/* * 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); /* * compare_swap_oom_score_adj() - compare and swap current's oom_score_adj * @old_val: old oom_score_adj for compare * @new_val: new oom_score_adj for swap * * Sets the oom_score_adj value for current to @new_val iff its present value is * @old_val. Usually used to reinstate a previous value to prevent racing with * userspacing tuning the value in the interim. */ void compare_swap_oom_score_adj(int old_val, int new_val) { struct sighand_struct *sighand = current->sighand; spin_lock_irq(&sighand->siglock); if (current->signal->oom_score_adj == old_val) current->signal->oom_score_adj = new_val; trace_oom_score_adj_update(current); spin_unlock_irq(&sighand->siglock); } /** * test_set_oom_score_adj() - set current's oom_score_adj and return old value * @new_val: new oom_score_adj value * * Sets the oom_score_adj value for current to @new_val with proper * synchronization and returns the old value. Usually used to temporarily * set a value, save the old value in the caller, and then reinstate it later. */ int test_set_oom_score_adj(int new_val) { struct sighand_struct *sighand = current->sighand; int old_val; spin_lock_irq(&sighand->siglock); old_val = current->signal->oom_score_adj; current->signal->oom_score_adj = new_val; trace_oom_score_adj_update(current); spin_unlock_irq(&sighand->siglock); return old_val; } #ifdef CONFIG_NUMA /** * has_intersects_mems_allowed() - check task eligiblity for kill * @tsk: 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 *tsk, const nodemask_t *mask) { struct task_struct *start = tsk; do { 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. */ if (mempolicy_nodemask_intersects(tsk, mask)) return true; } else { /* * This is not a mempolicy constrained oom, so only * check the mems of tsk's cpuset. */ if (cpuset_mems_allowed_intersects(current, tsk)) return true; } } while_each_thread(start, tsk); return false; } #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 = p; do { task_lock(t); if (likely(t->mm)) return t; task_unlock(t); } while_each_thread(p, t); return NULL; } /* return true if the task is not adequate as candidate victim task. */ static bool oom_unkillable_task(struct task_struct *p, const 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 = 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) + p->mm->nr_ptes + get_mm_counter(p->mm, MM_SWAPENTS); 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)) adj -= 30; /* 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_HIGH_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_softwall(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 /* * Simple selection loop. We chose the process with the highest * number of 'points'. We expect the caller will lock the tasklist. * * (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, struct mem_cgroup *memcg, const nodemask_t *nodemask, bool force_kill) { struct task_struct *g, *p; struct task_struct *chosen = NULL; unsigned long chosen_points = 0; do_each_thread(g, p) { unsigned int points; if (p->exit_state) continue; if (oom_unkillable_task(p, memcg, nodemask)) continue; /* * This task already has access to memory reserves and is * being killed. Don't allow any other task access to the * memory reserve. * * Note: this may have a chance of deadlock if it gets * blocked waiting for another task which itself is waiting * for memory. Is there a better alternative? */ if (test_tsk_thread_flag(p, TIF_MEMDIE)) { if (unlikely(frozen(p))) __thaw_task(p); if (!force_kill) return ERR_PTR(-1UL); } if (!p->mm) continue; if (p->flags & PF_EXITING) { /* * If p is the current task and is in the process of * releasing memory, we allow the "kill" to set * TIF_MEMDIE, which will allow it to gain access to * memory reserves. Otherwise, it may stall forever. * * The loop isn't broken here, however, in case other * threads are found to have already been oom killed. */ if (p == current) { chosen = p; chosen_points = ULONG_MAX; } else if (!force_kill) { /* * If this task is not being ptraced on exit, * then wait for it to finish before killing * some other task unnecessarily. */ if (!(p->group_leader->ptrace & PT_TRACE_EXIT)) return ERR_PTR(-1UL); } } points = oom_badness(p, memcg, nodemask, totalpages); if (points > chosen_points) { chosen = p; chosen_points = points; } } while_each_thread(g, p); *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, cpu, oom_adj * value, oom_score_adj value, and name. * * Call with tasklist_lock read-locked. */ static void dump_tasks(const struct mem_cgroup *memcg, const nodemask_t *nodemask) { struct task_struct *p; struct task_struct *task; pr_info("[ pid ] uid tgid total_vm rss cpu oom_adj oom_score_adj name\n"); 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 %3u %3d %5d %s\n", task->pid, from_kuid(&init_user_ns, task_uid(task)), task->tgid, task->mm->total_vm, get_mm_rss(task->mm), task_cpu(task), task->signal->oom_adj, task->signal->oom_score_adj, task->comm); task_unlock(task); } } 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_adj=%d, oom_score_adj=%d\n", current->comm, gfp_mask, order, current->signal->oom_adj, current->signal->oom_score_adj); cpuset_print_task_mems_allowed(current); task_unlock(current); dump_stack(); mem_cgroup_print_oom_info(memcg, p); show_mem(SHOW_MEM_FILTER_NODES); if (sysctl_oom_dump_tasks) dump_tasks(memcg, nodemask); } #define K(x) ((x) << (PAGE_SHIFT-10)) static 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 = p; 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 */ if (p->flags & PF_EXITING) { set_tsk_thread_flag(p, TIF_MEMDIE); return; } 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. */ do { 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) { victim = child; victim_points = child_points; } } } while_each_thread(p, t); victim = find_lock_task_mm(victim); if (!victim) return; /* mm cannot safely be dereferenced after task_unlock(victim) */ mm = victim->mm; 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. */ 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); } set_tsk_thread_flag(victim, TIF_MEMDIE); do_send_sig_info(SIGKILL, SEND_SIG_FORCED, victim, true); } #undef K /* * Determines whether the kernel must panic because of the panic_on_oom sysctl. */ static void check_panic_on_oom(enum oom_constraint constraint, gfp_t gfp_mask, int order, const nodemask_t *nodemask) { 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; } read_lock(&tasklist_lock); dump_header(NULL, gfp_mask, order, NULL, nodemask); read_unlock(&tasklist_lock); panic("Out of memory: %s panic_on_oom is enabled\n", sysctl_panic_on_oom == 2 ? "compulsory" : "system-wide"); } #ifdef CONFIG_CGROUP_MEM_RES_CTLR void mem_cgroup_out_of_memory(struct mem_cgroup *memcg, gfp_t gfp_mask, int order) { unsigned long limit; unsigned int points = 0; struct task_struct *p; /* * If current has a pending SIGKILL, then automatically select it. The * goal is to allow it to allocate so that it may quickly exit and free * its memory. */ if (fatal_signal_pending(current)) { set_thread_flag(TIF_MEMDIE); return; } check_panic_on_oom(CONSTRAINT_MEMCG, gfp_mask, order, NULL); limit = mem_cgroup_get_limit(memcg) >> PAGE_SHIFT ? : 1; read_lock(&tasklist_lock); p = select_bad_process(&points, limit, memcg, NULL, false); if (p && PTR_ERR(p) != -1UL) oom_kill_process(p, gfp_mask, order, points, limit, memcg, NULL, "Memory cgroup out of memory"); read_unlock(&tasklist_lock); } #endif 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. */ int try_set_zonelist_oom(struct zonelist *zonelist, gfp_t gfp_mask) { struct zoneref *z; struct zone *zone; int ret = 1; spin_lock(&zone_scan_lock); for_each_zone_zonelist(zone, z, zonelist, gfp_zone(gfp_mask)) { if (zone_is_oom_locked(zone)) { ret = 0; goto out; } } for_each_zone_zonelist(zone, z, zonelist, gfp_zone(gfp_mask)) { /* * Lock each zone in the zonelist under zone_scan_lock so a * parallel invocation of try_set_zonelist_oom() doesn't succeed * when it shouldn't. */ zone_set_flag(zone, ZONE_OOM_LOCKED); } 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 clear_zonelist_oom(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)) { zone_clear_flag(zone, ZONE_OOM_LOCKED); } spin_unlock(&zone_scan_lock); } /* * Try to acquire the oom killer lock for all system zones. Returns zero if a * parallel oom killing is taking place, otherwise locks all zones and returns * non-zero. */ static int try_set_system_oom(void) { struct zone *zone; int ret = 1; spin_lock(&zone_scan_lock); for_each_populated_zone(zone) if (zone_is_oom_locked(zone)) { ret = 0; goto out; } for_each_populated_zone(zone) zone_set_flag(zone, ZONE_OOM_LOCKED); out: spin_unlock(&zone_scan_lock); return ret; } /* * Clears ZONE_OOM_LOCKED for all system zones so that failed allocation * attempts or page faults may now recall the oom killer, if necessary. */ static void clear_system_oom(void) { struct zone *zone; spin_lock(&zone_scan_lock); for_each_populated_zone(zone) zone_clear_flag(zone, ZONE_OOM_LOCKED); 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. */ 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 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, then automatically select it. The * goal is to allow it to allocate so that it may quickly exit and free * its memory. */ if (fatal_signal_pending(current)) { set_thread_flag(TIF_MEMDIE); 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); read_lock(&tasklist_lock); if (sysctl_oom_kill_allocating_task && current->mm && !oom_unkillable_task(current, NULL, nodemask) && current->signal->oom_score_adj != OOM_SCORE_ADJ_MIN) { 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, NULL, mpol_mask, force_kill); /* Found nothing?!?! Either we hang forever, or we panic. */ if (!p) { dump_header(NULL, gfp_mask, order, NULL, mpol_mask); read_unlock(&tasklist_lock); panic("Out of memory and no killable processes...\n"); } if (PTR_ERR(p) != -1UL) { oom_kill_process(p, gfp_mask, order, points, totalpages, NULL, nodemask, "Out of memory"); killed = 1; } out: read_unlock(&tasklist_lock); /* * Give the killed threads a good chance of exiting before trying to * allocate memory again. */ if (killed) schedule_timeout_killable(1); } /* * The pagefault handler calls here because it is out of memory, so kill a * memory-hogging task. If a populated zone has ZONE_OOM_LOCKED set, a parallel * oom killing is already in progress so do nothing. If a task is found with * TIF_MEMDIE set, it has been killed so do nothing and allow it to exit. */ void pagefault_out_of_memory(void) { if (try_set_system_oom()) { out_of_memory(NULL, 0, 0, NULL, false); clear_system_oom(); } schedule_timeout_killable(1); }