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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 | * | |
8 | * The routines in this file are used to kill a process when | |
9 | * we're seriously out of memory. This gets called from __alloc_pages() | |
10 | * in mm/page_alloc.c when we really run out of memory. | |
11 | * | |
12 | * Since we won't call these routines often (on a well-configured | |
13 | * machine) this file will double as a 'coding guide' and a signpost | |
14 | * for newbie kernel hackers. It features several pointers to major | |
15 | * kernel subsystems and hints as to where to find out what things do. | |
16 | */ | |
17 | ||
18 | #include <linux/oom.h> | |
19 | #include <linux/mm.h> | |
20 | #include <linux/err.h> | |
21 | #include <linux/gfp.h> | |
22 | #include <linux/sched.h> | |
23 | #include <linux/swap.h> | |
24 | #include <linux/timex.h> | |
25 | #include <linux/jiffies.h> | |
26 | #include <linux/cpuset.h> | |
27 | #include <linux/module.h> | |
28 | #include <linux/notifier.h> | |
29 | #include <linux/memcontrol.h> | |
30 | #include <linux/security.h> | |
31 | ||
32 | int sysctl_panic_on_oom; | |
33 | int sysctl_oom_kill_allocating_task; | |
34 | int sysctl_oom_dump_tasks; | |
35 | static DEFINE_SPINLOCK(zone_scan_lock); | |
36 | /* #define DEBUG */ | |
37 | ||
38 | /* | |
39 | * Is all threads of the target process nodes overlap ours? | |
40 | */ | |
41 | static int has_intersects_mems_allowed(struct task_struct *tsk) | |
42 | { | |
43 | struct task_struct *t; | |
44 | ||
45 | t = tsk; | |
46 | do { | |
47 | if (cpuset_mems_allowed_intersects(current, t)) | |
48 | return 1; | |
49 | t = next_thread(t); | |
50 | } while (t != tsk); | |
51 | ||
52 | return 0; | |
53 | } | |
54 | ||
55 | /** | |
56 | * badness - calculate a numeric value for how bad this task has been | |
57 | * @p: task struct of which task we should calculate | |
58 | * @uptime: current uptime in seconds | |
59 | * | |
60 | * The formula used is relatively simple and documented inline in the | |
61 | * function. The main rationale is that we want to select a good task | |
62 | * to kill when we run out of memory. | |
63 | * | |
64 | * Good in this context means that: | |
65 | * 1) we lose the minimum amount of work done | |
66 | * 2) we recover a large amount of memory | |
67 | * 3) we don't kill anything innocent of eating tons of memory | |
68 | * 4) we want to kill the minimum amount of processes (one) | |
69 | * 5) we try to kill the process the user expects us to kill, this | |
70 | * algorithm has been meticulously tuned to meet the principle | |
71 | * of least surprise ... (be careful when you change it) | |
72 | */ | |
73 | ||
74 | unsigned long badness(struct task_struct *p, unsigned long uptime) | |
75 | { | |
76 | unsigned long points, cpu_time, run_time; | |
77 | struct mm_struct *mm; | |
78 | struct task_struct *child; | |
79 | int oom_adj = p->signal->oom_adj; | |
80 | struct task_cputime task_time; | |
81 | unsigned long utime; | |
82 | unsigned long stime; | |
83 | ||
84 | if (oom_adj == OOM_DISABLE) | |
85 | return 0; | |
86 | ||
87 | task_lock(p); | |
88 | mm = p->mm; | |
89 | if (!mm) { | |
90 | task_unlock(p); | |
91 | return 0; | |
92 | } | |
93 | ||
94 | /* | |
95 | * The memory size of the process is the basis for the badness. | |
96 | */ | |
97 | points = mm->total_vm; | |
98 | ||
99 | /* | |
100 | * After this unlock we can no longer dereference local variable `mm' | |
101 | */ | |
102 | task_unlock(p); | |
103 | ||
104 | /* | |
105 | * swapoff can easily use up all memory, so kill those first. | |
106 | */ | |
107 | if (p->flags & PF_OOM_ORIGIN) | |
108 | return ULONG_MAX; | |
109 | ||
110 | /* | |
111 | * Processes which fork a lot of child processes are likely | |
112 | * a good choice. We add half the vmsize of the children if they | |
113 | * have an own mm. This prevents forking servers to flood the | |
114 | * machine with an endless amount of children. In case a single | |
115 | * child is eating the vast majority of memory, adding only half | |
116 | * to the parents will make the child our kill candidate of choice. | |
117 | */ | |
118 | list_for_each_entry(child, &p->children, sibling) { | |
119 | task_lock(child); | |
120 | if (child->mm != mm && child->mm) | |
121 | points += child->mm->total_vm/2 + 1; | |
122 | task_unlock(child); | |
123 | } | |
124 | ||
125 | /* | |
126 | * CPU time is in tens of seconds and run time is in thousands | |
127 | * of seconds. There is no particular reason for this other than | |
128 | * that it turned out to work very well in practice. | |
129 | */ | |
130 | thread_group_cputime(p, &task_time); | |
131 | utime = cputime_to_jiffies(task_time.utime); | |
132 | stime = cputime_to_jiffies(task_time.stime); | |
133 | cpu_time = (utime + stime) >> (SHIFT_HZ + 3); | |
134 | ||
135 | ||
136 | if (uptime >= p->start_time.tv_sec) | |
137 | run_time = (uptime - p->start_time.tv_sec) >> 10; | |
138 | else | |
139 | run_time = 0; | |
140 | ||
141 | if (cpu_time) | |
142 | points /= int_sqrt(cpu_time); | |
143 | if (run_time) | |
144 | points /= int_sqrt(int_sqrt(run_time)); | |
145 | ||
146 | /* | |
147 | * Niced processes are most likely less important, so double | |
148 | * their badness points. | |
149 | */ | |
150 | if (task_nice(p) > 0) | |
151 | points *= 2; | |
152 | ||
153 | /* | |
154 | * Superuser processes are usually more important, so we make it | |
155 | * less likely that we kill those. | |
156 | */ | |
157 | if (has_capability_noaudit(p, CAP_SYS_ADMIN) || | |
158 | has_capability_noaudit(p, CAP_SYS_RESOURCE)) | |
159 | points /= 4; | |
160 | ||
161 | /* | |
162 | * We don't want to kill a process with direct hardware access. | |
163 | * Not only could that mess up the hardware, but usually users | |
164 | * tend to only have this flag set on applications they think | |
165 | * of as important. | |
166 | */ | |
167 | if (has_capability_noaudit(p, CAP_SYS_RAWIO)) | |
168 | points /= 4; | |
169 | ||
170 | /* | |
171 | * If p's nodes don't overlap ours, it may still help to kill p | |
172 | * because p may have allocated or otherwise mapped memory on | |
173 | * this node before. However it will be less likely. | |
174 | */ | |
175 | if (!has_intersects_mems_allowed(p)) | |
176 | points /= 8; | |
177 | ||
178 | /* | |
179 | * Adjust the score by oom_adj. | |
180 | */ | |
181 | if (oom_adj) { | |
182 | if (oom_adj > 0) { | |
183 | if (!points) | |
184 | points = 1; | |
185 | points <<= oom_adj; | |
186 | } else | |
187 | points >>= -(oom_adj); | |
188 | } | |
189 | ||
190 | #ifdef DEBUG | |
191 | printk(KERN_DEBUG "OOMkill: task %d (%s) got %lu points\n", | |
192 | p->pid, p->comm, points); | |
193 | #endif | |
194 | return points; | |
195 | } | |
196 | ||
197 | /* | |
198 | * Determine the type of allocation constraint. | |
199 | */ | |
200 | #ifdef CONFIG_NUMA | |
201 | static enum oom_constraint constrained_alloc(struct zonelist *zonelist, | |
202 | gfp_t gfp_mask, nodemask_t *nodemask) | |
203 | { | |
204 | struct zone *zone; | |
205 | struct zoneref *z; | |
206 | enum zone_type high_zoneidx = gfp_zone(gfp_mask); | |
207 | ||
208 | /* | |
209 | * Reach here only when __GFP_NOFAIL is used. So, we should avoid | |
210 | * to kill current.We have to random task kill in this case. | |
211 | * Hopefully, CONSTRAINT_THISNODE...but no way to handle it, now. | |
212 | */ | |
213 | if (gfp_mask & __GFP_THISNODE) | |
214 | return CONSTRAINT_NONE; | |
215 | ||
216 | /* | |
217 | * The nodemask here is a nodemask passed to alloc_pages(). Now, | |
218 | * cpuset doesn't use this nodemask for its hardwall/softwall/hierarchy | |
219 | * feature. mempolicy is an only user of nodemask here. | |
220 | * check mempolicy's nodemask contains all N_HIGH_MEMORY | |
221 | */ | |
222 | if (nodemask && !nodes_subset(node_states[N_HIGH_MEMORY], *nodemask)) | |
223 | return CONSTRAINT_MEMORY_POLICY; | |
224 | ||
225 | /* Check this allocation failure is caused by cpuset's wall function */ | |
226 | for_each_zone_zonelist_nodemask(zone, z, zonelist, | |
227 | high_zoneidx, nodemask) | |
228 | if (!cpuset_zone_allowed_softwall(zone, gfp_mask)) | |
229 | return CONSTRAINT_CPUSET; | |
230 | ||
231 | return CONSTRAINT_NONE; | |
232 | } | |
233 | #else | |
234 | static enum oom_constraint constrained_alloc(struct zonelist *zonelist, | |
235 | gfp_t gfp_mask, nodemask_t *nodemask) | |
236 | { | |
237 | return CONSTRAINT_NONE; | |
238 | } | |
239 | #endif | |
240 | ||
241 | /* | |
242 | * Simple selection loop. We chose the process with the highest | |
243 | * number of 'points'. We expect the caller will lock the tasklist. | |
244 | * | |
245 | * (not docbooked, we don't want this one cluttering up the manual) | |
246 | */ | |
247 | static struct task_struct *select_bad_process(unsigned long *ppoints, | |
248 | struct mem_cgroup *mem) | |
249 | { | |
250 | struct task_struct *p; | |
251 | struct task_struct *chosen = NULL; | |
252 | struct timespec uptime; | |
253 | *ppoints = 0; | |
254 | ||
255 | do_posix_clock_monotonic_gettime(&uptime); | |
256 | for_each_process(p) { | |
257 | unsigned long points; | |
258 | ||
259 | /* | |
260 | * skip kernel threads and tasks which have already released | |
261 | * their mm. | |
262 | */ | |
263 | if (!p->mm) | |
264 | continue; | |
265 | /* skip the init task */ | |
266 | if (is_global_init(p)) | |
267 | continue; | |
268 | if (mem && !task_in_mem_cgroup(p, mem)) | |
269 | continue; | |
270 | ||
271 | /* | |
272 | * This task already has access to memory reserves and is | |
273 | * being killed. Don't allow any other task access to the | |
274 | * memory reserve. | |
275 | * | |
276 | * Note: this may have a chance of deadlock if it gets | |
277 | * blocked waiting for another task which itself is waiting | |
278 | * for memory. Is there a better alternative? | |
279 | */ | |
280 | if (test_tsk_thread_flag(p, TIF_MEMDIE)) | |
281 | return ERR_PTR(-1UL); | |
282 | ||
283 | /* | |
284 | * This is in the process of releasing memory so wait for it | |
285 | * to finish before killing some other task by mistake. | |
286 | * | |
287 | * However, if p is the current task, we allow the 'kill' to | |
288 | * go ahead if it is exiting: this will simply set TIF_MEMDIE, | |
289 | * which will allow it to gain access to memory reserves in | |
290 | * the process of exiting and releasing its resources. | |
291 | * Otherwise we could get an easy OOM deadlock. | |
292 | */ | |
293 | if (p->flags & PF_EXITING) { | |
294 | if (p != current) | |
295 | return ERR_PTR(-1UL); | |
296 | ||
297 | chosen = p; | |
298 | *ppoints = ULONG_MAX; | |
299 | } | |
300 | ||
301 | if (p->signal->oom_adj == OOM_DISABLE) | |
302 | continue; | |
303 | ||
304 | points = badness(p, uptime.tv_sec); | |
305 | if (points > *ppoints || !chosen) { | |
306 | chosen = p; | |
307 | *ppoints = points; | |
308 | } | |
309 | } | |
310 | ||
311 | return chosen; | |
312 | } | |
313 | ||
314 | /** | |
315 | * dump_tasks - dump current memory state of all system tasks | |
316 | * @mem: target memory controller | |
317 | * | |
318 | * Dumps the current memory state of all system tasks, excluding kernel threads. | |
319 | * State information includes task's pid, uid, tgid, vm size, rss, cpu, oom_adj | |
320 | * score, and name. | |
321 | * | |
322 | * If the actual is non-NULL, only tasks that are a member of the mem_cgroup are | |
323 | * shown. | |
324 | * | |
325 | * Call with tasklist_lock read-locked. | |
326 | */ | |
327 | static void dump_tasks(const struct mem_cgroup *mem) | |
328 | { | |
329 | struct task_struct *g, *p; | |
330 | ||
331 | printk(KERN_INFO "[ pid ] uid tgid total_vm rss cpu oom_adj " | |
332 | "name\n"); | |
333 | do_each_thread(g, p) { | |
334 | struct mm_struct *mm; | |
335 | ||
336 | if (mem && !task_in_mem_cgroup(p, mem)) | |
337 | continue; | |
338 | if (!thread_group_leader(p)) | |
339 | continue; | |
340 | ||
341 | task_lock(p); | |
342 | mm = p->mm; | |
343 | if (!mm) { | |
344 | /* | |
345 | * total_vm and rss sizes do not exist for tasks with no | |
346 | * mm so there's no need to report them; they can't be | |
347 | * oom killed anyway. | |
348 | */ | |
349 | task_unlock(p); | |
350 | continue; | |
351 | } | |
352 | printk(KERN_INFO "[%5d] %5d %5d %8lu %8lu %3d %3d %s\n", | |
353 | p->pid, __task_cred(p)->uid, p->tgid, mm->total_vm, | |
354 | get_mm_rss(mm), (int)task_cpu(p), p->signal->oom_adj, | |
355 | p->comm); | |
356 | task_unlock(p); | |
357 | } while_each_thread(g, p); | |
358 | } | |
359 | ||
360 | static void dump_header(struct task_struct *p, gfp_t gfp_mask, int order, | |
361 | struct mem_cgroup *mem) | |
362 | { | |
363 | pr_warning("%s invoked oom-killer: gfp_mask=0x%x, order=%d, " | |
364 | "oom_adj=%d\n", | |
365 | current->comm, gfp_mask, order, current->signal->oom_adj); | |
366 | task_lock(current); | |
367 | cpuset_print_task_mems_allowed(current); | |
368 | task_unlock(current); | |
369 | dump_stack(); | |
370 | mem_cgroup_print_oom_info(mem, p); | |
371 | show_mem(); | |
372 | if (sysctl_oom_dump_tasks) | |
373 | dump_tasks(mem); | |
374 | } | |
375 | ||
376 | #define K(x) ((x) << (PAGE_SHIFT-10)) | |
377 | ||
378 | /* | |
379 | * Send SIGKILL to the selected process irrespective of CAP_SYS_RAW_IO | |
380 | * flag though it's unlikely that we select a process with CAP_SYS_RAW_IO | |
381 | * set. | |
382 | */ | |
383 | static void __oom_kill_task(struct task_struct *p, int verbose) | |
384 | { | |
385 | if (is_global_init(p)) { | |
386 | WARN_ON(1); | |
387 | printk(KERN_WARNING "tried to kill init!\n"); | |
388 | return; | |
389 | } | |
390 | ||
391 | task_lock(p); | |
392 | if (!p->mm) { | |
393 | WARN_ON(1); | |
394 | printk(KERN_WARNING "tried to kill an mm-less task %d (%s)!\n", | |
395 | task_pid_nr(p), p->comm); | |
396 | task_unlock(p); | |
397 | return; | |
398 | } | |
399 | ||
400 | if (verbose) | |
401 | printk(KERN_ERR "Killed process %d (%s) " | |
402 | "vsz:%lukB, anon-rss:%lukB, file-rss:%lukB\n", | |
403 | task_pid_nr(p), p->comm, | |
404 | K(p->mm->total_vm), | |
405 | K(get_mm_counter(p->mm, MM_ANONPAGES)), | |
406 | K(get_mm_counter(p->mm, MM_FILEPAGES))); | |
407 | task_unlock(p); | |
408 | ||
409 | /* | |
410 | * We give our sacrificial lamb high priority and access to | |
411 | * all the memory it needs. That way it should be able to | |
412 | * exit() and clear out its resources quickly... | |
413 | */ | |
414 | p->rt.time_slice = HZ; | |
415 | set_tsk_thread_flag(p, TIF_MEMDIE); | |
416 | ||
417 | force_sig(SIGKILL, p); | |
418 | } | |
419 | ||
420 | static int oom_kill_task(struct task_struct *p) | |
421 | { | |
422 | /* WARNING: mm may not be dereferenced since we did not obtain its | |
423 | * value from get_task_mm(p). This is OK since all we need to do is | |
424 | * compare mm to q->mm below. | |
425 | * | |
426 | * Furthermore, even if mm contains a non-NULL value, p->mm may | |
427 | * change to NULL at any time since we do not hold task_lock(p). | |
428 | * However, this is of no concern to us. | |
429 | */ | |
430 | if (!p->mm || p->signal->oom_adj == OOM_DISABLE) | |
431 | return 1; | |
432 | ||
433 | __oom_kill_task(p, 1); | |
434 | ||
435 | return 0; | |
436 | } | |
437 | ||
438 | static int oom_kill_process(struct task_struct *p, gfp_t gfp_mask, int order, | |
439 | unsigned long points, struct mem_cgroup *mem, | |
440 | const char *message) | |
441 | { | |
442 | struct task_struct *c; | |
443 | ||
444 | if (printk_ratelimit()) | |
445 | dump_header(p, gfp_mask, order, mem); | |
446 | ||
447 | /* | |
448 | * If the task is already exiting, don't alarm the sysadmin or kill | |
449 | * its children or threads, just set TIF_MEMDIE so it can die quickly | |
450 | */ | |
451 | if (p->flags & PF_EXITING) { | |
452 | __oom_kill_task(p, 0); | |
453 | return 0; | |
454 | } | |
455 | ||
456 | printk(KERN_ERR "%s: kill process %d (%s) score %li or a child\n", | |
457 | message, task_pid_nr(p), p->comm, points); | |
458 | ||
459 | /* Try to kill a child first */ | |
460 | list_for_each_entry(c, &p->children, sibling) { | |
461 | if (c->mm == p->mm) | |
462 | continue; | |
463 | if (mem && !task_in_mem_cgroup(c, mem)) | |
464 | continue; | |
465 | if (!oom_kill_task(c)) | |
466 | return 0; | |
467 | } | |
468 | return oom_kill_task(p); | |
469 | } | |
470 | ||
471 | #ifdef CONFIG_CGROUP_MEM_RES_CTLR | |
472 | void mem_cgroup_out_of_memory(struct mem_cgroup *mem, gfp_t gfp_mask) | |
473 | { | |
474 | unsigned long points = 0; | |
475 | struct task_struct *p; | |
476 | ||
477 | if (sysctl_panic_on_oom == 2) | |
478 | panic("out of memory(memcg). panic_on_oom is selected.\n"); | |
479 | read_lock(&tasklist_lock); | |
480 | retry: | |
481 | p = select_bad_process(&points, mem); | |
482 | if (!p || PTR_ERR(p) == -1UL) | |
483 | goto out; | |
484 | ||
485 | if (oom_kill_process(p, gfp_mask, 0, points, mem, | |
486 | "Memory cgroup out of memory")) | |
487 | goto retry; | |
488 | out: | |
489 | read_unlock(&tasklist_lock); | |
490 | } | |
491 | #endif | |
492 | ||
493 | static BLOCKING_NOTIFIER_HEAD(oom_notify_list); | |
494 | ||
495 | int register_oom_notifier(struct notifier_block *nb) | |
496 | { | |
497 | return blocking_notifier_chain_register(&oom_notify_list, nb); | |
498 | } | |
499 | EXPORT_SYMBOL_GPL(register_oom_notifier); | |
500 | ||
501 | int unregister_oom_notifier(struct notifier_block *nb) | |
502 | { | |
503 | return blocking_notifier_chain_unregister(&oom_notify_list, nb); | |
504 | } | |
505 | EXPORT_SYMBOL_GPL(unregister_oom_notifier); | |
506 | ||
507 | /* | |
508 | * Try to acquire the OOM killer lock for the zones in zonelist. Returns zero | |
509 | * if a parallel OOM killing is already taking place that includes a zone in | |
510 | * the zonelist. Otherwise, locks all zones in the zonelist and returns 1. | |
511 | */ | |
512 | int try_set_zone_oom(struct zonelist *zonelist, gfp_t gfp_mask) | |
513 | { | |
514 | struct zoneref *z; | |
515 | struct zone *zone; | |
516 | int ret = 1; | |
517 | ||
518 | spin_lock(&zone_scan_lock); | |
519 | for_each_zone_zonelist(zone, z, zonelist, gfp_zone(gfp_mask)) { | |
520 | if (zone_is_oom_locked(zone)) { | |
521 | ret = 0; | |
522 | goto out; | |
523 | } | |
524 | } | |
525 | ||
526 | for_each_zone_zonelist(zone, z, zonelist, gfp_zone(gfp_mask)) { | |
527 | /* | |
528 | * Lock each zone in the zonelist under zone_scan_lock so a | |
529 | * parallel invocation of try_set_zone_oom() doesn't succeed | |
530 | * when it shouldn't. | |
531 | */ | |
532 | zone_set_flag(zone, ZONE_OOM_LOCKED); | |
533 | } | |
534 | ||
535 | out: | |
536 | spin_unlock(&zone_scan_lock); | |
537 | return ret; | |
538 | } | |
539 | ||
540 | /* | |
541 | * Clears the ZONE_OOM_LOCKED flag for all zones in the zonelist so that failed | |
542 | * allocation attempts with zonelists containing them may now recall the OOM | |
543 | * killer, if necessary. | |
544 | */ | |
545 | void clear_zonelist_oom(struct zonelist *zonelist, gfp_t gfp_mask) | |
546 | { | |
547 | struct zoneref *z; | |
548 | struct zone *zone; | |
549 | ||
550 | spin_lock(&zone_scan_lock); | |
551 | for_each_zone_zonelist(zone, z, zonelist, gfp_zone(gfp_mask)) { | |
552 | zone_clear_flag(zone, ZONE_OOM_LOCKED); | |
553 | } | |
554 | spin_unlock(&zone_scan_lock); | |
555 | } | |
556 | ||
557 | /* | |
558 | * Must be called with tasklist_lock held for read. | |
559 | */ | |
560 | static void __out_of_memory(gfp_t gfp_mask, int order) | |
561 | { | |
562 | struct task_struct *p; | |
563 | unsigned long points; | |
564 | ||
565 | if (sysctl_oom_kill_allocating_task) | |
566 | if (!oom_kill_process(current, gfp_mask, order, 0, NULL, | |
567 | "Out of memory (oom_kill_allocating_task)")) | |
568 | return; | |
569 | retry: | |
570 | /* | |
571 | * Rambo mode: Shoot down a process and hope it solves whatever | |
572 | * issues we may have. | |
573 | */ | |
574 | p = select_bad_process(&points, NULL); | |
575 | ||
576 | if (PTR_ERR(p) == -1UL) | |
577 | return; | |
578 | ||
579 | /* Found nothing?!?! Either we hang forever, or we panic. */ | |
580 | if (!p) { | |
581 | read_unlock(&tasklist_lock); | |
582 | dump_header(NULL, gfp_mask, order, NULL); | |
583 | panic("Out of memory and no killable processes...\n"); | |
584 | } | |
585 | ||
586 | if (oom_kill_process(p, gfp_mask, order, points, NULL, | |
587 | "Out of memory")) | |
588 | goto retry; | |
589 | } | |
590 | ||
591 | /* | |
592 | * pagefault handler calls into here because it is out of memory but | |
593 | * doesn't know exactly how or why. | |
594 | */ | |
595 | void pagefault_out_of_memory(void) | |
596 | { | |
597 | unsigned long freed = 0; | |
598 | ||
599 | blocking_notifier_call_chain(&oom_notify_list, 0, &freed); | |
600 | if (freed > 0) | |
601 | /* Got some memory back in the last second. */ | |
602 | return; | |
603 | ||
604 | if (sysctl_panic_on_oom) | |
605 | panic("out of memory from page fault. panic_on_oom is selected.\n"); | |
606 | ||
607 | read_lock(&tasklist_lock); | |
608 | __out_of_memory(0, 0); /* unknown gfp_mask and order */ | |
609 | read_unlock(&tasklist_lock); | |
610 | ||
611 | /* | |
612 | * Give "p" a good chance of killing itself before we | |
613 | * retry to allocate memory. | |
614 | */ | |
615 | if (!test_thread_flag(TIF_MEMDIE)) | |
616 | schedule_timeout_uninterruptible(1); | |
617 | } | |
618 | ||
619 | /** | |
620 | * out_of_memory - kill the "best" process when we run out of memory | |
621 | * @zonelist: zonelist pointer | |
622 | * @gfp_mask: memory allocation flags | |
623 | * @order: amount of memory being requested as a power of 2 | |
624 | * | |
625 | * If we run out of memory, we have the choice between either | |
626 | * killing a random task (bad), letting the system crash (worse) | |
627 | * OR try to be smart about which process to kill. Note that we | |
628 | * don't have to be perfect here, we just have to be good. | |
629 | */ | |
630 | void out_of_memory(struct zonelist *zonelist, gfp_t gfp_mask, | |
631 | int order, nodemask_t *nodemask) | |
632 | { | |
633 | unsigned long freed = 0; | |
634 | enum oom_constraint constraint; | |
635 | ||
636 | blocking_notifier_call_chain(&oom_notify_list, 0, &freed); | |
637 | if (freed > 0) | |
638 | /* Got some memory back in the last second. */ | |
639 | return; | |
640 | ||
641 | if (sysctl_panic_on_oom == 2) { | |
642 | dump_header(NULL, gfp_mask, order, NULL); | |
643 | panic("out of memory. Compulsory panic_on_oom is selected.\n"); | |
644 | } | |
645 | ||
646 | /* | |
647 | * Check if there were limitations on the allocation (only relevant for | |
648 | * NUMA) that may require different handling. | |
649 | */ | |
650 | constraint = constrained_alloc(zonelist, gfp_mask, nodemask); | |
651 | read_lock(&tasklist_lock); | |
652 | ||
653 | switch (constraint) { | |
654 | case CONSTRAINT_MEMORY_POLICY: | |
655 | oom_kill_process(current, gfp_mask, order, 0, NULL, | |
656 | "No available memory (MPOL_BIND)"); | |
657 | break; | |
658 | ||
659 | case CONSTRAINT_NONE: | |
660 | if (sysctl_panic_on_oom) { | |
661 | dump_header(NULL, gfp_mask, order, NULL); | |
662 | panic("out of memory. panic_on_oom is selected\n"); | |
663 | } | |
664 | /* Fall-through */ | |
665 | case CONSTRAINT_CPUSET: | |
666 | __out_of_memory(gfp_mask, order); | |
667 | break; | |
668 | } | |
669 | ||
670 | read_unlock(&tasklist_lock); | |
671 | ||
672 | /* | |
673 | * Give "p" a good chance of killing itself before we | |
674 | * retry to allocate memory unless "p" is current | |
675 | */ | |
676 | if (!test_thread_flag(TIF_MEMDIE)) | |
677 | schedule_timeout_uninterruptible(1); | |
678 | } |