summaryrefslogtreecommitdiff
path: root/mm/oom_kill.c
blob: 612b5597d3af44610efde5474823298836de686d (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
// SPDX-License-Identifier: GPL-2.0-only
/*
 *  linux/mm/oom_kill.c
 * 
 *  Copyright (C)  1998,2000  Rik van Riel
 *	Thanks go out to Claus Fischer for some serious inspiration and
 *	for goading me into coding this file...
 *  Copyright (C)  2010  Google, Inc.
 *	Rewritten by David Rientjes
 *
 *  The routines in this file are used to kill a process when
 *  we're seriously out of memory. This gets called from __alloc_pages()
 *  in mm/page_alloc.c when we really run out of memory.
 *
 *  Since we won't call these routines often (on a well-configured
 *  machine) this file will double as a 'coding guide' and a signpost
 *  for newbie kernel hackers. It features several pointers to major
 *  kernel subsystems and hints as to where to find out what things do.
 */

#include <linux/oom.h>
#include <linux/mm.h>
#include <linux/err.h>
#include <linux/gfp.h>
#include <linux/sched.h>
#include <linux/sched/mm.h>
#include <linux/sched/coredump.h>
#include <linux/sched/task.h>
#include <linux/sched/debug.h>
#include <linux/swap.h>
#include <linux/syscalls.h>
#include <linux/timex.h>
#include <linux/jiffies.h>
#include <linux/cpuset.h>
#include <linux/export.h>
#include <linux/notifier.h>
#include <linux/memcontrol.h>
#include <linux/mempolicy.h>
#include <linux/security.h>
#include <linux/ptrace.h>
#include <linux/freezer.h>
#include <linux/ftrace.h>
#include <linux/ratelimit.h>
#include <linux/kthread.h>
#include <linux/init.h>
#include <linux/mmu_notifier.h>

#include <asm/tlb.h>
#include "internal.h"
#include "slab.h"

#define CREATE_TRACE_POINTS
#include <trace/events/oom.h>

static int sysctl_panic_on_oom;
static int sysctl_oom_kill_allocating_task;
static int sysctl_oom_dump_tasks = 1;

/*
 * Serializes oom killer invocations (out_of_memory()) from all contexts to
 * prevent from over eager oom killing (e.g. when the oom killer is invoked
 * from different domains).
 *
 * oom_killer_disable() relies on this lock to stabilize oom_killer_disabled
 * and mark_oom_victim
 */
DEFINE_MUTEX(oom_lock);
/* Serializes oom_score_adj and oom_score_adj_min updates */
DEFINE_MUTEX(oom_adj_mutex);

static inline bool is_memcg_oom(struct oom_control *oc)
{
	return oc->memcg != NULL;
}

#ifdef CONFIG_NUMA
/**
 * oom_cpuset_eligible() - check task eligibility for kill
 * @start: task struct of which task to consider
 * @oc: pointer to struct oom_control
 *
 * Task eligibility is determined by whether or not a candidate task, @tsk,
 * shares the same mempolicy nodes as current if it is bound by such a policy
 * and whether or not it has the same set of allowed cpuset nodes.
 *
 * This function is assuming oom-killer context and 'current' has triggered
 * the oom-killer.
 */
static bool oom_cpuset_eligible(struct task_struct *start,
				struct oom_control *oc)
{
	struct task_struct *tsk;
	bool ret = false;
	const nodemask_t *mask = oc->nodemask;

	rcu_read_lock();
	for_each_thread(start, tsk) {
		if (mask) {
			/*
			 * If this is a mempolicy constrained oom, tsk's
			 * cpuset is irrelevant.  Only return true if its
			 * mempolicy intersects current, otherwise it may be
			 * needlessly killed.
			 */
			ret = mempolicy_in_oom_domain(tsk, mask);
		} else {
			/*
			 * This is not a mempolicy constrained oom, so only
			 * check the mems of tsk's cpuset.
			 */
			ret = cpuset_mems_allowed_intersects(current, tsk);
		}
		if (ret)
			break;
	}
	rcu_read_unlock();

	return ret;
}
#else
static bool oom_cpuset_eligible(struct task_struct *tsk, struct oom_control *oc)
{
	return true;
}
#endif /* CONFIG_NUMA */

/*
 * The process p may have detached its own ->mm while exiting or through
 * kthread_use_mm(), but one or more of its subthreads may still have a valid
 * pointer.  Return p, or any of its subthreads with a valid ->mm, with
 * task_lock() held.
 */
struct task_struct *find_lock_task_mm(struct task_struct *p)
{
	struct task_struct *t;

	rcu_read_lock();

	for_each_thread(p, t) {
		task_lock(t);
		if (likely(t->mm))
			goto found;
		task_unlock(t);
	}
	t = NULL;
found:
	rcu_read_unlock();

	return t;
}

/*
 * order == -1 means the oom kill is required by sysrq, otherwise only
 * for display purposes.
 */
static inline bool is_sysrq_oom(struct oom_control *oc)
{
	return oc->order == -1;
}

/* return true if the task is not adequate as candidate victim task. */
static bool oom_unkillable_task(struct task_struct *p)
{
	if (is_global_init(p))
		return true;
	if (p->flags & PF_KTHREAD)
		return true;
	return false;
}

/*
 * Check whether unreclaimable slab amount is greater than
 * all user memory(LRU pages).
 * dump_unreclaimable_slab() could help in the case that
 * oom due to too much unreclaimable slab used by kernel.
*/
static bool should_dump_unreclaim_slab(void)
{
	unsigned long nr_lru;

	nr_lru = global_node_page_state(NR_ACTIVE_ANON) +
		 global_node_page_state(NR_INACTIVE_ANON) +
		 global_node_page_state(NR_ACTIVE_FILE) +
		 global_node_page_state(NR_INACTIVE_FILE) +
		 global_node_page_state(NR_ISOLATED_ANON) +
		 global_node_page_state(NR_ISOLATED_FILE) +
		 global_node_page_state(NR_UNEVICTABLE);

	return (global_node_page_state_pages(NR_SLAB_UNRECLAIMABLE_B) > nr_lru);
}

/**
 * oom_badness - heuristic function to determine which candidate task to kill
 * @p: task struct of which task we should calculate
 * @totalpages: total present RAM allowed for page allocation
 *
 * The heuristic for determining which task to kill is made to be as simple and
 * predictable as possible.  The goal is to return the highest value for the
 * task consuming the most memory to avoid subsequent oom failures.
 */
long oom_badness(struct task_struct *p, unsigned long totalpages)
{
	long points;
	long adj;

	if (oom_unkillable_task(p))
		return LONG_MIN;

	p = find_lock_task_mm(p);
	if (!p)
		return LONG_MIN;

	/*
	 * Do not even consider tasks which are explicitly marked oom
	 * unkillable or have been already oom reaped or the are in
	 * the middle of vfork
	 */
	adj = (long)p->signal->oom_score_adj;
	if (adj == OOM_SCORE_ADJ_MIN ||
			test_bit(MMF_OOM_SKIP, &p->mm->flags) ||
			in_vfork(p)) {
		task_unlock(p);
		return LONG_MIN;
	}

	/*
	 * The baseline for the badness score is the proportion of RAM that each
	 * task's rss, pagetable and swap space use.
	 */
	points = get_mm_rss(p->mm) + get_mm_counter(p->mm, MM_SWAPENTS) +
		mm_pgtables_bytes(p->mm) / PAGE_SIZE;
	task_unlock(p);

	/* Normalize to oom_score_adj units */
	adj *= totalpages / 1000;
	points += adj;

	return points;
}

static const char * const oom_constraint_text[] = {
	[CONSTRAINT_NONE] = "CONSTRAINT_NONE",
	[CONSTRAINT_CPUSET] = "CONSTRAINT_CPUSET",
	[CONSTRAINT_MEMORY_POLICY] = "CONSTRAINT_MEMORY_POLICY",
	[CONSTRAINT_MEMCG] = "CONSTRAINT_MEMCG",
};

/*
 * Determine the type of allocation constraint.
 */
static enum oom_constraint constrained_alloc(struct oom_control *oc)
{
	struct zone *zone;
	struct zoneref *z;
	enum zone_type highest_zoneidx = gfp_zone(oc->gfp_mask);
	bool cpuset_limited = false;
	int nid;

	if (is_memcg_oom(oc)) {
		oc->totalpages = mem_cgroup_get_max(oc->memcg) ?: 1;
		return CONSTRAINT_MEMCG;
	}

	/* Default to all available memory */
	oc->totalpages = totalram_pages() + total_swap_pages;

	if (!IS_ENABLED(CONFIG_NUMA))
		return CONSTRAINT_NONE;

	if (!oc->zonelist)
		return CONSTRAINT_NONE;
	/*
	 * Reach here only when __GFP_NOFAIL is used. So, we should avoid
	 * to kill current.We have to random task kill in this case.
	 * Hopefully, CONSTRAINT_THISNODE...but no way to handle it, now.
	 */
	if (oc->gfp_mask & __GFP_THISNODE)
		return CONSTRAINT_NONE;

	/*
	 * This is not a __GFP_THISNODE allocation, so a truncated nodemask in
	 * the page allocator means a mempolicy is in effect.  Cpuset policy
	 * is enforced in get_page_from_freelist().
	 */
	if (oc->nodemask &&
	    !nodes_subset(node_states[N_MEMORY], *oc->nodemask)) {
		oc->totalpages = total_swap_pages;
		for_each_node_mask(nid, *oc->nodemask)
			oc->totalpages += node_present_pages(nid);
		return CONSTRAINT_MEMORY_POLICY;
	}

	/* Check this allocation failure is caused by cpuset's wall function */
	for_each_zone_zonelist_nodemask(zone, z, oc->zonelist,
			highest_zoneidx, oc->nodemask)
		if (!cpuset_zone_allowed(zone, oc->gfp_mask))
			cpuset_limited = true;

	if (cpuset_limited) {
		oc->totalpages = total_swap_pages;
		for_each_node_mask(nid, cpuset_current_mems_allowed)
			oc->totalpages += node_present_pages(nid);
		return CONSTRAINT_CPUSET;
	}
	return CONSTRAINT_NONE;
}

static int oom_evaluate_task(struct task_struct *task, void *arg)
{
	struct oom_control *oc = arg;
	long points;

	if (oom_unkillable_task(task))
		goto next;

	/* p may not have freeable memory in nodemask */
	if (!is_memcg_oom(oc) && !oom_cpuset_eligible(task, oc))
		goto next;

	/*
	 * This task already has access to memory reserves and is being killed.
	 * Don't allow any other task to have access to the reserves unless
	 * the task has MMF_OOM_SKIP because chances that it would release
	 * any memory is quite low.
	 */
	if (!is_sysrq_oom(oc) && tsk_is_oom_victim(task)) {
		if (test_bit(MMF_OOM_SKIP, &task->signal->oom_mm->flags))
			goto next;
		goto abort;
	}

	/*
	 * If task is allocating a lot of memory and has been marked to be
	 * killed first if it triggers an oom, then select it.
	 */
	if (oom_task_origin(task)) {
		points = LONG_MAX;
		goto select;
	}

	points = oom_badness(task, oc->totalpages);
	if (points == LONG_MIN || points < oc->chosen_points)
		goto next;

select:
	if (oc->chosen)
		put_task_struct(oc->chosen);
	get_task_struct(task);
	oc->chosen = task;
	oc->chosen_points = points;
next:
	return 0;
abort:
	if (oc->chosen)
		put_task_struct(oc->chosen);
	oc->chosen = (void *)-1UL;
	return 1;
}

/*
 * Simple selection loop. We choose the process with the highest number of
 * 'points'. In case scan was aborted, oc->chosen is set to -1.
 */
static void select_bad_process(struct oom_control *oc)
{
	oc->chosen_points = LONG_MIN;

	if (is_memcg_oom(oc))
		mem_cgroup_scan_tasks(oc->memcg, oom_evaluate_task, oc);
	else {
		struct task_struct *p;

		rcu_read_lock();
		for_each_process(p)
			if (oom_evaluate_task(p, oc))
				break;
		rcu_read_unlock();
	}
}

static int dump_task(struct task_struct *p, void *arg)
{
	struct oom_control *oc = arg;
	struct task_struct *task;

	if (oom_unkillable_task(p))
		return 0;

	/* p may not have freeable memory in nodemask */
	if (!is_memcg_oom(oc) && !oom_cpuset_eligible(p, oc))
		return 0;

	task = find_lock_task_mm(p);
	if (!task) {
		/*
		 * All of p's threads have already detached their mm's. There's
		 * no need to report them; they can't be oom killed anyway.
		 */
		return 0;
	}

	pr_info("[%7d] %5d %5d %8lu %8lu %8ld %8lu         %5hd %s\n",
		task->pid, from_kuid(&init_user_ns, task_uid(task)),
		task->tgid, task->mm->total_vm, get_mm_rss(task->mm),
		mm_pgtables_bytes(task->mm),
		get_mm_counter(task->mm, MM_SWAPENTS),
		task->signal->oom_score_adj, task->comm);
	task_unlock(task);

	return 0;
}

/**
 * dump_tasks - dump current memory state of all system tasks
 * @oc: pointer to struct oom_control
 *
 * Dumps the current memory state of all eligible tasks.  Tasks not in the same
 * memcg, not in the same cpuset, or bound to a disjoint set of mempolicy nodes
 * are not shown.
 * State information includes task's pid, uid, tgid, vm size, rss,
 * pgtables_bytes, swapents, oom_score_adj value, and name.
 */
static void dump_tasks(struct oom_control *oc)
{
	pr_info("Tasks state (memory values in pages):\n");
	pr_info("[  pid  ]   uid  tgid total_vm      rss pgtables_bytes swapents oom_score_adj name\n");

	if (is_memcg_oom(oc))
		mem_cgroup_scan_tasks(oc->memcg, dump_task, oc);
	else {
		struct task_struct *p;

		rcu_read_lock();
		for_each_process(p)
			dump_task(p, oc);
		rcu_read_unlock();
	}
}

static void dump_oom_summary(struct oom_control *oc, struct task_struct *victim)
{
	/* one line summary of the oom killer context. */
	pr_info("oom-kill:constraint=%s,nodemask=%*pbl",
			oom_constraint_text[oc->constraint],
			nodemask_pr_args(oc->nodemask));
	cpuset_print_current_mems_allowed();
	mem_cgroup_print_oom_context(oc->memcg, victim);
	pr_cont(",task=%s,pid=%d,uid=%d\n", victim->comm, victim->pid,
		from_kuid(&init_user_ns, task_uid(victim)));
}

static void dump_header(struct oom_control *oc, struct task_struct *p)
{
	pr_warn("%s invoked oom-killer: gfp_mask=%#x(%pGg), order=%d, oom_score_adj=%hd\n",
		current->comm, oc->gfp_mask, &oc->gfp_mask, oc->order,
			current->signal->oom_score_adj);
	if (!IS_ENABLED(CONFIG_COMPACTION) && oc->order)
		pr_warn("COMPACTION is disabled!!!\n");

	dump_stack();
	if (is_memcg_oom(oc))
		mem_cgroup_print_oom_meminfo(oc->memcg);
	else {
		__show_mem(SHOW_MEM_FILTER_NODES, oc->nodemask, gfp_zone(oc->gfp_mask));
		if (should_dump_unreclaim_slab())
			dump_unreclaimable_slab();
	}
	if (sysctl_oom_dump_tasks)
		dump_tasks(oc);
	if (p)
		dump_oom_summary(oc, p);
}

/*
 * Number of OOM victims in flight
 */
static atomic_t oom_victims = ATOMIC_INIT(0);
static DECLARE_WAIT_QUEUE_HEAD(oom_victims_wait);

static bool oom_killer_disabled __read_mostly;

#define K(x) ((x) << (PAGE_SHIFT-10))

/*
 * task->mm can be NULL if the task is the exited group leader.  So to
 * determine whether the task is using a particular mm, we examine all the
 * task's threads: if one of those is using this mm then this task was also
 * using it.
 */
bool process_shares_mm(struct task_struct *p, struct mm_struct *mm)
{
	struct task_struct *t;

	for_each_thread(p, t) {
		struct mm_struct *t_mm = READ_ONCE(t->mm);
		if (t_mm)
			return t_mm == mm;
	}
	return false;
}

#ifdef CONFIG_MMU
/*
 * OOM Reaper kernel thread which tries to reap the memory used by the OOM
 * victim (if that is possible) to help the OOM killer to move on.
 */
static struct task_struct *oom_reaper_th;
static DECLARE_WAIT_QUEUE_HEAD(oom_reaper_wait);
static struct task_struct *oom_reaper_list;
static DEFINE_SPINLOCK(oom_reaper_lock);

static bool __oom_reap_task_mm(struct mm_struct *mm)
{
	struct vm_area_struct *vma;
	bool ret = true;
	VMA_ITERATOR(vmi, mm, 0);

	/*
	 * Tell all users of get_user/copy_from_user etc... that the content
	 * is no longer stable. No barriers really needed because unmapping
	 * should imply barriers already and the reader would hit a page fault
	 * if it stumbled over a reaped memory.
	 */
	set_bit(MMF_UNSTABLE, &mm->flags);

	for_each_vma(vmi, vma) {
		if (vma->vm_flags & (VM_HUGETLB|VM_PFNMAP))
			continue;

		/*
		 * Only anonymous pages have a good chance to be dropped
		 * without additional steps which we cannot afford as we
		 * are OOM already.
		 *
		 * We do not even care about fs backed pages because all
		 * which are reclaimable have already been reclaimed and
		 * we do not want to block exit_mmap by keeping mm ref
		 * count elevated without a good reason.
		 */
		if (vma_is_anonymous(vma) || !(vma->vm_flags & VM_SHARED)) {
			struct mmu_notifier_range range;
			struct mmu_gather tlb;

			mmu_notifier_range_init(&range, MMU_NOTIFY_UNMAP, 0,
						mm, vma->vm_start,
						vma->vm_end);
			tlb_gather_mmu(&tlb, mm);
			if (mmu_notifier_invalidate_range_start_nonblock(&range)) {
				tlb_finish_mmu(&tlb);
				ret = false;
				continue;
			}
			unmap_page_range(&tlb, vma, range.start, range.end, NULL);
			mmu_notifier_invalidate_range_end(&range);
			tlb_finish_mmu(&tlb);
		}
	}

	return ret;
}

/*
 * Reaps the address space of the give task.
 *
 * Returns true on success and false if none or part of the address space
 * has been reclaimed and the caller should retry later.
 */
static bool oom_reap_task_mm(struct task_struct *tsk, struct mm_struct *mm)
{
	bool ret = true;

	if (!mmap_read_trylock(mm)) {
		trace_skip_task_reaping(tsk->pid);
		return false;
	}

	/*
	 * MMF_OOM_SKIP is set by exit_mmap when the OOM reaper can't
	 * work on the mm anymore. The check for MMF_OOM_SKIP must run
	 * under mmap_lock for reading because it serializes against the
	 * mmap_write_lock();mmap_write_unlock() cycle in exit_mmap().
	 */
	if (test_bit(MMF_OOM_SKIP, &mm->flags)) {
		trace_skip_task_reaping(tsk->pid);
		goto out_unlock;
	}

	trace_start_task_reaping(tsk->pid);

	/* failed to reap part of the address space. Try again later */
	ret = __oom_reap_task_mm(mm);
	if (!ret)
		goto out_finish;

	pr_info("oom_reaper: reaped process %d (%s), now anon-rss:%lukB, file-rss:%lukB, shmem-rss:%lukB\n",
			task_pid_nr(tsk), tsk->comm,
			K(get_mm_counter(mm, MM_ANONPAGES)),
			K(get_mm_counter(mm, MM_FILEPAGES)),
			K(get_mm_counter(mm, MM_SHMEMPAGES)));
out_finish:
	trace_finish_task_reaping(tsk->pid);
out_unlock:
	mmap_read_unlock(mm);

	return ret;
}

#define MAX_OOM_REAP_RETRIES 10
static void oom_reap_task(struct task_struct *tsk)
{
	int attempts = 0;
	struct mm_struct *mm = tsk->signal->oom_mm;

	/* Retry the mmap_read_trylock(mm) a few times */
	while (attempts++ < MAX_OOM_REAP_RETRIES && !oom_reap_task_mm(tsk, mm))
		schedule_timeout_idle(HZ/10);

	if (attempts <= MAX_OOM_REAP_RETRIES ||
	    test_bit(MMF_OOM_SKIP, &mm->flags))
		goto done;

	pr_info("oom_reaper: unable to reap pid:%d (%s)\n",
		task_pid_nr(tsk), tsk->comm);
	sched_show_task(tsk);
	debug_show_all_locks();

done:
	tsk->oom_reaper_list = NULL;

	/*
	 * Hide this mm from OOM killer because it has been either reaped or
	 * somebody can't call mmap_write_unlock(mm).
	 */
	set_bit(MMF_OOM_SKIP, &mm->flags);

	/* Drop a reference taken by queue_oom_reaper */
	put_task_struct(tsk);
}

static int oom_reaper(void *unused)
{
	set_freezable();

	while (true) {
		struct task_struct *tsk = NULL;

		wait_event_freezable(oom_reaper_wait, oom_reaper_list != NULL);
		spin_lock_irq(&oom_reaper_lock);
		if (oom_reaper_list != NULL) {
			tsk = oom_reaper_list;
			oom_reaper_list = tsk->oom_reaper_list;
		}
		spin_unlock_irq(&oom_reaper_lock);

		if (tsk)
			oom_reap_task(tsk);
	}

	return 0;
}

static void wake_oom_reaper(struct timer_list *timer)
{
	struct task_struct *tsk = container_of(timer, struct task_struct,
			oom_reaper_timer);
	struct mm_struct *mm = tsk->signal->oom_mm;
	unsigned long flags;

	/* The victim managed to terminate on its own - see exit_mmap */
	if (test_bit(MMF_OOM_SKIP, &mm->flags)) {
		put_task_struct(tsk);
		return;
	}

	spin_lock_irqsave(&oom_reaper_lock, flags);
	tsk->oom_reaper_list = oom_reaper_list;
	oom_reaper_list = tsk;
	spin_unlock_irqrestore(&oom_reaper_lock, flags);
	trace_wake_reaper(tsk->pid);
	wake_up(&oom_reaper_wait);
}

/*
 * Give the OOM victim time to exit naturally before invoking the oom_reaping.
 * The timers timeout is arbitrary... the longer it is, the longer the worst
 * case scenario for the OOM can take. If it is too small, the oom_reaper can
 * get in the way and release resources needed by the process exit path.
 * e.g. The futex robust list can sit in Anon|Private memory that gets reaped
 * before the exit path is able to wake the futex waiters.
 */
#define OOM_REAPER_DELAY (2*HZ)
static void queue_oom_reaper(struct task_struct *tsk)
{
	/* mm is already queued? */
	if (test_and_set_bit(MMF_OOM_REAP_QUEUED, &tsk->signal->oom_mm->flags))
		return;

	get_task_struct(tsk);
	timer_setup(&tsk->oom_reaper_timer, wake_oom_reaper, 0);
	tsk->oom_reaper_timer.expires = jiffies + OOM_REAPER_DELAY;
	add_timer(&tsk->oom_reaper_timer);
}

#ifdef CONFIG_SYSCTL
static struct ctl_table vm_oom_kill_table[] = {
	{
		.procname	= "panic_on_oom",
		.data		= &sysctl_panic_on_oom,
		.maxlen		= sizeof(sysctl_panic_on_oom),
		.mode		= 0644,
		.proc_handler	= proc_dointvec_minmax,
		.extra1		= SYSCTL_ZERO,
		.extra2		= SYSCTL_TWO,
	},
	{
		.procname	= "oom_kill_allocating_task",
		.data		= &sysctl_oom_kill_allocating_task,
		.maxlen		= sizeof(sysctl_oom_kill_allocating_task),
		.mode		= 0644,
		.proc_handler	= proc_dointvec,
	},
	{
		.procname	= "oom_dump_tasks",
		.data		= &sysctl_oom_dump_tasks,
		.maxlen		= sizeof(sysctl_oom_dump_tasks),
		.mode		= 0644,
		.proc_handler	= proc_dointvec,
	},
	{}
};
#endif

static int __init oom_init(void)
{
	oom_reaper_th = kthread_run(oom_reaper, NULL, "oom_reaper");
#ifdef CONFIG_SYSCTL
	register_sysctl_init("vm", vm_oom_kill_table);
#endif
	return 0;
}
subsys_initcall(oom_init)
#else
static inline void queue_oom_reaper(struct task_struct *tsk)
{
}
#endif /* CONFIG_MMU */

/**
 * mark_oom_victim - mark the given task as OOM victim
 * @tsk: task to mark
 *
 * Has to be called with oom_lock held and never after
 * oom has been disabled already.
 *
 * tsk->mm has to be non NULL and caller has to guarantee it is stable (either
 * under task_lock or operate on the current).
 */
static void mark_oom_victim(struct task_struct *tsk)
{
	struct mm_struct *mm = tsk->mm;

	WARN_ON(oom_killer_disabled);
	/* OOM killer might race with memcg OOM */
	if (test_and_set_tsk_thread_flag(tsk, TIF_MEMDIE))
		return;

	/* oom_mm is bound to the signal struct life time. */
	if (!cmpxchg(&tsk->signal->oom_mm, NULL, mm))
		mmgrab(tsk->signal->oom_mm);

	/*
	 * Make sure that the task is woken up from uninterruptible sleep
	 * if it is frozen because OOM killer wouldn't be able to free
	 * any memory and livelock. freezing_slow_path will tell the freezer
	 * that TIF_MEMDIE tasks should be ignored.
	 */
	__thaw_task(tsk);
	atomic_inc(&oom_victims);
	trace_mark_victim(tsk->pid);
}

/**
 * exit_oom_victim - note the exit of an OOM victim
 */
void exit_oom_victim(void)
{
	clear_thread_flag(TIF_MEMDIE);

	if (!atomic_dec_return(&oom_victims))
		wake_up_all(&oom_victims_wait);
}

/**
 * oom_killer_enable - enable OOM killer
 */
void oom_killer_enable(void)
{
	oom_killer_disabled = false;
	pr_info("OOM killer enabled.\n");
}

/**
 * oom_killer_disable - disable OOM killer
 * @timeout: maximum timeout to wait for oom victims in jiffies
 *
 * Forces all page allocations to fail rather than trigger OOM killer.
 * Will block and wait until all OOM victims are killed or the given
 * timeout expires.
 *
 * The function cannot be called when there are runnable user tasks because
 * the userspace would see unexpected allocation failures as a result. Any
 * new usage of this function should be consulted with MM people.
 *
 * Returns true if successful and false if the OOM killer cannot be
 * disabled.
 */
bool oom_killer_disable(signed long timeout)
{
	signed long ret;

	/*
	 * Make sure to not race with an ongoing OOM killer. Check that the
	 * current is not killed (possibly due to sharing the victim's memory).
	 */
	if (mutex_lock_killable(&oom_lock))
		return false;
	oom_killer_disabled = true;
	mutex_unlock(&oom_lock);

	ret = wait_event_interruptible_timeout(oom_victims_wait,
			!atomic_read(&oom_victims), timeout);
	if (ret <= 0) {
		oom_killer_enable();
		return false;
	}
	pr_info("OOM killer disabled.\n");

	return true;
}

static inline bool __task_will_free_mem(struct task_struct *task)
{
	struct signal_struct *sig = task->signal;

	/*
	 * A coredumping process may sleep for an extended period in
	 * coredump_task_exit(), so the oom killer cannot assume that
	 * the process will promptly exit and release memory.
	 */
	if (sig->core_state)
		return false;

	if (sig->flags & SIGNAL_GROUP_EXIT)
		return true;

	if (thread_group_empty(task) && (task->flags & PF_EXITING))
		return true;

	return false;
}

/*
 * Checks whether the given task is dying or exiting and likely to
 * release its address space. This means that all threads and processes
 * sharing the same mm have to be killed or exiting.
 * Caller has to make sure that task->mm is stable (hold task_lock or
 * it operates on the current).
 */
static bool task_will_free_mem(struct task_struct *task)
{
	struct mm_struct *mm = task->mm;
	struct task_struct *p;
	bool ret = true;

	/*
	 * Skip tasks without mm because it might have passed its exit_mm and
	 * exit_oom_victim. oom_reaper could have rescued that but do not rely
	 * on that for now. We can consider find_lock_task_mm in future.
	 */
	if (!mm)
		return false;

	if (!__task_will_free_mem(task))
		return false;

	/*
	 * This task has already been drained by the oom reaper so there are
	 * only small chances it will free some more
	 */
	if (test_bit(MMF_OOM_SKIP, &mm->flags))
		return false;

	if (atomic_read(&mm->mm_users) <= 1)
		return true;

	/*
	 * Make sure that all tasks which share the mm with the given tasks
	 * are dying as well to make sure that a) nobody pins its mm and
	 * b) the task is also reapable by the oom reaper.
	 */
	rcu_read_lock();
	for_each_process(p) {
		if (!process_shares_mm(p, mm))
			continue;
		if (same_thread_group(task, p))
			continue;
		ret = __task_will_free_mem(p);
		if (!ret)
			break;
	}
	rcu_read_unlock();

	return ret;
}

static void __oom_kill_process(struct task_struct *victim, const char *message)
{
	struct task_struct *p;
	struct mm_struct *mm;
	bool can_oom_reap = true;

	p = find_lock_task_mm(victim);
	if (!p) {
		pr_info("%s: OOM victim %d (%s) is already exiting. Skip killing the task\n",
			message, task_pid_nr(victim), victim->comm);
		put_task_struct(victim);
		return;
	} else if (victim != p) {
		get_task_struct(p);
		put_task_struct(victim);
		victim = p;
	}

	/* Get a reference to safely compare mm after task_unlock(victim) */
	mm = victim->mm;
	mmgrab(mm);

	/* Raise event before sending signal: task reaper must see this */
	count_vm_event(OOM_KILL);
	memcg_memory_event_mm(mm, MEMCG_OOM_KILL);

	/*
	 * We should send SIGKILL before granting access to memory reserves
	 * in order to prevent the OOM victim from depleting the memory
	 * reserves from the user space under its control.
	 */
	do_send_sig_info(SIGKILL, SEND_SIG_PRIV, victim, PIDTYPE_TGID);
	mark_oom_victim(victim);
	pr_err("%s: Killed process %d (%s) total-vm:%lukB, anon-rss:%lukB, file-rss:%lukB, shmem-rss:%lukB, UID:%u pgtables:%lukB oom_score_adj:%hd\n",
		message, task_pid_nr(victim), victim->comm, K(mm->total_vm),
		K(get_mm_counter(mm, MM_ANONPAGES)),
		K(get_mm_counter(mm, MM_FILEPAGES)),
		K(get_mm_counter(mm, MM_SHMEMPAGES)),
		from_kuid(&init_user_ns, task_uid(victim)),
		mm_pgtables_bytes(mm) >> 10, victim->signal->oom_score_adj);
	task_unlock(victim);

	/*
	 * Kill all user processes sharing victim->mm in other thread groups, if
	 * any.  They don't get access to memory reserves, though, to avoid
	 * depletion of all memory.  This prevents mm->mmap_lock livelock when an
	 * oom killed thread cannot exit because it requires the semaphore and
	 * its contended by another thread trying to allocate memory itself.
	 * That thread will now get access to memory reserves since it has a
	 * pending fatal signal.
	 */
	rcu_read_lock();
	for_each_process(p) {
		if (!process_shares_mm(p, mm))
			continue;
		if (same_thread_group(p, victim))
			continue;
		if (is_global_init(p)) {
			can_oom_reap = false;
			set_bit(MMF_OOM_SKIP, &mm->flags);
			pr_info("oom killer %d (%s) has mm pinned by %d (%s)\n",
					task_pid_nr(victim), victim->comm,
					task_pid_nr(p), p->comm);
			continue;
		}
		/*
		 * No kthread_use_mm() user needs to read from the userspace so
		 * we are ok to reap it.
		 */
		if (unlikely(p->flags & PF_KTHREAD))
			continue;
		do_send_sig_info(SIGKILL, SEND_SIG_PRIV, p, PIDTYPE_TGID);
	}
	rcu_read_unlock();

	if (can_oom_reap)
		queue_oom_reaper(victim);

	mmdrop(mm);
	put_task_struct(victim);
}
#undef K

/*
 * Kill provided task unless it's secured by setting
 * oom_score_adj to OOM_SCORE_ADJ_MIN.
 */
static int oom_kill_memcg_member(struct task_struct *task, void *message)
{
	if (task->signal->oom_score_adj != OOM_SCORE_ADJ_MIN &&
	    !is_global_init(task)) {
		get_task_struct(task);
		__oom_kill_process(task, message);
	}
	return 0;
}

static void oom_kill_process(struct oom_control *oc, const char *message)
{
	struct task_struct *victim = oc->chosen;
	struct mem_cgroup *oom_group;
	static DEFINE_RATELIMIT_STATE(oom_rs, DEFAULT_RATELIMIT_INTERVAL,
					      DEFAULT_RATELIMIT_BURST);

	/*
	 * If the task is already exiting, don't alarm the sysadmin or kill
	 * its children or threads, just give it access to memory reserves
	 * so it can die quickly
	 */
	task_lock(victim);
	if (task_will_free_mem(victim)) {
		mark_oom_victim(victim);
		queue_oom_reaper(victim);
		task_unlock(victim);
		put_task_struct(victim);
		return;
	}
	task_unlock(victim);

	if (__ratelimit(&oom_rs))
		dump_header(oc, victim);

	/*
	 * Do we need to kill the entire memory cgroup?
	 * Or even one of the ancestor memory cgroups?
	 * Check this out before killing the victim task.
	 */
	oom_group = mem_cgroup_get_oom_group(victim, oc->memcg);

	__oom_kill_process(victim, message);

	/*
	 * If necessary, kill all tasks in the selected memory cgroup.
	 */
	if (oom_group) {
		memcg_memory_event(oom_group, MEMCG_OOM_GROUP_KILL);
		mem_cgroup_print_oom_group(oom_group);
		mem_cgroup_scan_tasks(oom_group, oom_kill_memcg_member,
				      (void *)message);
		mem_cgroup_put(oom_group);
	}
}

/*
 * Determines whether the kernel must panic because of the panic_on_oom sysctl.
 */
static void check_panic_on_oom(struct oom_control *oc)
{
	if (likely(!sysctl_panic_on_oom))
		return;
	if (sysctl_panic_on_oom != 2) {
		/*
		 * panic_on_oom == 1 only affects CONSTRAINT_NONE, the kernel
		 * does not panic for cpuset, mempolicy, or memcg allocation
		 * failures.
		 */
		if (oc->constraint != CONSTRAINT_NONE)
			return;
	}
	/* Do not panic for oom kills triggered by sysrq */
	if (is_sysrq_oom(oc))
		return;
	dump_header(oc, NULL);
	panic("Out of memory: %s panic_on_oom is enabled\n",
		sysctl_panic_on_oom == 2 ? "compulsory" : "system-wide");
}

static BLOCKING_NOTIFIER_HEAD(oom_notify_list);

int register_oom_notifier(struct notifier_block *nb)
{
	return blocking_notifier_chain_register(&oom_notify_list, nb);
}
EXPORT_SYMBOL_GPL(register_oom_notifier);

int unregister_oom_notifier(struct notifier_block *nb)
{
	return blocking_notifier_chain_unregister(&oom_notify_list, nb);
}
EXPORT_SYMBOL_GPL(unregister_oom_notifier);

/**
 * out_of_memory - kill the "best" process when we run out of memory
 * @oc: pointer to struct oom_control
 *
 * If we run out of memory, we have the choice between either
 * killing a random task (bad), letting the system crash (worse)
 * OR try to be smart about which process to kill. Note that we
 * don't have to be perfect here, we just have to be good.
 */
bool out_of_memory(struct oom_control *oc)
{
	unsigned long freed = 0;

	if (oom_killer_disabled)
		return false;

	if (!is_memcg_oom(oc)) {
		blocking_notifier_call_chain(&oom_notify_list, 0, &freed);
		if (freed > 0 && !is_sysrq_oom(oc))
			/* Got some memory back in the last second. */
			return true;
	}

	/*
	 * If current has a pending SIGKILL or is exiting, then automatically
	 * select it.  The goal is to allow it to allocate so that it may
	 * quickly exit and free its memory.
	 */
	if (task_will_free_mem(current)) {
		mark_oom_victim(current);
		queue_oom_reaper(current);
		return true;
	}

	/*
	 * The OOM killer does not compensate for IO-less reclaim.
	 * But mem_cgroup_oom() has to invoke the OOM killer even
	 * if it is a GFP_NOFS allocation.
	 */
	if (!(oc->gfp_mask & __GFP_FS) && !is_memcg_oom(oc))
		return true;

	/*
	 * Check if there were limitations on the allocation (only relevant for
	 * NUMA and memcg) that may require different handling.
	 */
	oc->constraint = constrained_alloc(oc);
	if (oc->constraint != CONSTRAINT_MEMORY_POLICY)
		oc->nodemask = NULL;
	check_panic_on_oom(oc);

	if (!is_memcg_oom(oc) && sysctl_oom_kill_allocating_task &&
	    current->mm && !oom_unkillable_task(current) &&
	    oom_cpuset_eligible(current, oc) &&
	    current->signal->oom_score_adj != OOM_SCORE_ADJ_MIN) {
		get_task_struct(current);
		oc->chosen = current;
		oom_kill_process(oc, "Out of memory (oom_kill_allocating_task)");
		return true;
	}

	select_bad_process(oc);
	/* Found nothing?!?! */
	if (!oc->chosen) {
		dump_header(oc, NULL);
		pr_warn("Out of memory and no killable processes...\n");
		/*
		 * If we got here due to an actual allocation at the
		 * system level, we cannot survive this and will enter
		 * an endless loop in the allocator. Bail out now.
		 */
		if (!is_sysrq_oom(oc) && !is_memcg_oom(oc))
			panic("System is deadlocked on memory\n");
	}
	if (oc->chosen && oc->chosen != (void *)-1UL)
		oom_kill_process(oc, !is_memcg_oom(oc) ? "Out of memory" :
				 "Memory cgroup out of memory");
	return !!oc->chosen;
}

/*
 * The pagefault handler calls here because some allocation has failed. We have
 * to take care of the memcg OOM here because this is the only safe context without
 * any locks held but let the oom killer triggered from the allocation context care
 * about the global OOM.
 */
void pagefault_out_of_memory(void)
{
	static DEFINE_RATELIMIT_STATE(pfoom_rs, DEFAULT_RATELIMIT_INTERVAL,
				      DEFAULT_RATELIMIT_BURST);

	if (mem_cgroup_oom_synchronize(true))
		return;

	if (fatal_signal_pending(current))
		return;

	if (__ratelimit(&pfoom_rs))
		pr_warn("Huh VM_FAULT_OOM leaked out to the #PF handler. Retrying PF\n");
}

SYSCALL_DEFINE2(process_mrelease, int, pidfd, unsigned int, flags)
{
#ifdef CONFIG_MMU
	struct mm_struct *mm = NULL;
	struct task_struct *task;
	struct task_struct *p;
	unsigned int f_flags;
	bool reap = false;
	long ret = 0;

	if (flags)
		return -EINVAL;

	task = pidfd_get_task(pidfd, &f_flags);
	if (IS_ERR(task))
		return PTR_ERR(task);

	/*
	 * Make sure to choose a thread which still has a reference to mm
	 * during the group exit
	 */
	p = find_lock_task_mm(task);
	if (!p) {
		ret = -ESRCH;
		goto put_task;
	}

	mm = p->mm;
	mmgrab(mm);

	if (task_will_free_mem(p))
		reap = true;
	else {
		/* Error only if the work has not been done already */
		if (!test_bit(MMF_OOM_SKIP, &mm->flags))
			ret = -EINVAL;
	}
	task_unlock(p);

	if (!reap)
		goto drop_mm;

	if (mmap_read_lock_killable(mm)) {
		ret = -EINTR;
		goto drop_mm;
	}
	/*
	 * Check MMF_OOM_SKIP again under mmap_read_lock protection to ensure
	 * possible change in exit_mmap is seen
	 */
	if (!test_bit(MMF_OOM_SKIP, &mm->flags) && !__oom_reap_task_mm(mm))
		ret = -EAGAIN;
	mmap_read_unlock(mm);

drop_mm:
	mmdrop(mm);
put_task:
	put_task_struct(task);
	return ret;
#else
	return -ENOSYS;
#endif /* CONFIG_MMU */
}