oom_kill.c revision a96cfd6e9176ad442233001b7d15e9ed42234320
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/mempolicy.h> 31#include <linux/security.h> 32 33int sysctl_panic_on_oom; 34int sysctl_oom_kill_allocating_task; 35int sysctl_oom_dump_tasks = 1; 36static DEFINE_SPINLOCK(zone_scan_lock); 37/* #define DEBUG */ 38 39#ifdef CONFIG_NUMA 40/** 41 * has_intersects_mems_allowed() - check task eligiblity for kill 42 * @tsk: task struct of which task to consider 43 * @mask: nodemask passed to page allocator for mempolicy ooms 44 * 45 * Task eligibility is determined by whether or not a candidate task, @tsk, 46 * shares the same mempolicy nodes as current if it is bound by such a policy 47 * and whether or not it has the same set of allowed cpuset nodes. 48 */ 49static bool has_intersects_mems_allowed(struct task_struct *tsk, 50 const nodemask_t *mask) 51{ 52 struct task_struct *start = tsk; 53 54 do { 55 if (mask) { 56 /* 57 * If this is a mempolicy constrained oom, tsk's 58 * cpuset is irrelevant. Only return true if its 59 * mempolicy intersects current, otherwise it may be 60 * needlessly killed. 61 */ 62 if (mempolicy_nodemask_intersects(tsk, mask)) 63 return true; 64 } else { 65 /* 66 * This is not a mempolicy constrained oom, so only 67 * check the mems of tsk's cpuset. 68 */ 69 if (cpuset_mems_allowed_intersects(current, tsk)) 70 return true; 71 } 72 tsk = next_thread(tsk); 73 } while (tsk != start); 74 return false; 75} 76#else 77static bool has_intersects_mems_allowed(struct task_struct *tsk, 78 const nodemask_t *mask) 79{ 80 return true; 81} 82#endif /* CONFIG_NUMA */ 83 84/* 85 * The process p may have detached its own ->mm while exiting or through 86 * use_mm(), but one or more of its subthreads may still have a valid 87 * pointer. Return p, or any of its subthreads with a valid ->mm, with 88 * task_lock() held. 89 */ 90static struct task_struct *find_lock_task_mm(struct task_struct *p) 91{ 92 struct task_struct *t = p; 93 94 do { 95 task_lock(t); 96 if (likely(t->mm)) 97 return t; 98 task_unlock(t); 99 } while_each_thread(p, t); 100 101 return NULL; 102} 103 104/* return true if the task is not adequate as candidate victim task. */ 105static bool oom_unkillable_task(struct task_struct *p, struct mem_cgroup *mem, 106 const nodemask_t *nodemask) 107{ 108 if (is_global_init(p)) 109 return true; 110 if (p->flags & PF_KTHREAD) 111 return true; 112 113 /* When mem_cgroup_out_of_memory() and p is not member of the group */ 114 if (mem && !task_in_mem_cgroup(p, mem)) 115 return true; 116 117 /* p may not have freeable memory in nodemask */ 118 if (!has_intersects_mems_allowed(p, nodemask)) 119 return true; 120 121 return false; 122} 123 124/** 125 * badness - calculate a numeric value for how bad this task has been 126 * @p: task struct of which task we should calculate 127 * @uptime: current uptime in seconds 128 * 129 * The formula used is relatively simple and documented inline in the 130 * function. The main rationale is that we want to select a good task 131 * to kill when we run out of memory. 132 * 133 * Good in this context means that: 134 * 1) we lose the minimum amount of work done 135 * 2) we recover a large amount of memory 136 * 3) we don't kill anything innocent of eating tons of memory 137 * 4) we want to kill the minimum amount of processes (one) 138 * 5) we try to kill the process the user expects us to kill, this 139 * algorithm has been meticulously tuned to meet the principle 140 * of least surprise ... (be careful when you change it) 141 */ 142unsigned long badness(struct task_struct *p, struct mem_cgroup *mem, 143 const nodemask_t *nodemask, unsigned long uptime) 144{ 145 unsigned long points, cpu_time, run_time; 146 struct task_struct *child; 147 struct task_struct *c, *t; 148 int oom_adj = p->signal->oom_adj; 149 struct task_cputime task_time; 150 unsigned long utime; 151 unsigned long stime; 152 153 if (oom_unkillable_task(p, mem, nodemask)) 154 return 0; 155 if (oom_adj == OOM_DISABLE) 156 return 0; 157 158 p = find_lock_task_mm(p); 159 if (!p) 160 return 0; 161 162 /* 163 * The memory size of the process is the basis for the badness. 164 */ 165 points = p->mm->total_vm; 166 task_unlock(p); 167 168 /* 169 * swapoff can easily use up all memory, so kill those first. 170 */ 171 if (p->flags & PF_OOM_ORIGIN) 172 return ULONG_MAX; 173 174 /* 175 * Processes which fork a lot of child processes are likely 176 * a good choice. We add half the vmsize of the children if they 177 * have an own mm. This prevents forking servers to flood the 178 * machine with an endless amount of children. In case a single 179 * child is eating the vast majority of memory, adding only half 180 * to the parents will make the child our kill candidate of choice. 181 */ 182 t = p; 183 do { 184 list_for_each_entry(c, &t->children, sibling) { 185 child = find_lock_task_mm(c); 186 if (child) { 187 if (child->mm != p->mm) 188 points += child->mm->total_vm/2 + 1; 189 task_unlock(child); 190 } 191 } 192 } while_each_thread(p, t); 193 194 /* 195 * CPU time is in tens of seconds and run time is in thousands 196 * of seconds. There is no particular reason for this other than 197 * that it turned out to work very well in practice. 198 */ 199 thread_group_cputime(p, &task_time); 200 utime = cputime_to_jiffies(task_time.utime); 201 stime = cputime_to_jiffies(task_time.stime); 202 cpu_time = (utime + stime) >> (SHIFT_HZ + 3); 203 204 205 if (uptime >= p->start_time.tv_sec) 206 run_time = (uptime - p->start_time.tv_sec) >> 10; 207 else 208 run_time = 0; 209 210 if (cpu_time) 211 points /= int_sqrt(cpu_time); 212 if (run_time) 213 points /= int_sqrt(int_sqrt(run_time)); 214 215 /* 216 * Niced processes are most likely less important, so double 217 * their badness points. 218 */ 219 if (task_nice(p) > 0) 220 points *= 2; 221 222 /* 223 * Superuser processes are usually more important, so we make it 224 * less likely that we kill those. 225 */ 226 if (has_capability_noaudit(p, CAP_SYS_ADMIN) || 227 has_capability_noaudit(p, CAP_SYS_RESOURCE)) 228 points /= 4; 229 230 /* 231 * We don't want to kill a process with direct hardware access. 232 * Not only could that mess up the hardware, but usually users 233 * tend to only have this flag set on applications they think 234 * of as important. 235 */ 236 if (has_capability_noaudit(p, CAP_SYS_RAWIO)) 237 points /= 4; 238 239 /* 240 * Adjust the score by oom_adj. 241 */ 242 if (oom_adj) { 243 if (oom_adj > 0) { 244 if (!points) 245 points = 1; 246 points <<= oom_adj; 247 } else 248 points >>= -(oom_adj); 249 } 250 251#ifdef DEBUG 252 printk(KERN_DEBUG "OOMkill: task %d (%s) got %lu points\n", 253 p->pid, p->comm, points); 254#endif 255 return points; 256} 257 258/* 259 * Determine the type of allocation constraint. 260 */ 261#ifdef CONFIG_NUMA 262static enum oom_constraint constrained_alloc(struct zonelist *zonelist, 263 gfp_t gfp_mask, nodemask_t *nodemask) 264{ 265 struct zone *zone; 266 struct zoneref *z; 267 enum zone_type high_zoneidx = gfp_zone(gfp_mask); 268 269 /* 270 * Reach here only when __GFP_NOFAIL is used. So, we should avoid 271 * to kill current.We have to random task kill in this case. 272 * Hopefully, CONSTRAINT_THISNODE...but no way to handle it, now. 273 */ 274 if (gfp_mask & __GFP_THISNODE) 275 return CONSTRAINT_NONE; 276 277 /* 278 * The nodemask here is a nodemask passed to alloc_pages(). Now, 279 * cpuset doesn't use this nodemask for its hardwall/softwall/hierarchy 280 * feature. mempolicy is an only user of nodemask here. 281 * check mempolicy's nodemask contains all N_HIGH_MEMORY 282 */ 283 if (nodemask && !nodes_subset(node_states[N_HIGH_MEMORY], *nodemask)) 284 return CONSTRAINT_MEMORY_POLICY; 285 286 /* Check this allocation failure is caused by cpuset's wall function */ 287 for_each_zone_zonelist_nodemask(zone, z, zonelist, 288 high_zoneidx, nodemask) 289 if (!cpuset_zone_allowed_softwall(zone, gfp_mask)) 290 return CONSTRAINT_CPUSET; 291 292 return CONSTRAINT_NONE; 293} 294#else 295static enum oom_constraint constrained_alloc(struct zonelist *zonelist, 296 gfp_t gfp_mask, nodemask_t *nodemask) 297{ 298 return CONSTRAINT_NONE; 299} 300#endif 301 302/* 303 * Simple selection loop. We chose the process with the highest 304 * number of 'points'. We expect the caller will lock the tasklist. 305 * 306 * (not docbooked, we don't want this one cluttering up the manual) 307 */ 308static struct task_struct *select_bad_process(unsigned long *ppoints, 309 struct mem_cgroup *mem, const nodemask_t *nodemask) 310{ 311 struct task_struct *p; 312 struct task_struct *chosen = NULL; 313 struct timespec uptime; 314 *ppoints = 0; 315 316 do_posix_clock_monotonic_gettime(&uptime); 317 for_each_process(p) { 318 unsigned long points; 319 320 if (oom_unkillable_task(p, mem, nodemask)) 321 continue; 322 323 /* 324 * This task already has access to memory reserves and is 325 * being killed. Don't allow any other task access to the 326 * memory reserve. 327 * 328 * Note: this may have a chance of deadlock if it gets 329 * blocked waiting for another task which itself is waiting 330 * for memory. Is there a better alternative? 331 */ 332 if (test_tsk_thread_flag(p, TIF_MEMDIE)) 333 return ERR_PTR(-1UL); 334 335 /* 336 * This is in the process of releasing memory so wait for it 337 * to finish before killing some other task by mistake. 338 * 339 * However, if p is the current task, we allow the 'kill' to 340 * go ahead if it is exiting: this will simply set TIF_MEMDIE, 341 * which will allow it to gain access to memory reserves in 342 * the process of exiting and releasing its resources. 343 * Otherwise we could get an easy OOM deadlock. 344 */ 345 if ((p->flags & PF_EXITING) && p->mm) { 346 if (p != current) 347 return ERR_PTR(-1UL); 348 349 chosen = p; 350 *ppoints = ULONG_MAX; 351 } 352 353 points = badness(p, mem, nodemask, uptime.tv_sec); 354 if (points > *ppoints || !chosen) { 355 chosen = p; 356 *ppoints = points; 357 } 358 } 359 360 return chosen; 361} 362 363/** 364 * dump_tasks - dump current memory state of all system tasks 365 * @mem: current's memory controller, if constrained 366 * 367 * Dumps the current memory state of all system tasks, excluding kernel threads. 368 * State information includes task's pid, uid, tgid, vm size, rss, cpu, oom_adj 369 * score, and name. 370 * 371 * If the actual is non-NULL, only tasks that are a member of the mem_cgroup are 372 * shown. 373 * 374 * Call with tasklist_lock read-locked. 375 */ 376static void dump_tasks(const struct mem_cgroup *mem) 377{ 378 struct task_struct *p; 379 struct task_struct *task; 380 381 printk(KERN_INFO "[ pid ] uid tgid total_vm rss cpu oom_adj " 382 "name\n"); 383 for_each_process(p) { 384 if (p->flags & PF_KTHREAD) 385 continue; 386 if (mem && !task_in_mem_cgroup(p, mem)) 387 continue; 388 389 task = find_lock_task_mm(p); 390 if (!task) { 391 /* 392 * This is a kthread or all of p's threads have already 393 * detached their mm's. There's no need to report 394 * them; they can't be oom killed anyway. 395 */ 396 continue; 397 } 398 399 printk(KERN_INFO "[%5d] %5d %5d %8lu %8lu %3u %3d %s\n", 400 task->pid, __task_cred(task)->uid, task->tgid, 401 task->mm->total_vm, get_mm_rss(task->mm), 402 task_cpu(task), task->signal->oom_adj, task->comm); 403 task_unlock(task); 404 } 405} 406 407static void dump_header(struct task_struct *p, gfp_t gfp_mask, int order, 408 struct mem_cgroup *mem) 409{ 410 task_lock(current); 411 pr_warning("%s invoked oom-killer: gfp_mask=0x%x, order=%d, " 412 "oom_adj=%d\n", 413 current->comm, gfp_mask, order, current->signal->oom_adj); 414 cpuset_print_task_mems_allowed(current); 415 task_unlock(current); 416 dump_stack(); 417 mem_cgroup_print_oom_info(mem, p); 418 show_mem(); 419 if (sysctl_oom_dump_tasks) 420 dump_tasks(mem); 421} 422 423#define K(x) ((x) << (PAGE_SHIFT-10)) 424static int oom_kill_task(struct task_struct *p) 425{ 426 p = find_lock_task_mm(p); 427 if (!p) { 428 task_unlock(p); 429 return 1; 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 p->rt.time_slice = HZ; 438 set_tsk_thread_flag(p, TIF_MEMDIE); 439 force_sig(SIGKILL, p); 440 return 0; 441} 442#undef K 443 444static int oom_kill_process(struct task_struct *p, gfp_t gfp_mask, int order, 445 unsigned long points, struct mem_cgroup *mem, 446 nodemask_t *nodemask, const char *message) 447{ 448 struct task_struct *victim = p; 449 struct task_struct *child; 450 struct task_struct *t = p; 451 unsigned long victim_points = 0; 452 struct timespec uptime; 453 454 if (printk_ratelimit()) 455 dump_header(p, gfp_mask, order, mem); 456 457 /* 458 * If the task is already exiting, don't alarm the sysadmin or kill 459 * its children or threads, just set TIF_MEMDIE so it can die quickly 460 */ 461 if (p->flags & PF_EXITING) { 462 set_tsk_thread_flag(p, TIF_MEMDIE); 463 return 0; 464 } 465 466 task_lock(p); 467 pr_err("%s: Kill process %d (%s) score %lu or sacrifice child\n", 468 message, task_pid_nr(p), p->comm, points); 469 task_unlock(p); 470 471 /* 472 * If any of p's children has a different mm and is eligible for kill, 473 * the one with the highest badness() score is sacrificed for its 474 * parent. This attempts to lose the minimal amount of work done while 475 * still freeing memory. 476 */ 477 do_posix_clock_monotonic_gettime(&uptime); 478 do { 479 list_for_each_entry(child, &t->children, sibling) { 480 unsigned long child_points; 481 482 if (child->mm == p->mm) 483 continue; 484 485 /* badness() returns 0 if the thread is unkillable */ 486 child_points = badness(child, mem, nodemask, 487 uptime.tv_sec); 488 if (child_points > victim_points) { 489 victim = child; 490 victim_points = child_points; 491 } 492 } 493 } while_each_thread(p, t); 494 495 return oom_kill_task(victim); 496} 497 498/* 499 * Determines whether the kernel must panic because of the panic_on_oom sysctl. 500 */ 501static void check_panic_on_oom(enum oom_constraint constraint, gfp_t gfp_mask, 502 int order) 503{ 504 if (likely(!sysctl_panic_on_oom)) 505 return; 506 if (sysctl_panic_on_oom != 2) { 507 /* 508 * panic_on_oom == 1 only affects CONSTRAINT_NONE, the kernel 509 * does not panic for cpuset, mempolicy, or memcg allocation 510 * failures. 511 */ 512 if (constraint != CONSTRAINT_NONE) 513 return; 514 } 515 read_lock(&tasklist_lock); 516 dump_header(NULL, gfp_mask, order, NULL); 517 read_unlock(&tasklist_lock); 518 panic("Out of memory: %s panic_on_oom is enabled\n", 519 sysctl_panic_on_oom == 2 ? "compulsory" : "system-wide"); 520} 521 522#ifdef CONFIG_CGROUP_MEM_RES_CTLR 523void mem_cgroup_out_of_memory(struct mem_cgroup *mem, gfp_t gfp_mask) 524{ 525 unsigned long points = 0; 526 struct task_struct *p; 527 528 check_panic_on_oom(CONSTRAINT_MEMCG, gfp_mask, 0); 529 read_lock(&tasklist_lock); 530retry: 531 p = select_bad_process(&points, mem, NULL); 532 if (!p || PTR_ERR(p) == -1UL) 533 goto out; 534 535 if (oom_kill_process(p, gfp_mask, 0, points, mem, NULL, 536 "Memory cgroup out of memory")) 537 goto retry; 538out: 539 read_unlock(&tasklist_lock); 540} 541#endif 542 543static BLOCKING_NOTIFIER_HEAD(oom_notify_list); 544 545int register_oom_notifier(struct notifier_block *nb) 546{ 547 return blocking_notifier_chain_register(&oom_notify_list, nb); 548} 549EXPORT_SYMBOL_GPL(register_oom_notifier); 550 551int unregister_oom_notifier(struct notifier_block *nb) 552{ 553 return blocking_notifier_chain_unregister(&oom_notify_list, nb); 554} 555EXPORT_SYMBOL_GPL(unregister_oom_notifier); 556 557/* 558 * Try to acquire the OOM killer lock for the zones in zonelist. Returns zero 559 * if a parallel OOM killing is already taking place that includes a zone in 560 * the zonelist. Otherwise, locks all zones in the zonelist and returns 1. 561 */ 562int try_set_zonelist_oom(struct zonelist *zonelist, gfp_t gfp_mask) 563{ 564 struct zoneref *z; 565 struct zone *zone; 566 int ret = 1; 567 568 spin_lock(&zone_scan_lock); 569 for_each_zone_zonelist(zone, z, zonelist, gfp_zone(gfp_mask)) { 570 if (zone_is_oom_locked(zone)) { 571 ret = 0; 572 goto out; 573 } 574 } 575 576 for_each_zone_zonelist(zone, z, zonelist, gfp_zone(gfp_mask)) { 577 /* 578 * Lock each zone in the zonelist under zone_scan_lock so a 579 * parallel invocation of try_set_zonelist_oom() doesn't succeed 580 * when it shouldn't. 581 */ 582 zone_set_flag(zone, ZONE_OOM_LOCKED); 583 } 584 585out: 586 spin_unlock(&zone_scan_lock); 587 return ret; 588} 589 590/* 591 * Clears the ZONE_OOM_LOCKED flag for all zones in the zonelist so that failed 592 * allocation attempts with zonelists containing them may now recall the OOM 593 * killer, if necessary. 594 */ 595void clear_zonelist_oom(struct zonelist *zonelist, gfp_t gfp_mask) 596{ 597 struct zoneref *z; 598 struct zone *zone; 599 600 spin_lock(&zone_scan_lock); 601 for_each_zone_zonelist(zone, z, zonelist, gfp_zone(gfp_mask)) { 602 zone_clear_flag(zone, ZONE_OOM_LOCKED); 603 } 604 spin_unlock(&zone_scan_lock); 605} 606 607/* 608 * Try to acquire the oom killer lock for all system zones. Returns zero if a 609 * parallel oom killing is taking place, otherwise locks all zones and returns 610 * non-zero. 611 */ 612static int try_set_system_oom(void) 613{ 614 struct zone *zone; 615 int ret = 1; 616 617 spin_lock(&zone_scan_lock); 618 for_each_populated_zone(zone) 619 if (zone_is_oom_locked(zone)) { 620 ret = 0; 621 goto out; 622 } 623 for_each_populated_zone(zone) 624 zone_set_flag(zone, ZONE_OOM_LOCKED); 625out: 626 spin_unlock(&zone_scan_lock); 627 return ret; 628} 629 630/* 631 * Clears ZONE_OOM_LOCKED for all system zones so that failed allocation 632 * attempts or page faults may now recall the oom killer, if necessary. 633 */ 634static void clear_system_oom(void) 635{ 636 struct zone *zone; 637 638 spin_lock(&zone_scan_lock); 639 for_each_populated_zone(zone) 640 zone_clear_flag(zone, ZONE_OOM_LOCKED); 641 spin_unlock(&zone_scan_lock); 642} 643 644/** 645 * out_of_memory - kill the "best" process when we run out of memory 646 * @zonelist: zonelist pointer 647 * @gfp_mask: memory allocation flags 648 * @order: amount of memory being requested as a power of 2 649 * @nodemask: nodemask passed to page allocator 650 * 651 * If we run out of memory, we have the choice between either 652 * killing a random task (bad), letting the system crash (worse) 653 * OR try to be smart about which process to kill. Note that we 654 * don't have to be perfect here, we just have to be good. 655 */ 656void out_of_memory(struct zonelist *zonelist, gfp_t gfp_mask, 657 int order, nodemask_t *nodemask) 658{ 659 struct task_struct *p; 660 unsigned long freed = 0; 661 unsigned long points; 662 enum oom_constraint constraint = CONSTRAINT_NONE; 663 664 blocking_notifier_call_chain(&oom_notify_list, 0, &freed); 665 if (freed > 0) 666 /* Got some memory back in the last second. */ 667 return; 668 669 /* 670 * If current has a pending SIGKILL, then automatically select it. The 671 * goal is to allow it to allocate so that it may quickly exit and free 672 * its memory. 673 */ 674 if (fatal_signal_pending(current)) { 675 set_thread_flag(TIF_MEMDIE); 676 return; 677 } 678 679 /* 680 * Check if there were limitations on the allocation (only relevant for 681 * NUMA) that may require different handling. 682 */ 683 if (zonelist) 684 constraint = constrained_alloc(zonelist, gfp_mask, nodemask); 685 check_panic_on_oom(constraint, gfp_mask, order); 686 687 read_lock(&tasklist_lock); 688 if (sysctl_oom_kill_allocating_task && 689 !oom_unkillable_task(current, NULL, nodemask) && 690 (current->signal->oom_adj != OOM_DISABLE)) { 691 /* 692 * oom_kill_process() needs tasklist_lock held. If it returns 693 * non-zero, current could not be killed so we must fallback to 694 * the tasklist scan. 695 */ 696 if (!oom_kill_process(current, gfp_mask, order, 0, NULL, 697 nodemask, 698 "Out of memory (oom_kill_allocating_task)")) 699 return; 700 } 701 702retry: 703 p = select_bad_process(&points, NULL, 704 constraint == CONSTRAINT_MEMORY_POLICY ? nodemask : 705 NULL); 706 if (PTR_ERR(p) == -1UL) 707 return; 708 709 /* Found nothing?!?! Either we hang forever, or we panic. */ 710 if (!p) { 711 dump_header(NULL, gfp_mask, order, NULL); 712 read_unlock(&tasklist_lock); 713 panic("Out of memory and no killable processes...\n"); 714 } 715 716 if (oom_kill_process(p, gfp_mask, order, points, NULL, nodemask, 717 "Out of memory")) 718 goto retry; 719 read_unlock(&tasklist_lock); 720 721 /* 722 * Give "p" a good chance of killing itself before we 723 * retry to allocate memory unless "p" is current 724 */ 725 if (!test_thread_flag(TIF_MEMDIE)) 726 schedule_timeout_uninterruptible(1); 727} 728 729/* 730 * The pagefault handler calls here because it is out of memory, so kill a 731 * memory-hogging task. If a populated zone has ZONE_OOM_LOCKED set, a parallel 732 * oom killing is already in progress so do nothing. If a task is found with 733 * TIF_MEMDIE set, it has been killed so do nothing and allow it to exit. 734 */ 735void pagefault_out_of_memory(void) 736{ 737 if (try_set_system_oom()) { 738 out_of_memory(NULL, 0, 0, NULL); 739 clear_system_oom(); 740 } 741 if (!test_thread_flag(TIF_MEMDIE)) 742 schedule_timeout_uninterruptible(1); 743} 744