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1da177e4 LT |
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 | |
a49335cc PJ |
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. | |
1da177e4 LT |
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 | ||
8ac773b4 | 18 | #include <linux/oom.h> |
1da177e4 LT |
19 | #include <linux/mm.h> |
20 | #include <linux/sched.h> | |
21 | #include <linux/swap.h> | |
22 | #include <linux/timex.h> | |
23 | #include <linux/jiffies.h> | |
ef08e3b4 | 24 | #include <linux/cpuset.h> |
8bc719d3 MS |
25 | #include <linux/module.h> |
26 | #include <linux/notifier.h> | |
1da177e4 | 27 | |
fadd8fbd | 28 | int sysctl_panic_on_oom; |
1da177e4 LT |
29 | /* #define DEBUG */ |
30 | ||
31 | /** | |
6937a25c | 32 | * badness - calculate a numeric value for how bad this task has been |
1da177e4 | 33 | * @p: task struct of which task we should calculate |
a49335cc | 34 | * @uptime: current uptime in seconds |
1da177e4 LT |
35 | * |
36 | * The formula used is relatively simple and documented inline in the | |
37 | * function. The main rationale is that we want to select a good task | |
38 | * to kill when we run out of memory. | |
39 | * | |
40 | * Good in this context means that: | |
41 | * 1) we lose the minimum amount of work done | |
42 | * 2) we recover a large amount of memory | |
43 | * 3) we don't kill anything innocent of eating tons of memory | |
44 | * 4) we want to kill the minimum amount of processes (one) | |
45 | * 5) we try to kill the process the user expects us to kill, this | |
46 | * algorithm has been meticulously tuned to meet the principle | |
47 | * of least surprise ... (be careful when you change it) | |
48 | */ | |
49 | ||
50 | unsigned long badness(struct task_struct *p, unsigned long uptime) | |
51 | { | |
52 | unsigned long points, cpu_time, run_time, s; | |
97c2c9b8 AM |
53 | struct mm_struct *mm; |
54 | struct task_struct *child; | |
1da177e4 | 55 | |
97c2c9b8 AM |
56 | task_lock(p); |
57 | mm = p->mm; | |
58 | if (!mm) { | |
59 | task_unlock(p); | |
1da177e4 | 60 | return 0; |
97c2c9b8 | 61 | } |
1da177e4 LT |
62 | |
63 | /* | |
64 | * The memory size of the process is the basis for the badness. | |
65 | */ | |
97c2c9b8 AM |
66 | points = mm->total_vm; |
67 | ||
68 | /* | |
69 | * After this unlock we can no longer dereference local variable `mm' | |
70 | */ | |
71 | task_unlock(p); | |
1da177e4 | 72 | |
7ba34859 HD |
73 | /* |
74 | * swapoff can easily use up all memory, so kill those first. | |
75 | */ | |
76 | if (p->flags & PF_SWAPOFF) | |
77 | return ULONG_MAX; | |
78 | ||
1da177e4 LT |
79 | /* |
80 | * Processes which fork a lot of child processes are likely | |
9827b781 | 81 | * a good choice. We add half the vmsize of the children if they |
1da177e4 | 82 | * have an own mm. This prevents forking servers to flood the |
9827b781 KG |
83 | * machine with an endless amount of children. In case a single |
84 | * child is eating the vast majority of memory, adding only half | |
85 | * to the parents will make the child our kill candidate of choice. | |
1da177e4 | 86 | */ |
97c2c9b8 AM |
87 | list_for_each_entry(child, &p->children, sibling) { |
88 | task_lock(child); | |
89 | if (child->mm != mm && child->mm) | |
90 | points += child->mm->total_vm/2 + 1; | |
91 | task_unlock(child); | |
1da177e4 LT |
92 | } |
93 | ||
94 | /* | |
95 | * CPU time is in tens of seconds and run time is in thousands | |
96 | * of seconds. There is no particular reason for this other than | |
97 | * that it turned out to work very well in practice. | |
98 | */ | |
99 | cpu_time = (cputime_to_jiffies(p->utime) + cputime_to_jiffies(p->stime)) | |
100 | >> (SHIFT_HZ + 3); | |
101 | ||
102 | if (uptime >= p->start_time.tv_sec) | |
103 | run_time = (uptime - p->start_time.tv_sec) >> 10; | |
104 | else | |
105 | run_time = 0; | |
106 | ||
107 | s = int_sqrt(cpu_time); | |
108 | if (s) | |
109 | points /= s; | |
110 | s = int_sqrt(int_sqrt(run_time)); | |
111 | if (s) | |
112 | points /= s; | |
113 | ||
114 | /* | |
115 | * Niced processes are most likely less important, so double | |
116 | * their badness points. | |
117 | */ | |
118 | if (task_nice(p) > 0) | |
119 | points *= 2; | |
120 | ||
121 | /* | |
122 | * Superuser processes are usually more important, so we make it | |
123 | * less likely that we kill those. | |
124 | */ | |
125 | if (cap_t(p->cap_effective) & CAP_TO_MASK(CAP_SYS_ADMIN) || | |
126 | p->uid == 0 || p->euid == 0) | |
127 | points /= 4; | |
128 | ||
129 | /* | |
130 | * We don't want to kill a process with direct hardware access. | |
131 | * Not only could that mess up the hardware, but usually users | |
132 | * tend to only have this flag set on applications they think | |
133 | * of as important. | |
134 | */ | |
135 | if (cap_t(p->cap_effective) & CAP_TO_MASK(CAP_SYS_RAWIO)) | |
136 | points /= 4; | |
137 | ||
7887a3da NP |
138 | /* |
139 | * If p's nodes don't overlap ours, it may still help to kill p | |
140 | * because p may have allocated or otherwise mapped memory on | |
141 | * this node before. However it will be less likely. | |
142 | */ | |
143 | if (!cpuset_excl_nodes_overlap(p)) | |
144 | points /= 8; | |
145 | ||
1da177e4 LT |
146 | /* |
147 | * Adjust the score by oomkilladj. | |
148 | */ | |
149 | if (p->oomkilladj) { | |
150 | if (p->oomkilladj > 0) | |
151 | points <<= p->oomkilladj; | |
152 | else | |
153 | points >>= -(p->oomkilladj); | |
154 | } | |
155 | ||
156 | #ifdef DEBUG | |
157 | printk(KERN_DEBUG "OOMkill: task %d (%s) got %d points\n", | |
158 | p->pid, p->comm, points); | |
159 | #endif | |
160 | return points; | |
161 | } | |
162 | ||
9b0f8b04 CL |
163 | /* |
164 | * Types of limitations to the nodes from which allocations may occur | |
165 | */ | |
166 | #define CONSTRAINT_NONE 1 | |
167 | #define CONSTRAINT_MEMORY_POLICY 2 | |
168 | #define CONSTRAINT_CPUSET 3 | |
169 | ||
170 | /* | |
171 | * Determine the type of allocation constraint. | |
172 | */ | |
173 | static inline int constrained_alloc(struct zonelist *zonelist, gfp_t gfp_mask) | |
174 | { | |
175 | #ifdef CONFIG_NUMA | |
176 | struct zone **z; | |
96ac5913 KH |
177 | nodemask_t nodes; |
178 | int node; | |
3d124cbb HD |
179 | |
180 | nodes_clear(nodes); | |
96ac5913 KH |
181 | /* node has memory ? */ |
182 | for_each_online_node(node) | |
183 | if (NODE_DATA(node)->node_present_pages) | |
184 | node_set(node, nodes); | |
9b0f8b04 CL |
185 | |
186 | for (z = zonelist->zones; *z; z++) | |
02a0e53d | 187 | if (cpuset_zone_allowed_softwall(*z, gfp_mask)) |
89fa3024 | 188 | node_clear(zone_to_nid(*z), nodes); |
9b0f8b04 CL |
189 | else |
190 | return CONSTRAINT_CPUSET; | |
191 | ||
192 | if (!nodes_empty(nodes)) | |
193 | return CONSTRAINT_MEMORY_POLICY; | |
194 | #endif | |
195 | ||
196 | return CONSTRAINT_NONE; | |
197 | } | |
198 | ||
1da177e4 LT |
199 | /* |
200 | * Simple selection loop. We chose the process with the highest | |
201 | * number of 'points'. We expect the caller will lock the tasklist. | |
202 | * | |
203 | * (not docbooked, we don't want this one cluttering up the manual) | |
204 | */ | |
9827b781 | 205 | static struct task_struct *select_bad_process(unsigned long *ppoints) |
1da177e4 | 206 | { |
1da177e4 LT |
207 | struct task_struct *g, *p; |
208 | struct task_struct *chosen = NULL; | |
209 | struct timespec uptime; | |
9827b781 | 210 | *ppoints = 0; |
1da177e4 LT |
211 | |
212 | do_posix_clock_monotonic_gettime(&uptime); | |
a49335cc PJ |
213 | do_each_thread(g, p) { |
214 | unsigned long points; | |
a49335cc | 215 | |
28324d1d ON |
216 | /* |
217 | * skip kernel threads and tasks which have already released | |
218 | * their mm. | |
219 | */ | |
5081dde3 NP |
220 | if (!p->mm) |
221 | continue; | |
28324d1d ON |
222 | /* skip the init task */ |
223 | if (is_init(p)) | |
a49335cc | 224 | continue; |
ef08e3b4 | 225 | |
b78483a4 NP |
226 | /* |
227 | * This task already has access to memory reserves and is | |
228 | * being killed. Don't allow any other task access to the | |
229 | * memory reserve. | |
230 | * | |
231 | * Note: this may have a chance of deadlock if it gets | |
232 | * blocked waiting for another task which itself is waiting | |
233 | * for memory. Is there a better alternative? | |
234 | */ | |
235 | if (test_tsk_thread_flag(p, TIF_MEMDIE)) | |
236 | return ERR_PTR(-1UL); | |
237 | ||
a49335cc | 238 | /* |
6937a25c | 239 | * This is in the process of releasing memory so wait for it |
a49335cc | 240 | * to finish before killing some other task by mistake. |
50ec3bbf NP |
241 | * |
242 | * However, if p is the current task, we allow the 'kill' to | |
243 | * go ahead if it is exiting: this will simply set TIF_MEMDIE, | |
244 | * which will allow it to gain access to memory reserves in | |
245 | * the process of exiting and releasing its resources. | |
b78483a4 | 246 | * Otherwise we could get an easy OOM deadlock. |
a49335cc | 247 | */ |
b78483a4 NP |
248 | if (p->flags & PF_EXITING) { |
249 | if (p != current) | |
250 | return ERR_PTR(-1UL); | |
251 | ||
972c4ea5 ON |
252 | chosen = p; |
253 | *ppoints = ULONG_MAX; | |
50ec3bbf | 254 | } |
972c4ea5 | 255 | |
4a3ede10 NP |
256 | if (p->oomkilladj == OOM_DISABLE) |
257 | continue; | |
a49335cc PJ |
258 | |
259 | points = badness(p, uptime.tv_sec); | |
9827b781 | 260 | if (points > *ppoints || !chosen) { |
a49335cc | 261 | chosen = p; |
9827b781 | 262 | *ppoints = points; |
1da177e4 | 263 | } |
a49335cc | 264 | } while_each_thread(g, p); |
972c4ea5 | 265 | |
1da177e4 LT |
266 | return chosen; |
267 | } | |
268 | ||
269 | /** | |
5a291b98 RG |
270 | * Send SIGKILL to the selected process irrespective of CAP_SYS_RAW_IO |
271 | * flag though it's unlikely that we select a process with CAP_SYS_RAW_IO | |
272 | * set. | |
1da177e4 | 273 | */ |
f3af38d3 | 274 | static void __oom_kill_task(struct task_struct *p, int verbose) |
1da177e4 | 275 | { |
f400e198 | 276 | if (is_init(p)) { |
1da177e4 LT |
277 | WARN_ON(1); |
278 | printk(KERN_WARNING "tried to kill init!\n"); | |
279 | return; | |
280 | } | |
281 | ||
01017a22 | 282 | if (!p->mm) { |
1da177e4 LT |
283 | WARN_ON(1); |
284 | printk(KERN_WARNING "tried to kill an mm-less task!\n"); | |
1da177e4 LT |
285 | return; |
286 | } | |
50ec3bbf | 287 | |
f3af38d3 NP |
288 | if (verbose) |
289 | printk(KERN_ERR "Killed process %d (%s)\n", p->pid, p->comm); | |
1da177e4 LT |
290 | |
291 | /* | |
292 | * We give our sacrificial lamb high priority and access to | |
293 | * all the memory it needs. That way it should be able to | |
294 | * exit() and clear out its resources quickly... | |
295 | */ | |
296 | p->time_slice = HZ; | |
297 | set_tsk_thread_flag(p, TIF_MEMDIE); | |
298 | ||
299 | force_sig(SIGKILL, p); | |
300 | } | |
301 | ||
f3af38d3 | 302 | static int oom_kill_task(struct task_struct *p) |
1da177e4 | 303 | { |
01315922 | 304 | struct mm_struct *mm; |
36c8b586 | 305 | struct task_struct *g, *q; |
1da177e4 | 306 | |
01315922 DP |
307 | mm = p->mm; |
308 | ||
309 | /* WARNING: mm may not be dereferenced since we did not obtain its | |
310 | * value from get_task_mm(p). This is OK since all we need to do is | |
311 | * compare mm to q->mm below. | |
312 | * | |
313 | * Furthermore, even if mm contains a non-NULL value, p->mm may | |
314 | * change to NULL at any time since we do not hold task_lock(p). | |
315 | * However, this is of no concern to us. | |
316 | */ | |
317 | ||
01017a22 | 318 | if (mm == NULL) |
01315922 | 319 | return 1; |
1da177e4 | 320 | |
c33e0fca NP |
321 | /* |
322 | * Don't kill the process if any threads are set to OOM_DISABLE | |
323 | */ | |
324 | do_each_thread(g, q) { | |
35ae834f | 325 | if (q->mm == mm && q->oomkilladj == OOM_DISABLE) |
c33e0fca NP |
326 | return 1; |
327 | } while_each_thread(g, q); | |
328 | ||
f3af38d3 | 329 | __oom_kill_task(p, 1); |
c33e0fca | 330 | |
1da177e4 LT |
331 | /* |
332 | * kill all processes that share the ->mm (i.e. all threads), | |
f2a2a710 NP |
333 | * but are in a different thread group. Don't let them have access |
334 | * to memory reserves though, otherwise we might deplete all memory. | |
1da177e4 | 335 | */ |
c33e0fca | 336 | do_each_thread(g, q) { |
1da177e4 | 337 | if (q->mm == mm && q->tgid != p->tgid) |
650a7c97 | 338 | force_sig(SIGKILL, q); |
c33e0fca | 339 | } while_each_thread(g, q); |
1da177e4 | 340 | |
01315922 | 341 | return 0; |
1da177e4 LT |
342 | } |
343 | ||
01315922 DP |
344 | static int oom_kill_process(struct task_struct *p, unsigned long points, |
345 | const char *message) | |
1da177e4 | 346 | { |
1da177e4 LT |
347 | struct task_struct *c; |
348 | struct list_head *tsk; | |
349 | ||
50ec3bbf NP |
350 | /* |
351 | * If the task is already exiting, don't alarm the sysadmin or kill | |
352 | * its children or threads, just set TIF_MEMDIE so it can die quickly | |
353 | */ | |
354 | if (p->flags & PF_EXITING) { | |
f3af38d3 | 355 | __oom_kill_task(p, 0); |
50ec3bbf NP |
356 | return 0; |
357 | } | |
358 | ||
f3af38d3 NP |
359 | printk(KERN_ERR "%s: kill process %d (%s) score %li or a child\n", |
360 | message, p->pid, p->comm, points); | |
361 | ||
1da177e4 LT |
362 | /* Try to kill a child first */ |
363 | list_for_each(tsk, &p->children) { | |
364 | c = list_entry(tsk, struct task_struct, sibling); | |
365 | if (c->mm == p->mm) | |
366 | continue; | |
f3af38d3 | 367 | if (!oom_kill_task(c)) |
01315922 | 368 | return 0; |
1da177e4 | 369 | } |
f3af38d3 | 370 | return oom_kill_task(p); |
1da177e4 LT |
371 | } |
372 | ||
8bc719d3 MS |
373 | static BLOCKING_NOTIFIER_HEAD(oom_notify_list); |
374 | ||
375 | int register_oom_notifier(struct notifier_block *nb) | |
376 | { | |
377 | return blocking_notifier_chain_register(&oom_notify_list, nb); | |
378 | } | |
379 | EXPORT_SYMBOL_GPL(register_oom_notifier); | |
380 | ||
381 | int unregister_oom_notifier(struct notifier_block *nb) | |
382 | { | |
383 | return blocking_notifier_chain_unregister(&oom_notify_list, nb); | |
384 | } | |
385 | EXPORT_SYMBOL_GPL(unregister_oom_notifier); | |
386 | ||
1da177e4 | 387 | /** |
6937a25c | 388 | * out_of_memory - kill the "best" process when we run out of memory |
1da177e4 LT |
389 | * |
390 | * If we run out of memory, we have the choice between either | |
391 | * killing a random task (bad), letting the system crash (worse) | |
392 | * OR try to be smart about which process to kill. Note that we | |
393 | * don't have to be perfect here, we just have to be good. | |
394 | */ | |
9b0f8b04 | 395 | void out_of_memory(struct zonelist *zonelist, gfp_t gfp_mask, int order) |
1da177e4 | 396 | { |
36c8b586 | 397 | struct task_struct *p; |
d6713e04 | 398 | unsigned long points = 0; |
8bc719d3 MS |
399 | unsigned long freed = 0; |
400 | ||
401 | blocking_notifier_call_chain(&oom_notify_list, 0, &freed); | |
402 | if (freed > 0) | |
403 | /* Got some memory back in the last second. */ | |
404 | return; | |
1da177e4 | 405 | |
42639269 | 406 | if (printk_ratelimit()) { |
b72f1604 NP |
407 | printk(KERN_WARNING "%s invoked oom-killer: " |
408 | "gfp_mask=0x%x, order=%d, oomkilladj=%d\n", | |
409 | current->comm, gfp_mask, order, current->oomkilladj); | |
b958f7d9 | 410 | dump_stack(); |
42639269 AB |
411 | show_mem(); |
412 | } | |
578c2fd6 | 413 | |
505970b9 | 414 | cpuset_lock(); |
1da177e4 | 415 | read_lock(&tasklist_lock); |
9b0f8b04 CL |
416 | |
417 | /* | |
418 | * Check if there were limitations on the allocation (only relevant for | |
419 | * NUMA) that may require different handling. | |
420 | */ | |
421 | switch (constrained_alloc(zonelist, gfp_mask)) { | |
422 | case CONSTRAINT_MEMORY_POLICY: | |
01315922 | 423 | oom_kill_process(current, points, |
9b0f8b04 CL |
424 | "No available memory (MPOL_BIND)"); |
425 | break; | |
426 | ||
427 | case CONSTRAINT_CPUSET: | |
01315922 | 428 | oom_kill_process(current, points, |
9b0f8b04 CL |
429 | "No available memory in cpuset"); |
430 | break; | |
431 | ||
432 | case CONSTRAINT_NONE: | |
fadd8fbd KH |
433 | if (sysctl_panic_on_oom) |
434 | panic("out of memory. panic_on_oom is selected\n"); | |
1da177e4 | 435 | retry: |
9b0f8b04 CL |
436 | /* |
437 | * Rambo mode: Shoot down a process and hope it solves whatever | |
438 | * issues we may have. | |
439 | */ | |
440 | p = select_bad_process(&points); | |
1da177e4 | 441 | |
9b0f8b04 CL |
442 | if (PTR_ERR(p) == -1UL) |
443 | goto out; | |
1da177e4 | 444 | |
9b0f8b04 CL |
445 | /* Found nothing?!?! Either we hang forever, or we panic. */ |
446 | if (!p) { | |
447 | read_unlock(&tasklist_lock); | |
448 | cpuset_unlock(); | |
449 | panic("Out of memory and no killable processes...\n"); | |
450 | } | |
1da177e4 | 451 | |
01315922 | 452 | if (oom_kill_process(p, points, "Out of memory")) |
9b0f8b04 CL |
453 | goto retry; |
454 | ||
455 | break; | |
456 | } | |
1da177e4 | 457 | |
9b0f8b04 | 458 | out: |
140ffcec | 459 | read_unlock(&tasklist_lock); |
505970b9 | 460 | cpuset_unlock(); |
1da177e4 LT |
461 | |
462 | /* | |
463 | * Give "p" a good chance of killing itself before we | |
2f659f46 | 464 | * retry to allocate memory unless "p" is current |
1da177e4 | 465 | */ |
2f659f46 | 466 | if (!test_thread_flag(TIF_MEMDIE)) |
140ffcec | 467 | schedule_timeout_uninterruptible(1); |
1da177e4 | 468 | } |