/* * 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; DEFINE_MUTEX(oom_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; } /* * order == -1 means the oom kill is required by sysrq, otherwise only * for display purposes. */ static inline bool is_sysrq_oom(struct oom_control *oc) { return oc->order == -1; } /* 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 oom_control *oc, unsigned long *totalpages) { struct zone *zone; struct zoneref *z; enum zone_type high_zoneidx = gfp_zone(oc->gfp_mask); bool cpuset_limited = false; int nid; /* Default to all available memory */ *totalpages = totalram_pages + total_swap_pages; if (!oc->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 (oc->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 (oc->nodemask && !nodes_subset(node_states[N_MEMORY], *oc->nodemask)) { *totalpages = total_swap_pages; for_each_node_mask(nid, *oc->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, oc->zonelist, high_zoneidx, oc->nodemask) if (!cpuset_zone_allowed(zone, oc->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 oom_control *oc, unsigned long *totalpages) { *totalpages = totalram_pages + total_swap_pages; return CONSTRAINT_NONE; } #endif enum oom_scan_t oom_scan_process_thread(struct oom_control *oc, struct task_struct *task, unsigned long totalpages) { if (oom_unkillable_task(task, NULL, oc->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 (!is_sysrq_oom(oc)) 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) && !is_sysrq_oom(oc)) 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. */ static struct task_struct *select_bad_process(struct oom_control *oc, unsigned int *ppoints, unsigned long totalpages) { 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(oc, p, totalpages)) { 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, oc->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 oom_control *oc, struct task_struct *p, struct mem_cgroup *memcg) { pr_warning("%s invoked oom-killer: gfp_mask=0x%x, order=%d, oom_score_adj=%hd\n", current->comm, oc->gfp_mask, oc->order, current->signal->oom_score_adj); cpuset_print_current_mems_allowed(); 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, oc->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; /** * mark_oom_victim - mark the given task as OOM victim * @tsk: task to mark * * Has to be called with oom_lock held and never after * oom has been disabled already. */ void mark_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); } /** * exit_oom_victim - note the exit of an OOM victim */ void exit_oom_victim(void) { clear_thread_flag(TIF_MEMDIE); if (!atomic_dec_return(&oom_victims)) wake_up_all(&oom_victims_wait); } /** * 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. */ mutex_lock(&oom_lock); if (test_thread_flag(TIF_MEMDIE)) { mutex_unlock(&oom_lock); return false; } oom_killer_disabled = true; mutex_unlock(&oom_lock); wait_event(oom_victims_wait, !atomic_read(&oom_victims)); return true; } /** * oom_killer_enable - enable OOM killer */ void oom_killer_enable(void) { oom_killer_disabled = false; } /* * task->mm can be NULL if the task is the exited group leader. So to * determine whether the task is using a particular mm, we examine all the * task's threads: if one of those is using this mm then this task was also * using it. */ static bool process_shares_mm(struct task_struct *p, struct mm_struct *mm) { struct task_struct *t; for_each_thread(p, t) { struct mm_struct *t_mm = READ_ONCE(t->mm); if (t_mm) return t_mm == mm; } return false; } #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 oom_control *oc, struct task_struct *p, unsigned int points, unsigned long totalpages, struct mem_cgroup *memcg, 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_oom_victim(p); task_unlock(p); put_task_struct(p); return; } task_unlock(p); if (__ratelimit(&oom_rs)) dump_header(oc, p, memcg); pr_err("%s: Kill process %d (%s) score %u or sacrifice child\n", message, task_pid_nr(p), p->comm, points); /* * 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); /* * The task 'p' might have already exited before reaching here. The * put_task_struct() will free task_struct 'p' while the loop still try * to access the field of 'p', so, get an extra reference. */ get_task_struct(p); for_each_thread(p, t) { list_for_each_entry(child, &t->children, sibling) { unsigned int child_points; if (process_shares_mm(child, p->mm)) continue; /* * oom_badness() returns 0 if the thread is unkillable */ child_points = oom_badness(child, memcg, oc->nodemask, totalpages); if (child_points > victim_points) { put_task_struct(victim); victim = child; victim_points = child_points; get_task_struct(victim); } } } put_task_struct(p); 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; } /* Get a reference to safely compare mm after task_unlock(victim) */ mm = victim->mm; atomic_inc(&mm->mm_count); /* * We should send SIGKILL before setting TIF_MEMDIE in order to prevent * the OOM victim from depleting the memory reserves from the user * space under its control. */ do_send_sig_info(SIGKILL, SEND_SIG_FORCED, victim, true); mark_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 (!process_shares_mm(p, mm)) continue; if (same_thread_group(p, victim)) continue; if (unlikely(p->flags & PF_KTHREAD)) continue; if (is_global_init(p)) continue; if (p->signal->oom_score_adj == OOM_SCORE_ADJ_MIN) continue; do_send_sig_info(SIGKILL, SEND_SIG_FORCED, p, true); } rcu_read_unlock(); mmdrop(mm); put_task_struct(victim); } #undef K /* * Determines whether the kernel must panic because of the panic_on_oom sysctl. */ void check_panic_on_oom(struct oom_control *oc, enum oom_constraint constraint, 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; } /* Do not panic for oom kills triggered by sysrq */ if (is_sysrq_oom(oc)) return; dump_header(oc, NULL, memcg); 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); /** * out_of_memory - kill the "best" process when we run out of memory * @oc: pointer to struct oom_control * * 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. */ bool out_of_memory(struct oom_control *oc) { struct task_struct *p; unsigned long totalpages; unsigned long freed = 0; unsigned int uninitialized_var(points); enum oom_constraint constraint = CONSTRAINT_NONE; if (oom_killer_disabled) return false; blocking_notifier_call_chain(&oom_notify_list, 0, &freed); if (freed > 0) /* Got some memory back in the last second. */ return true; /* * 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_oom_victim(current); return true; } /* * Check if there were limitations on the allocation (only relevant for * NUMA) that may require different handling. */ constraint = constrained_alloc(oc, &totalpages); if (constraint != CONSTRAINT_MEMORY_POLICY) oc->nodemask = NULL; check_panic_on_oom(oc, constraint, NULL); if (sysctl_oom_kill_allocating_task && current->mm && !oom_unkillable_task(current, NULL, oc->nodemask) && current->signal->oom_score_adj != OOM_SCORE_ADJ_MIN) { get_task_struct(current); oom_kill_process(oc, current, 0, totalpages, NULL, "Out of memory (oom_kill_allocating_task)"); return true; } p = select_bad_process(oc, &points, totalpages); /* Found nothing?!?! Either we hang forever, or we panic. */ if (!p && !is_sysrq_oom(oc)) { dump_header(oc, NULL, NULL); panic("Out of memory and no killable processes...\n"); } if (p && p != (void *)-1UL) { oom_kill_process(oc, p, points, totalpages, NULL, "Out of memory"); /* * Give the killed process a good chance to exit before trying * to allocate memory again. */ schedule_timeout_killable(1); } return true; } /* * 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 oom_control oc = { .zonelist = NULL, .nodemask = NULL, .gfp_mask = 0, .order = 0, }; if (mem_cgroup_oom_synchronize(true)) return; if (fatal_signal_pending(current)) return; if (!mutex_trylock(&oom_lock)) return; if (!out_of_memory(&oc)) { /* * There shouldn't be any user tasks runnable 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)); } mutex_unlock(&oom_lock); }