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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/module.h> | |
30 | #include <linux/notifier.h> | |
31 | #include <linux/memcontrol.h> | |
32 | #include <linux/mempolicy.h> | |
33 | #include <linux/security.h> | |
34 | ||
35 | int sysctl_panic_on_oom; | |
36 | int sysctl_oom_kill_allocating_task; | |
37 | int sysctl_oom_dump_tasks = 1; | |
38 | static DEFINE_SPINLOCK(zone_scan_lock); | |
39 | ||
40 | #ifdef CONFIG_NUMA | |
41 | /** | |
42 | * has_intersects_mems_allowed() - check task eligiblity for kill | |
43 | * @tsk: task struct of which task to consider | |
44 | * @mask: nodemask passed to page allocator for mempolicy ooms | |
45 | * | |
46 | * Task eligibility is determined by whether or not a candidate task, @tsk, | |
47 | * shares the same mempolicy nodes as current if it is bound by such a policy | |
48 | * and whether or not it has the same set of allowed cpuset nodes. | |
49 | */ | |
50 | static bool has_intersects_mems_allowed(struct task_struct *tsk, | |
51 | const nodemask_t *mask) | |
52 | { | |
53 | struct task_struct *start = tsk; | |
54 | ||
55 | do { | |
56 | if (mask) { | |
57 | /* | |
58 | * If this is a mempolicy constrained oom, tsk's | |
59 | * cpuset is irrelevant. Only return true if its | |
60 | * mempolicy intersects current, otherwise it may be | |
61 | * needlessly killed. | |
62 | */ | |
63 | if (mempolicy_nodemask_intersects(tsk, mask)) | |
64 | return true; | |
65 | } else { | |
66 | /* | |
67 | * This is not a mempolicy constrained oom, so only | |
68 | * check the mems of tsk's cpuset. | |
69 | */ | |
70 | if (cpuset_mems_allowed_intersects(current, tsk)) | |
71 | return true; | |
72 | } | |
73 | } while_each_thread(start, tsk); | |
74 | ||
75 | return false; | |
76 | } | |
77 | #else | |
78 | static bool has_intersects_mems_allowed(struct task_struct *tsk, | |
79 | const nodemask_t *mask) | |
80 | { | |
81 | return true; | |
82 | } | |
83 | #endif /* CONFIG_NUMA */ | |
84 | ||
85 | /* | |
86 | * If this is a system OOM (not a memcg OOM) and the task selected to be | |
87 | * killed is not already running at high (RT) priorities, speed up the | |
88 | * recovery by boosting the dying task to the lowest FIFO priority. | |
89 | * That helps with the recovery and avoids interfering with RT tasks. | |
90 | */ | |
91 | static void boost_dying_task_prio(struct task_struct *p, | |
92 | struct mem_cgroup *mem) | |
93 | { | |
94 | struct sched_param param = { .sched_priority = 1 }; | |
95 | ||
96 | if (mem) | |
97 | return; | |
98 | ||
99 | if (!rt_task(p)) | |
100 | sched_setscheduler_nocheck(p, SCHED_FIFO, ¶m); | |
101 | } | |
102 | ||
103 | /* | |
104 | * The process p may have detached its own ->mm while exiting or through | |
105 | * use_mm(), but one or more of its subthreads may still have a valid | |
106 | * pointer. Return p, or any of its subthreads with a valid ->mm, with | |
107 | * task_lock() held. | |
108 | */ | |
109 | struct task_struct *find_lock_task_mm(struct task_struct *p) | |
110 | { | |
111 | struct task_struct *t = p; | |
112 | ||
113 | do { | |
114 | task_lock(t); | |
115 | if (likely(t->mm)) | |
116 | return t; | |
117 | task_unlock(t); | |
118 | } while_each_thread(p, t); | |
119 | ||
120 | return NULL; | |
121 | } | |
122 | ||
123 | /* return true if the task is not adequate as candidate victim task. */ | |
124 | static bool oom_unkillable_task(struct task_struct *p, | |
125 | const struct mem_cgroup *mem, const nodemask_t *nodemask) | |
126 | { | |
127 | if (is_global_init(p)) | |
128 | return true; | |
129 | if (p->flags & PF_KTHREAD) | |
130 | return true; | |
131 | ||
132 | /* When mem_cgroup_out_of_memory() and p is not member of the group */ | |
133 | if (mem && !task_in_mem_cgroup(p, mem)) | |
134 | return true; | |
135 | ||
136 | /* p may not have freeable memory in nodemask */ | |
137 | if (!has_intersects_mems_allowed(p, nodemask)) | |
138 | return true; | |
139 | ||
140 | return false; | |
141 | } | |
142 | ||
143 | /** | |
144 | * oom_badness - heuristic function to determine which candidate task to kill | |
145 | * @p: task struct of which task we should calculate | |
146 | * @totalpages: total present RAM allowed for page allocation | |
147 | * | |
148 | * The heuristic for determining which task to kill is made to be as simple and | |
149 | * predictable as possible. The goal is to return the highest value for the | |
150 | * task consuming the most memory to avoid subsequent oom failures. | |
151 | */ | |
152 | unsigned int oom_badness(struct task_struct *p, struct mem_cgroup *mem, | |
153 | const nodemask_t *nodemask, unsigned long totalpages) | |
154 | { | |
155 | int points; | |
156 | ||
157 | if (oom_unkillable_task(p, mem, nodemask)) | |
158 | return 0; | |
159 | ||
160 | p = find_lock_task_mm(p); | |
161 | if (!p) | |
162 | return 0; | |
163 | ||
164 | /* | |
165 | * Shortcut check for a thread sharing p->mm that is OOM_SCORE_ADJ_MIN | |
166 | * so the entire heuristic doesn't need to be executed for something | |
167 | * that cannot be killed. | |
168 | */ | |
169 | if (atomic_read(&p->mm->oom_disable_count)) { | |
170 | task_unlock(p); | |
171 | return 0; | |
172 | } | |
173 | ||
174 | /* | |
175 | * When the PF_OOM_ORIGIN bit is set, it indicates the task should have | |
176 | * priority for oom killing. | |
177 | */ | |
178 | if (p->flags & PF_OOM_ORIGIN) { | |
179 | task_unlock(p); | |
180 | return 1000; | |
181 | } | |
182 | ||
183 | /* | |
184 | * The memory controller may have a limit of 0 bytes, so avoid a divide | |
185 | * by zero, if necessary. | |
186 | */ | |
187 | if (!totalpages) | |
188 | totalpages = 1; | |
189 | ||
190 | /* | |
191 | * The baseline for the badness score is the proportion of RAM that each | |
192 | * task's rss and swap space use. | |
193 | */ | |
194 | points = (get_mm_rss(p->mm) + get_mm_counter(p->mm, MM_SWAPENTS)) * 1000 / | |
195 | totalpages; | |
196 | task_unlock(p); | |
197 | ||
198 | /* | |
199 | * Root processes get 3% bonus, just like the __vm_enough_memory() | |
200 | * implementation used by LSMs. | |
201 | */ | |
202 | if (has_capability_noaudit(p, CAP_SYS_ADMIN)) | |
203 | points -= 30; | |
204 | ||
205 | /* | |
206 | * /proc/pid/oom_score_adj ranges from -1000 to +1000 such that it may | |
207 | * either completely disable oom killing or always prefer a certain | |
208 | * task. | |
209 | */ | |
210 | points += p->signal->oom_score_adj; | |
211 | ||
212 | /* | |
213 | * Never return 0 for an eligible task that may be killed since it's | |
214 | * possible that no single user task uses more than 0.1% of memory and | |
215 | * no single admin tasks uses more than 3.0%. | |
216 | */ | |
217 | if (points <= 0) | |
218 | return 1; | |
219 | return (points < 1000) ? points : 1000; | |
220 | } | |
221 | ||
222 | /* | |
223 | * Determine the type of allocation constraint. | |
224 | */ | |
225 | #ifdef CONFIG_NUMA | |
226 | static enum oom_constraint constrained_alloc(struct zonelist *zonelist, | |
227 | gfp_t gfp_mask, nodemask_t *nodemask, | |
228 | unsigned long *totalpages) | |
229 | { | |
230 | struct zone *zone; | |
231 | struct zoneref *z; | |
232 | enum zone_type high_zoneidx = gfp_zone(gfp_mask); | |
233 | bool cpuset_limited = false; | |
234 | int nid; | |
235 | ||
236 | /* Default to all available memory */ | |
237 | *totalpages = totalram_pages + total_swap_pages; | |
238 | ||
239 | if (!zonelist) | |
240 | return CONSTRAINT_NONE; | |
241 | /* | |
242 | * Reach here only when __GFP_NOFAIL is used. So, we should avoid | |
243 | * to kill current.We have to random task kill in this case. | |
244 | * Hopefully, CONSTRAINT_THISNODE...but no way to handle it, now. | |
245 | */ | |
246 | if (gfp_mask & __GFP_THISNODE) | |
247 | return CONSTRAINT_NONE; | |
248 | ||
249 | /* | |
250 | * This is not a __GFP_THISNODE allocation, so a truncated nodemask in | |
251 | * the page allocator means a mempolicy is in effect. Cpuset policy | |
252 | * is enforced in get_page_from_freelist(). | |
253 | */ | |
254 | if (nodemask && !nodes_subset(node_states[N_HIGH_MEMORY], *nodemask)) { | |
255 | *totalpages = total_swap_pages; | |
256 | for_each_node_mask(nid, *nodemask) | |
257 | *totalpages += node_spanned_pages(nid); | |
258 | return CONSTRAINT_MEMORY_POLICY; | |
259 | } | |
260 | ||
261 | /* Check this allocation failure is caused by cpuset's wall function */ | |
262 | for_each_zone_zonelist_nodemask(zone, z, zonelist, | |
263 | high_zoneidx, nodemask) | |
264 | if (!cpuset_zone_allowed_softwall(zone, gfp_mask)) | |
265 | cpuset_limited = true; | |
266 | ||
267 | if (cpuset_limited) { | |
268 | *totalpages = total_swap_pages; | |
269 | for_each_node_mask(nid, cpuset_current_mems_allowed) | |
270 | *totalpages += node_spanned_pages(nid); | |
271 | return CONSTRAINT_CPUSET; | |
272 | } | |
273 | return CONSTRAINT_NONE; | |
274 | } | |
275 | #else | |
276 | static enum oom_constraint constrained_alloc(struct zonelist *zonelist, | |
277 | gfp_t gfp_mask, nodemask_t *nodemask, | |
278 | unsigned long *totalpages) | |
279 | { | |
280 | *totalpages = totalram_pages + total_swap_pages; | |
281 | return CONSTRAINT_NONE; | |
282 | } | |
283 | #endif | |
284 | ||
285 | /* | |
286 | * Simple selection loop. We chose the process with the highest | |
287 | * number of 'points'. We expect the caller will lock the tasklist. | |
288 | * | |
289 | * (not docbooked, we don't want this one cluttering up the manual) | |
290 | */ | |
291 | static struct task_struct *select_bad_process(unsigned int *ppoints, | |
292 | unsigned long totalpages, struct mem_cgroup *mem, | |
293 | const nodemask_t *nodemask) | |
294 | { | |
295 | struct task_struct *p; | |
296 | struct task_struct *chosen = NULL; | |
297 | *ppoints = 0; | |
298 | ||
299 | for_each_process(p) { | |
300 | unsigned int points; | |
301 | ||
302 | if (oom_unkillable_task(p, mem, nodemask)) | |
303 | continue; | |
304 | ||
305 | /* | |
306 | * This task already has access to memory reserves and is | |
307 | * being killed. Don't allow any other task access to the | |
308 | * memory reserve. | |
309 | * | |
310 | * Note: this may have a chance of deadlock if it gets | |
311 | * blocked waiting for another task which itself is waiting | |
312 | * for memory. Is there a better alternative? | |
313 | */ | |
314 | if (test_tsk_thread_flag(p, TIF_MEMDIE)) | |
315 | return ERR_PTR(-1UL); | |
316 | ||
317 | /* | |
318 | * This is in the process of releasing memory so wait for it | |
319 | * to finish before killing some other task by mistake. | |
320 | * | |
321 | * However, if p is the current task, we allow the 'kill' to | |
322 | * go ahead if it is exiting: this will simply set TIF_MEMDIE, | |
323 | * which will allow it to gain access to memory reserves in | |
324 | * the process of exiting and releasing its resources. | |
325 | * Otherwise we could get an easy OOM deadlock. | |
326 | */ | |
327 | if (thread_group_empty(p) && (p->flags & PF_EXITING) && p->mm) { | |
328 | if (p != current) | |
329 | return ERR_PTR(-1UL); | |
330 | ||
331 | chosen = p; | |
332 | *ppoints = 1000; | |
333 | } | |
334 | ||
335 | points = oom_badness(p, mem, nodemask, totalpages); | |
336 | if (points > *ppoints) { | |
337 | chosen = p; | |
338 | *ppoints = points; | |
339 | } | |
340 | } | |
341 | ||
342 | return chosen; | |
343 | } | |
344 | ||
345 | /** | |
346 | * dump_tasks - dump current memory state of all system tasks | |
347 | * @mem: current's memory controller, if constrained | |
348 | * @nodemask: nodemask passed to page allocator for mempolicy ooms | |
349 | * | |
350 | * Dumps the current memory state of all eligible tasks. Tasks not in the same | |
351 | * memcg, not in the same cpuset, or bound to a disjoint set of mempolicy nodes | |
352 | * are not shown. | |
353 | * State information includes task's pid, uid, tgid, vm size, rss, cpu, oom_adj | |
354 | * value, oom_score_adj value, and name. | |
355 | * | |
356 | * Call with tasklist_lock read-locked. | |
357 | */ | |
358 | static void dump_tasks(const struct mem_cgroup *mem, const nodemask_t *nodemask) | |
359 | { | |
360 | struct task_struct *p; | |
361 | struct task_struct *task; | |
362 | ||
363 | pr_info("[ pid ] uid tgid total_vm rss cpu oom_adj oom_score_adj name\n"); | |
364 | for_each_process(p) { | |
365 | if (oom_unkillable_task(p, mem, nodemask)) | |
366 | continue; | |
367 | ||
368 | task = find_lock_task_mm(p); | |
369 | if (!task) { | |
370 | /* | |
371 | * This is a kthread or all of p's threads have already | |
372 | * detached their mm's. There's no need to report | |
373 | * them; they can't be oom killed anyway. | |
374 | */ | |
375 | continue; | |
376 | } | |
377 | ||
378 | pr_info("[%5d] %5d %5d %8lu %8lu %3u %3d %5d %s\n", | |
379 | task->pid, task_uid(task), task->tgid, | |
380 | task->mm->total_vm, get_mm_rss(task->mm), | |
381 | task_cpu(task), task->signal->oom_adj, | |
382 | task->signal->oom_score_adj, task->comm); | |
383 | task_unlock(task); | |
384 | } | |
385 | } | |
386 | ||
387 | static void dump_header(struct task_struct *p, gfp_t gfp_mask, int order, | |
388 | struct mem_cgroup *mem, const nodemask_t *nodemask) | |
389 | { | |
390 | task_lock(current); | |
391 | pr_warning("%s invoked oom-killer: gfp_mask=0x%x, order=%d, " | |
392 | "oom_adj=%d, oom_score_adj=%d\n", | |
393 | current->comm, gfp_mask, order, current->signal->oom_adj, | |
394 | current->signal->oom_score_adj); | |
395 | cpuset_print_task_mems_allowed(current); | |
396 | task_unlock(current); | |
397 | dump_stack(); | |
398 | mem_cgroup_print_oom_info(mem, p); | |
399 | show_mem(); | |
400 | if (sysctl_oom_dump_tasks) | |
401 | dump_tasks(mem, nodemask); | |
402 | } | |
403 | ||
404 | #define K(x) ((x) << (PAGE_SHIFT-10)) | |
405 | static int oom_kill_task(struct task_struct *p, struct mem_cgroup *mem) | |
406 | { | |
407 | struct task_struct *q; | |
408 | struct mm_struct *mm; | |
409 | ||
410 | p = find_lock_task_mm(p); | |
411 | if (!p) | |
412 | return 1; | |
413 | ||
414 | /* mm cannot be safely dereferenced after task_unlock(p) */ | |
415 | mm = p->mm; | |
416 | ||
417 | pr_err("Killed process %d (%s) total-vm:%lukB, anon-rss:%lukB, file-rss:%lukB\n", | |
418 | task_pid_nr(p), p->comm, K(p->mm->total_vm), | |
419 | K(get_mm_counter(p->mm, MM_ANONPAGES)), | |
420 | K(get_mm_counter(p->mm, MM_FILEPAGES))); | |
421 | task_unlock(p); | |
422 | ||
423 | /* | |
424 | * Kill all processes sharing p->mm in other thread groups, if any. | |
425 | * They don't get access to memory reserves or a higher scheduler | |
426 | * priority, though, to avoid depletion of all memory or task | |
427 | * starvation. This prevents mm->mmap_sem livelock when an oom killed | |
428 | * task cannot exit because it requires the semaphore and its contended | |
429 | * by another thread trying to allocate memory itself. That thread will | |
430 | * now get access to memory reserves since it has a pending fatal | |
431 | * signal. | |
432 | */ | |
433 | for_each_process(q) | |
434 | if (q->mm == mm && !same_thread_group(q, p)) { | |
435 | task_lock(q); /* Protect ->comm from prctl() */ | |
436 | pr_err("Kill process %d (%s) sharing same memory\n", | |
437 | task_pid_nr(q), q->comm); | |
438 | task_unlock(q); | |
439 | force_sig(SIGKILL, q); | |
440 | } | |
441 | ||
442 | set_tsk_thread_flag(p, TIF_MEMDIE); | |
443 | force_sig(SIGKILL, p); | |
444 | ||
445 | /* | |
446 | * We give our sacrificial lamb high priority and access to | |
447 | * all the memory it needs. That way it should be able to | |
448 | * exit() and clear out its resources quickly... | |
449 | */ | |
450 | boost_dying_task_prio(p, mem); | |
451 | ||
452 | return 0; | |
453 | } | |
454 | #undef K | |
455 | ||
456 | static int oom_kill_process(struct task_struct *p, gfp_t gfp_mask, int order, | |
457 | unsigned int points, unsigned long totalpages, | |
458 | struct mem_cgroup *mem, nodemask_t *nodemask, | |
459 | const char *message) | |
460 | { | |
461 | struct task_struct *victim = p; | |
462 | struct task_struct *child; | |
463 | struct task_struct *t = p; | |
464 | unsigned int victim_points = 0; | |
465 | ||
466 | if (printk_ratelimit()) | |
467 | dump_header(p, gfp_mask, order, mem, nodemask); | |
468 | ||
469 | /* | |
470 | * If the task is already exiting, don't alarm the sysadmin or kill | |
471 | * its children or threads, just set TIF_MEMDIE so it can die quickly | |
472 | */ | |
473 | if (p->flags & PF_EXITING) { | |
474 | set_tsk_thread_flag(p, TIF_MEMDIE); | |
475 | boost_dying_task_prio(p, mem); | |
476 | return 0; | |
477 | } | |
478 | ||
479 | task_lock(p); | |
480 | pr_err("%s: Kill process %d (%s) score %d or sacrifice child\n", | |
481 | message, task_pid_nr(p), p->comm, points); | |
482 | task_unlock(p); | |
483 | ||
484 | /* | |
485 | * If any of p's children has a different mm and is eligible for kill, | |
486 | * the one with the highest badness() score is sacrificed for its | |
487 | * parent. This attempts to lose the minimal amount of work done while | |
488 | * still freeing memory. | |
489 | */ | |
490 | do { | |
491 | list_for_each_entry(child, &t->children, sibling) { | |
492 | unsigned int child_points; | |
493 | ||
494 | /* | |
495 | * oom_badness() returns 0 if the thread is unkillable | |
496 | */ | |
497 | child_points = oom_badness(child, mem, nodemask, | |
498 | totalpages); | |
499 | if (child_points > victim_points) { | |
500 | victim = child; | |
501 | victim_points = child_points; | |
502 | } | |
503 | } | |
504 | } while_each_thread(p, t); | |
505 | ||
506 | return oom_kill_task(victim, mem); | |
507 | } | |
508 | ||
509 | /* | |
510 | * Determines whether the kernel must panic because of the panic_on_oom sysctl. | |
511 | */ | |
512 | static void check_panic_on_oom(enum oom_constraint constraint, gfp_t gfp_mask, | |
513 | int order, const nodemask_t *nodemask) | |
514 | { | |
515 | if (likely(!sysctl_panic_on_oom)) | |
516 | return; | |
517 | if (sysctl_panic_on_oom != 2) { | |
518 | /* | |
519 | * panic_on_oom == 1 only affects CONSTRAINT_NONE, the kernel | |
520 | * does not panic for cpuset, mempolicy, or memcg allocation | |
521 | * failures. | |
522 | */ | |
523 | if (constraint != CONSTRAINT_NONE) | |
524 | return; | |
525 | } | |
526 | read_lock(&tasklist_lock); | |
527 | dump_header(NULL, gfp_mask, order, NULL, nodemask); | |
528 | read_unlock(&tasklist_lock); | |
529 | panic("Out of memory: %s panic_on_oom is enabled\n", | |
530 | sysctl_panic_on_oom == 2 ? "compulsory" : "system-wide"); | |
531 | } | |
532 | ||
533 | #ifdef CONFIG_CGROUP_MEM_RES_CTLR | |
534 | void mem_cgroup_out_of_memory(struct mem_cgroup *mem, gfp_t gfp_mask) | |
535 | { | |
536 | unsigned long limit; | |
537 | unsigned int points = 0; | |
538 | struct task_struct *p; | |
539 | ||
540 | check_panic_on_oom(CONSTRAINT_MEMCG, gfp_mask, 0, NULL); | |
541 | limit = mem_cgroup_get_limit(mem) >> PAGE_SHIFT; | |
542 | read_lock(&tasklist_lock); | |
543 | retry: | |
544 | p = select_bad_process(&points, limit, mem, NULL); | |
545 | if (!p || PTR_ERR(p) == -1UL) | |
546 | goto out; | |
547 | ||
548 | if (oom_kill_process(p, gfp_mask, 0, points, limit, mem, NULL, | |
549 | "Memory cgroup out of memory")) | |
550 | goto retry; | |
551 | out: | |
552 | read_unlock(&tasklist_lock); | |
553 | } | |
554 | #endif | |
555 | ||
556 | static BLOCKING_NOTIFIER_HEAD(oom_notify_list); | |
557 | ||
558 | int register_oom_notifier(struct notifier_block *nb) | |
559 | { | |
560 | return blocking_notifier_chain_register(&oom_notify_list, nb); | |
561 | } | |
562 | EXPORT_SYMBOL_GPL(register_oom_notifier); | |
563 | ||
564 | int unregister_oom_notifier(struct notifier_block *nb) | |
565 | { | |
566 | return blocking_notifier_chain_unregister(&oom_notify_list, nb); | |
567 | } | |
568 | EXPORT_SYMBOL_GPL(unregister_oom_notifier); | |
569 | ||
570 | /* | |
571 | * Try to acquire the OOM killer lock for the zones in zonelist. Returns zero | |
572 | * if a parallel OOM killing is already taking place that includes a zone in | |
573 | * the zonelist. Otherwise, locks all zones in the zonelist and returns 1. | |
574 | */ | |
575 | int try_set_zonelist_oom(struct zonelist *zonelist, gfp_t gfp_mask) | |
576 | { | |
577 | struct zoneref *z; | |
578 | struct zone *zone; | |
579 | int ret = 1; | |
580 | ||
581 | spin_lock(&zone_scan_lock); | |
582 | for_each_zone_zonelist(zone, z, zonelist, gfp_zone(gfp_mask)) { | |
583 | if (zone_is_oom_locked(zone)) { | |
584 | ret = 0; | |
585 | goto out; | |
586 | } | |
587 | } | |
588 | ||
589 | for_each_zone_zonelist(zone, z, zonelist, gfp_zone(gfp_mask)) { | |
590 | /* | |
591 | * Lock each zone in the zonelist under zone_scan_lock so a | |
592 | * parallel invocation of try_set_zonelist_oom() doesn't succeed | |
593 | * when it shouldn't. | |
594 | */ | |
595 | zone_set_flag(zone, ZONE_OOM_LOCKED); | |
596 | } | |
597 | ||
598 | out: | |
599 | spin_unlock(&zone_scan_lock); | |
600 | return ret; | |
601 | } | |
602 | ||
603 | /* | |
604 | * Clears the ZONE_OOM_LOCKED flag for all zones in the zonelist so that failed | |
605 | * allocation attempts with zonelists containing them may now recall the OOM | |
606 | * killer, if necessary. | |
607 | */ | |
608 | void clear_zonelist_oom(struct zonelist *zonelist, gfp_t gfp_mask) | |
609 | { | |
610 | struct zoneref *z; | |
611 | struct zone *zone; | |
612 | ||
613 | spin_lock(&zone_scan_lock); | |
614 | for_each_zone_zonelist(zone, z, zonelist, gfp_zone(gfp_mask)) { | |
615 | zone_clear_flag(zone, ZONE_OOM_LOCKED); | |
616 | } | |
617 | spin_unlock(&zone_scan_lock); | |
618 | } | |
619 | ||
620 | /* | |
621 | * Try to acquire the oom killer lock for all system zones. Returns zero if a | |
622 | * parallel oom killing is taking place, otherwise locks all zones and returns | |
623 | * non-zero. | |
624 | */ | |
625 | static int try_set_system_oom(void) | |
626 | { | |
627 | struct zone *zone; | |
628 | int ret = 1; | |
629 | ||
630 | spin_lock(&zone_scan_lock); | |
631 | for_each_populated_zone(zone) | |
632 | if (zone_is_oom_locked(zone)) { | |
633 | ret = 0; | |
634 | goto out; | |
635 | } | |
636 | for_each_populated_zone(zone) | |
637 | zone_set_flag(zone, ZONE_OOM_LOCKED); | |
638 | out: | |
639 | spin_unlock(&zone_scan_lock); | |
640 | return ret; | |
641 | } | |
642 | ||
643 | /* | |
644 | * Clears ZONE_OOM_LOCKED for all system zones so that failed allocation | |
645 | * attempts or page faults may now recall the oom killer, if necessary. | |
646 | */ | |
647 | static void clear_system_oom(void) | |
648 | { | |
649 | struct zone *zone; | |
650 | ||
651 | spin_lock(&zone_scan_lock); | |
652 | for_each_populated_zone(zone) | |
653 | zone_clear_flag(zone, ZONE_OOM_LOCKED); | |
654 | spin_unlock(&zone_scan_lock); | |
655 | } | |
656 | ||
657 | /** | |
658 | * out_of_memory - kill the "best" process when we run out of memory | |
659 | * @zonelist: zonelist pointer | |
660 | * @gfp_mask: memory allocation flags | |
661 | * @order: amount of memory being requested as a power of 2 | |
662 | * @nodemask: nodemask passed to page allocator | |
663 | * | |
664 | * If we run out of memory, we have the choice between either | |
665 | * killing a random task (bad), letting the system crash (worse) | |
666 | * OR try to be smart about which process to kill. Note that we | |
667 | * don't have to be perfect here, we just have to be good. | |
668 | */ | |
669 | void out_of_memory(struct zonelist *zonelist, gfp_t gfp_mask, | |
670 | int order, nodemask_t *nodemask) | |
671 | { | |
672 | const nodemask_t *mpol_mask; | |
673 | struct task_struct *p; | |
674 | unsigned long totalpages; | |
675 | unsigned long freed = 0; | |
676 | unsigned int points; | |
677 | enum oom_constraint constraint = CONSTRAINT_NONE; | |
678 | int killed = 0; | |
679 | ||
680 | blocking_notifier_call_chain(&oom_notify_list, 0, &freed); | |
681 | if (freed > 0) | |
682 | /* Got some memory back in the last second. */ | |
683 | return; | |
684 | ||
685 | /* | |
686 | * If current has a pending SIGKILL, then automatically select it. The | |
687 | * goal is to allow it to allocate so that it may quickly exit and free | |
688 | * its memory. | |
689 | */ | |
690 | if (fatal_signal_pending(current)) { | |
691 | set_thread_flag(TIF_MEMDIE); | |
692 | boost_dying_task_prio(current, NULL); | |
693 | return; | |
694 | } | |
695 | ||
696 | /* | |
697 | * Check if there were limitations on the allocation (only relevant for | |
698 | * NUMA) that may require different handling. | |
699 | */ | |
700 | constraint = constrained_alloc(zonelist, gfp_mask, nodemask, | |
701 | &totalpages); | |
702 | mpol_mask = (constraint == CONSTRAINT_MEMORY_POLICY) ? nodemask : NULL; | |
703 | check_panic_on_oom(constraint, gfp_mask, order, mpol_mask); | |
704 | ||
705 | read_lock(&tasklist_lock); | |
706 | if (sysctl_oom_kill_allocating_task && | |
707 | !oom_unkillable_task(current, NULL, nodemask) && | |
708 | current->mm && !atomic_read(¤t->mm->oom_disable_count)) { | |
709 | /* | |
710 | * oom_kill_process() needs tasklist_lock held. If it returns | |
711 | * non-zero, current could not be killed so we must fallback to | |
712 | * the tasklist scan. | |
713 | */ | |
714 | if (!oom_kill_process(current, gfp_mask, order, 0, totalpages, | |
715 | NULL, nodemask, | |
716 | "Out of memory (oom_kill_allocating_task)")) | |
717 | goto out; | |
718 | } | |
719 | ||
720 | retry: | |
721 | p = select_bad_process(&points, totalpages, NULL, mpol_mask); | |
722 | if (PTR_ERR(p) == -1UL) | |
723 | goto out; | |
724 | ||
725 | /* Found nothing?!?! Either we hang forever, or we panic. */ | |
726 | if (!p) { | |
727 | dump_header(NULL, gfp_mask, order, NULL, mpol_mask); | |
728 | read_unlock(&tasklist_lock); | |
729 | panic("Out of memory and no killable processes...\n"); | |
730 | } | |
731 | ||
732 | if (oom_kill_process(p, gfp_mask, order, points, totalpages, NULL, | |
733 | nodemask, "Out of memory")) | |
734 | goto retry; | |
735 | killed = 1; | |
736 | out: | |
737 | read_unlock(&tasklist_lock); | |
738 | ||
739 | /* | |
740 | * Give "p" a good chance of killing itself before we | |
741 | * retry to allocate memory unless "p" is current | |
742 | */ | |
743 | if (killed && !test_thread_flag(TIF_MEMDIE)) | |
744 | schedule_timeout_uninterruptible(1); | |
745 | } | |
746 | ||
747 | /* | |
748 | * The pagefault handler calls here because it is out of memory, so kill a | |
749 | * memory-hogging task. If a populated zone has ZONE_OOM_LOCKED set, a parallel | |
750 | * oom killing is already in progress so do nothing. If a task is found with | |
751 | * TIF_MEMDIE set, it has been killed so do nothing and allow it to exit. | |
752 | */ | |
753 | void pagefault_out_of_memory(void) | |
754 | { | |
755 | if (try_set_system_oom()) { | |
756 | out_of_memory(NULL, 0, 0, NULL); | |
757 | clear_system_oom(); | |
758 | } | |
759 | if (!test_thread_flag(TIF_MEMDIE)) | |
760 | schedule_timeout_uninterruptible(1); | |
761 | } |