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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 | } |
762 |
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