linux/mm/oom_kill.c
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   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
  42int sysctl_panic_on_oom;
  43int sysctl_oom_kill_allocating_task;
  44int sysctl_oom_dump_tasks = 1;
  45static 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 */
  57static 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
  85static 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 */
  98struct 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. */
 113static 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 */
 141unsigned 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
 190static 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
 240static 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
 249enum 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 */
 295static 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 */
 346static 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
 378static 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        if (memcg)
 390                mem_cgroup_print_oom_info(memcg, p);
 391        else
 392                show_mem(SHOW_MEM_FILTER_NODES);
 393        if (sysctl_oom_dump_tasks)
 394                dump_tasks(memcg, nodemask);
 395}
 396
 397#define K(x) ((x) << (PAGE_SHIFT-10))
 398/*
 399 * Must be called while holding a reference to p, which will be released upon
 400 * returning.
 401 */
 402void oom_kill_process(struct task_struct *p, gfp_t gfp_mask, int order,
 403                      unsigned int points, unsigned long totalpages,
 404                      struct mem_cgroup *memcg, nodemask_t *nodemask,
 405                      const char *message)
 406{
 407        struct task_struct *victim = p;
 408        struct task_struct *child;
 409        struct task_struct *t = p;
 410        struct mm_struct *mm;
 411        unsigned int victim_points = 0;
 412        static DEFINE_RATELIMIT_STATE(oom_rs, DEFAULT_RATELIMIT_INTERVAL,
 413                                              DEFAULT_RATELIMIT_BURST);
 414
 415        /*
 416         * If the task is already exiting, don't alarm the sysadmin or kill
 417         * its children or threads, just set TIF_MEMDIE so it can die quickly
 418         */
 419        if (p->flags & PF_EXITING) {
 420                set_tsk_thread_flag(p, TIF_MEMDIE);
 421                put_task_struct(p);
 422                return;
 423        }
 424
 425        if (__ratelimit(&oom_rs))
 426                dump_header(p, gfp_mask, order, memcg, nodemask);
 427
 428        task_lock(p);
 429        pr_err("%s: Kill process %d (%s) score %d or sacrifice child\n",
 430                message, task_pid_nr(p), p->comm, points);
 431        task_unlock(p);
 432
 433        /*
 434         * If any of p's children has a different mm and is eligible for kill,
 435         * the one with the highest oom_badness() score is sacrificed for its
 436         * parent.  This attempts to lose the minimal amount of work done while
 437         * still freeing memory.
 438         */
 439        read_lock(&tasklist_lock);
 440        do {
 441                list_for_each_entry(child, &t->children, sibling) {
 442                        unsigned int child_points;
 443
 444                        if (child->mm == p->mm)
 445                                continue;
 446                        /*
 447                         * oom_badness() returns 0 if the thread is unkillable
 448                         */
 449                        child_points = oom_badness(child, memcg, nodemask,
 450                                                                totalpages);
 451                        if (child_points > victim_points) {
 452                                put_task_struct(victim);
 453                                victim = child;
 454                                victim_points = child_points;
 455                                get_task_struct(victim);
 456                        }
 457                }
 458        } while_each_thread(p, t);
 459        read_unlock(&tasklist_lock);
 460
 461        rcu_read_lock();
 462        p = find_lock_task_mm(victim);
 463        if (!p) {
 464                rcu_read_unlock();
 465                put_task_struct(victim);
 466                return;
 467        } else if (victim != p) {
 468                get_task_struct(p);
 469                put_task_struct(victim);
 470                victim = p;
 471        }
 472
 473        /* mm cannot safely be dereferenced after task_unlock(victim) */
 474        mm = victim->mm;
 475        pr_err("Killed process %d (%s) total-vm:%lukB, anon-rss:%lukB, file-rss:%lukB\n",
 476                task_pid_nr(victim), victim->comm, K(victim->mm->total_vm),
 477                K(get_mm_counter(victim->mm, MM_ANONPAGES)),
 478                K(get_mm_counter(victim->mm, MM_FILEPAGES)));
 479        task_unlock(victim);
 480
 481        /*
 482         * Kill all user processes sharing victim->mm in other thread groups, if
 483         * any.  They don't get access to memory reserves, though, to avoid
 484         * depletion of all memory.  This prevents mm->mmap_sem livelock when an
 485         * oom killed thread cannot exit because it requires the semaphore and
 486         * its contended by another thread trying to allocate memory itself.
 487         * That thread will now get access to memory reserves since it has a
 488         * pending fatal signal.
 489         */
 490        for_each_process(p)
 491                if (p->mm == mm && !same_thread_group(p, victim) &&
 492                    !(p->flags & PF_KTHREAD)) {
 493                        if (p->signal->oom_score_adj == OOM_SCORE_ADJ_MIN)
 494                                continue;
 495
 496                        task_lock(p);   /* Protect ->comm from prctl() */
 497                        pr_err("Kill process %d (%s) sharing same memory\n",
 498                                task_pid_nr(p), p->comm);
 499                        task_unlock(p);
 500                        do_send_sig_info(SIGKILL, SEND_SIG_FORCED, p, true);
 501                }
 502        rcu_read_unlock();
 503
 504        set_tsk_thread_flag(victim, TIF_MEMDIE);
 505        do_send_sig_info(SIGKILL, SEND_SIG_FORCED, victim, true);
 506        put_task_struct(victim);
 507}
 508#undef K
 509
 510/*
 511 * Determines whether the kernel must panic because of the panic_on_oom sysctl.
 512 */
 513void check_panic_on_oom(enum oom_constraint constraint, gfp_t gfp_mask,
 514                        int order, const nodemask_t *nodemask)
 515{
 516        if (likely(!sysctl_panic_on_oom))
 517                return;
 518        if (sysctl_panic_on_oom != 2) {
 519                /*
 520                 * panic_on_oom == 1 only affects CONSTRAINT_NONE, the kernel
 521                 * does not panic for cpuset, mempolicy, or memcg allocation
 522                 * failures.
 523                 */
 524                if (constraint != CONSTRAINT_NONE)
 525                        return;
 526        }
 527        dump_header(NULL, gfp_mask, order, NULL, nodemask);
 528        panic("Out of memory: %s panic_on_oom is enabled\n",
 529                sysctl_panic_on_oom == 2 ? "compulsory" : "system-wide");
 530}
 531
 532static BLOCKING_NOTIFIER_HEAD(oom_notify_list);
 533
 534int register_oom_notifier(struct notifier_block *nb)
 535{
 536        return blocking_notifier_chain_register(&oom_notify_list, nb);
 537}
 538EXPORT_SYMBOL_GPL(register_oom_notifier);
 539
 540int unregister_oom_notifier(struct notifier_block *nb)
 541{
 542        return blocking_notifier_chain_unregister(&oom_notify_list, nb);
 543}
 544EXPORT_SYMBOL_GPL(unregister_oom_notifier);
 545
 546/*
 547 * Try to acquire the OOM killer lock for the zones in zonelist.  Returns zero
 548 * if a parallel OOM killing is already taking place that includes a zone in
 549 * the zonelist.  Otherwise, locks all zones in the zonelist and returns 1.
 550 */
 551int try_set_zonelist_oom(struct zonelist *zonelist, gfp_t gfp_mask)
 552{
 553        struct zoneref *z;
 554        struct zone *zone;
 555        int ret = 1;
 556
 557        spin_lock(&zone_scan_lock);
 558        for_each_zone_zonelist(zone, z, zonelist, gfp_zone(gfp_mask)) {
 559                if (zone_is_oom_locked(zone)) {
 560                        ret = 0;
 561                        goto out;
 562                }
 563        }
 564
 565        for_each_zone_zonelist(zone, z, zonelist, gfp_zone(gfp_mask)) {
 566                /*
 567                 * Lock each zone in the zonelist under zone_scan_lock so a
 568                 * parallel invocation of try_set_zonelist_oom() doesn't succeed
 569                 * when it shouldn't.
 570                 */
 571                zone_set_flag(zone, ZONE_OOM_LOCKED);
 572        }
 573
 574out:
 575        spin_unlock(&zone_scan_lock);
 576        return ret;
 577}
 578
 579/*
 580 * Clears the ZONE_OOM_LOCKED flag for all zones in the zonelist so that failed
 581 * allocation attempts with zonelists containing them may now recall the OOM
 582 * killer, if necessary.
 583 */
 584void clear_zonelist_oom(struct zonelist *zonelist, gfp_t gfp_mask)
 585{
 586        struct zoneref *z;
 587        struct zone *zone;
 588
 589        spin_lock(&zone_scan_lock);
 590        for_each_zone_zonelist(zone, z, zonelist, gfp_zone(gfp_mask)) {
 591                zone_clear_flag(zone, ZONE_OOM_LOCKED);
 592        }
 593        spin_unlock(&zone_scan_lock);
 594}
 595
 596/**
 597 * out_of_memory - kill the "best" process when we run out of memory
 598 * @zonelist: zonelist pointer
 599 * @gfp_mask: memory allocation flags
 600 * @order: amount of memory being requested as a power of 2
 601 * @nodemask: nodemask passed to page allocator
 602 * @force_kill: true if a task must be killed, even if others are exiting
 603 *
 604 * If we run out of memory, we have the choice between either
 605 * killing a random task (bad), letting the system crash (worse)
 606 * OR try to be smart about which process to kill. Note that we
 607 * don't have to be perfect here, we just have to be good.
 608 */
 609void out_of_memory(struct zonelist *zonelist, gfp_t gfp_mask,
 610                int order, nodemask_t *nodemask, bool force_kill)
 611{
 612        const nodemask_t *mpol_mask;
 613        struct task_struct *p;
 614        unsigned long totalpages;
 615        unsigned long freed = 0;
 616        unsigned int uninitialized_var(points);
 617        enum oom_constraint constraint = CONSTRAINT_NONE;
 618        int killed = 0;
 619
 620        blocking_notifier_call_chain(&oom_notify_list, 0, &freed);
 621        if (freed > 0)
 622                /* Got some memory back in the last second. */
 623                return;
 624
 625        /*
 626         * If current has a pending SIGKILL or is exiting, then automatically
 627         * select it.  The goal is to allow it to allocate so that it may
 628         * quickly exit and free its memory.
 629         */
 630        if (fatal_signal_pending(current) || current->flags & PF_EXITING) {
 631                set_thread_flag(TIF_MEMDIE);
 632                return;
 633        }
 634
 635        /*
 636         * Check if there were limitations on the allocation (only relevant for
 637         * NUMA) that may require different handling.
 638         */
 639        constraint = constrained_alloc(zonelist, gfp_mask, nodemask,
 640                                                &totalpages);
 641        mpol_mask = (constraint == CONSTRAINT_MEMORY_POLICY) ? nodemask : NULL;
 642        check_panic_on_oom(constraint, gfp_mask, order, mpol_mask);
 643
 644        if (sysctl_oom_kill_allocating_task && current->mm &&
 645            !oom_unkillable_task(current, NULL, nodemask) &&
 646            current->signal->oom_score_adj != OOM_SCORE_ADJ_MIN) {
 647                get_task_struct(current);
 648                oom_kill_process(current, gfp_mask, order, 0, totalpages, NULL,
 649                                 nodemask,
 650                                 "Out of memory (oom_kill_allocating_task)");
 651                goto out;
 652        }
 653
 654        p = select_bad_process(&points, totalpages, mpol_mask, force_kill);
 655        /* Found nothing?!?! Either we hang forever, or we panic. */
 656        if (!p) {
 657                dump_header(NULL, gfp_mask, order, NULL, mpol_mask);
 658                panic("Out of memory and no killable processes...\n");
 659        }
 660        if (PTR_ERR(p) != -1UL) {
 661                oom_kill_process(p, gfp_mask, order, points, totalpages, NULL,
 662                                 nodemask, "Out of memory");
 663                killed = 1;
 664        }
 665out:
 666        /*
 667         * Give the killed threads a good chance of exiting before trying to
 668         * allocate memory again.
 669         */
 670        if (killed)
 671                schedule_timeout_killable(1);
 672}
 673
 674/*
 675 * The pagefault handler calls here because it is out of memory, so kill a
 676 * memory-hogging task.  If any populated zone has ZONE_OOM_LOCKED set, a
 677 * parallel oom killing is already in progress so do nothing.
 678 */
 679void pagefault_out_of_memory(void)
 680{
 681        struct zonelist *zonelist = node_zonelist(first_online_node,
 682                                                  GFP_KERNEL);
 683
 684        if (try_set_zonelist_oom(zonelist, GFP_KERNEL)) {
 685                out_of_memory(NULL, 0, 0, NULL, false);
 686                clear_zonelist_oom(zonelist, GFP_KERNEL);
 687        }
 688}
 689
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