask)
262 *totalpages += node_spanned_pages(nid);
263 return CONSTRAINT_MEMORY_POLICY;
266 /* Check this allocation failure is caused by cpuset's wall function */
267 for_each_zone_zonelist_nodemask(zone, z, zonelist,
268 high_zoneidx, nodemask)
269 if (!cpuset_zone_allowed_softwall(zone, gfp_mask))
270 cpuset_limited = true;
272 if (cpuset_limited) {
273 *totalpages = total_swap_pages;
274 for_each_node_mask(nid, cpuset_current_mems_allowed)
275 *totalpages += node_spanned_pages(nid);
276 return CONSTRAINT_CPUSET;
278 return CONSTRAINT_NONE;
281 static enum oom_constraint constrained_alloc(struct zonelist *zonelist,
282 gfp_t gfp_mask, nodemask_t *nodemask,
283 unsigned long *totalpages)
285 *totalpages = totalram_pages + total_swap_pages;
286 return CONSTRAINT_NONE;
291 * Simple selection loop. We chose the process with the highest
292 * number of 'points'. We expect the caller will lock the tasklist.
294 * (not docbooked, we don't want this one cluttering up the manual)
296 static struct task_struct *select_bad_process(unsigned int *ppoints,
297 unsigned long totalpages, struct mem_cgroup *mem,
298 const nodemask_t *nodemask)
300 struct task_struct *g, *p;
301 struct task_struct *chosen = NULL;
304 do_each_thread(g, p) {
309 if (oom_unkillable_task(p, mem, nodemask))
313 * This task already has access to memory reserves and is
314 * being killed. Don't allow any other task access to the
317 * Note: this may have a chance of deadlock if it gets
318 * blocked waiting for another task which itself is waiting
319 * for memory. Is there a better alternative?
321 if (test_tsk_thread_flag(p, TIF_MEMDIE)) {
322 if (unlikely(frozen(p)))
324 return ERR_PTR(-1UL);
329 if (p->flags & PF_EXITING) {
331 * If p is the current task and is in the process of
332 * releasing memory, we allow the "kill" to set
333 * TIF_MEMDIE, which will allow it to gain access to
334 * memory reserves. Otherwise, it may stall forever.
336 * The loop isn't broken here, however, in case other
337 * threads are found to have already been oom killed.
344 * If this task is not being ptraced on exit,
345 * then wait for it to finish before killing
346 * some other task unnecessarily.
348 if (!(p->group_leader->ptrace & PT_TRACE_EXIT))
349 return ERR_PTR(-1UL);
353 points = oom_badness(p, mem, nodemask, totalpages);
354 if (points > *ppoints) {
358 } while_each_thread(g, p);
364 * dump_tasks - dump current memory state of all system tasks
365 * @mem: current's memory controller, if constrained
366 * @nodemask: nodemask passed to page allocator for mempolicy ooms
368 * Dumps the current memory state of all eligible tasks. Tasks not in the same
369 * memcg, not in the same cpuset, or bound to a disjoint set of mempolicy nodes
371 * State information includes task's pid, uid, tgid, vm size, rss, cpu, oom_adj
372 * value, oom_score_adj value, and name.
374 * Call with tasklist_lock read-locked.
376 static void dump_tasks(const struct mem_cgroup *mem, const nodemask_t *nodemask)
378 struct task_struct *p;
379 struct task_struct *task;
381 pr_info("[ pid ] uid tgid total_vm rss cpu oom_adj oom_score_adj name\n");
382 for_each_process(p) {
383 if (oom_unkillable_task(p, mem, nodemask))
386 task = find_lock_task_mm(p);
389 * This is a kthread or all of p's threads have already
390 * detached their mm's. There's no need to report
391 * them; they can't be oom killed anyway.
396 pr_info("[%5d] %5d %5d %8lu %8lu %3u %3d %5d %s\n",
397 task->pid, task_uid(task), task->tgid,
398 task->mm->total_vm, get_mm_rss(task->mm),
399 task_cpu(task), task->signal->oom_adj,
400 task->signal->oom_score_adj, task->comm);
405 static void dump_header(struct task_struct *p, gfp_t gfp_mask, int order,
406 struct mem_cgroup *mem, const nodemask_t *nodemask)
409 pr_warning("%s invoked oom-killer: gfp_mask=0x%x, order=%d, "
410 "oom_adj=%d, oom_score_adj=%d\n",
411 current->comm, gfp_mask, order, current->signal->oom_adj,
412 current->signal->oom_score_adj);
413 cpuset_print_task_mems_allowed(current);
414 task_unlock(current);
416 mem_cgroup_print_oom_info(mem, p);
417 show_mem(SHOW_MEM_FILTER_NODES);
418 if (sysctl_oom_dump_tasks)
419 dump_tasks(mem, nodemask);
422 #define K(x) ((x) << (PAGE_SHIFT-10))
423 static int oom_kill_task(struct task_struct *p, struct mem_cgroup *mem)
425 struct task_struct *q;
426 struct mm_struct *mm;
428 p = find_lock_task_mm(p);
432 /* mm cannot be safely dereferenced after task_unlock(p) */
435 pr_err("Killed process %d (%s) total-vm:%lukB, anon-rss:%lukB, file-rss:%lukB\n",
436 task_pid_nr(p), p->comm, K(p->mm->total_vm),
437 K(get_mm_counter(p->mm, MM_ANONPAGES)),
438 K(get_mm_counter(p->mm, MM_FILEPAGES)));
442 * Kill all user processes sharing p->mm in other thread groups, if any.
443 * They don't get access to memory reserves or a higher scheduler
444 * priority, though, to avoid depletion of all memory or task
445 * starvation. This prevents mm->mmap_sem livelock when an oom killed
446 * task cannot exit because it requires the semaphore and its contended
447 * by another thread trying to allocate memory itself. That thread will
448 * now get access to memory reserves since it has a pending fatal
452 if (q->mm == mm && !same_thread_group(q, p) &&
453 !(q->flags & PF_KTHREAD)) {
454 task_lock(q); /* Protect ->comm from prctl() */
455 pr_err("Kill process %d (%s) sharing same memory\n",
456 task_pid_nr(q), q->comm);
458 force_sig(SIGKILL, q);
461 set_tsk_thread_flag(p, TIF_MEMDIE);
462 force_sig(SIGKILL, p);
468 static int oom_kill_process(struct task_struct *p, gfp_t gfp_mask, int order,
469 unsigned int points, unsigned long totalpages,
470 struct mem_cgroup *mem, nodemask_t *nodemask,
473 struct task_struct *victim = p;
474 struct task_struct *child;
475 struct task_struct *t = p;
476 unsigned int victim_points = 0;
478 if (printk_ratelimit())
479 dump_header(p, gfp_mask, order, mem, nodemask);
482 * If the task is already exiting, don't alarm the sysadmin or kill
483 * its children or threads, just set TIF_MEMDIE so it can die quickly
485 if (p->flags & PF_EXITING) {
486 set_tsk_thread_flag(p, TIF_MEMDIE);
491 pr_err("%s: Kill process %d (%s) score %d or sacrifice child\n",
492 message, task_pid_nr(p), p->comm, points);
496 * If any of p's children has a different mm and is eligible for kill,
497 * the one with the highest oom_badness() score is sacrificed for its
498 * parent. This attempts to lose the minimal amount of work done while
499 * still freeing memory.
502 list_for_each_entry(child, &t->children, sibling) {
503 unsigned int child_points;
505 if (child->mm == p->mm)
508 * oom_badness() returns 0 if the thread is unkillable
510 child_points = oom_badness(child, mem, nodemask,
512 if (child_points > victim_points) {
514 victim_points = child_points;
517 } while_each_thread(p, t);
519 return oom_kill_task(victim, mem);
523 * Determines whether the kernel must panic because of the panic_on_oom sysctl.
525 static void check_panic_on_oom(enum oom_constraint constraint, gfp_t gfp_mask,
526 int order, const nodemask_t *nodemask)
528 if (likely(!sysctl_panic_on_oom))
530 if (sysctl_panic_on_oom != 2) {
532 * panic_on_oom == 1 only affects CONSTRAINT_NONE, the kernel
533 * does not panic for cpuset, mempolicy, or memcg allocation
536 if (constraint != CONSTRAINT_NONE)
539 read_lock(&tasklist_lock);
540 dump_header(NULL, gfp_mask, order, NULL, nodemask);
541 read_unlock(&tasklist_lock);
542 panic("Out of memory: %s panic_on_oom is enabled\n",
543 sysctl_panic_on_oom == 2 ? "compulsory" : "system-wide");
546 #ifdef CONFIG_CGROUP_MEM_RES_CTLR
547 void mem_cgroup_out_of_memory(struct mem_cgroup *mem, gfp_t gfp_mask)
550 unsigned int points = 0;
551 struct task_struct *p;
554 * If current has a pending SIGKILL, then automatically select it. The
555 * goal is to allow it to allocate so that it may quickly exit and free
558 if (fatal_signal_pending(current)) {
559 set_thread_flag(TIF_MEMDIE);
563 check_panic_on_oom(CONSTRAINT_MEMCG, gfp_mask, 0, NULL);
564 limit = mem_cgroup_get_limit(mem) >> PAGE_SHIFT;
565 read_lock(&tasklist_lock);
567 p = select_bad_process(&points, limit, mem, NULL);
568 if (!p || PTR_ERR(p) == -1UL)
571 if (oom_kill_process(p, gfp_mask, 0, points, limit, mem, NULL,
572 "Memory cgroup out of memory"))
575 read_unlock(&tasklist_lock);
579 static BLOCKING_NOTIFIER_HEAD(oom_notify_list);
581 int register_oom_notifier(struct notifier_block *nb)
583 return blocking_notifier_chain_register(&oom_notify_list, nb);
585 EXPORT_SYMBOL_GPL(register_oom_notifier);
587 int unregister_oom_notifier(struct notifier_block *nb)
589 return blocking_notifier_chain_unregister(&oom_notify_list, nb);
591 EXPORT_SYMBOL_GPL(unregister_oom_notifier);
594 * Try to acquire the OOM killer lock for the zones in zonelist. Returns zero
595 * if a parallel OOM killing is already taking place that includes a zone in
596 * the zonelist. Otherwise, locks all zones in the zonelist and returns 1.
598 int try_set_zonelist_oom(struct zonelist *zonelist, gfp_t gfp_mask)
604 spin_lock(&zone_scan_lock);
605 for_each_zone_zonelist(zone, z, zonelist, gfp_zone(gfp_mask)) {
606 if (zone_is_oom_locked(zone)) {
612 for_each_zone_zonelist(zone, z, zonelist, gfp_zone(gfp_mask)) {
614 * Lock each zone in the zonelist under zone_scan_lock so a
615 * parallel invocation of try_set_zonelist_oom() doesn't succeed
618 zone_set_flag(zone, ZONE_OOM_LOCKED);
622 spin_unlock(&zone_scan_lock);
627 * Clears the ZONE_OOM_LOCKED flag for all zones in the zonelist so that failed
628 * allocation attempts with zonelists containing them may now recall the OOM
629 * killer, if necessary.
631 void clear_zonelist_oom(struct zonelist *zonelist, gfp_t gfp_mask)
636 spin_lock(&zone_scan_lock);
637 for_each_zone_zonelist(zone, z, zonelist, gfp_zone(gfp_mask)) {
638 zone_clear_flag(zone, ZONE_OOM_LOCKED);
640 spin_unlock(&zone_scan_lock);
644 * Try to acquire the oom killer lock for all system zones. Returns zero if a
645 * parallel oom killing is taking place, otherwise locks all zones and returns
648 static int try_set_system_oom(void)
653 spin_lock(&zone_scan_lock);
654 for_each_populated_zone(zone)
655 if (zone_is_oom_locked(zone)) {
659 for_each_populated_zone(zone)
660 zone_set_flag(zone, ZONE_OOM_LOCKED);
662 spin_unlock(&zone_scan_lock);
667 * Clears ZONE_OOM_LOCKED for all system zones so that failed allocation
668 * attempts or page faults may now recall the oom killer, if necessary.
670 static void clear_system_oom(void)
674 spin_lock(&zone_scan_lock);
675 for_each_populated_zone(zone)
676 zone_clear_flag(zone, ZONE_OOM_LOCKED);
677 spin_unlock(&zone_scan_lock);
681 * out_of_memory - kill the "best" process when we run out of memory
682 * @zonelist: zonelist pointer
683 * @gfp_mask: memory allocation flags
684 * @order: amount of memory being requested as a power of 2
685 * @nodemask: nodemask passed to page allocator
687 * If we run out of memory, we have the choice between either
688 * killing a random task (bad), letting the system crash (worse)
689 * OR try to be smart about which process to kill. Note that we
690 * don't have to be perfect here, we just have to be good.
692 void out_of_memory(struct zonelist *zonelist, gfp_t gfp_mask,
693 int order, nodemask_t *nodemask)
695 const nodemask_t *mpol_mask;
696 struct task_struct *p;
697 unsigned long totalpages;
698 unsigned long freed = 0;
700 enum oom_constraint constraint = CONSTRAINT_NONE;
703 blocking_notifier_call_chain(&oom_notify_list, 0, &freed);
705 /* Got some memory back in the last second. */
709 * If current has a pending SIGKILL, then automatically select it. The
710 * goal is to allow it to allocate so that it may quickly exit and free
713 if (fatal_signal_pending(current)) {
714 set_thread_flag(TIF_MEMDIE);
719 * Check if there were limitations on the allocation (only relevant for
720 * NUMA) that may require different handling.
722 constraint = constrained_alloc(zonelist, gfp_mask, nodemask,
724 mpol_mask = (constraint == CONSTRAINT_MEMORY_POLICY) ? nodemask : NULL;
725 check_panic_on_oom(constraint, gfp_mask, order, mpol_mask);
727 read_lock(&tasklist_lock);
728 if (sysctl_oom_kill_allocating_task &&
729 !oom_unkillable_task(current, NULL, nodemask) &&
730 current->mm && !atomic_read(¤t->mm->oom_disable_count)) {
732 * oom_kill_process() needs tasklist_lock held. If it returns
733 * non-zero, current could not be killed so we must fallback to
736 if (!oom_kill_process(current, gfp_mask, order, 0, totalpages,
738 "Out of memory (oom_kill_allocating_task)"))
743 p = select_bad_process(&points, totalpages, NULL, mpol_mask);
744 if (PTR_ERR(p) == -1UL)
747 /* Found nothing?!?! Either we hang forever, or we panic. */
749 dump_header(NULL, gfp_mask, order, NULL, mpol_mask);
750 read_unlock(&tasklist_lock);
751 panic("Out of memory and no killable processes...\n");
754 if (oom_kill_process(p, gfp_mask, order, points, totalpages, NULL,
755 nodemask, "Out of memory"))
759 read_unlock(&tasklist_lock);
762 * Give "p" a good chance of killing itself before we
763 * retry to allocate memory unless "p" is current
765 if (killed && !test_thread_flag(TIF_MEMDIE))
766 schedule_timeout_uninterruptible(1);
770 * The pagefault handler calls here because it is out of memory, so kill a
771 * memory-hogging task. If a populated zone has ZONE_OOM_LOCKED set, a parallel
772 * oom killing is already in progress so do nothing. If a task is found with
773 * TIF_MEMDIE set, it has been killed so do nothing and allow it to exit.
775 void pagefault_out_of_memory(void)
777 if (try_set_system_oom()) {
778 out_of_memory(NULL, 0, 0, NULL);
781 if (!test_thread_flag(TIF_MEMDIE))
782 schedule_timeout_uninterruptible(1);