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 #include <linux/ptrace.h> 35 36 int sysctl_panic_on_oom; 37 int sysctl_oom_kill_allocating_task; 38 int sysctl_oom_dump_tasks = 1; 39 static DEFINE_SPINLOCK(zone_scan_lock); 40 41 /** 42 * test_set_oom_score_adj() - set current's oom_score_adj and return old value 43 * @new_val: new oom_score_adj value 44 * 45 * Sets the oom_score_adj value for current to @new_val with proper 46 * synchronization and returns the old value. Usually used to temporarily 47 * set a value, save the old value in the caller, and then reinstate it later. 48 */ 49 int test_set_oom_score_adj(int new_val) 50 { 51 struct sighand_struct *sighand = current->sighand; 52 int old_val; 53 54 spin_lock_irq(&sighand->siglock); 55 old_val = current->signal->oom_score_adj; 56 if (new_val != old_val) { 57 if (new_val == OOM_SCORE_ADJ_MIN) 58 atomic_inc(¤t->mm->oom_disable_count); 59 else if (old_val == OOM_SCORE_ADJ_MIN) 60 atomic_dec(¤t->mm->oom_disable_count); 61 current->signal->oom_score_adj = new_val; 62 } 63 spin_unlock_irq(&sighand->siglock); 64 65 return old_val; 66 } 67 68 #ifdef CONFIG_NUMA 69 /** 70 * has_intersects_mems_allowed() - check task eligiblity for kill 71 * @tsk: task struct of which task to consider 72 * @mask: nodemask passed to page allocator for mempolicy ooms 73 * 74 * Task eligibility is determined by whether or not a candidate task, @tsk, 75 * shares the same mempolicy nodes as current if it is bound by such a policy 76 * and whether or not it has the same set of allowed cpuset nodes. 77 */ 78 static bool has_intersects_mems_allowed(struct task_struct *tsk, 79 const nodemask_t *mask) 80 { 81 struct task_struct *start = tsk; 82 83 do { 84 if (mask) { 85 /* 86 * If this is a mempolicy constrained oom, tsk's 87 * cpuset is irrelevant. Only return true if its 88 * mempolicy intersects current, otherwise it may be 89 * needlessly killed. 90 */ 91 if (mempolicy_nodemask_intersects(tsk, mask)) 92 return true; 93 } else { 94 /* 95 * This is not a mempolicy constrained oom, so only 96 * check the mems of tsk's cpuset. 97 */ 98 if (cpuset_mems_allowed_intersects(current, tsk)) 99 return true; 100 } 101 } while_each_thread(start, tsk); 102 103 return false; 104 } 105 #else 106 static bool has_intersects_mems_allowed(struct task_struct *tsk, 107 const nodemask_t *mask) 108 { 109 return true; 110 } 111 #endif /* CONFIG_NUMA */ 112 113 /* 114 * The process p may have detached its own ->mm while exiting or through 115 * use_mm(), but one or more of its subthreads may still have a valid 116 * pointer. Return p, or any of its subthreads with a valid ->mm, with 117 * task_lock() held. 118 */ 119 struct task_struct *find_lock_task_mm(struct task_struct *p) 120 { 121 struct task_struct *t = p; 122 123 do { 124 task_lock(t); 125 if (likely(t->mm)) 126 return t; 127 task_unlock(t); 128 } while_each_thread(p, t); 129 130 return NULL; 131 } 132 133 /* return true if the task is not adequate as candidate victim task. */ 134 static bool oom_unkillable_task(struct task_struct *p, 135 const struct mem_cgroup *mem, const nodemask_t *nodemask) 136 { 137 if (is_global_init(p)) 138 return true; 139 if (p->flags & PF_KTHREAD) 140 return true; 141 142 /* When mem_cgroup_out_of_memory() and p is not member of the group */ 143 if (mem && !task_in_mem_cgroup(p, mem)) 144 return true; 145 146 /* p may not have freeable memory in nodemask */ 147 if (!has_intersects_mems_allowed(p, nodemask)) 148 return true; 149 150 return false; 151 } 152 153 /** 154 * oom_badness - heuristic function to determine which candidate task to kill 155 * @p: task struct of which task we should calculate 156 * @totalpages: total present RAM allowed for page allocation 157 * 158 * The heuristic for determining which task to kill is made to be as simple and 159 * predictable as possible. The goal is to return the highest value for the 160 * task consuming the most memory to avoid subsequent oom failures. 161 */ 162 unsigned int oom_badness(struct task_struct *p, struct mem_cgroup *mem, 163 const nodemask_t *nodemask, unsigned long totalpages) 164 { 165 int points; 166 167 if (oom_unkillable_task(p, mem, nodemask)) 168 return 0; 169 170 p = find_lock_task_mm(p); 171 if (!p) 172 return 0; 173 174 /* 175 * Shortcut check for a thread sharing p->mm that is OOM_SCORE_ADJ_MIN 176 * so the entire heuristic doesn't need to be executed for something 177 * that cannot be killed. 178 */ 179 if (atomic_read(&p->mm->oom_disable_count)) { 180 task_unlock(p); 181 return 0; 182 } 183 184 /* 185 * The memory controller may have a limit of 0 bytes, so avoid a divide 186 * by zero, if necessary. 187 */ 188 if (!totalpages) 189 totalpages = 1; 190 191 /* 192 * The baseline for the badness score is the proportion of RAM that each 193 * task's rss, pagetable and swap space use. 194 */ 195 points = get_mm_rss(p->mm) + p->mm->nr_ptes; 196 points += get_mm_counter(p->mm, MM_SWAPENTS); 197 198 points *= 1000; 199 points /= totalpages; 200 task_unlock(p); 201 202 /* 203 * Root processes get 3% bonus, just like the __vm_enough_memory() 204 * implementation used by LSMs. 205 */ 206 if (has_capability_noaudit(p, CAP_SYS_ADMIN)) 207 points -= 30; 208 209 /* 210 * /proc/pid/oom_score_adj ranges from -1000 to +1000 such that it may 211 * either completely disable oom killing or always prefer a certain 212 * task. 213 */ 214 points += p->signal->oom_score_adj; 215 216 /* 217 * Never return 0 for an eligible task that may be killed since it's 218 * possible that no single user task uses more than 0.1% of memory and 219 * no single admin tasks uses more than 3.0%. 220 */ 221 if (points <= 0) 222 return 1; 223 return (points < 1000) ? points : 1000; 224 } 225 226 /* 227 * Determine the type of allocation constraint. 228 */ 229 #ifdef CONFIG_NUMA 230 static enum oom_constraint constrained_alloc(struct zonelist *zonelist, 231 gfp_t gfp_mask, nodemask_t *nodemask, 232 unsigned long *totalpages) 233 { 234 struct zone *zone; 235 struct zoneref *z; 236 enum zone_type high_zoneidx = gfp_zone(gfp_mask); 237 bool cpuset_limited = false; 238 int nid; 239 240 /* Default to all available memory */ 241 *totalpages = totalram_pages + total_swap_pages; 242 243 if (!zonelist) 244 return CONSTRAINT_NONE; 245 /* 246 * Reach here only when __GFP_NOFAIL is used. So, we should avoid 247 * to kill current.We have to random task kill in this case. 248 * Hopefully, CONSTRAINT_THISNODE...but no way to handle it, now. 249 */ 250 if (gfp_mask & __GFP_THISNODE) 251 return CONSTRAINT_NONE; 252 253 /* 254 * This is not a __GFP_THISNODE allocation, so a truncated nodemask in 255 * the page allocator means a mempolicy is in effect. Cpuset policy 256 * is enforced in get_page_from_freelist(). 257 */ 258 if (nodemask && !nodes_subset(node_states[N_HIGH_MEMORY], *nodemask)) { 259 *totalpages = total_swap_pages; 260 for_each_node_mask(nid, *nodemask) 261 *totalpages += node_spanned_pages(nid); 262 return CONSTRAINT_MEMORY_POLICY; 263 } 264 265 /* Check this allocation failure is caused by cpuset's wall function */ 266 for_each_zone_zonelist_nodemask(zone, z, zonelist, 267 high_zoneidx, nodemask) 268 if (!cpuset_zone_allowed_softwall(zone, gfp_mask)) 269 cpuset_limited = true; 270 271 if (cpuset_limited) { 272 *totalpages = total_swap_pages; 273 for_each_node_mask(nid, cpuset_current_mems_allowed) 274 *totalpages += node_spanned_pages(nid); 275 return CONSTRAINT_CPUSET; 276 } 277 return CONSTRAINT_NONE; 278 } 279 #else 280 static enum oom_constraint constrained_alloc(struct zonelist *zonelist, 281 gfp_t gfp_mask, nodemask_t *nodemask, 282 unsigned long *totalpages) 283 { 284 *totalpages = totalram_pages + total_swap_pages; 285 return CONSTRAINT_NONE; 286 } 287 #endif 288 289 /* 290 * Simple selection loop. We chose the process with the highest 291 * number of 'points'. We expect the caller will lock the tasklist. 292 * 293 * (not docbooked, we don't want this one cluttering up the manual) 294 */ 295 static struct task_struct *select_bad_process(unsigned int *ppoints, 296 unsigned long totalpages, struct mem_cgroup *mem, 297 const nodemask_t *nodemask) 298 { 299 struct task_struct *g, *p; 300 struct task_struct *chosen = NULL; 301 *ppoints = 0; 302 303 do_each_thread(g, p) { 304 unsigned int points; 305 306 if (p->exit_state) 307 continue; 308 if (oom_unkillable_task(p, mem, nodemask)) 309 continue; 310 311 /* 312 * This task already has access to memory reserves and is 313 * being killed. Don't allow any other task access to the 314 * memory reserve. 315 * 316 * Note: this may have a chance of deadlock if it gets 317 * blocked waiting for another task which itself is waiting 318 * for memory. Is there a better alternative? 319 */ 320 if (test_tsk_thread_flag(p, TIF_MEMDIE)) 321 return ERR_PTR(-1UL); 322 if (!p->mm) 323 continue; 324 325 if (p->flags & PF_EXITING) { 326 /* 327 * If p is the current task and is in the process of 328 * releasing memory, we allow the "kill" to set 329 * TIF_MEMDIE, which will allow it to gain access to 330 * memory reserves. Otherwise, it may stall forever. 331 * 332 * The loop isn't broken here, however, in case other 333 * threads are found to have already been oom killed. 334 */ 335 if (p == current) { 336 chosen = p; 337 *ppoints = 1000; 338 } else { 339 /* 340 * If this task is not being ptraced on exit, 341 * then wait for it to finish before killing 342 * some other task unnecessarily. 343 */ 344 if (!(p->group_leader->ptrace & PT_TRACE_EXIT)) 345 return ERR_PTR(-1UL); 346 } 347 } 348 349 points = oom_badness(p, mem, nodemask, totalpages); 350 if (points > *ppoints) { 351 chosen = p; 352 *ppoints = points; 353 } 354 } while_each_thread(g, p); 355 356 return chosen; 357 } 358 359 /** 360 * dump_tasks - dump current memory state of all system tasks 361 * @mem: current's memory controller, if constrained 362 * @nodemask: nodemask passed to page allocator for mempolicy ooms 363 * 364 * Dumps the current memory state of all eligible tasks. Tasks not in the same 365 * memcg, not in the same cpuset, or bound to a disjoint set of mempolicy nodes 366 * are not shown. 367 * State information includes task's pid, uid, tgid, vm size, rss, cpu, oom_adj 368 * value, oom_score_adj value, and name. 369 * 370 * Call with tasklist_lock read-locked. 371 */ 372 static void dump_tasks(const struct mem_cgroup *mem, const nodemask_t *nodemask) 373 { 374 struct task_struct *p; 375 struct task_struct *task; 376 377 pr_info("[ pid ] uid tgid total_vm rss cpu oom_adj oom_score_adj name\n"); 378 for_each_process(p) { 379 if (oom_unkillable_task(p, mem, nodemask)) 380 continue; 381 382 task = find_lock_task_mm(p); 383 if (!task) { 384 /* 385 * This is a kthread or all of p's threads have already 386 * detached their mm's. There's no need to report 387 * them; they can't be oom killed anyway. 388 */ 389 continue; 390 } 391 392 pr_info("[%5d] %5d %5d %8lu %8lu %3u %3d %5d %s\n", 393 task->pid, task_uid(task), task->tgid, 394 task->mm->total_vm, get_mm_rss(task->mm), 395 task_cpu(task), task->signal->oom_adj, 396 task->signal->oom_score_adj, task->comm); 397 task_unlock(task); 398 } 399 } 400 401 static void dump_header(struct task_struct *p, gfp_t gfp_mask, int order, 402 struct mem_cgroup *mem, const nodemask_t *nodemask) 403 { 404 task_lock(current); 405 pr_warning("%s invoked oom-killer: gfp_mask=0x%x, order=%d, " 406 "oom_adj=%d, oom_score_adj=%d\n", 407 current->comm, gfp_mask, order, current->signal->oom_adj, 408 current->signal->oom_score_adj); 409 cpuset_print_task_mems_allowed(current); 410 task_unlock(current); 411 dump_stack(); 412 mem_cgroup_print_oom_info(mem, p); 413 show_mem(SHOW_MEM_FILTER_NODES); 414 if (sysctl_oom_dump_tasks) 415 dump_tasks(mem, nodemask); 416 } 417 418 #define K(x) ((x) << (PAGE_SHIFT-10)) 419 static int oom_kill_task(struct task_struct *p, struct mem_cgroup *mem) 420 { 421 struct task_struct *q; 422 struct mm_struct *mm; 423 424 p = find_lock_task_mm(p); 425 if (!p) 426 return 1; 427 428 /* mm cannot be safely dereferenced after task_unlock(p) */ 429 mm = p->mm; 430 431 pr_err("Killed process %d (%s) total-vm:%lukB, anon-rss:%lukB, file-rss:%lukB\n", 432 task_pid_nr(p), p->comm, K(p->mm->total_vm), 433 K(get_mm_counter(p->mm, MM_ANONPAGES)), 434 K(get_mm_counter(p->mm, MM_FILEPAGES))); 435 task_unlock(p); 436 437 /* 438 * Kill all processes sharing p->mm in other thread groups, if any. 439 * They don't get access to memory reserves or a higher scheduler 440 * priority, though, to avoid depletion of all memory or task 441 * starvation. This prevents mm->mmap_sem livelock when an oom killed 442 * task cannot exit because it requires the semaphore and its contended 443 * by another thread trying to allocate memory itself. That thread will 444 * now get access to memory reserves since it has a pending fatal 445 * signal. 446 */ 447 for_each_process(q) 448 if (q->mm == mm && !same_thread_group(q, p)) { 449 task_lock(q); /* Protect ->comm from prctl() */ 450 pr_err("Kill process %d (%s) sharing same memory\n", 451 task_pid_nr(q), q->comm); 452 task_unlock(q); 453 force_sig(SIGKILL, q); 454 } 455 456 set_tsk_thread_flag(p, TIF_MEMDIE); 457 force_sig(SIGKILL, p); 458 459 return 0; 460 } 461 #undef K 462 463 static int oom_kill_process(struct task_struct *p, gfp_t gfp_mask, int order, 464 unsigned int points, unsigned long totalpages, 465 struct mem_cgroup *mem, nodemask_t *nodemask, 466 const char *message) 467 { 468 struct task_struct *victim = p; 469 struct task_struct *child; 470 struct task_struct *t = p; 471 unsigned int victim_points = 0; 472 473 if (printk_ratelimit()) 474 dump_header(p, gfp_mask, order, mem, nodemask); 475 476 /* 477 * If the task is already exiting, don't alarm the sysadmin or kill 478 * its children or threads, just set TIF_MEMDIE so it can die quickly 479 */ 480 if (p->flags & PF_EXITING) { 481 set_tsk_thread_flag(p, TIF_MEMDIE); 482 return 0; 483 } 484 485 task_lock(p); 486 pr_err("%s: Kill process %d (%s) score %d or sacrifice child\n", 487 message, task_pid_nr(p), p->comm, points); 488 task_unlock(p); 489 490 /* 491 * If any of p's children has a different mm and is eligible for kill, 492 * the one with the highest oom_badness() score is sacrificed for its 493 * parent. This attempts to lose the minimal amount of work done while 494 * still freeing memory. 495 */ 496 do { 497 list_for_each_entry(child, &t->children, sibling) { 498 unsigned int child_points; 499 500 if (child->mm == p->mm) 501 continue; 502 /* 503 * oom_badness() returns 0 if the thread is unkillable 504 */ 505 child_points = oom_badness(child, mem, nodemask, 506 totalpages); 507 if (child_points > victim_points) { 508 victim = child; 509 victim_points = child_points; 510 } 511 } 512 } while_each_thread(p, t); 513 514 return oom_kill_task(victim, mem); 515 } 516 517 /* 518 * Determines whether the kernel must panic because of the panic_on_oom sysctl. 519 */ 520 static void check_panic_on_oom(enum oom_constraint constraint, gfp_t gfp_mask, 521 int order, const nodemask_t *nodemask) 522 { 523 if (likely(!sysctl_panic_on_oom)) 524 return; 525 if (sysctl_panic_on_oom != 2) { 526 /* 527 * panic_on_oom == 1 only affects CONSTRAINT_NONE, the kernel 528 * does not panic for cpuset, mempolicy, or memcg allocation 529 * failures. 530 */ 531 if (constraint != CONSTRAINT_NONE) 532 return; 533 } 534 read_lock(&tasklist_lock); 535 dump_header(NULL, gfp_mask, order, NULL, nodemask); 536 read_unlock(&tasklist_lock); 537 panic("Out of memory: %s panic_on_oom is enabled\n", 538 sysctl_panic_on_oom == 2 ? "compulsory" : "system-wide"); 539 } 540 541 #ifdef CONFIG_CGROUP_MEM_RES_CTLR 542 void mem_cgroup_out_of_memory(struct mem_cgroup *mem, gfp_t gfp_mask) 543 { 544 unsigned long limit; 545 unsigned int points = 0; 546 struct task_struct *p; 547 548 /* 549 * If current has a pending SIGKILL, then automatically select it. The 550 * goal is to allow it to allocate so that it may quickly exit and free 551 * its memory. 552 */ 553 if (fatal_signal_pending(current)) { 554 set_thread_flag(TIF_MEMDIE); 555 return; 556 } 557 558 check_panic_on_oom(CONSTRAINT_MEMCG, gfp_mask, 0, NULL); 559 limit = mem_cgroup_get_limit(mem) >> PAGE_SHIFT; 560 read_lock(&tasklist_lock); 561 retry: 562 p = select_bad_process(&points, limit, mem, NULL); 563 if (!p || PTR_ERR(p) == -1UL) 564 goto out; 565 566 if (oom_kill_process(p, gfp_mask, 0, points, limit, mem, NULL, 567 "Memory cgroup out of memory")) 568 goto retry; 569 out: 570 read_unlock(&tasklist_lock); 571 } 572 #endif 573 574 static BLOCKING_NOTIFIER_HEAD(oom_notify_list); 575 576 int register_oom_notifier(struct notifier_block *nb) 577 { 578 return blocking_notifier_chain_register(&oom_notify_list, nb); 579 } 580 EXPORT_SYMBOL_GPL(register_oom_notifier); 581 582 int unregister_oom_notifier(struct notifier_block *nb) 583 { 584 return blocking_notifier_chain_unregister(&oom_notify_list, nb); 585 } 586 EXPORT_SYMBOL_GPL(unregister_oom_notifier); 587 588 /* 589 * Try to acquire the OOM killer lock for the zones in zonelist. Returns zero 590 * if a parallel OOM killing is already taking place that includes a zone in 591 * the zonelist. Otherwise, locks all zones in the zonelist and returns 1. 592 */ 593 int try_set_zonelist_oom(struct zonelist *zonelist, gfp_t gfp_mask) 594 { 595 struct zoneref *z; 596 struct zone *zone; 597 int ret = 1; 598 599 spin_lock(&zone_scan_lock); 600 for_each_zone_zonelist(zone, z, zonelist, gfp_zone(gfp_mask)) { 601 if (zone_is_oom_locked(zone)) { 602 ret = 0; 603 goto out; 604 } 605 } 606 607 for_each_zone_zonelist(zone, z, zonelist, gfp_zone(gfp_mask)) { 608 /* 609 * Lock each zone in the zonelist under zone_scan_lock so a 610 * parallel invocation of try_set_zonelist_oom() doesn't succeed 611 * when it shouldn't. 612 */ 613 zone_set_flag(zone, ZONE_OOM_LOCKED); 614 } 615 616 out: 617 spin_unlock(&zone_scan_lock); 618 return ret; 619 } 620 621 /* 622 * Clears the ZONE_OOM_LOCKED flag for all zones in the zonelist so that failed 623 * allocation attempts with zonelists containing them may now recall the OOM 624 * killer, if necessary. 625 */ 626 void clear_zonelist_oom(struct zonelist *zonelist, gfp_t gfp_mask) 627 { 628 struct zoneref *z; 629 struct zone *zone; 630 631 spin_lock(&zone_scan_lock); 632 for_each_zone_zonelist(zone, z, zonelist, gfp_zone(gfp_mask)) { 633 zone_clear_flag(zone, ZONE_OOM_LOCKED); 634 } 635 spin_unlock(&zone_scan_lock); 636 } 637 638 /* 639 * Try to acquire the oom killer lock for all system zones. Returns zero if a 640 * parallel oom killing is taking place, otherwise locks all zones and returns 641 * non-zero. 642 */ 643 static int try_set_system_oom(void) 644 { 645 struct zone *zone; 646 int ret = 1; 647 648 spin_lock(&zone_scan_lock); 649 for_each_populated_zone(zone) 650 if (zone_is_oom_locked(zone)) { 651 ret = 0; 652 goto out; 653 } 654 for_each_populated_zone(zone) 655 zone_set_flag(zone, ZONE_OOM_LOCKED); 656 out: 657 spin_unlock(&zone_scan_lock); 658 return ret; 659 } 660 661 /* 662 * Clears ZONE_OOM_LOCKED for all system zones so that failed allocation 663 * attempts or page faults may now recall the oom killer, if necessary. 664 */ 665 static void clear_system_oom(void) 666 { 667 struct zone *zone; 668 669 spin_lock(&zone_scan_lock); 670 for_each_populated_zone(zone) 671 zone_clear_flag(zone, ZONE_OOM_LOCKED); 672 spin_unlock(&zone_scan_lock); 673 } 674 675 /** 676 * out_of_memory - kill the "best" process when we run out of memory 677 * @zonelist: zonelist pointer 678 * @gfp_mask: memory allocation flags 679 * @order: amount of memory being requested as a power of 2 680 * @nodemask: nodemask passed to page allocator 681 * 682 * If we run out of memory, we have the choice between either 683 * killing a random task (bad), letting the system crash (worse) 684 * OR try to be smart about which process to kill. Note that we 685 * don't have to be perfect here, we just have to be good. 686 */ 687 void out_of_memory(struct zonelist *zonelist, gfp_t gfp_mask, 688 int order, nodemask_t *nodemask) 689 { 690 const nodemask_t *mpol_mask; 691 struct task_struct *p; 692 unsigned long totalpages; 693 unsigned long freed = 0; 694 unsigned int points; 695 enum oom_constraint constraint = CONSTRAINT_NONE; 696 int killed = 0; 697 698 blocking_notifier_call_chain(&oom_notify_list, 0, &freed); 699 if (freed > 0) 700 /* Got some memory back in the last second. */ 701 return; 702 703 /* 704 * If current has a pending SIGKILL, then automatically select it. The 705 * goal is to allow it to allocate so that it may quickly exit and free 706 * its memory. 707 */ 708 if (fatal_signal_pending(current)) { 709 set_thread_flag(TIF_MEMDIE); 710 return; 711 } 712 713 /* 714 * Check if there were limitations on the allocation (only relevant for 715 * NUMA) that may require different handling. 716 */ 717 constraint = constrained_alloc(zonelist, gfp_mask, nodemask, 718 &totalpages); 719 mpol_mask = (constraint == CONSTRAINT_MEMORY_POLICY) ? nodemask : NULL; 720 check_panic_on_oom(constraint, gfp_mask, order, mpol_mask); 721 722 read_lock(&tasklist_lock); 723 if (sysctl_oom_kill_allocating_task && 724 !oom_unkillable_task(current, NULL, nodemask) && 725 current->mm && !atomic_read(¤t->mm->oom_disable_count)) { 726 /* 727 * oom_kill_process() needs tasklist_lock held. If it returns 728 * non-zero, current could not be killed so we must fallback to 729 * the tasklist scan. 730 */ 731 if (!oom_kill_process(current, gfp_mask, order, 0, totalpages, 732 NULL, nodemask, 733 "Out of memory (oom_kill_allocating_task)")) 734 goto out; 735 } 736 737 retry: 738 p = select_bad_process(&points, totalpages, NULL, mpol_mask); 739 if (PTR_ERR(p) == -1UL) 740 goto out; 741 742 /* Found nothing?!?! Either we hang forever, or we panic. */ 743 if (!p) { 744 dump_header(NULL, gfp_mask, order, NULL, mpol_mask); 745 read_unlock(&tasklist_lock); 746 panic("Out of memory and no killable processes...\n"); 747 } 748 749 if (oom_kill_process(p, gfp_mask, order, points, totalpages, NULL, 750 nodemask, "Out of memory")) 751 goto retry; 752 killed = 1; 753 out: 754 read_unlock(&tasklist_lock); 755 756 /* 757 * Give "p" a good chance of killing itself before we 758 * retry to allocate memory unless "p" is current 759 */ 760 if (killed && !test_thread_flag(TIF_MEMDIE)) 761 schedule_timeout_uninterruptible(1); 762 } 763 764 /* 765 * The pagefault handler calls here because it is out of memory, so kill a 766 * memory-hogging task. If a populated zone has ZONE_OOM_LOCKED set, a parallel 767 * oom killing is already in progress so do nothing. If a task is found with 768 * TIF_MEMDIE set, it has been killed so do nothing and allow it to exit. 769 */ 770 void pagefault_out_of_memory(void) 771 { 772 if (try_set_system_oom()) { 773 out_of_memory(NULL, 0, 0, NULL); 774 clear_system_oom(); 775 } 776 if (!test_thread_flag(TIF_MEMDIE)) 777 schedule_timeout_uninterruptible(1); 778 } 779