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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
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);
46
47	/*
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
51	*
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.
55	*/
56	void compare_swap_oom_score_adj(int old_val, int new_val)
57	{
58	struct sighand_struct *sighand = current->sighand;
59
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);
65	}
66
67	/**
68	* test_set_oom_score_adj() - set current's oom_score_adj and return old value
69	* @new_val: new oom_score_adj value
70	*
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.
74	*/
75	int test_set_oom_score_adj(int new_val)
76	{
77	struct sighand_struct *sighand = current->sighand;
78	int old_val;
79
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);
85
86	return old_val;
87	}
88
89	#ifdef CONFIG_NUMA
90	/**
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
94	*
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.
98	*/
99	static bool has_intersects_mems_allowed(struct task_struct *tsk,
100	const nodemask_t *mask)
101	{
102	struct task_struct *start = tsk;
103
104	do {
105	if (mask) {
106	/*
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
110	* needlessly killed.
111	*/
112	if (mempolicy_nodemask_intersects(tsk, mask))
113	return true;
114	} else {
115	/*
116	* This is not a mempolicy constrained oom, so only
117	* check the mems of tsk's cpuset.
118	*/
119	if (cpuset_mems_allowed_intersects(current, tsk))
120	return true;
121	}
122	} while_each_thread(start, tsk);
123
124	return false;
125	}
126	#else
127	static bool has_intersects_mems_allowed(struct task_struct *tsk,
128	const nodemask_t *mask)
129	{
130	return true;
131	}
132	#endif /* CONFIG_NUMA */
133
134	/*
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
138	* task_lock() held.
139	*/
140	struct task_struct find_lock_task_mm(struct task_struct p)
141	{
142	struct task_struct *t = p;
143
144	do {
145	task_lock(t);
146	if (likely(t->mm))
147	return t;
148	task_unlock(t);
149	} while_each_thread(p, t);
150
151	return NULL;
152	}
153
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)
157	{
158	if (is_global_init(p))
159	return true;
160	if (p->flags & PF_KTHREAD)
161	return true;
162
163	/* When mem_cgroup_out_of_memory() and p is not member of the group */
164	if (memcg && !task_in_mem_cgroup(p, memcg))
165	return true;
166
167	/* p may not have freeable memory in nodemask */
168	if (!has_intersects_mems_allowed(p, nodemask))
169	return true;
170
171	return false;
172	}
173
174	/**
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
178	*
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.
182	*/
183	unsigned long oom_badness(struct task_struct p, struct mem_cgroup memcg,
184	const nodemask_t *nodemask, unsigned long totalpages)
185	{
186	long points;
187	long adj;
188
189	if (oom_unkillable_task(p, memcg, nodemask))
190	return 0;
191
192	p = find_lock_task_mm(p);
193	if (!p)
194	return 0;
195
196	adj = p->signal->oom_score_adj;
197	if (adj == OOM_SCORE_ADJ_MIN) {
198	task_unlock(p);
199	return 0;
200	}
201
202	/*
203	* The baseline for the badness score is the proportion of RAM that each
204	* task's rss, pagetable and swap space use.
205	*/
206	points = get_mm_rss(p->mm) + p->mm->nr_ptes +
207	get_mm_counter(p->mm, MM_SWAPENTS);
208	task_unlock(p);
209
210	/*
211	* Root processes get 3% bonus, just like the __vm_enough_memory()
212	* implementation used by LSMs.
213	*/
214	if (has_capability_noaudit(p, CAP_SYS_ADMIN))
215	adj -= 30;
216
217	/* Normalize to oom_score_adj units */
218	adj *= totalpages / 1000;
219	points += adj;
220
221	/*
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).
224	*/
225	return points > 0 ? points : 1;
226	}
227
228	/*
229	* Determine the type of allocation constraint.
230	*/
231	#ifdef CONFIG_NUMA
232	static enum oom_constraint constrained_alloc(struct zonelist *zonelist,
233	gfp_t gfp_mask, nodemask_t *nodemask,
234	unsigned long *totalpages)
235	{
236	struct zone *zone;
237	struct zoneref *z;
238	enum zone_type high_zoneidx = gfp_zone(gfp_mask);
239	bool cpuset_limited = false;
240	int nid;
241
242	/* Default to all available memory */
243	*totalpages = totalram_pages + total_swap_pages;
244
245	if (!zonelist)
246	return CONSTRAINT_NONE;
247	/*
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.
251	*/
252	if (gfp_mask & __GFP_THISNODE)
253	return CONSTRAINT_NONE;
254
255	/*
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().
259	*/
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;
265	}
266
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;
272
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;
278	}
279	return CONSTRAINT_NONE;
280	}
281	#else
282	static enum oom_constraint constrained_alloc(struct zonelist *zonelist,
283	gfp_t gfp_mask, nodemask_t *nodemask,
284	unsigned long *totalpages)
285	{
286	*totalpages = totalram_pages + total_swap_pages;
287	return CONSTRAINT_NONE;
288	}
289	#endif
290
291	enum oom_scan_t oom_scan_process_thread(struct task_struct *task,
292	unsigned long totalpages, const nodemask_t *nodemask,
293	bool force_kill)
294	{
295	if (task->exit_state)
296	return OOM_SCAN_CONTINUE;
297	if (oom_unkillable_task(task, NULL, nodemask))
298	return OOM_SCAN_CONTINUE;
299
300	/*
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.
303	*/
304	if (test_tsk_thread_flag(task, TIF_MEMDIE)) {
305	if (unlikely(frozen(task)))
306	__thaw_task(task);
307	if (!force_kill)
308	return OOM_SCAN_ABORT;
309	}
310	if (!task->mm)
311	return OOM_SCAN_CONTINUE;
312
313	if (task->flags & PF_EXITING) {
314	/*
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.
318	*
319	* The iteration isn't broken here, however, in case other
320	* threads are found to have already been oom killed.
321	*/
322	if (task == current)
323	return OOM_SCAN_SELECT;
324	else if (!force_kill) {
325	/*
326	* If this task is not being ptraced on exit, then wait
327	* for it to finish before killing some other task
328	* unnecessarily.
329	*/
330	if (!(task->group_leader->ptrace & PT_TRACE_EXIT))
331	return OOM_SCAN_ABORT;
332	}
333	}
334	return OOM_SCAN_OK;
335	}
336
337	/*
338	* Simple selection loop. We chose the process with the highest
339	* number of 'points'.
340	*
341	* (not docbooked, we don't want this one cluttering up the manual)
342	*/
343	static struct task_struct select_bad_process(unsigned int ppoints,
344	unsigned long totalpages, const nodemask_t *nodemask,
345	bool force_kill)
346	{
347	struct task_struct g, p;
348	struct task_struct *chosen = NULL;
349	unsigned long chosen_points = 0;
350
351	rcu_read_lock();
352	do_each_thread(g, p) {
353	unsigned int points;
354
355	switch (oom_scan_process_thread(p, totalpages, nodemask,
356	force_kill)) {
357	case OOM_SCAN_SELECT:
358	chosen = p;
359	chosen_points = ULONG_MAX;
360	/* fall through */
361	case OOM_SCAN_CONTINUE:
362	continue;
363	case OOM_SCAN_ABORT:
364	rcu_read_unlock();
365	return ERR_PTR(-1UL);
366	case OOM_SCAN_OK:
367	break;
368	};
369	points = oom_badness(p, NULL, nodemask, totalpages);
370	if (points > chosen_points) {
371	chosen = p;
372	chosen_points = points;
373	}
374	} while_each_thread(g, p);
375	if (chosen)
376	get_task_struct(chosen);
377	rcu_read_unlock();
378
379	ppoints = chosen_points 1000 / totalpages;
380	return chosen;
381	}
382
383	/**
384	* dump_tasks - dump current memory state of all system tasks
385	* @memcg: current's memory controller, if constrained
386	* @nodemask: nodemask passed to page allocator for mempolicy ooms
387	*
388	* Dumps the current memory state of all eligible tasks. Tasks not in the same
389	* memcg, not in the same cpuset, or bound to a disjoint set of mempolicy nodes
390	* are not shown.
391	* State information includes task's pid, uid, tgid, vm size, rss, nr_ptes,
392	* swapents, oom_score_adj value, and name.
393	*/
394	static void dump_tasks(const struct mem_cgroup memcg, const nodemask_t nodemask)
395	{
396	struct task_struct *p;
397	struct task_struct *task;
398
399	pr_info("[ pid ] uid tgid total_vm rss nr_ptes swapents oom_score_adj name\n");
400	rcu_read_lock();
401	for_each_process(p) {
402	if (oom_unkillable_task(p, memcg, nodemask))
403	continue;
404
405	task = find_lock_task_mm(p);
406	if (!task) {
407	/*
408	* This is a kthread or all of p's threads have already
409	* detached their mm's. There's no need to report
410	* them; they can't be oom killed anyway.
411	*/
412	continue;
413	}
414
415	pr_info("[%5d] %5d %5d %8lu %8lu %7lu %8lu %5d %s\n",
416	task->pid, from_kuid(&init_user_ns, task_uid(task)),
417	task->tgid, task->mm->total_vm, get_mm_rss(task->mm),
418	task->mm->nr_ptes,
419	get_mm_counter(task->mm, MM_SWAPENTS),
420	task->signal->oom_score_adj, task->comm);
421	task_unlock(task);
422	}
423	rcu_read_unlock();
424	}
425
426	static void dump_header(struct task_struct *p, gfp_t gfp_mask, int order,
427	struct mem_cgroup memcg, const nodemask_t nodemask)
428	{
429	task_lock(current);
430	pr_warning("%s invoked oom-killer: gfp_mask=0x%x, order=%d, "
431	"oom_adj=%d, oom_score_adj=%d\n",
432	current->comm, gfp_mask, order, current->signal->oom_adj,
433	current->signal->oom_score_adj);
434	cpuset_print_task_mems_allowed(current);
435	task_unlock(current);
436	dump_stack();
437	mem_cgroup_print_oom_info(memcg, p);
438	show_mem(SHOW_MEM_FILTER_NODES);
439	if (sysctl_oom_dump_tasks)
440	dump_tasks(memcg, nodemask);
441	}
442
443	#define K(x) ((x) << (PAGE_SHIFT-10))
444	/*
445	* Must be called while holding a reference to p, which will be released upon
446	* returning.
447	*/
448	void oom_kill_process(struct task_struct *p, gfp_t gfp_mask, int order,
449	unsigned int points, unsigned long totalpages,
450	struct mem_cgroup memcg, nodemask_t nodemask,
451	const char *message)
452	{
453	struct task_struct *victim = p;
454	struct task_struct *child;
455	struct task_struct *t = p;
456	struct mm_struct *mm;
457	unsigned int victim_points = 0;
458	static DEFINE_RATELIMIT_STATE(oom_rs, DEFAULT_RATELIMIT_INTERVAL,
459	DEFAULT_RATELIMIT_BURST);
460
461	/*
462	* If the task is already exiting, don't alarm the sysadmin or kill
463	* its children or threads, just set TIF_MEMDIE so it can die quickly
464	*/
465	if (p->flags & PF_EXITING) {
466	set_tsk_thread_flag(p, TIF_MEMDIE);
467	put_task_struct(p);
468	return;
469	}
470
471	if (__ratelimit(&oom_rs))
472	dump_header(p, gfp_mask, order, memcg, nodemask);
473
474	task_lock(p);
475	pr_err("%s: Kill process %d (%s) score %d or sacrifice child\n",
476	message, task_pid_nr(p), p->comm, points);
477	task_unlock(p);
478
479	/*
480	* If any of p's children has a different mm and is eligible for kill,
481	* the one with the highest oom_badness() score is sacrificed for its
482	* parent. This attempts to lose the minimal amount of work done while
483	* still freeing memory.
484	*/
485	read_lock(&tasklist_lock);
486	do {
487	list_for_each_entry(child, &t->children, sibling) {
488	unsigned int child_points;
489
490	if (child->mm == p->mm)
491	continue;
492	/*
493	* oom_badness() returns 0 if the thread is unkillable
494	*/
495	child_points = oom_badness(child, memcg, nodemask,
496	totalpages);
497	if (child_points > victim_points) {
498	put_task_struct(victim);
499	victim = child;
500	victim_points = child_points;
501	get_task_struct(victim);
502	}
503	}
504	} while_each_thread(p, t);
505	read_unlock(&tasklist_lock);
506
507	rcu_read_lock();
508	p = find_lock_task_mm(victim);
509	if (!p) {
510	rcu_read_unlock();
511	put_task_struct(victim);
512	return;
513	} else if (victim != p) {
514	get_task_struct(p);
515	put_task_struct(victim);
516	victim = p;
517	}
518
519	/* mm cannot safely be dereferenced after task_unlock(victim) */
520	mm = victim->mm;
521	pr_err("Killed process %d (%s) total-vm:%lukB, anon-rss:%lukB, file-rss:%lukB\n",
522	task_pid_nr(victim), victim->comm, K(victim->mm->total_vm),
523	K(get_mm_counter(victim->mm, MM_ANONPAGES)),
524	K(get_mm_counter(victim->mm, MM_FILEPAGES)));
525	task_unlock(victim);
526
527	/*
528	* Kill all user processes sharing victim->mm in other thread groups, if
529	* any. They don't get access to memory reserves, though, to avoid
530	* depletion of all memory. This prevents mm->mmap_sem livelock when an
531	* oom killed thread cannot exit because it requires the semaphore and
532	* its contended by another thread trying to allocate memory itself.
533	* That thread will now get access to memory reserves since it has a
534	* pending fatal signal.
535	*/
536	for_each_process(p)
537	if (p->mm == mm && !same_thread_group(p, victim) &&
538	!(p->flags & PF_KTHREAD)) {
539	if (p->signal->oom_score_adj == OOM_SCORE_ADJ_MIN)
540	continue;
541
542	task_lock(p); /* Protect ->comm from prctl() */
543	pr_err("Kill process %d (%s) sharing same memory\n",
544	task_pid_nr(p), p->comm);
545	task_unlock(p);
546	do_send_sig_info(SIGKILL, SEND_SIG_FORCED, p, true);
547	}
548	rcu_read_unlock();
549
550	set_tsk_thread_flag(victim, TIF_MEMDIE);
551	do_send_sig_info(SIGKILL, SEND_SIG_FORCED, victim, true);
552	put_task_struct(victim);
553	}
554	#undef K
555
556	/*
557	* Determines whether the kernel must panic because of the panic_on_oom sysctl.
558	*/
559	void check_panic_on_oom(enum oom_constraint constraint, gfp_t gfp_mask,
560	int order, const nodemask_t *nodemask)
561	{
562	if (likely(!sysctl_panic_on_oom))
563	return;
564	if (sysctl_panic_on_oom != 2) {
565	/*
566	* panic_on_oom == 1 only affects CONSTRAINT_NONE, the kernel
567	* does not panic for cpuset, mempolicy, or memcg allocation
568	* failures.
569	*/
570	if (constraint != CONSTRAINT_NONE)
571	return;
572	}
573	dump_header(NULL, gfp_mask, order, NULL, nodemask);
574	panic("Out of memory: %s panic_on_oom is enabled\n",
575	sysctl_panic_on_oom == 2 ? "compulsory" : "system-wide");
576	}
577
578	static BLOCKING_NOTIFIER_HEAD(oom_notify_list);
579
580	int register_oom_notifier(struct notifier_block *nb)
581	{
582	return blocking_notifier_chain_register(&oom_notify_list, nb);
583	}
584	EXPORT_SYMBOL_GPL(register_oom_notifier);
585
586	int unregister_oom_notifier(struct notifier_block *nb)
587	{
588	return blocking_notifier_chain_unregister(&oom_notify_list, nb);
589	}
590	EXPORT_SYMBOL_GPL(unregister_oom_notifier);
591
592	/*
593	* Try to acquire the OOM killer lock for the zones in zonelist. Returns zero
594	* if a parallel OOM killing is already taking place that includes a zone in
595	* the zonelist. Otherwise, locks all zones in the zonelist and returns 1.
596	*/
597	int try_set_zonelist_oom(struct zonelist *zonelist, gfp_t gfp_mask)
598	{
599	struct zoneref *z;
600	struct zone *zone;
601	int ret = 1;
602
603	spin_lock(&zone_scan_lock);
604	for_each_zone_zonelist(zone, z, zonelist, gfp_zone(gfp_mask)) {
605	if (zone_is_oom_locked(zone)) {
606	ret = 0;
607	goto out;
608	}
609	}
610
611	for_each_zone_zonelist(zone, z, zonelist, gfp_zone(gfp_mask)) {
612	/*
613	* Lock each zone in the zonelist under zone_scan_lock so a
614	* parallel invocation of try_set_zonelist_oom() doesn't succeed
615	* when it shouldn't.
616	*/
617	zone_set_flag(zone, ZONE_OOM_LOCKED);
618	}
619
620	out:
621	spin_unlock(&zone_scan_lock);
622	return ret;
623	}
624
625	/*
626	* Clears the ZONE_OOM_LOCKED flag for all zones in the zonelist so that failed
627	* allocation attempts with zonelists containing them may now recall the OOM
628	* killer, if necessary.
629	*/
630	void clear_zonelist_oom(struct zonelist *zonelist, gfp_t gfp_mask)
631	{
632	struct zoneref *z;
633	struct zone *zone;
634
635	spin_lock(&zone_scan_lock);
636	for_each_zone_zonelist(zone, z, zonelist, gfp_zone(gfp_mask)) {
637	zone_clear_flag(zone, ZONE_OOM_LOCKED);
638	}
639	spin_unlock(&zone_scan_lock);
640	}
641
642	/*
643	* Try to acquire the oom killer lock for all system zones. Returns zero if a
644	* parallel oom killing is taking place, otherwise locks all zones and returns
645	* non-zero.
646	*/
647	static int try_set_system_oom(void)
648	{
649	struct zone *zone;
650	int ret = 1;
651
652	spin_lock(&zone_scan_lock);
653	for_each_populated_zone(zone)
654	if (zone_is_oom_locked(zone)) {
655	ret = 0;
656	goto out;
657	}
658	for_each_populated_zone(zone)
659	zone_set_flag(zone, ZONE_OOM_LOCKED);
660	out:
661	spin_unlock(&zone_scan_lock);
662	return ret;
663	}
664
665	/*
666	* Clears ZONE_OOM_LOCKED for all system zones so that failed allocation
667	* attempts or page faults may now recall the oom killer, if necessary.
668	*/
669	static void clear_system_oom(void)
670	{
671	struct zone *zone;
672
673	spin_lock(&zone_scan_lock);
674	for_each_populated_zone(zone)
675	zone_clear_flag(zone, ZONE_OOM_LOCKED);
676	spin_unlock(&zone_scan_lock);
677	}
678
679	/**
680	* out_of_memory - kill the "best" process when we run out of memory
681	* @zonelist: zonelist pointer
682	* @gfp_mask: memory allocation flags
683	* @order: amount of memory being requested as a power of 2
684	* @nodemask: nodemask passed to page allocator
685	* @force_kill: true if a task must be killed, even if others are exiting
686	*
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.
691	*/
692	void out_of_memory(struct zonelist *zonelist, gfp_t gfp_mask,
693	int order, nodemask_t *nodemask, bool force_kill)
694	{
695	const nodemask_t *mpol_mask;
696	struct task_struct *p;
697	unsigned long totalpages;
698	unsigned long freed = 0;
699	unsigned int uninitialized_var(points);
700	enum oom_constraint constraint = CONSTRAINT_NONE;
701	int killed = 0;
702
703	blocking_notifier_call_chain(&oom_notify_list, 0, &freed);
704	if (freed > 0)
705	/* Got some memory back in the last second. */
706	return;
707
708	/*
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
711	* its memory.
712	*/
713	if (fatal_signal_pending(current)) {
714	set_thread_flag(TIF_MEMDIE);
715	return;
716	}
717
718	/*
719	* Check if there were limitations on the allocation (only relevant for
720	* NUMA) that may require different handling.
721	*/
722	constraint = constrained_alloc(zonelist, gfp_mask, nodemask,
723	&totalpages);
724	mpol_mask = (constraint == CONSTRAINT_MEMORY_POLICY) ? nodemask : NULL;
725	check_panic_on_oom(constraint, gfp_mask, order, mpol_mask);
726
727	if (sysctl_oom_kill_allocating_task && current->mm &&
728	!oom_unkillable_task(current, NULL, nodemask) &&
729	current->signal->oom_score_adj != OOM_SCORE_ADJ_MIN) {
730	get_task_struct(current);
731	oom_kill_process(current, gfp_mask, order, 0, totalpages, NULL,
732	nodemask,
733	"Out of memory (oom_kill_allocating_task)");
734	goto out;
735	}
736
737	p = select_bad_process(&points, totalpages, mpol_mask, force_kill);
738	/* Found nothing?!?! Either we hang forever, or we panic. */
739	if (!p) {
740	dump_header(NULL, gfp_mask, order, NULL, mpol_mask);
741	panic("Out of memory and no killable processes...\n");
742	}
743	if (PTR_ERR(p) != -1UL) {
744	oom_kill_process(p, gfp_mask, order, points, totalpages, NULL,
745	nodemask, "Out of memory");
746	killed = 1;
747	}
748	out:
749	/*
750	* Give the killed threads a good chance of exiting before trying to
751	* allocate memory again.
752	*/
753	if (killed)
754	schedule_timeout_killable(1);
755	}
756
757	/*
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.
762	*/
763	void pagefault_out_of_memory(void)
764	{
765	if (try_set_system_oom()) {
766	out_of_memory(NULL, 0, 0, NULL, false);
767	clear_system_oom();
768	}
769	schedule_timeout_killable(1);
770	}
771

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