Line data Source code
1 : // SPDX-License-Identifier: GPL-2.0-only
2 : /*
3 : * linux/mm/oom_kill.c
4 : *
5 : * Copyright (C) 1998,2000 Rik van Riel
6 : * Thanks go out to Claus Fischer for some serious inspiration and
7 : * for goading me into coding this file...
8 : * Copyright (C) 2010 Google, Inc.
9 : * Rewritten by David Rientjes
10 : *
11 : * The routines in this file are used to kill a process when
12 : * we're seriously out of memory. This gets called from __alloc_pages()
13 : * in mm/page_alloc.c when we really run out of memory.
14 : *
15 : * Since we won't call these routines often (on a well-configured
16 : * machine) this file will double as a 'coding guide' and a signpost
17 : * for newbie kernel hackers. It features several pointers to major
18 : * kernel subsystems and hints as to where to find out what things do.
19 : */
20 :
21 : #include <linux/oom.h>
22 : #include <linux/mm.h>
23 : #include <linux/err.h>
24 : #include <linux/gfp.h>
25 : #include <linux/sched.h>
26 : #include <linux/sched/mm.h>
27 : #include <linux/sched/coredump.h>
28 : #include <linux/sched/task.h>
29 : #include <linux/sched/debug.h>
30 : #include <linux/swap.h>
31 : #include <linux/syscalls.h>
32 : #include <linux/timex.h>
33 : #include <linux/jiffies.h>
34 : #include <linux/cpuset.h>
35 : #include <linux/export.h>
36 : #include <linux/notifier.h>
37 : #include <linux/memcontrol.h>
38 : #include <linux/mempolicy.h>
39 : #include <linux/security.h>
40 : #include <linux/ptrace.h>
41 : #include <linux/freezer.h>
42 : #include <linux/ftrace.h>
43 : #include <linux/ratelimit.h>
44 : #include <linux/kthread.h>
45 : #include <linux/init.h>
46 : #include <linux/mmu_notifier.h>
47 :
48 : #include <asm/tlb.h>
49 : #include "internal.h"
50 : #include "slab.h"
51 :
52 : #define CREATE_TRACE_POINTS
53 : #include <trace/events/oom.h>
54 :
55 : static int sysctl_panic_on_oom;
56 : static int sysctl_oom_kill_allocating_task;
57 : static int sysctl_oom_dump_tasks = 1;
58 :
59 : /*
60 : * Serializes oom killer invocations (out_of_memory()) from all contexts to
61 : * prevent from over eager oom killing (e.g. when the oom killer is invoked
62 : * from different domains).
63 : *
64 : * oom_killer_disable() relies on this lock to stabilize oom_killer_disabled
65 : * and mark_oom_victim
66 : */
67 : DEFINE_MUTEX(oom_lock);
68 : /* Serializes oom_score_adj and oom_score_adj_min updates */
69 : DEFINE_MUTEX(oom_adj_mutex);
70 :
71 : static inline bool is_memcg_oom(struct oom_control *oc)
72 : {
73 : return oc->memcg != NULL;
74 : }
75 :
76 : #ifdef CONFIG_NUMA
77 : /**
78 : * oom_cpuset_eligible() - check task eligibility for kill
79 : * @start: task struct of which task to consider
80 : * @oc: pointer to struct oom_control
81 : *
82 : * Task eligibility is determined by whether or not a candidate task, @tsk,
83 : * shares the same mempolicy nodes as current if it is bound by such a policy
84 : * and whether or not it has the same set of allowed cpuset nodes.
85 : *
86 : * This function is assuming oom-killer context and 'current' has triggered
87 : * the oom-killer.
88 : */
89 : static bool oom_cpuset_eligible(struct task_struct *start,
90 : struct oom_control *oc)
91 : {
92 : struct task_struct *tsk;
93 : bool ret = false;
94 : const nodemask_t *mask = oc->nodemask;
95 :
96 : rcu_read_lock();
97 : for_each_thread(start, tsk) {
98 : if (mask) {
99 : /*
100 : * If this is a mempolicy constrained oom, tsk's
101 : * cpuset is irrelevant. Only return true if its
102 : * mempolicy intersects current, otherwise it may be
103 : * needlessly killed.
104 : */
105 : ret = mempolicy_in_oom_domain(tsk, mask);
106 : } else {
107 : /*
108 : * This is not a mempolicy constrained oom, so only
109 : * check the mems of tsk's cpuset.
110 : */
111 : ret = cpuset_mems_allowed_intersects(current, tsk);
112 : }
113 : if (ret)
114 : break;
115 : }
116 : rcu_read_unlock();
117 :
118 : return ret;
119 : }
120 : #else
121 : static bool oom_cpuset_eligible(struct task_struct *tsk, struct oom_control *oc)
122 : {
123 : return true;
124 : }
125 : #endif /* CONFIG_NUMA */
126 :
127 : /*
128 : * The process p may have detached its own ->mm while exiting or through
129 : * kthread_use_mm(), but one or more of its subthreads may still have a valid
130 : * pointer. Return p, or any of its subthreads with a valid ->mm, with
131 : * task_lock() held.
132 : */
133 15 : struct task_struct *find_lock_task_mm(struct task_struct *p)
134 : {
135 : struct task_struct *t;
136 :
137 : rcu_read_lock();
138 :
139 30 : for_each_thread(p, t) {
140 15 : task_lock(t);
141 15 : if (likely(t->mm))
142 : goto found;
143 15 : task_unlock(t);
144 : }
145 : t = NULL;
146 : found:
147 : rcu_read_unlock();
148 :
149 15 : return t;
150 : }
151 :
152 : /*
153 : * order == -1 means the oom kill is required by sysrq, otherwise only
154 : * for display purposes.
155 : */
156 : static inline bool is_sysrq_oom(struct oom_control *oc)
157 : {
158 : return oc->order == -1;
159 : }
160 :
161 : /* return true if the task is not adequate as candidate victim task. */
162 : static bool oom_unkillable_task(struct task_struct *p)
163 : {
164 0 : if (is_global_init(p))
165 : return true;
166 0 : if (p->flags & PF_KTHREAD)
167 : return true;
168 : return false;
169 : }
170 :
171 : /*
172 : * Check whether unreclaimable slab amount is greater than
173 : * all user memory(LRU pages).
174 : * dump_unreclaimable_slab() could help in the case that
175 : * oom due to too much unreclaimable slab used by kernel.
176 : */
177 : static bool should_dump_unreclaim_slab(void)
178 : {
179 : unsigned long nr_lru;
180 :
181 0 : nr_lru = global_node_page_state(NR_ACTIVE_ANON) +
182 0 : global_node_page_state(NR_INACTIVE_ANON) +
183 0 : global_node_page_state(NR_ACTIVE_FILE) +
184 0 : global_node_page_state(NR_INACTIVE_FILE) +
185 0 : global_node_page_state(NR_ISOLATED_ANON) +
186 0 : global_node_page_state(NR_ISOLATED_FILE) +
187 0 : global_node_page_state(NR_UNEVICTABLE);
188 :
189 0 : return (global_node_page_state_pages(NR_SLAB_UNRECLAIMABLE_B) > nr_lru);
190 : }
191 :
192 : /**
193 : * oom_badness - heuristic function to determine which candidate task to kill
194 : * @p: task struct of which task we should calculate
195 : * @totalpages: total present RAM allowed for page allocation
196 : *
197 : * The heuristic for determining which task to kill is made to be as simple and
198 : * predictable as possible. The goal is to return the highest value for the
199 : * task consuming the most memory to avoid subsequent oom failures.
200 : */
201 0 : long oom_badness(struct task_struct *p, unsigned long totalpages)
202 : {
203 : long points;
204 : long adj;
205 :
206 0 : if (oom_unkillable_task(p))
207 : return LONG_MIN;
208 :
209 0 : p = find_lock_task_mm(p);
210 0 : if (!p)
211 : return LONG_MIN;
212 :
213 : /*
214 : * Do not even consider tasks which are explicitly marked oom
215 : * unkillable or have been already oom reaped or the are in
216 : * the middle of vfork
217 : */
218 0 : adj = (long)p->signal->oom_score_adj;
219 0 : if (adj == OOM_SCORE_ADJ_MIN ||
220 0 : test_bit(MMF_OOM_SKIP, &p->mm->flags) ||
221 0 : in_vfork(p)) {
222 : task_unlock(p);
223 0 : return LONG_MIN;
224 : }
225 :
226 : /*
227 : * The baseline for the badness score is the proportion of RAM that each
228 : * task's rss, pagetable and swap space use.
229 : */
230 0 : points = get_mm_rss(p->mm) + get_mm_counter(p->mm, MM_SWAPENTS) +
231 0 : mm_pgtables_bytes(p->mm) / PAGE_SIZE;
232 : task_unlock(p);
233 :
234 : /* Normalize to oom_score_adj units */
235 0 : adj *= totalpages / 1000;
236 0 : points += adj;
237 :
238 0 : return points;
239 : }
240 :
241 : static const char * const oom_constraint_text[] = {
242 : [CONSTRAINT_NONE] = "CONSTRAINT_NONE",
243 : [CONSTRAINT_CPUSET] = "CONSTRAINT_CPUSET",
244 : [CONSTRAINT_MEMORY_POLICY] = "CONSTRAINT_MEMORY_POLICY",
245 : [CONSTRAINT_MEMCG] = "CONSTRAINT_MEMCG",
246 : };
247 :
248 : /*
249 : * Determine the type of allocation constraint.
250 : */
251 : static enum oom_constraint constrained_alloc(struct oom_control *oc)
252 : {
253 : struct zone *zone;
254 : struct zoneref *z;
255 0 : enum zone_type highest_zoneidx = gfp_zone(oc->gfp_mask);
256 0 : bool cpuset_limited = false;
257 : int nid;
258 :
259 0 : if (is_memcg_oom(oc)) {
260 0 : oc->totalpages = mem_cgroup_get_max(oc->memcg) ?: 1;
261 : return CONSTRAINT_MEMCG;
262 : }
263 :
264 : /* Default to all available memory */
265 0 : oc->totalpages = totalram_pages() + total_swap_pages;
266 :
267 : if (!IS_ENABLED(CONFIG_NUMA))
268 : return CONSTRAINT_NONE;
269 :
270 : if (!oc->zonelist)
271 : return CONSTRAINT_NONE;
272 : /*
273 : * Reach here only when __GFP_NOFAIL is used. So, we should avoid
274 : * to kill current.We have to random task kill in this case.
275 : * Hopefully, CONSTRAINT_THISNODE...but no way to handle it, now.
276 : */
277 : if (oc->gfp_mask & __GFP_THISNODE)
278 : return CONSTRAINT_NONE;
279 :
280 : /*
281 : * This is not a __GFP_THISNODE allocation, so a truncated nodemask in
282 : * the page allocator means a mempolicy is in effect. Cpuset policy
283 : * is enforced in get_page_from_freelist().
284 : */
285 : if (oc->nodemask &&
286 : !nodes_subset(node_states[N_MEMORY], *oc->nodemask)) {
287 : oc->totalpages = total_swap_pages;
288 : for_each_node_mask(nid, *oc->nodemask)
289 : oc->totalpages += node_present_pages(nid);
290 : return CONSTRAINT_MEMORY_POLICY;
291 : }
292 :
293 : /* Check this allocation failure is caused by cpuset's wall function */
294 : for_each_zone_zonelist_nodemask(zone, z, oc->zonelist,
295 : highest_zoneidx, oc->nodemask)
296 : if (!cpuset_zone_allowed(zone, oc->gfp_mask))
297 : cpuset_limited = true;
298 :
299 : if (cpuset_limited) {
300 : oc->totalpages = total_swap_pages;
301 : for_each_node_mask(nid, cpuset_current_mems_allowed)
302 : oc->totalpages += node_present_pages(nid);
303 : return CONSTRAINT_CPUSET;
304 : }
305 : return CONSTRAINT_NONE;
306 : }
307 :
308 0 : static int oom_evaluate_task(struct task_struct *task, void *arg)
309 : {
310 0 : struct oom_control *oc = arg;
311 : long points;
312 :
313 0 : if (oom_unkillable_task(task))
314 : goto next;
315 :
316 : /* p may not have freeable memory in nodemask */
317 0 : if (!is_memcg_oom(oc) && !oom_cpuset_eligible(task, oc))
318 : goto next;
319 :
320 : /*
321 : * This task already has access to memory reserves and is being killed.
322 : * Don't allow any other task to have access to the reserves unless
323 : * the task has MMF_OOM_SKIP because chances that it would release
324 : * any memory is quite low.
325 : */
326 0 : if (!is_sysrq_oom(oc) && tsk_is_oom_victim(task)) {
327 0 : if (test_bit(MMF_OOM_SKIP, &task->signal->oom_mm->flags))
328 : goto next;
329 : goto abort;
330 : }
331 :
332 : /*
333 : * If task is allocating a lot of memory and has been marked to be
334 : * killed first if it triggers an oom, then select it.
335 : */
336 0 : if (oom_task_origin(task)) {
337 : points = LONG_MAX;
338 : goto select;
339 : }
340 :
341 0 : points = oom_badness(task, oc->totalpages);
342 0 : if (points == LONG_MIN || points < oc->chosen_points)
343 : goto next;
344 :
345 : select:
346 0 : if (oc->chosen)
347 0 : put_task_struct(oc->chosen);
348 0 : get_task_struct(task);
349 0 : oc->chosen = task;
350 0 : oc->chosen_points = points;
351 : next:
352 : return 0;
353 : abort:
354 0 : if (oc->chosen)
355 0 : put_task_struct(oc->chosen);
356 0 : oc->chosen = (void *)-1UL;
357 0 : return 1;
358 : }
359 :
360 : /*
361 : * Simple selection loop. We choose the process with the highest number of
362 : * 'points'. In case scan was aborted, oc->chosen is set to -1.
363 : */
364 0 : static void select_bad_process(struct oom_control *oc)
365 : {
366 0 : oc->chosen_points = LONG_MIN;
367 :
368 0 : if (is_memcg_oom(oc))
369 : mem_cgroup_scan_tasks(oc->memcg, oom_evaluate_task, oc);
370 : else {
371 : struct task_struct *p;
372 :
373 : rcu_read_lock();
374 0 : for_each_process(p)
375 0 : if (oom_evaluate_task(p, oc))
376 : break;
377 : rcu_read_unlock();
378 : }
379 0 : }
380 :
381 0 : static int dump_task(struct task_struct *p, void *arg)
382 : {
383 0 : struct oom_control *oc = arg;
384 : struct task_struct *task;
385 :
386 0 : if (oom_unkillable_task(p))
387 : return 0;
388 :
389 : /* p may not have freeable memory in nodemask */
390 0 : if (!is_memcg_oom(oc) && !oom_cpuset_eligible(p, oc))
391 : return 0;
392 :
393 0 : task = find_lock_task_mm(p);
394 0 : if (!task) {
395 : /*
396 : * All of p's threads have already detached their mm's. There's
397 : * no need to report them; they can't be oom killed anyway.
398 : */
399 : return 0;
400 : }
401 :
402 0 : pr_info("[%7d] %5d %5d %8lu %8lu %8ld %8lu %5hd %s\n",
403 : task->pid, from_kuid(&init_user_ns, task_uid(task)),
404 : task->tgid, task->mm->total_vm, get_mm_rss(task->mm),
405 : mm_pgtables_bytes(task->mm),
406 : get_mm_counter(task->mm, MM_SWAPENTS),
407 : task->signal->oom_score_adj, task->comm);
408 : task_unlock(task);
409 :
410 0 : return 0;
411 : }
412 :
413 : /**
414 : * dump_tasks - dump current memory state of all system tasks
415 : * @oc: pointer to struct oom_control
416 : *
417 : * Dumps the current memory state of all eligible tasks. Tasks not in the same
418 : * memcg, not in the same cpuset, or bound to a disjoint set of mempolicy nodes
419 : * are not shown.
420 : * State information includes task's pid, uid, tgid, vm size, rss,
421 : * pgtables_bytes, swapents, oom_score_adj value, and name.
422 : */
423 0 : static void dump_tasks(struct oom_control *oc)
424 : {
425 0 : pr_info("Tasks state (memory values in pages):\n");
426 0 : pr_info("[ pid ] uid tgid total_vm rss pgtables_bytes swapents oom_score_adj name\n");
427 :
428 0 : if (is_memcg_oom(oc))
429 : mem_cgroup_scan_tasks(oc->memcg, dump_task, oc);
430 : else {
431 : struct task_struct *p;
432 :
433 : rcu_read_lock();
434 0 : for_each_process(p)
435 0 : dump_task(p, oc);
436 : rcu_read_unlock();
437 : }
438 0 : }
439 :
440 0 : static void dump_oom_summary(struct oom_control *oc, struct task_struct *victim)
441 : {
442 : /* one line summary of the oom killer context. */
443 0 : pr_info("oom-kill:constraint=%s,nodemask=%*pbl",
444 : oom_constraint_text[oc->constraint],
445 : nodemask_pr_args(oc->nodemask));
446 : cpuset_print_current_mems_allowed();
447 0 : mem_cgroup_print_oom_context(oc->memcg, victim);
448 0 : pr_cont(",task=%s,pid=%d,uid=%d\n", victim->comm, victim->pid,
449 : from_kuid(&init_user_ns, task_uid(victim)));
450 0 : }
451 :
452 0 : static void dump_header(struct oom_control *oc, struct task_struct *p)
453 : {
454 0 : pr_warn("%s invoked oom-killer: gfp_mask=%#x(%pGg), order=%d, oom_score_adj=%hd\n",
455 : current->comm, oc->gfp_mask, &oc->gfp_mask, oc->order,
456 : current->signal->oom_score_adj);
457 : if (!IS_ENABLED(CONFIG_COMPACTION) && oc->order)
458 : pr_warn("COMPACTION is disabled!!!\n");
459 :
460 0 : dump_stack();
461 0 : if (is_memcg_oom(oc))
462 : mem_cgroup_print_oom_meminfo(oc->memcg);
463 : else {
464 0 : __show_mem(SHOW_MEM_FILTER_NODES, oc->nodemask, gfp_zone(oc->gfp_mask));
465 0 : if (should_dump_unreclaim_slab())
466 0 : dump_unreclaimable_slab();
467 : }
468 0 : if (sysctl_oom_dump_tasks)
469 0 : dump_tasks(oc);
470 0 : if (p)
471 0 : dump_oom_summary(oc, p);
472 0 : }
473 :
474 : /*
475 : * Number of OOM victims in flight
476 : */
477 : static atomic_t oom_victims = ATOMIC_INIT(0);
478 : static DECLARE_WAIT_QUEUE_HEAD(oom_victims_wait);
479 :
480 : static bool oom_killer_disabled __read_mostly;
481 :
482 : #define K(x) ((x) << (PAGE_SHIFT-10))
483 :
484 : /*
485 : * task->mm can be NULL if the task is the exited group leader. So to
486 : * determine whether the task is using a particular mm, we examine all the
487 : * task's threads: if one of those is using this mm then this task was also
488 : * using it.
489 : */
490 0 : bool process_shares_mm(struct task_struct *p, struct mm_struct *mm)
491 : {
492 : struct task_struct *t;
493 :
494 0 : for_each_thread(p, t) {
495 0 : struct mm_struct *t_mm = READ_ONCE(t->mm);
496 0 : if (t_mm)
497 0 : return t_mm == mm;
498 : }
499 : return false;
500 : }
501 :
502 : #ifdef CONFIG_MMU
503 : /*
504 : * OOM Reaper kernel thread which tries to reap the memory used by the OOM
505 : * victim (if that is possible) to help the OOM killer to move on.
506 : */
507 : static struct task_struct *oom_reaper_th;
508 : static DECLARE_WAIT_QUEUE_HEAD(oom_reaper_wait);
509 : static struct task_struct *oom_reaper_list;
510 : static DEFINE_SPINLOCK(oom_reaper_lock);
511 :
512 0 : static bool __oom_reap_task_mm(struct mm_struct *mm)
513 : {
514 : struct vm_area_struct *vma;
515 0 : bool ret = true;
516 0 : VMA_ITERATOR(vmi, mm, 0);
517 :
518 : /*
519 : * Tell all users of get_user/copy_from_user etc... that the content
520 : * is no longer stable. No barriers really needed because unmapping
521 : * should imply barriers already and the reader would hit a page fault
522 : * if it stumbled over a reaped memory.
523 : */
524 0 : set_bit(MMF_UNSTABLE, &mm->flags);
525 :
526 0 : for_each_vma(vmi, vma) {
527 0 : if (vma->vm_flags & (VM_HUGETLB|VM_PFNMAP))
528 0 : continue;
529 :
530 : /*
531 : * Only anonymous pages have a good chance to be dropped
532 : * without additional steps which we cannot afford as we
533 : * are OOM already.
534 : *
535 : * We do not even care about fs backed pages because all
536 : * which are reclaimable have already been reclaimed and
537 : * we do not want to block exit_mmap by keeping mm ref
538 : * count elevated without a good reason.
539 : */
540 0 : if (vma_is_anonymous(vma) || !(vma->vm_flags & VM_SHARED)) {
541 : struct mmu_notifier_range range;
542 : struct mmu_gather tlb;
543 :
544 0 : mmu_notifier_range_init(&range, MMU_NOTIFY_UNMAP, 0,
545 : mm, vma->vm_start,
546 : vma->vm_end);
547 0 : tlb_gather_mmu(&tlb, mm);
548 0 : if (mmu_notifier_invalidate_range_start_nonblock(&range)) {
549 : tlb_finish_mmu(&tlb);
550 : ret = false;
551 : continue;
552 : }
553 0 : unmap_page_range(&tlb, vma, range.start, range.end, NULL);
554 0 : mmu_notifier_invalidate_range_end(&range);
555 0 : tlb_finish_mmu(&tlb);
556 : }
557 : }
558 :
559 0 : return ret;
560 : }
561 :
562 : /*
563 : * Reaps the address space of the give task.
564 : *
565 : * Returns true on success and false if none or part of the address space
566 : * has been reclaimed and the caller should retry later.
567 : */
568 0 : static bool oom_reap_task_mm(struct task_struct *tsk, struct mm_struct *mm)
569 : {
570 0 : bool ret = true;
571 :
572 0 : if (!mmap_read_trylock(mm)) {
573 : trace_skip_task_reaping(tsk->pid);
574 : return false;
575 : }
576 :
577 : /*
578 : * MMF_OOM_SKIP is set by exit_mmap when the OOM reaper can't
579 : * work on the mm anymore. The check for MMF_OOM_SKIP must run
580 : * under mmap_lock for reading because it serializes against the
581 : * mmap_write_lock();mmap_write_unlock() cycle in exit_mmap().
582 : */
583 0 : if (test_bit(MMF_OOM_SKIP, &mm->flags)) {
584 : trace_skip_task_reaping(tsk->pid);
585 : goto out_unlock;
586 : }
587 :
588 0 : trace_start_task_reaping(tsk->pid);
589 :
590 : /* failed to reap part of the address space. Try again later */
591 0 : ret = __oom_reap_task_mm(mm);
592 0 : if (!ret)
593 : goto out_finish;
594 :
595 0 : pr_info("oom_reaper: reaped process %d (%s), now anon-rss:%lukB, file-rss:%lukB, shmem-rss:%lukB\n",
596 : task_pid_nr(tsk), tsk->comm,
597 : K(get_mm_counter(mm, MM_ANONPAGES)),
598 : K(get_mm_counter(mm, MM_FILEPAGES)),
599 : K(get_mm_counter(mm, MM_SHMEMPAGES)));
600 : out_finish:
601 0 : trace_finish_task_reaping(tsk->pid);
602 : out_unlock:
603 0 : mmap_read_unlock(mm);
604 :
605 0 : return ret;
606 : }
607 :
608 : #define MAX_OOM_REAP_RETRIES 10
609 0 : static void oom_reap_task(struct task_struct *tsk)
610 : {
611 0 : int attempts = 0;
612 0 : struct mm_struct *mm = tsk->signal->oom_mm;
613 :
614 : /* Retry the mmap_read_trylock(mm) a few times */
615 0 : while (attempts++ < MAX_OOM_REAP_RETRIES && !oom_reap_task_mm(tsk, mm))
616 0 : schedule_timeout_idle(HZ/10);
617 :
618 0 : if (attempts <= MAX_OOM_REAP_RETRIES ||
619 0 : test_bit(MMF_OOM_SKIP, &mm->flags))
620 : goto done;
621 :
622 0 : pr_info("oom_reaper: unable to reap pid:%d (%s)\n",
623 : task_pid_nr(tsk), tsk->comm);
624 0 : sched_show_task(tsk);
625 : debug_show_all_locks();
626 :
627 : done:
628 0 : tsk->oom_reaper_list = NULL;
629 :
630 : /*
631 : * Hide this mm from OOM killer because it has been either reaped or
632 : * somebody can't call mmap_write_unlock(mm).
633 : */
634 0 : set_bit(MMF_OOM_SKIP, &mm->flags);
635 :
636 : /* Drop a reference taken by queue_oom_reaper */
637 0 : put_task_struct(tsk);
638 0 : }
639 :
640 1 : static int oom_reaper(void *unused)
641 : {
642 1 : set_freezable();
643 :
644 : while (true) {
645 1 : struct task_struct *tsk = NULL;
646 :
647 1 : wait_event_freezable(oom_reaper_wait, oom_reaper_list != NULL);
648 0 : spin_lock_irq(&oom_reaper_lock);
649 0 : if (oom_reaper_list != NULL) {
650 0 : tsk = oom_reaper_list;
651 0 : oom_reaper_list = tsk->oom_reaper_list;
652 : }
653 0 : spin_unlock_irq(&oom_reaper_lock);
654 :
655 0 : if (tsk)
656 0 : oom_reap_task(tsk);
657 : }
658 :
659 : return 0;
660 : }
661 :
662 0 : static void wake_oom_reaper(struct timer_list *timer)
663 : {
664 0 : struct task_struct *tsk = container_of(timer, struct task_struct,
665 : oom_reaper_timer);
666 0 : struct mm_struct *mm = tsk->signal->oom_mm;
667 : unsigned long flags;
668 :
669 : /* The victim managed to terminate on its own - see exit_mmap */
670 0 : if (test_bit(MMF_OOM_SKIP, &mm->flags)) {
671 0 : put_task_struct(tsk);
672 0 : return;
673 : }
674 :
675 0 : spin_lock_irqsave(&oom_reaper_lock, flags);
676 0 : tsk->oom_reaper_list = oom_reaper_list;
677 0 : oom_reaper_list = tsk;
678 0 : spin_unlock_irqrestore(&oom_reaper_lock, flags);
679 0 : trace_wake_reaper(tsk->pid);
680 0 : wake_up(&oom_reaper_wait);
681 : }
682 :
683 : /*
684 : * Give the OOM victim time to exit naturally before invoking the oom_reaping.
685 : * The timers timeout is arbitrary... the longer it is, the longer the worst
686 : * case scenario for the OOM can take. If it is too small, the oom_reaper can
687 : * get in the way and release resources needed by the process exit path.
688 : * e.g. The futex robust list can sit in Anon|Private memory that gets reaped
689 : * before the exit path is able to wake the futex waiters.
690 : */
691 : #define OOM_REAPER_DELAY (2*HZ)
692 0 : static void queue_oom_reaper(struct task_struct *tsk)
693 : {
694 : /* mm is already queued? */
695 0 : if (test_and_set_bit(MMF_OOM_REAP_QUEUED, &tsk->signal->oom_mm->flags))
696 : return;
697 :
698 0 : get_task_struct(tsk);
699 0 : timer_setup(&tsk->oom_reaper_timer, wake_oom_reaper, 0);
700 0 : tsk->oom_reaper_timer.expires = jiffies + OOM_REAPER_DELAY;
701 0 : add_timer(&tsk->oom_reaper_timer);
702 : }
703 :
704 : #ifdef CONFIG_SYSCTL
705 : static struct ctl_table vm_oom_kill_table[] = {
706 : {
707 : .procname = "panic_on_oom",
708 : .data = &sysctl_panic_on_oom,
709 : .maxlen = sizeof(sysctl_panic_on_oom),
710 : .mode = 0644,
711 : .proc_handler = proc_dointvec_minmax,
712 : .extra1 = SYSCTL_ZERO,
713 : .extra2 = SYSCTL_TWO,
714 : },
715 : {
716 : .procname = "oom_kill_allocating_task",
717 : .data = &sysctl_oom_kill_allocating_task,
718 : .maxlen = sizeof(sysctl_oom_kill_allocating_task),
719 : .mode = 0644,
720 : .proc_handler = proc_dointvec,
721 : },
722 : {
723 : .procname = "oom_dump_tasks",
724 : .data = &sysctl_oom_dump_tasks,
725 : .maxlen = sizeof(sysctl_oom_dump_tasks),
726 : .mode = 0644,
727 : .proc_handler = proc_dointvec,
728 : },
729 : {}
730 : };
731 : #endif
732 :
733 1 : static int __init oom_init(void)
734 : {
735 2 : oom_reaper_th = kthread_run(oom_reaper, NULL, "oom_reaper");
736 : #ifdef CONFIG_SYSCTL
737 1 : register_sysctl_init("vm", vm_oom_kill_table);
738 : #endif
739 1 : return 0;
740 : }
741 : subsys_initcall(oom_init)
742 : #else
743 : static inline void queue_oom_reaper(struct task_struct *tsk)
744 : {
745 : }
746 : #endif /* CONFIG_MMU */
747 :
748 : /**
749 : * mark_oom_victim - mark the given task as OOM victim
750 : * @tsk: task to mark
751 : *
752 : * Has to be called with oom_lock held and never after
753 : * oom has been disabled already.
754 : *
755 : * tsk->mm has to be non NULL and caller has to guarantee it is stable (either
756 : * under task_lock or operate on the current).
757 : */
758 0 : static void mark_oom_victim(struct task_struct *tsk)
759 : {
760 0 : struct mm_struct *mm = tsk->mm;
761 :
762 0 : WARN_ON(oom_killer_disabled);
763 : /* OOM killer might race with memcg OOM */
764 0 : if (test_and_set_tsk_thread_flag(tsk, TIF_MEMDIE))
765 : return;
766 :
767 : /* oom_mm is bound to the signal struct life time. */
768 0 : if (!cmpxchg(&tsk->signal->oom_mm, NULL, mm))
769 0 : mmgrab(tsk->signal->oom_mm);
770 :
771 : /*
772 : * Make sure that the task is woken up from uninterruptible sleep
773 : * if it is frozen because OOM killer wouldn't be able to free
774 : * any memory and livelock. freezing_slow_path will tell the freezer
775 : * that TIF_MEMDIE tasks should be ignored.
776 : */
777 0 : __thaw_task(tsk);
778 0 : atomic_inc(&oom_victims);
779 0 : trace_mark_victim(tsk->pid);
780 : }
781 :
782 : /**
783 : * exit_oom_victim - note the exit of an OOM victim
784 : */
785 0 : void exit_oom_victim(void)
786 : {
787 0 : clear_thread_flag(TIF_MEMDIE);
788 :
789 0 : if (!atomic_dec_return(&oom_victims))
790 0 : wake_up_all(&oom_victims_wait);
791 0 : }
792 :
793 : /**
794 : * oom_killer_enable - enable OOM killer
795 : */
796 0 : void oom_killer_enable(void)
797 : {
798 0 : oom_killer_disabled = false;
799 0 : pr_info("OOM killer enabled.\n");
800 0 : }
801 :
802 : /**
803 : * oom_killer_disable - disable OOM killer
804 : * @timeout: maximum timeout to wait for oom victims in jiffies
805 : *
806 : * Forces all page allocations to fail rather than trigger OOM killer.
807 : * Will block and wait until all OOM victims are killed or the given
808 : * timeout expires.
809 : *
810 : * The function cannot be called when there are runnable user tasks because
811 : * the userspace would see unexpected allocation failures as a result. Any
812 : * new usage of this function should be consulted with MM people.
813 : *
814 : * Returns true if successful and false if the OOM killer cannot be
815 : * disabled.
816 : */
817 0 : bool oom_killer_disable(signed long timeout)
818 : {
819 : signed long ret;
820 :
821 : /*
822 : * Make sure to not race with an ongoing OOM killer. Check that the
823 : * current is not killed (possibly due to sharing the victim's memory).
824 : */
825 0 : if (mutex_lock_killable(&oom_lock))
826 : return false;
827 0 : oom_killer_disabled = true;
828 0 : mutex_unlock(&oom_lock);
829 :
830 0 : ret = wait_event_interruptible_timeout(oom_victims_wait,
831 : !atomic_read(&oom_victims), timeout);
832 0 : if (ret <= 0) {
833 : oom_killer_enable();
834 0 : return false;
835 : }
836 0 : pr_info("OOM killer disabled.\n");
837 :
838 0 : return true;
839 : }
840 :
841 : static inline bool __task_will_free_mem(struct task_struct *task)
842 : {
843 0 : struct signal_struct *sig = task->signal;
844 :
845 : /*
846 : * A coredumping process may sleep for an extended period in
847 : * coredump_task_exit(), so the oom killer cannot assume that
848 : * the process will promptly exit and release memory.
849 : */
850 0 : if (sig->core_state)
851 : return false;
852 :
853 0 : if (sig->flags & SIGNAL_GROUP_EXIT)
854 : return true;
855 :
856 0 : if (thread_group_empty(task) && (task->flags & PF_EXITING))
857 : return true;
858 :
859 : return false;
860 : }
861 :
862 : /*
863 : * Checks whether the given task is dying or exiting and likely to
864 : * release its address space. This means that all threads and processes
865 : * sharing the same mm have to be killed or exiting.
866 : * Caller has to make sure that task->mm is stable (hold task_lock or
867 : * it operates on the current).
868 : */
869 0 : static bool task_will_free_mem(struct task_struct *task)
870 : {
871 0 : struct mm_struct *mm = task->mm;
872 : struct task_struct *p;
873 0 : bool ret = true;
874 :
875 : /*
876 : * Skip tasks without mm because it might have passed its exit_mm and
877 : * exit_oom_victim. oom_reaper could have rescued that but do not rely
878 : * on that for now. We can consider find_lock_task_mm in future.
879 : */
880 0 : if (!mm)
881 : return false;
882 :
883 0 : if (!__task_will_free_mem(task))
884 : return false;
885 :
886 : /*
887 : * This task has already been drained by the oom reaper so there are
888 : * only small chances it will free some more
889 : */
890 0 : if (test_bit(MMF_OOM_SKIP, &mm->flags))
891 : return false;
892 :
893 0 : if (atomic_read(&mm->mm_users) <= 1)
894 : return true;
895 :
896 : /*
897 : * Make sure that all tasks which share the mm with the given tasks
898 : * are dying as well to make sure that a) nobody pins its mm and
899 : * b) the task is also reapable by the oom reaper.
900 : */
901 : rcu_read_lock();
902 0 : for_each_process(p) {
903 0 : if (!process_shares_mm(p, mm))
904 0 : continue;
905 0 : if (same_thread_group(task, p))
906 0 : continue;
907 0 : ret = __task_will_free_mem(p);
908 0 : if (!ret)
909 : break;
910 : }
911 : rcu_read_unlock();
912 :
913 0 : return ret;
914 : }
915 :
916 0 : static void __oom_kill_process(struct task_struct *victim, const char *message)
917 : {
918 : struct task_struct *p;
919 : struct mm_struct *mm;
920 0 : bool can_oom_reap = true;
921 :
922 0 : p = find_lock_task_mm(victim);
923 0 : if (!p) {
924 0 : pr_info("%s: OOM victim %d (%s) is already exiting. Skip killing the task\n",
925 : message, task_pid_nr(victim), victim->comm);
926 0 : put_task_struct(victim);
927 0 : return;
928 0 : } else if (victim != p) {
929 0 : get_task_struct(p);
930 0 : put_task_struct(victim);
931 0 : victim = p;
932 : }
933 :
934 : /* Get a reference to safely compare mm after task_unlock(victim) */
935 0 : mm = victim->mm;
936 0 : mmgrab(mm);
937 :
938 : /* Raise event before sending signal: task reaper must see this */
939 0 : count_vm_event(OOM_KILL);
940 0 : memcg_memory_event_mm(mm, MEMCG_OOM_KILL);
941 :
942 : /*
943 : * We should send SIGKILL before granting access to memory reserves
944 : * in order to prevent the OOM victim from depleting the memory
945 : * reserves from the user space under its control.
946 : */
947 0 : do_send_sig_info(SIGKILL, SEND_SIG_PRIV, victim, PIDTYPE_TGID);
948 0 : mark_oom_victim(victim);
949 0 : pr_err("%s: Killed process %d (%s) total-vm:%lukB, anon-rss:%lukB, file-rss:%lukB, shmem-rss:%lukB, UID:%u pgtables:%lukB oom_score_adj:%hd\n",
950 : message, task_pid_nr(victim), victim->comm, K(mm->total_vm),
951 : K(get_mm_counter(mm, MM_ANONPAGES)),
952 : K(get_mm_counter(mm, MM_FILEPAGES)),
953 : K(get_mm_counter(mm, MM_SHMEMPAGES)),
954 : from_kuid(&init_user_ns, task_uid(victim)),
955 : mm_pgtables_bytes(mm) >> 10, victim->signal->oom_score_adj);
956 0 : task_unlock(victim);
957 :
958 : /*
959 : * Kill all user processes sharing victim->mm in other thread groups, if
960 : * any. They don't get access to memory reserves, though, to avoid
961 : * depletion of all memory. This prevents mm->mmap_lock livelock when an
962 : * oom killed thread cannot exit because it requires the semaphore and
963 : * its contended by another thread trying to allocate memory itself.
964 : * That thread will now get access to memory reserves since it has a
965 : * pending fatal signal.
966 : */
967 : rcu_read_lock();
968 0 : for_each_process(p) {
969 0 : if (!process_shares_mm(p, mm))
970 0 : continue;
971 0 : if (same_thread_group(p, victim))
972 0 : continue;
973 0 : if (is_global_init(p)) {
974 0 : can_oom_reap = false;
975 0 : set_bit(MMF_OOM_SKIP, &mm->flags);
976 0 : pr_info("oom killer %d (%s) has mm pinned by %d (%s)\n",
977 : task_pid_nr(victim), victim->comm,
978 : task_pid_nr(p), p->comm);
979 0 : continue;
980 : }
981 : /*
982 : * No kthread_use_mm() user needs to read from the userspace so
983 : * we are ok to reap it.
984 : */
985 0 : if (unlikely(p->flags & PF_KTHREAD))
986 0 : continue;
987 0 : do_send_sig_info(SIGKILL, SEND_SIG_PRIV, p, PIDTYPE_TGID);
988 : }
989 : rcu_read_unlock();
990 :
991 0 : if (can_oom_reap)
992 0 : queue_oom_reaper(victim);
993 :
994 0 : mmdrop(mm);
995 0 : put_task_struct(victim);
996 : }
997 : #undef K
998 :
999 : /*
1000 : * Kill provided task unless it's secured by setting
1001 : * oom_score_adj to OOM_SCORE_ADJ_MIN.
1002 : */
1003 : static int oom_kill_memcg_member(struct task_struct *task, void *message)
1004 : {
1005 : if (task->signal->oom_score_adj != OOM_SCORE_ADJ_MIN &&
1006 : !is_global_init(task)) {
1007 : get_task_struct(task);
1008 : __oom_kill_process(task, message);
1009 : }
1010 : return 0;
1011 : }
1012 :
1013 0 : static void oom_kill_process(struct oom_control *oc, const char *message)
1014 : {
1015 0 : struct task_struct *victim = oc->chosen;
1016 : struct mem_cgroup *oom_group;
1017 : static DEFINE_RATELIMIT_STATE(oom_rs, DEFAULT_RATELIMIT_INTERVAL,
1018 : DEFAULT_RATELIMIT_BURST);
1019 :
1020 : /*
1021 : * If the task is already exiting, don't alarm the sysadmin or kill
1022 : * its children or threads, just give it access to memory reserves
1023 : * so it can die quickly
1024 : */
1025 0 : task_lock(victim);
1026 0 : if (task_will_free_mem(victim)) {
1027 0 : mark_oom_victim(victim);
1028 0 : queue_oom_reaper(victim);
1029 0 : task_unlock(victim);
1030 0 : put_task_struct(victim);
1031 0 : return;
1032 : }
1033 0 : task_unlock(victim);
1034 :
1035 0 : if (__ratelimit(&oom_rs))
1036 0 : dump_header(oc, victim);
1037 :
1038 : /*
1039 : * Do we need to kill the entire memory cgroup?
1040 : * Or even one of the ancestor memory cgroups?
1041 : * Check this out before killing the victim task.
1042 : */
1043 0 : oom_group = mem_cgroup_get_oom_group(victim, oc->memcg);
1044 :
1045 0 : __oom_kill_process(victim, message);
1046 :
1047 : /*
1048 : * If necessary, kill all tasks in the selected memory cgroup.
1049 : */
1050 : if (oom_group) {
1051 : memcg_memory_event(oom_group, MEMCG_OOM_GROUP_KILL);
1052 : mem_cgroup_print_oom_group(oom_group);
1053 : mem_cgroup_scan_tasks(oom_group, oom_kill_memcg_member,
1054 : (void *)message);
1055 : mem_cgroup_put(oom_group);
1056 : }
1057 : }
1058 :
1059 : /*
1060 : * Determines whether the kernel must panic because of the panic_on_oom sysctl.
1061 : */
1062 0 : static void check_panic_on_oom(struct oom_control *oc)
1063 : {
1064 0 : if (likely(!sysctl_panic_on_oom))
1065 : return;
1066 0 : if (sysctl_panic_on_oom != 2) {
1067 : /*
1068 : * panic_on_oom == 1 only affects CONSTRAINT_NONE, the kernel
1069 : * does not panic for cpuset, mempolicy, or memcg allocation
1070 : * failures.
1071 : */
1072 0 : if (oc->constraint != CONSTRAINT_NONE)
1073 : return;
1074 : }
1075 : /* Do not panic for oom kills triggered by sysrq */
1076 0 : if (is_sysrq_oom(oc))
1077 : return;
1078 0 : dump_header(oc, NULL);
1079 0 : panic("Out of memory: %s panic_on_oom is enabled\n",
1080 0 : sysctl_panic_on_oom == 2 ? "compulsory" : "system-wide");
1081 : }
1082 :
1083 : static BLOCKING_NOTIFIER_HEAD(oom_notify_list);
1084 :
1085 0 : int register_oom_notifier(struct notifier_block *nb)
1086 : {
1087 0 : return blocking_notifier_chain_register(&oom_notify_list, nb);
1088 : }
1089 : EXPORT_SYMBOL_GPL(register_oom_notifier);
1090 :
1091 0 : int unregister_oom_notifier(struct notifier_block *nb)
1092 : {
1093 0 : return blocking_notifier_chain_unregister(&oom_notify_list, nb);
1094 : }
1095 : EXPORT_SYMBOL_GPL(unregister_oom_notifier);
1096 :
1097 : /**
1098 : * out_of_memory - kill the "best" process when we run out of memory
1099 : * @oc: pointer to struct oom_control
1100 : *
1101 : * If we run out of memory, we have the choice between either
1102 : * killing a random task (bad), letting the system crash (worse)
1103 : * OR try to be smart about which process to kill. Note that we
1104 : * don't have to be perfect here, we just have to be good.
1105 : */
1106 0 : bool out_of_memory(struct oom_control *oc)
1107 : {
1108 0 : unsigned long freed = 0;
1109 :
1110 0 : if (oom_killer_disabled)
1111 : return false;
1112 :
1113 0 : if (!is_memcg_oom(oc)) {
1114 0 : blocking_notifier_call_chain(&oom_notify_list, 0, &freed);
1115 0 : if (freed > 0 && !is_sysrq_oom(oc))
1116 : /* Got some memory back in the last second. */
1117 : return true;
1118 : }
1119 :
1120 : /*
1121 : * If current has a pending SIGKILL or is exiting, then automatically
1122 : * select it. The goal is to allow it to allocate so that it may
1123 : * quickly exit and free its memory.
1124 : */
1125 0 : if (task_will_free_mem(current)) {
1126 0 : mark_oom_victim(current);
1127 0 : queue_oom_reaper(current);
1128 0 : return true;
1129 : }
1130 :
1131 : /*
1132 : * The OOM killer does not compensate for IO-less reclaim.
1133 : * pagefault_out_of_memory lost its gfp context so we have to
1134 : * make sure exclude 0 mask - all other users should have at least
1135 : * ___GFP_DIRECT_RECLAIM to get here. But mem_cgroup_oom() has to
1136 : * invoke the OOM killer even if it is a GFP_NOFS allocation.
1137 : */
1138 0 : if (oc->gfp_mask && !(oc->gfp_mask & __GFP_FS) && !is_memcg_oom(oc))
1139 : return true;
1140 :
1141 : /*
1142 : * Check if there were limitations on the allocation (only relevant for
1143 : * NUMA and memcg) that may require different handling.
1144 : */
1145 0 : oc->constraint = constrained_alloc(oc);
1146 0 : if (oc->constraint != CONSTRAINT_MEMORY_POLICY)
1147 0 : oc->nodemask = NULL;
1148 0 : check_panic_on_oom(oc);
1149 :
1150 0 : if (!is_memcg_oom(oc) && sysctl_oom_kill_allocating_task &&
1151 0 : current->mm && !oom_unkillable_task(current) &&
1152 0 : oom_cpuset_eligible(current, oc) &&
1153 0 : current->signal->oom_score_adj != OOM_SCORE_ADJ_MIN) {
1154 0 : get_task_struct(current);
1155 0 : oc->chosen = current;
1156 0 : oom_kill_process(oc, "Out of memory (oom_kill_allocating_task)");
1157 0 : return true;
1158 : }
1159 :
1160 0 : select_bad_process(oc);
1161 : /* Found nothing?!?! */
1162 0 : if (!oc->chosen) {
1163 0 : dump_header(oc, NULL);
1164 0 : pr_warn("Out of memory and no killable processes...\n");
1165 : /*
1166 : * If we got here due to an actual allocation at the
1167 : * system level, we cannot survive this and will enter
1168 : * an endless loop in the allocator. Bail out now.
1169 : */
1170 0 : if (!is_sysrq_oom(oc) && !is_memcg_oom(oc))
1171 0 : panic("System is deadlocked on memory\n");
1172 : }
1173 0 : if (oc->chosen && oc->chosen != (void *)-1UL)
1174 0 : oom_kill_process(oc, !is_memcg_oom(oc) ? "Out of memory" :
1175 : "Memory cgroup out of memory");
1176 0 : return !!oc->chosen;
1177 : }
1178 :
1179 : /*
1180 : * The pagefault handler calls here because some allocation has failed. We have
1181 : * to take care of the memcg OOM here because this is the only safe context without
1182 : * any locks held but let the oom killer triggered from the allocation context care
1183 : * about the global OOM.
1184 : */
1185 0 : void pagefault_out_of_memory(void)
1186 : {
1187 : static DEFINE_RATELIMIT_STATE(pfoom_rs, DEFAULT_RATELIMIT_INTERVAL,
1188 : DEFAULT_RATELIMIT_BURST);
1189 :
1190 0 : if (mem_cgroup_oom_synchronize(true))
1191 : return;
1192 :
1193 0 : if (fatal_signal_pending(current))
1194 : return;
1195 :
1196 0 : if (__ratelimit(&pfoom_rs))
1197 0 : pr_warn("Huh VM_FAULT_OOM leaked out to the #PF handler. Retrying PF\n");
1198 : }
1199 :
1200 0 : SYSCALL_DEFINE2(process_mrelease, int, pidfd, unsigned int, flags)
1201 : {
1202 : #ifdef CONFIG_MMU
1203 0 : struct mm_struct *mm = NULL;
1204 : struct task_struct *task;
1205 : struct task_struct *p;
1206 : unsigned int f_flags;
1207 0 : bool reap = false;
1208 0 : long ret = 0;
1209 :
1210 0 : if (flags)
1211 : return -EINVAL;
1212 :
1213 0 : task = pidfd_get_task(pidfd, &f_flags);
1214 0 : if (IS_ERR(task))
1215 0 : return PTR_ERR(task);
1216 :
1217 : /*
1218 : * Make sure to choose a thread which still has a reference to mm
1219 : * during the group exit
1220 : */
1221 0 : p = find_lock_task_mm(task);
1222 0 : if (!p) {
1223 : ret = -ESRCH;
1224 : goto put_task;
1225 : }
1226 :
1227 0 : mm = p->mm;
1228 0 : mmgrab(mm);
1229 :
1230 0 : if (task_will_free_mem(p))
1231 : reap = true;
1232 : else {
1233 : /* Error only if the work has not been done already */
1234 0 : if (!test_bit(MMF_OOM_SKIP, &mm->flags))
1235 0 : ret = -EINVAL;
1236 : }
1237 : task_unlock(p);
1238 :
1239 0 : if (!reap)
1240 : goto drop_mm;
1241 :
1242 0 : if (mmap_read_lock_killable(mm)) {
1243 : ret = -EINTR;
1244 : goto drop_mm;
1245 : }
1246 : /*
1247 : * Check MMF_OOM_SKIP again under mmap_read_lock protection to ensure
1248 : * possible change in exit_mmap is seen
1249 : */
1250 0 : if (!test_bit(MMF_OOM_SKIP, &mm->flags) && !__oom_reap_task_mm(mm))
1251 0 : ret = -EAGAIN;
1252 : mmap_read_unlock(mm);
1253 :
1254 : drop_mm:
1255 : mmdrop(mm);
1256 : put_task:
1257 0 : put_task_struct(task);
1258 0 : return ret;
1259 : #else
1260 : return -ENOSYS;
1261 : #endif /* CONFIG_MMU */
1262 : }
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