mm/oom_kill.c

   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/export.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 #include <linux/freezer.h>
  36 #include <linux/ftrace.h>
  37 #include <linux/ratelimit.h>
  38
  39 #define CREATE_TRACE_POINTS
  40 #include <trace/events/oom.h>
  41
  42 int sysctl_panic_on_oom;
  43 int sysctl_oom_kill_allocating_task;
  44 int sysctl_oom_dump_tasks = 1;
  45 static DEFINE_SPINLOCK(zone_scan_lock);
  46
  47 #ifdef CONFIG_NUMA
  48 /**
  49  * has_intersects_mems_allowed() - check task eligiblity for kill
  50  * @tsk: task struct of which task to consider
  51  * @mask: nodemask passed to page allocator for mempolicy ooms
  52  *
  53  * Task eligibility is determined by whether or not a candidate task, @tsk,
  54  * shares the same mempolicy nodes as current if it is bound by such a policy
  55  * and whether or not it has the same set of allowed cpuset nodes.
  56  */
  57 static bool has_intersects_mems_allowed(struct task_struct *tsk,
  58                                         const nodemask_t *mask)
  59 {
  60         struct task_struct *start = tsk;
  61
  62         do {
  63                 if (mask) {
  64                         /*
  65                          * If this is a mempolicy constrained oom, tsk's
  66                          * cpuset is irrelevant.  Only return true if its
  67                          * mempolicy intersects current, otherwise it may be
  68                          * needlessly killed.
  69                          */
  70                         if (mempolicy_nodemask_intersects(tsk, mask))
  71                                 return true;
  72                 } else {
  73                         /*
  74                          * This is not a mempolicy constrained oom, so only
  75                          * check the mems of tsk's cpuset.
  76                          */
  77                         if (cpuset_mems_allowed_intersects(current, tsk))
  78                                 return true;
  79                 }
  80         } while_each_thread(start, tsk);
  81
  82         return false;
  83 }
  84 #else
  85 static bool has_intersects_mems_allowed(struct task_struct *tsk,
  86                                         const nodemask_t *mask)
  87 {
  88         return true;
  89 }
  90 #endif /* CONFIG_NUMA */
  91
  92 /*
  93  * The process p may have detached its own ->mm while exiting or through
  94  * use_mm(), but one or more of its subthreads may still have a valid
  95  * pointer.  Return p, or any of its subthreads with a valid ->mm, with
  96  * task_lock() held.
  97  */
  98 struct task_struct *find_lock_task_mm(struct task_struct *p)
  99 {
 100         struct task_struct *t = p;
 101
 102         do {
 103                 task_lock(t);
 104                 if (likely(t->mm))
 105                         return t;
 106                 task_unlock(t);
 107         } while_each_thread(p, t);
 108
 109         return NULL;
 110 }
 111
 112 /* return true if the task is not adequate as candidate victim task. */
 113 static bool oom_unkillable_task(struct task_struct *p,
 114                 const struct mem_cgroup *memcg, const nodemask_t *nodemask)
 115 {
 116         if (is_global_init(p))
 117                 return true;
 118         if (p->flags & PF_KTHREAD)
 119                 return true;
 120
 121         /* When mem_cgroup_out_of_memory() and p is not member of the group */
 122         if (memcg && !task_in_mem_cgroup(p, memcg))
 123                 return true;
 124
 125         /* p may not have freeable memory in nodemask */
 126         if (!has_intersects_mems_allowed(p, nodemask))
 127                 return true;
 128
 129         return false;
 130 }
 131
 132 /**
 133  * oom_badness - heuristic function to determine which candidate task to kill
 134  * @p: task struct of which task we should calculate
 135  * @totalpages: total present RAM allowed for page allocation
 136  *
 137  * The heuristic for determining which task to kill is made to be as simple and
 138  * predictable as possible.  The goal is to return the highest value for the
 139  * task consuming the most memory to avoid subsequent oom failures.
 140  */
 141 unsigned long oom_badness(struct task_struct *p, struct mem_cgroup *memcg,
 142                           const nodemask_t *nodemask, unsigned long totalpages)
 143 {
 144         long points;
 145         long adj;
 146
 147         if (oom_unkillable_task(p, memcg, nodemask))
 148                 return 0;
 149
 150         p = find_lock_task_mm(p);
 151         if (!p)
 152                 return 0;
 153
 154         adj = (long)p->signal->oom_score_adj;
 155         if (adj == OOM_SCORE_ADJ_MIN) {
 156                 task_unlock(p);
 157                 return 0;
 158         }
 159
 160         /*
 161          * The baseline for the badness score is the proportion of RAM that each
 162          * task's rss, pagetable and swap space use.
 163          */
 164         points = get_mm_rss(p->mm) + p->mm->nr_ptes +
 165                  get_mm_counter(p->mm, MM_SWAPENTS);
 166         task_unlock(p);
 167
 168         /*
 169          * Root processes get 3% bonus, just like the __vm_enough_memory()
 170          * implementation used by LSMs.
 171          */
 172         if (has_capability_noaudit(p, CAP_SYS_ADMIN))
 173                 adj -= 30;
 174
 175         /* Normalize to oom_score_adj units */
 176         adj *= totalpages / 1000;
 177         points += adj;
 178
 179         /*
 180          * Never return 0 for an eligible task regardless of the root bonus and
 181          * oom_score_adj (oom_score_adj can't be OOM_SCORE_ADJ_MIN here).
 182          */
 183         return points > 0 ? points : 1;
 184 }
 185
 186 /*
 187  * Determine the type of allocation constraint.
 188  */
 189 #ifdef CONFIG_NUMA
 190 static enum oom_constraint constrained_alloc(struct zonelist *zonelist,
 191                                 gfp_t gfp_mask, nodemask_t *nodemask,
 192                                 unsigned long *totalpages)
 193 {
 194         struct zone *zone;
 195         struct zoneref *z;
 196         enum zone_type high_zoneidx = gfp_zone(gfp_mask);
 197         bool cpuset_limited = false;
 198         int nid;
 199
 200         /* Default to all available memory */
 201         *totalpages = totalram_pages + total_swap_pages;
 202
 203         if (!zonelist)
 204                 return CONSTRAINT_NONE;
 205         /*
 206          * Reach here only when __GFP_NOFAIL is used. So, we should avoid
 207          * to kill current.We have to random task kill in this case.
 208          * Hopefully, CONSTRAINT_THISNODE...but no way to handle it, now.
 209          */
 210         if (gfp_mask & __GFP_THISNODE)
 211                 return CONSTRAINT_NONE;
 212
 213         /*
 214          * This is not a __GFP_THISNODE allocation, so a truncated nodemask in
 215          * the page allocator means a mempolicy is in effect.  Cpuset policy
 216          * is enforced in get_page_from_freelist().
 217          */
 218         if (nodemask && !nodes_subset(node_states[N_MEMORY], *nodemask)) {
 219                 *totalpages = total_swap_pages;
 220                 for_each_node_mask(nid, *nodemask)
 221                         *totalpages += node_spanned_pages(nid);
 222                 return CONSTRAINT_MEMORY_POLICY;
 223         }
 224
 225         /* Check this allocation failure is caused by cpuset's wall function */
 226         for_each_zone_zonelist_nodemask(zone, z, zonelist,
 227                         high_zoneidx, nodemask)
 228                 if (!cpuset_zone_allowed_softwall(zone, gfp_mask))
 229                         cpuset_limited = true;
 230
 231         if (cpuset_limited) {
 232                 *totalpages = total_swap_pages;
 233                 for_each_node_mask(nid, cpuset_current_mems_allowed)
 234                         *totalpages += node_spanned_pages(nid);
 235                 return CONSTRAINT_CPUSET;
 236         }
 237         return CONSTRAINT_NONE;
 238 }
 239 #else
 240 static enum oom_constraint constrained_alloc(struct zonelist *zonelist,
 241                                 gfp_t gfp_mask, nodemask_t *nodemask,
 242                                 unsigned long *totalpages)
 243 {
 244         *totalpages = totalram_pages + total_swap_pages;
 245         return CONSTRAINT_NONE;
 246 }
 247 #endif
 248
 249 enum oom_scan_t oom_scan_process_thread(struct task_struct *task,
 250                 unsigned long totalpages, const nodemask_t *nodemask,
 251                 bool force_kill)
 252 {
 253         if (task->exit_state)
 254                 return OOM_SCAN_CONTINUE;
 255         if (oom_unkillable_task(task, NULL, nodemask))
 256                 return OOM_SCAN_CONTINUE;
 257
 258         /*
 259          * This task already has access to memory reserves and is being killed.
 260          * Don't allow any other task to have access to the reserves.
 261          */
 262         if (test_tsk_thread_flag(task, TIF_MEMDIE)) {
 263                 if (unlikely(frozen(task)))
 264                         __thaw_task(task);
 265                 if (!force_kill)
 266                         return OOM_SCAN_ABORT;
 267         }
 268         if (!task->mm)
 269                 return OOM_SCAN_CONTINUE;
 270
 271         /*
 272          * If task is allocating a lot of memory and has been marked to be
 273          * killed first if it triggers an oom, then select it.
 274          */
 275         if (oom_task_origin(task))
 276                 return OOM_SCAN_SELECT;
 277
 278         if (task->flags & PF_EXITING && !force_kill) {
 279                 /*
 280                  * If this task is not being ptraced on exit, then wait for it
 281                  * to finish before killing some other task unnecessarily.
 282                  */
 283                 if (!(task->group_leader->ptrace & PT_TRACE_EXIT))
 284                         return OOM_SCAN_ABORT;
 285         }
 286         return OOM_SCAN_OK;
 287 }
 288
 289 /*
 290  * Simple selection loop. We chose the process with the highest
 291  * number of 'points'.
 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, const nodemask_t *nodemask,
 297                 bool force_kill)
 298 {
 299         struct task_struct *g, *p;
 300         struct task_struct *chosen = NULL;
 301         unsigned long chosen_points = 0;
 302
 303         rcu_read_lock();
 304         do_each_thread(g, p) {
 305                 unsigned int points;
 306
 307                 switch (oom_scan_process_thread(p, totalpages, nodemask,
 308                                                 force_kill)) {
 309                 case OOM_SCAN_SELECT:
 310                         chosen = p;
 311                         chosen_points = ULONG_MAX;
 312                         /* fall through */
 313                 case OOM_SCAN_CONTINUE:
 314                         continue;
 315                 case OOM_SCAN_ABORT:
 316                         rcu_read_unlock();
 317                         return ERR_PTR(-1UL);
 318                 case OOM_SCAN_OK:
 319                         break;
 320                 };
 321                 points = oom_badness(p, NULL, nodemask, totalpages);
 322                 if (points > chosen_points) {
 323                         chosen = p;
 324                         chosen_points = points;
 325                 }
 326         } while_each_thread(g, p);
 327         if (chosen)
 328                 get_task_struct(chosen);
 329         rcu_read_unlock();
 330
 331         *ppoints = chosen_points * 1000 / totalpages;
 332         return chosen;
 333 }
 334
 335 /**
 336  * dump_tasks - dump current memory state of all system tasks
 337  * @memcg: current's memory controller, if constrained
 338  * @nodemask: nodemask passed to page allocator for mempolicy ooms
 339  *
 340  * Dumps the current memory state of all eligible tasks.  Tasks not in the same
 341  * memcg, not in the same cpuset, or bound to a disjoint set of mempolicy nodes
 342  * are not shown.
 343  * State information includes task's pid, uid, tgid, vm size, rss, nr_ptes,
 344  * swapents, oom_score_adj value, and name.
 345  */
 346 static void dump_tasks(const struct mem_cgroup *memcg, const nodemask_t *nodemask)
 347 {
 348         struct task_struct *p;
 349         struct task_struct *task;
 350
 351         pr_info("[ pid ]   uid  tgid total_vm      rss nr_ptes swapents oom_score_adj name\n");
 352         rcu_read_lock();
 353         for_each_process(p) {
 354                 if (oom_unkillable_task(p, memcg, nodemask))
 355                         continue;
 356
 357                 task = find_lock_task_mm(p);
 358                 if (!task) {
 359                         /*
 360                          * This is a kthread or all of p's threads have already
 361                          * detached their mm's.  There's no need to report
 362                          * them; they can't be oom killed anyway.
 363                          */
 364                         continue;
 365                 }
 366
 367                 pr_info("[%5d] %5d %5d %8lu %8lu %7lu %8lu         %5hd %s\n",
 368                         task->pid, from_kuid(&init_user_ns, task_uid(task)),
 369                         task->tgid, task->mm->total_vm, get_mm_rss(task->mm),
 370                         task->mm->nr_ptes,
 371                         get_mm_counter(task->mm, MM_SWAPENTS),
 372                         task->signal->oom_score_adj, task->comm);
 373                 task_unlock(task);
 374         }
 375         rcu_read_unlock();
 376 }
 377
 378 static void dump_header(struct task_struct *p, gfp_t gfp_mask, int order,
 379                         struct mem_cgroup *memcg, const nodemask_t *nodemask)
 380 {
 381         task_lock(current);
 382         pr_warning("%s invoked oom-killer: gfp_mask=0x%x, order=%d, "
 383                 "oom_score_adj=%hd\n",
 384                 current->comm, gfp_mask, order,
 385                 current->signal->oom_score_adj);
 386         cpuset_print_task_mems_allowed(current);
 387         task_unlock(current);
 388         dump_stack();
 389         mem_cgroup_print_oom_info(memcg, p);
 390         show_mem(SHOW_MEM_FILTER_NODES);
 391         if (sysctl_oom_dump_tasks)
 392                 dump_tasks(memcg, nodemask);
 393 }
 394
 395 #define K(x) ((x) << (PAGE_SHIFT-10))
 396 /*
 397  * Must be called while holding a reference to p, which will be released upon
 398  * returning.
 399  */
 400 void oom_kill_process(struct task_struct *p, gfp_t gfp_mask, int order,
 401                       unsigned int points, unsigned long totalpages,
 402                       struct mem_cgroup *memcg, nodemask_t *nodemask,
 403                       const char *message)
 404 {
 405         struct task_struct *victim = p;
 406         struct task_struct *child;
 407         struct task_struct *t = p;
 408         struct mm_struct *mm;
 409         unsigned int victim_points = 0;
 410         static DEFINE_RATELIMIT_STATE(oom_rs, DEFAULT_RATELIMIT_INTERVAL,
 411                                               DEFAULT_RATELIMIT_BURST);
 412
 413         /*
 414          * If the task is already exiting, don't alarm the sysadmin or kill
 415          * its children or threads, just set TIF_MEMDIE so it can die quickly
 416          */
 417         if (p->flags & PF_EXITING) {
 418                 set_tsk_thread_flag(p, TIF_MEMDIE);
 419                 put_task_struct(p);
 420                 return;
 421         }
 422
 423         if (__ratelimit(&oom_rs))
 424                 dump_header(p, gfp_mask, order, memcg, nodemask);
 425
 426         task_lock(p);
 427         pr_err("%s: Kill process %d (%s) score %d or sacrifice child\n",
 428                 message, task_pid_nr(p), p->comm, points);
 429         task_unlock(p);
 430
 431         /*
 432          * If any of p's children has a different mm and is eligible for kill,
 433          * the one with the highest oom_badness() score is sacrificed for its
 434          * parent.  This attempts to lose the minimal amount of work done while
 435          * still freeing memory.
 436          */
 437         read_lock(&tasklist_lock);
 438         do {
 439                 list_for_each_entry(child, &t->children, sibling) {
 440                         unsigned int child_points;
 441
 442                         if (child->mm == p->mm)
 443                                 continue;
 444                         /*
 445                          * oom_badness() returns 0 if the thread is unkillable
 446                          */
 447                         child_points = oom_badness(child, memcg, nodemask,
 448                                                                 totalpages);
 449                         if (child_points > victim_points) {
 450                                 put_task_struct(victim);
 451                                 victim = child;
 452                                 victim_points = child_points;
 453                                 get_task_struct(victim);
 454                         }
 455                 }
 456         } while_each_thread(p, t);
 457         read_unlock(&tasklist_lock);
 458
 459         rcu_read_lock();
 460         p = find_lock_task_mm(victim);
 461         if (!p) {
 462                 rcu_read_unlock();
 463                 put_task_struct(victim);
 464                 return;
 465         } else if (victim != p) {
 466                 get_task_struct(p);
 467                 put_task_struct(victim);
 468                 victim = p;
 469         }
 470
 471         /* mm cannot safely be dereferenced after task_unlock(victim) */
 472         mm = victim->mm;
 473         pr_err("Killed process %d (%s) total-vm:%lukB, anon-rss:%lukB, file-rss:%lukB\n",
 474                 task_pid_nr(victim), victim->comm, K(victim->mm->total_vm),
 475                 K(get_mm_counter(victim->mm, MM_ANONPAGES)),
 476                 K(get_mm_counter(victim->mm, MM_FILEPAGES)));
 477         task_unlock(victim);
 478
 479         /*
 480          * Kill all user processes sharing victim->mm in other thread groups, if
 481          * any.  They don't get access to memory reserves, though, to avoid
 482          * depletion of all memory.  This prevents mm->mmap_sem livelock when an
 483          * oom killed thread cannot exit because it requires the semaphore and
 484          * its contended by another thread trying to allocate memory itself.
 485          * That thread will now get access to memory reserves since it has a
 486          * pending fatal signal.
 487          */
 488         for_each_process(p)
 489                 if (p->mm == mm && !same_thread_group(p, victim) &&
 490                     !(p->flags & PF_KTHREAD)) {
 491                         if (p->signal->oom_score_adj == OOM_SCORE_ADJ_MIN)
 492                                 continue;
 493
 494                         task_lock(p);   /* Protect ->comm from prctl() */
 495                         pr_err("Kill process %d (%s) sharing same memory\n",
 496                                 task_pid_nr(p), p->comm);
 497                         task_unlock(p);
 498                         do_send_sig_info(SIGKILL, SEND_SIG_FORCED, p, true);
 499                 }
 500         rcu_read_unlock();
 501
 502         set_tsk_thread_flag(victim, TIF_MEMDIE);
 503         do_send_sig_info(SIGKILL, SEND_SIG_FORCED, victim, true);
 504         put_task_struct(victim);
 505 }
 506 #undef K
 507
 508 /*
 509  * Determines whether the kernel must panic because of the panic_on_oom sysctl.
 510  */
 511 void check_panic_on_oom(enum oom_constraint constraint, gfp_t gfp_mask,
 512                         int order, const nodemask_t *nodemask)
 513 {
 514         if (likely(!sysctl_panic_on_oom))
 515                 return;
 516         if (sysctl_panic_on_oom != 2) {
 517                 /*
 518                  * panic_on_oom == 1 only affects CONSTRAINT_NONE, the kernel
 519                  * does not panic for cpuset, mempolicy, or memcg allocation
 520                  * failures.
 521                  */
 522                 if (constraint != CONSTRAINT_NONE)
 523                         return;
 524         }
 525         dump_header(NULL, gfp_mask, order, NULL, nodemask);
 526         panic("Out of memory: %s panic_on_oom is enabled\n",
 527                 sysctl_panic_on_oom == 2 ? "compulsory" : "system-wide");
 528 }
 529
 530 static BLOCKING_NOTIFIER_HEAD(oom_notify_list);
 531
 532 int register_oom_notifier(struct notifier_block *nb)
 533 {
 534         return blocking_notifier_chain_register(&oom_notify_list, nb);
 535 }
 536 EXPORT_SYMBOL_GPL(register_oom_notifier);
 537
 538 int unregister_oom_notifier(struct notifier_block *nb)
 539 {
 540         return blocking_notifier_chain_unregister(&oom_notify_list, nb);
 541 }
 542 EXPORT_SYMBOL_GPL(unregister_oom_notifier);
 543
 544 /*
 545  * Try to acquire the OOM killer lock for the zones in zonelist.  Returns zero
 546  * if a parallel OOM killing is already taking place that includes a zone in
 547  * the zonelist.  Otherwise, locks all zones in the zonelist and returns 1.
 548  */
 549 int try_set_zonelist_oom(struct zonelist *zonelist, gfp_t gfp_mask)
 550 {
 551         struct zoneref *z;
 552         struct zone *zone;
 553         int ret = 1;
 554
 555         spin_lock(&zone_scan_lock);
 556         for_each_zone_zonelist(zone, z, zonelist, gfp_zone(gfp_mask)) {
 557                 if (zone_is_oom_locked(zone)) {
 558                         ret = 0;
 559                         goto out;
 560                 }
 561         }
 562
 563         for_each_zone_zonelist(zone, z, zonelist, gfp_zone(gfp_mask)) {
 564                 /*
 565                  * Lock each zone in the zonelist under zone_scan_lock so a
 566                  * parallel invocation of try_set_zonelist_oom() doesn't succeed
 567                  * when it shouldn't.
 568                  */
 569                 zone_set_flag(zone, ZONE_OOM_LOCKED);
 570         }
 571
 572 out:
 573         spin_unlock(&zone_scan_lock);
 574         return ret;
 575 }
 576
 577 /*
 578  * Clears the ZONE_OOM_LOCKED flag for all zones in the zonelist so that failed
 579  * allocation attempts with zonelists containing them may now recall the OOM
 580  * killer, if necessary.
 581  */
 582 void clear_zonelist_oom(struct zonelist *zonelist, gfp_t gfp_mask)
 583 {
 584         struct zoneref *z;
 585         struct zone *zone;
 586
 587         spin_lock(&zone_scan_lock);
 588         for_each_zone_zonelist(zone, z, zonelist, gfp_zone(gfp_mask)) {
 589                 zone_clear_flag(zone, ZONE_OOM_LOCKED);
 590         }
 591         spin_unlock(&zone_scan_lock);
 592 }
 593
 594 /**
 595  * out_of_memory - kill the "best" process when we run out of memory
 596  * @zonelist: zonelist pointer
 597  * @gfp_mask: memory allocation flags
 598  * @order: amount of memory being requested as a power of 2
 599  * @nodemask: nodemask passed to page allocator
 600  * @force_kill: true if a task must be killed, even if others are exiting
 601  *
 602  * If we run out of memory, we have the choice between either
 603  * killing a random task (bad), letting the system crash (worse)
 604  * OR try to be smart about which process to kill. Note that we
 605  * don't have to be perfect here, we just have to be good.
 606  */
 607 void out_of_memory(struct zonelist *zonelist, gfp_t gfp_mask,
 608                 int order, nodemask_t *nodemask, bool force_kill)
 609 {
 610         const nodemask_t *mpol_mask;
 611         struct task_struct *p;
 612         unsigned long totalpages;
 613         unsigned long freed = 0;
 614         unsigned int uninitialized_var(points);
 615         enum oom_constraint constraint = CONSTRAINT_NONE;
 616         int killed = 0;
 617
 618         blocking_notifier_call_chain(&oom_notify_list, 0, &freed);
 619         if (freed > 0)
 620                 /* Got some memory back in the last second. */
 621                 return;
 622
 623         /*
 624          * If current has a pending SIGKILL or is exiting, then automatically
 625          * select it.  The goal is to allow it to allocate so that it may
 626          * quickly exit and free its memory.
 627          */
 628         if (fatal_signal_pending(current) || current->flags & PF_EXITING) {
 629                 set_thread_flag(TIF_MEMDIE);
 630                 return;
 631         }
 632
 633         /*
 634          * Check if there were limitations on the allocation (only relevant for
 635          * NUMA) that may require different handling.
 636          */
 637         constraint = constrained_alloc(zonelist, gfp_mask, nodemask,
 638                                                 &totalpages);
 639         mpol_mask = (constraint == CONSTRAINT_MEMORY_POLICY) ? nodemask : NULL;
 640         check_panic_on_oom(constraint, gfp_mask, order, mpol_mask);
 641
 642         if (sysctl_oom_kill_allocating_task && current->mm &&
 643             !oom_unkillable_task(current, NULL, nodemask) &&
 644             current->signal->oom_score_adj != OOM_SCORE_ADJ_MIN) {
 645                 get_task_struct(current);
 646                 oom_kill_process(current, gfp_mask, order, 0, totalpages, NULL,
 647                                  nodemask,
 648                                  "Out of memory (oom_kill_allocating_task)");
 649                 goto out;
 650         }
 651
 652         p = select_bad_process(&points, totalpages, mpol_mask, force_kill);
 653         /* Found nothing?!?! Either we hang forever, or we panic. */
 654         if (!p) {
 655                 dump_header(NULL, gfp_mask, order, NULL, mpol_mask);
 656                 panic("Out of memory and no killable processes...\n");
 657         }
 658         if (PTR_ERR(p) != -1UL) {
 659                 oom_kill_process(p, gfp_mask, order, points, totalpages, NULL,
 660                                  nodemask, "Out of memory");
 661                 killed = 1;
 662         }
 663 out:
 664         /*
 665          * Give the killed threads a good chance of exiting before trying to
 666          * allocate memory again.
 667          */
 668         if (killed)
 669                 schedule_timeout_killable(1);
 670 }
 671
 672 /*
 673  * The pagefault handler calls here because it is out of memory, so kill a
 674  * memory-hogging task.  If any populated zone has ZONE_OOM_LOCKED set, a
 675  * parallel oom killing is already in progress so do nothing.
 676  */
 677 void pagefault_out_of_memory(void)
 678 {
 679         struct zonelist *zonelist = node_zonelist(first_online_node,
 680                                                   GFP_KERNEL);
 681
 682         if (try_set_zonelist_oom(zonelist, GFP_KERNEL)) {
 683                 out_of_memory(NULL, 0, 0, NULL, false);
 684                 clear_zonelist_oom(zonelist, GFP_KERNEL);
 685         }
 686 }