From 57f0f512b273f60d52568b8c6b77e17f5636edc0 Mon Sep 17 00:00:00 2001 From: André Fabian Silva Delgado Date: Wed, 5 Aug 2015 17:04:01 -0300 Subject: Initial import --- mm/oom_kill.c | 832 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 832 insertions(+) create mode 100644 mm/oom_kill.c (limited to 'mm/oom_kill.c') diff --git a/mm/oom_kill.c b/mm/oom_kill.c new file mode 100644 index 000000000..2b665da1b --- /dev/null +++ b/mm/oom_kill.c @@ -0,0 +1,832 @@ +/* + * linux/mm/oom_kill.c + * + * Copyright (C) 1998,2000 Rik van Riel + * Thanks go out to Claus Fischer for some serious inspiration and + * for goading me into coding this file... + * Copyright (C) 2010 Google, Inc. + * Rewritten by David Rientjes + * + * The routines in this file are used to kill a process when + * we're seriously out of memory. This gets called from __alloc_pages() + * in mm/page_alloc.c when we really run out of memory. + * + * Since we won't call these routines often (on a well-configured + * machine) this file will double as a 'coding guide' and a signpost + * for newbie kernel hackers. It features several pointers to major + * kernel subsystems and hints as to where to find out what things do. + */ + +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + +#define CREATE_TRACE_POINTS +#include + +int sysctl_panic_on_oom; +int sysctl_oom_kill_allocating_task; +int sysctl_oom_dump_tasks = 1; +static DEFINE_SPINLOCK(zone_scan_lock); + +#ifdef CONFIG_NUMA +/** + * has_intersects_mems_allowed() - check task eligiblity for kill + * @start: task struct of which task to consider + * @mask: nodemask passed to page allocator for mempolicy ooms + * + * Task eligibility is determined by whether or not a candidate task, @tsk, + * shares the same mempolicy nodes as current if it is bound by such a policy + * and whether or not it has the same set of allowed cpuset nodes. + */ +static bool has_intersects_mems_allowed(struct task_struct *start, + const nodemask_t *mask) +{ + struct task_struct *tsk; + bool ret = false; + + rcu_read_lock(); + for_each_thread(start, tsk) { + if (mask) { + /* + * If this is a mempolicy constrained oom, tsk's + * cpuset is irrelevant. Only return true if its + * mempolicy intersects current, otherwise it may be + * needlessly killed. + */ + ret = mempolicy_nodemask_intersects(tsk, mask); + } else { + /* + * This is not a mempolicy constrained oom, so only + * check the mems of tsk's cpuset. + */ + ret = cpuset_mems_allowed_intersects(current, tsk); + } + if (ret) + break; + } + rcu_read_unlock(); + + return ret; +} +#else +static bool has_intersects_mems_allowed(struct task_struct *tsk, + const nodemask_t *mask) +{ + return true; +} +#endif /* CONFIG_NUMA */ + +/* + * The process p may have detached its own ->mm while exiting or through + * use_mm(), but one or more of its subthreads may still have a valid + * pointer. Return p, or any of its subthreads with a valid ->mm, with + * task_lock() held. + */ +struct task_struct *find_lock_task_mm(struct task_struct *p) +{ + struct task_struct *t; + + rcu_read_lock(); + + for_each_thread(p, t) { + task_lock(t); + if (likely(t->mm)) + goto found; + task_unlock(t); + } + t = NULL; +found: + rcu_read_unlock(); + + return t; +} + +/* return true if the task is not adequate as candidate victim task. */ +static bool oom_unkillable_task(struct task_struct *p, + struct mem_cgroup *memcg, const nodemask_t *nodemask) +{ + if (is_global_init(p)) + return true; + if (p->flags & PF_KTHREAD) + return true; + + /* When mem_cgroup_out_of_memory() and p is not member of the group */ + if (memcg && !task_in_mem_cgroup(p, memcg)) + return true; + + /* p may not have freeable memory in nodemask */ + if (!has_intersects_mems_allowed(p, nodemask)) + return true; + + return false; +} + +/** + * oom_badness - heuristic function to determine which candidate task to kill + * @p: task struct of which task we should calculate + * @totalpages: total present RAM allowed for page allocation + * + * The heuristic for determining which task to kill is made to be as simple and + * predictable as possible. The goal is to return the highest value for the + * task consuming the most memory to avoid subsequent oom failures. + */ +unsigned long oom_badness(struct task_struct *p, struct mem_cgroup *memcg, + const nodemask_t *nodemask, unsigned long totalpages) +{ + long points; + long adj; + + if (oom_unkillable_task(p, memcg, nodemask)) + return 0; + + p = find_lock_task_mm(p); + if (!p) + return 0; + + adj = (long)p->signal->oom_score_adj; + if (adj == OOM_SCORE_ADJ_MIN) { + task_unlock(p); + return 0; + } + + /* + * The baseline for the badness score is the proportion of RAM that each + * task's rss, pagetable and swap space use. + */ + points = get_mm_rss(p->mm) + get_mm_counter(p->mm, MM_SWAPENTS) + + atomic_long_read(&p->mm->nr_ptes) + mm_nr_pmds(p->mm); + task_unlock(p); + + /* + * Root processes get 3% bonus, just like the __vm_enough_memory() + * implementation used by LSMs. + */ + if (has_capability_noaudit(p, CAP_SYS_ADMIN)) + points -= (points * 3) / 100; + + /* Normalize to oom_score_adj units */ + adj *= totalpages / 1000; + points += adj; + + /* + * Never return 0 for an eligible task regardless of the root bonus and + * oom_score_adj (oom_score_adj can't be OOM_SCORE_ADJ_MIN here). + */ + return points > 0 ? points : 1; +} + +/* + * Determine the type of allocation constraint. + */ +#ifdef CONFIG_NUMA +static enum oom_constraint constrained_alloc(struct zonelist *zonelist, + gfp_t gfp_mask, nodemask_t *nodemask, + unsigned long *totalpages) +{ + struct zone *zone; + struct zoneref *z; + enum zone_type high_zoneidx = gfp_zone(gfp_mask); + bool cpuset_limited = false; + int nid; + + /* Default to all available memory */ + *totalpages = totalram_pages + total_swap_pages; + + if (!zonelist) + return CONSTRAINT_NONE; + /* + * Reach here only when __GFP_NOFAIL is used. So, we should avoid + * to kill current.We have to random task kill in this case. + * Hopefully, CONSTRAINT_THISNODE...but no way to handle it, now. + */ + if (gfp_mask & __GFP_THISNODE) + return CONSTRAINT_NONE; + + /* + * This is not a __GFP_THISNODE allocation, so a truncated nodemask in + * the page allocator means a mempolicy is in effect. Cpuset policy + * is enforced in get_page_from_freelist(). + */ + if (nodemask && !nodes_subset(node_states[N_MEMORY], *nodemask)) { + *totalpages = total_swap_pages; + for_each_node_mask(nid, *nodemask) + *totalpages += node_spanned_pages(nid); + return CONSTRAINT_MEMORY_POLICY; + } + + /* Check this allocation failure is caused by cpuset's wall function */ + for_each_zone_zonelist_nodemask(zone, z, zonelist, + high_zoneidx, nodemask) + if (!cpuset_zone_allowed(zone, gfp_mask)) + cpuset_limited = true; + + if (cpuset_limited) { + *totalpages = total_swap_pages; + for_each_node_mask(nid, cpuset_current_mems_allowed) + *totalpages += node_spanned_pages(nid); + return CONSTRAINT_CPUSET; + } + return CONSTRAINT_NONE; +} +#else +static enum oom_constraint constrained_alloc(struct zonelist *zonelist, + gfp_t gfp_mask, nodemask_t *nodemask, + unsigned long *totalpages) +{ + *totalpages = totalram_pages + total_swap_pages; + return CONSTRAINT_NONE; +} +#endif + +enum oom_scan_t oom_scan_process_thread(struct task_struct *task, + unsigned long totalpages, const nodemask_t *nodemask, + bool force_kill) +{ + if (oom_unkillable_task(task, NULL, nodemask)) + return OOM_SCAN_CONTINUE; + + /* + * This task already has access to memory reserves and is being killed. + * Don't allow any other task to have access to the reserves. + */ + if (test_tsk_thread_flag(task, TIF_MEMDIE)) { + if (!force_kill) + return OOM_SCAN_ABORT; + } + if (!task->mm) + return OOM_SCAN_CONTINUE; + + /* + * If task is allocating a lot of memory and has been marked to be + * killed first if it triggers an oom, then select it. + */ + if (oom_task_origin(task)) + return OOM_SCAN_SELECT; + + if (task_will_free_mem(task) && !force_kill) + return OOM_SCAN_ABORT; + + return OOM_SCAN_OK; +} + +/* + * Simple selection loop. We chose the process with the highest + * number of 'points'. Returns -1 on scan abort. + * + * (not docbooked, we don't want this one cluttering up the manual) + */ +static struct task_struct *select_bad_process(unsigned int *ppoints, + unsigned long totalpages, const nodemask_t *nodemask, + bool force_kill) +{ + struct task_struct *g, *p; + struct task_struct *chosen = NULL; + unsigned long chosen_points = 0; + + rcu_read_lock(); + for_each_process_thread(g, p) { + unsigned int points; + + switch (oom_scan_process_thread(p, totalpages, nodemask, + force_kill)) { + case OOM_SCAN_SELECT: + chosen = p; + chosen_points = ULONG_MAX; + /* fall through */ + case OOM_SCAN_CONTINUE: + continue; + case OOM_SCAN_ABORT: + rcu_read_unlock(); + return (struct task_struct *)(-1UL); + case OOM_SCAN_OK: + break; + }; + points = oom_badness(p, NULL, nodemask, totalpages); + if (!points || points < chosen_points) + continue; + /* Prefer thread group leaders for display purposes */ + if (points == chosen_points && thread_group_leader(chosen)) + continue; + + chosen = p; + chosen_points = points; + } + if (chosen) + get_task_struct(chosen); + rcu_read_unlock(); + + *ppoints = chosen_points * 1000 / totalpages; + return chosen; +} + +/** + * dump_tasks - dump current memory state of all system tasks + * @memcg: current's memory controller, if constrained + * @nodemask: nodemask passed to page allocator for mempolicy ooms + * + * Dumps the current memory state of all eligible tasks. Tasks not in the same + * memcg, not in the same cpuset, or bound to a disjoint set of mempolicy nodes + * are not shown. + * State information includes task's pid, uid, tgid, vm size, rss, nr_ptes, + * swapents, oom_score_adj value, and name. + */ +static void dump_tasks(struct mem_cgroup *memcg, const nodemask_t *nodemask) +{ + struct task_struct *p; + struct task_struct *task; + + pr_info("[ pid ] uid tgid total_vm rss nr_ptes nr_pmds swapents oom_score_adj name\n"); + rcu_read_lock(); + for_each_process(p) { + if (oom_unkillable_task(p, memcg, nodemask)) + continue; + + task = find_lock_task_mm(p); + if (!task) { + /* + * This is a kthread or all of p's threads have already + * detached their mm's. There's no need to report + * them; they can't be oom killed anyway. + */ + continue; + } + + pr_info("[%5d] %5d %5d %8lu %8lu %7ld %7ld %8lu %5hd %s\n", + task->pid, from_kuid(&init_user_ns, task_uid(task)), + task->tgid, task->mm->total_vm, get_mm_rss(task->mm), + atomic_long_read(&task->mm->nr_ptes), + mm_nr_pmds(task->mm), + get_mm_counter(task->mm, MM_SWAPENTS), + task->signal->oom_score_adj, task->comm); + task_unlock(task); + } + rcu_read_unlock(); +} + +static void dump_header(struct task_struct *p, gfp_t gfp_mask, int order, + struct mem_cgroup *memcg, const nodemask_t *nodemask) +{ + task_lock(current); + pr_warning("%s invoked oom-killer: gfp_mask=0x%x, order=%d, " + "oom_score_adj=%hd\n", + current->comm, gfp_mask, order, + current->signal->oom_score_adj); + cpuset_print_task_mems_allowed(current); + task_unlock(current); + dump_stack(); + if (memcg) + mem_cgroup_print_oom_info(memcg, p); + else + show_mem(SHOW_MEM_FILTER_NODES); + if (sysctl_oom_dump_tasks) + dump_tasks(memcg, nodemask); +} + +/* + * Number of OOM victims in flight + */ +static atomic_t oom_victims = ATOMIC_INIT(0); +static DECLARE_WAIT_QUEUE_HEAD(oom_victims_wait); + +bool oom_killer_disabled __read_mostly; +static DECLARE_RWSEM(oom_sem); + +/** + * mark_tsk_oom_victim - marks the given task as OOM victim. + * @tsk: task to mark + * + * Has to be called with oom_sem taken for read and never after + * oom has been disabled already. + */ +void mark_tsk_oom_victim(struct task_struct *tsk) +{ + WARN_ON(oom_killer_disabled); + /* OOM killer might race with memcg OOM */ + if (test_and_set_tsk_thread_flag(tsk, TIF_MEMDIE)) + return; + /* + * Make sure that the task is woken up from uninterruptible sleep + * if it is frozen because OOM killer wouldn't be able to free + * any memory and livelock. freezing_slow_path will tell the freezer + * that TIF_MEMDIE tasks should be ignored. + */ + __thaw_task(tsk); + atomic_inc(&oom_victims); +} + +/** + * unmark_oom_victim - unmarks the current task as OOM victim. + * + * Wakes up all waiters in oom_killer_disable() + */ +void unmark_oom_victim(void) +{ + if (!test_and_clear_thread_flag(TIF_MEMDIE)) + return; + + down_read(&oom_sem); + /* + * There is no need to signal the lasst oom_victim if there + * is nobody who cares. + */ + if (!atomic_dec_return(&oom_victims) && oom_killer_disabled) + wake_up_all(&oom_victims_wait); + up_read(&oom_sem); +} + +/** + * oom_killer_disable - disable OOM killer + * + * Forces all page allocations to fail rather than trigger OOM killer. + * Will block and wait until all OOM victims are killed. + * + * The function cannot be called when there are runnable user tasks because + * the userspace would see unexpected allocation failures as a result. Any + * new usage of this function should be consulted with MM people. + * + * Returns true if successful and false if the OOM killer cannot be + * disabled. + */ +bool oom_killer_disable(void) +{ + /* + * Make sure to not race with an ongoing OOM killer + * and that the current is not the victim. + */ + down_write(&oom_sem); + if (test_thread_flag(TIF_MEMDIE)) { + up_write(&oom_sem); + return false; + } + + oom_killer_disabled = true; + up_write(&oom_sem); + + wait_event(oom_victims_wait, !atomic_read(&oom_victims)); + + return true; +} + +/** + * oom_killer_enable - enable OOM killer + */ +void oom_killer_enable(void) +{ + down_write(&oom_sem); + oom_killer_disabled = false; + up_write(&oom_sem); +} + +#define K(x) ((x) << (PAGE_SHIFT-10)) +/* + * Must be called while holding a reference to p, which will be released upon + * returning. + */ +void oom_kill_process(struct task_struct *p, gfp_t gfp_mask, int order, + unsigned int points, unsigned long totalpages, + struct mem_cgroup *memcg, nodemask_t *nodemask, + const char *message) +{ + struct task_struct *victim = p; + struct task_struct *child; + struct task_struct *t; + struct mm_struct *mm; + unsigned int victim_points = 0; + static DEFINE_RATELIMIT_STATE(oom_rs, DEFAULT_RATELIMIT_INTERVAL, + DEFAULT_RATELIMIT_BURST); + + /* + * If the task is already exiting, don't alarm the sysadmin or kill + * its children or threads, just set TIF_MEMDIE so it can die quickly + */ + task_lock(p); + if (p->mm && task_will_free_mem(p)) { + mark_tsk_oom_victim(p); + task_unlock(p); + put_task_struct(p); + return; + } + task_unlock(p); + + if (__ratelimit(&oom_rs)) + dump_header(p, gfp_mask, order, memcg, nodemask); + + task_lock(p); + pr_err("%s: Kill process %d (%s) score %d or sacrifice child\n", + message, task_pid_nr(p), p->comm, points); + task_unlock(p); + + /* + * If any of p's children has a different mm and is eligible for kill, + * the one with the highest oom_badness() score is sacrificed for its + * parent. This attempts to lose the minimal amount of work done while + * still freeing memory. + */ + read_lock(&tasklist_lock); + for_each_thread(p, t) { + list_for_each_entry(child, &t->children, sibling) { + unsigned int child_points; + + if (child->mm == p->mm) + continue; + /* + * oom_badness() returns 0 if the thread is unkillable + */ + child_points = oom_badness(child, memcg, nodemask, + totalpages); + if (child_points > victim_points) { + put_task_struct(victim); + victim = child; + victim_points = child_points; + get_task_struct(victim); + } + } + } + read_unlock(&tasklist_lock); + + p = find_lock_task_mm(victim); + if (!p) { + put_task_struct(victim); + return; + } else if (victim != p) { + get_task_struct(p); + put_task_struct(victim); + victim = p; + } + + /* mm cannot safely be dereferenced after task_unlock(victim) */ + mm = victim->mm; + mark_tsk_oom_victim(victim); + pr_err("Killed process %d (%s) total-vm:%lukB, anon-rss:%lukB, file-rss:%lukB\n", + task_pid_nr(victim), victim->comm, K(victim->mm->total_vm), + K(get_mm_counter(victim->mm, MM_ANONPAGES)), + K(get_mm_counter(victim->mm, MM_FILEPAGES))); + task_unlock(victim); + + /* + * Kill all user processes sharing victim->mm in other thread groups, if + * any. They don't get access to memory reserves, though, to avoid + * depletion of all memory. This prevents mm->mmap_sem livelock when an + * oom killed thread cannot exit because it requires the semaphore and + * its contended by another thread trying to allocate memory itself. + * That thread will now get access to memory reserves since it has a + * pending fatal signal. + */ + rcu_read_lock(); + for_each_process(p) + if (p->mm == mm && !same_thread_group(p, victim) && + !(p->flags & PF_KTHREAD)) { + if (p->signal->oom_score_adj == OOM_SCORE_ADJ_MIN) + continue; + + task_lock(p); /* Protect ->comm from prctl() */ + pr_err("Kill process %d (%s) sharing same memory\n", + task_pid_nr(p), p->comm); + task_unlock(p); + do_send_sig_info(SIGKILL, SEND_SIG_FORCED, p, true); + } + rcu_read_unlock(); + + do_send_sig_info(SIGKILL, SEND_SIG_FORCED, victim, true); + put_task_struct(victim); +} +#undef K + +/* + * Determines whether the kernel must panic because of the panic_on_oom sysctl. + */ +void check_panic_on_oom(enum oom_constraint constraint, gfp_t gfp_mask, + int order, const nodemask_t *nodemask, + struct mem_cgroup *memcg) +{ + if (likely(!sysctl_panic_on_oom)) + return; + if (sysctl_panic_on_oom != 2) { + /* + * panic_on_oom == 1 only affects CONSTRAINT_NONE, the kernel + * does not panic for cpuset, mempolicy, or memcg allocation + * failures. + */ + if (constraint != CONSTRAINT_NONE) + return; + } + dump_header(NULL, gfp_mask, order, memcg, nodemask); + panic("Out of memory: %s panic_on_oom is enabled\n", + sysctl_panic_on_oom == 2 ? "compulsory" : "system-wide"); +} + +static BLOCKING_NOTIFIER_HEAD(oom_notify_list); + +int register_oom_notifier(struct notifier_block *nb) +{ + return blocking_notifier_chain_register(&oom_notify_list, nb); +} +EXPORT_SYMBOL_GPL(register_oom_notifier); + +int unregister_oom_notifier(struct notifier_block *nb) +{ + return blocking_notifier_chain_unregister(&oom_notify_list, nb); +} +EXPORT_SYMBOL_GPL(unregister_oom_notifier); + +/* + * Try to acquire the OOM killer lock for the zones in zonelist. Returns zero + * if a parallel OOM killing is already taking place that includes a zone in + * the zonelist. Otherwise, locks all zones in the zonelist and returns 1. + */ +bool oom_zonelist_trylock(struct zonelist *zonelist, gfp_t gfp_mask) +{ + struct zoneref *z; + struct zone *zone; + bool ret = true; + + spin_lock(&zone_scan_lock); + for_each_zone_zonelist(zone, z, zonelist, gfp_zone(gfp_mask)) + if (test_bit(ZONE_OOM_LOCKED, &zone->flags)) { + ret = false; + goto out; + } + + /* + * Lock each zone in the zonelist under zone_scan_lock so a parallel + * call to oom_zonelist_trylock() doesn't succeed when it shouldn't. + */ + for_each_zone_zonelist(zone, z, zonelist, gfp_zone(gfp_mask)) + set_bit(ZONE_OOM_LOCKED, &zone->flags); + +out: + spin_unlock(&zone_scan_lock); + return ret; +} + +/* + * Clears the ZONE_OOM_LOCKED flag for all zones in the zonelist so that failed + * allocation attempts with zonelists containing them may now recall the OOM + * killer, if necessary. + */ +void oom_zonelist_unlock(struct zonelist *zonelist, gfp_t gfp_mask) +{ + struct zoneref *z; + struct zone *zone; + + spin_lock(&zone_scan_lock); + for_each_zone_zonelist(zone, z, zonelist, gfp_zone(gfp_mask)) + clear_bit(ZONE_OOM_LOCKED, &zone->flags); + spin_unlock(&zone_scan_lock); +} + +/** + * __out_of_memory - kill the "best" process when we run out of memory + * @zonelist: zonelist pointer + * @gfp_mask: memory allocation flags + * @order: amount of memory being requested as a power of 2 + * @nodemask: nodemask passed to page allocator + * @force_kill: true if a task must be killed, even if others are exiting + * + * If we run out of memory, we have the choice between either + * killing a random task (bad), letting the system crash (worse) + * OR try to be smart about which process to kill. Note that we + * don't have to be perfect here, we just have to be good. + */ +static void __out_of_memory(struct zonelist *zonelist, gfp_t gfp_mask, + int order, nodemask_t *nodemask, bool force_kill) +{ + const nodemask_t *mpol_mask; + struct task_struct *p; + unsigned long totalpages; + unsigned long freed = 0; + unsigned int uninitialized_var(points); + enum oom_constraint constraint = CONSTRAINT_NONE; + int killed = 0; + + blocking_notifier_call_chain(&oom_notify_list, 0, &freed); + if (freed > 0) + /* Got some memory back in the last second. */ + return; + + /* + * If current has a pending SIGKILL or is exiting, then automatically + * select it. The goal is to allow it to allocate so that it may + * quickly exit and free its memory. + * + * But don't select if current has already released its mm and cleared + * TIF_MEMDIE flag at exit_mm(), otherwise an OOM livelock may occur. + */ + if (current->mm && + (fatal_signal_pending(current) || task_will_free_mem(current))) { + mark_tsk_oom_victim(current); + return; + } + + /* + * Check if there were limitations on the allocation (only relevant for + * NUMA) that may require different handling. + */ + constraint = constrained_alloc(zonelist, gfp_mask, nodemask, + &totalpages); + mpol_mask = (constraint == CONSTRAINT_MEMORY_POLICY) ? nodemask : NULL; + check_panic_on_oom(constraint, gfp_mask, order, mpol_mask, NULL); + + if (sysctl_oom_kill_allocating_task && current->mm && + !oom_unkillable_task(current, NULL, nodemask) && + current->signal->oom_score_adj != OOM_SCORE_ADJ_MIN) { + get_task_struct(current); + oom_kill_process(current, gfp_mask, order, 0, totalpages, NULL, + nodemask, + "Out of memory (oom_kill_allocating_task)"); + goto out; + } + + p = select_bad_process(&points, totalpages, mpol_mask, force_kill); + /* Found nothing?!?! Either we hang forever, or we panic. */ + if (!p) { + dump_header(NULL, gfp_mask, order, NULL, mpol_mask); + panic("Out of memory and no killable processes...\n"); + } + if (p != (void *)-1UL) { + oom_kill_process(p, gfp_mask, order, points, totalpages, NULL, + nodemask, "Out of memory"); + killed = 1; + } +out: + /* + * Give the killed threads a good chance of exiting before trying to + * allocate memory again. + */ + if (killed) + schedule_timeout_killable(1); +} + +/** + * out_of_memory - tries to invoke OOM killer. + * @zonelist: zonelist pointer + * @gfp_mask: memory allocation flags + * @order: amount of memory being requested as a power of 2 + * @nodemask: nodemask passed to page allocator + * @force_kill: true if a task must be killed, even if others are exiting + * + * invokes __out_of_memory if the OOM is not disabled by oom_killer_disable() + * when it returns false. Otherwise returns true. + */ +bool out_of_memory(struct zonelist *zonelist, gfp_t gfp_mask, + int order, nodemask_t *nodemask, bool force_kill) +{ + bool ret = false; + + down_read(&oom_sem); + if (!oom_killer_disabled) { + __out_of_memory(zonelist, gfp_mask, order, nodemask, force_kill); + ret = true; + } + up_read(&oom_sem); + + return ret; +} + +/* + * The pagefault handler calls here because it is out of memory, so kill a + * memory-hogging task. If any populated zone has ZONE_OOM_LOCKED set, a + * parallel oom killing is already in progress so do nothing. + */ +void pagefault_out_of_memory(void) +{ + struct zonelist *zonelist; + + down_read(&oom_sem); + if (mem_cgroup_oom_synchronize(true)) + goto unlock; + + zonelist = node_zonelist(first_memory_node, GFP_KERNEL); + if (oom_zonelist_trylock(zonelist, GFP_KERNEL)) { + if (!oom_killer_disabled) + __out_of_memory(NULL, 0, 0, NULL, false); + else + /* + * There shouldn't be any user tasks runable while the + * OOM killer is disabled so the current task has to + * be a racing OOM victim for which oom_killer_disable() + * is waiting for. + */ + WARN_ON(test_thread_flag(TIF_MEMDIE)); + + oom_zonelist_unlock(zonelist, GFP_KERNEL); + } +unlock: + up_read(&oom_sem); +} -- cgit v1.2.3-54-g00ecf