/* * 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 <linux/oom.h> #include <linux/mm.h> #include <linux/err.h> #include <linux/gfp.h> #include <linux/sched.h> #include <linux/swap.h> #include <linux/timex.h> #include <linux/jiffies.h> #include <linux/cpuset.h> #include <linux/module.h> #include <linux/notifier.h> #include <linux/memcontrol.h> #include <linux/mempolicy.h> #include <linux/security.h> 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 * @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 */ /* * If this is a system OOM (not a memcg OOM) and the task selected to be * killed is not already running at high (RT) priorities, speed up the * recovery by boosting the dying task to the lowest FIFO priority. * That helps with the recovery and avoids interfering with RT tasks. */ static void boost_dying_task_prio(struct task_struct *p, struct mem_cgroup *mem) { struct sched_param param = { .sched_priority = 1 }; if (mem) return; if (!rt_task(p)) sched_setscheduler_nocheck(p, SCHED_FIFO, ¶m); } /* * 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 *mem, 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 (mem && !task_in_mem_cgroup(p, mem)) 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 int oom_badness(struct task_struct *p, struct mem_cgroup *mem, const nodemask_t *nodemask, unsigned long totalpages) { int points; if (oom_unkillable_task(p, mem, nodemask)) return 0; p = find_lock_task_mm(p); if (!p) return 0; /* * Shortcut check for a thread sharing p->mm that is OOM_SCORE_ADJ_MIN * so the entire heuristic doesn't need to be executed for something * that cannot be killed. */ if (atomic_read(&p->mm->oom_disable_count)) { task_unlock(p); return 0; } /* * When the PF_OOM_ORIGIN bit is set, it indicates the task should have * priority for oom killing. */ if (p->flags & PF_OOM_ORIGIN) { task_unlock(p); return 1000; } /* * The memory controller may have a limit of 0 bytes, so avoid a divide * by zero, if necessary. */ if (!totalpages) totalpages = 1; /* * The baseline for the badness score is the proportion of RAM that each * task's rss and swap space use. */ points = (get_mm_rss(p->mm) + get_mm_counter(p->mm, MM_SWAPENTS)) * 1000 / totalpages; 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 -= 30; /* * /proc/pid/oom_score_adj ranges from -1000 to +1000 such that it may * either completely disable oom killing or always prefer a certain * task. */ points += p->signal->oom_score_adj; /* * Never return 0 for an eligible task that may be killed since it's * possible that no single user task uses more than 0.1% of memory and * no single admin tasks uses more than 3.0%. */ if (points <= 0) return 1; return (points < 1000) ? points : 1000; } /* * 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 *mem, const nodemask_t *nodemask) { struct task_struct *p; struct task_struct *chosen = NULL; *ppoints = 0; for_each_process(p) { unsigned int points; if (oom_unkillable_task(p, mem, 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)) return ERR_PTR(-1UL); /* * This is in the process of releasing memory so wait for it * to finish before killing some other task by mistake. * * However, if p is the current task, we allow the 'kill' to * go ahead if it is exiting: this will simply set TIF_MEMDIE, * which will allow it to gain access to memory reserves in * the process of exiting and releasing its resources. * Otherwise we could get an easy OOM deadlock. */ if (thread_group_empty(p) && (p->flags & PF_EXITING) && p->mm) { if (p != current) return ERR_PTR(-1UL); chosen = p; *ppoints = 1000; } points = oom_badness(p, mem, nodemask, totalpages); if (points > *ppoints) { chosen = p; *ppoints = points; } } return chosen; } /** * dump_tasks - dump current memory state of all system tasks * @mem: 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 *mem, 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, mem, 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, 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 *mem, 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(mem, p); show_mem(); if (sysctl_oom_dump_tasks) dump_tasks(mem, nodemask); } #define K(x) ((x) << (PAGE_SHIFT-10)) static int oom_kill_task(struct task_struct *p, struct mem_cgroup *mem) { struct task_struct *q; struct mm_struct *mm; p = find_lock_task_mm(p); if (!p) return 1; /* mm cannot be safely dereferenced after task_unlock(p) */ mm = p->mm; pr_err("Killed process %d (%s) total-vm:%lukB, anon-rss:%lukB, file-rss:%lukB\n", task_pid_nr(p), p->comm, K(p->mm->total_vm), K(get_mm_counter(p->mm, MM_ANONPAGES)), K(get_mm_counter(p->mm, MM_FILEPAGES))); task_unlock(p); /* * Kill all processes sharing p->mm in other thread groups, if any. * They don't get access to memory reserves or a higher scheduler * priority, though, to avoid depletion of all memory or task * starvation. This prevents mm->mmap_sem livelock when an oom killed * task 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(q) if (q->mm == mm && !same_thread_group(q, p)) { task_lock(q); /* Protect ->comm from prctl() */ pr_err("Kill process %d (%s) sharing same memory\n", task_pid_nr(q), q->comm); task_unlock(q); force_sig(SIGKILL, q); } set_tsk_thread_flag(p, TIF_MEMDIE); force_sig(SIGKILL, p); /* * We give our sacrificial lamb high priority and access to * all the memory it needs. That way it should be able to * exit() and clear out its resources quickly... */ boost_dying_task_prio(p, mem); return 0; } #undef K static int oom_kill_process(struct task_struct *p, gfp_t gfp_mask, int order, unsigned int points, unsigned long totalpages, struct mem_cgroup *mem, nodemask_t *nodemask, const char *message) { struct task_struct *victim = p; struct task_struct *child; struct task_struct *t = p; unsigned int victim_points = 0; if (printk_ratelimit()) dump_header(p, gfp_mask, order, mem, nodemask); /* * 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); boost_dying_task_prio(p, mem); return 0; } 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 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; /* * oom_badness() returns 0 if the thread is unkillable */ child_points = oom_badness(child, mem, nodemask, totalpages); if (child_points > victim_points) { victim = child; victim_points = child_points; } } } while_each_thread(p, t); return oom_kill_task(victim, mem); } /* * 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 *mem, gfp_t gfp_mask) { unsigned long limit; unsigned int points = 0; struct task_struct *p; check_panic_on_oom(CONSTRAINT_MEMCG, gfp_mask, 0, NULL); limit = mem_cgroup_get_limit(mem) >> PAGE_SHIFT; read_lock(&tasklist_lock); retry: p = select_bad_process(&points, limit, mem, NULL); if (!p || PTR_ERR(p) == -1UL) goto out; if (oom_kill_process(p, gfp_mask, 0, points, limit, mem, NULL, "Memory cgroup out of memory")) goto retry; out: 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 * * 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) { 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); boost_dying_task_prio(current, NULL); 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 && !oom_unkillable_task(current, NULL, nodemask) && current->mm && !atomic_read(¤t->mm->oom_disable_count)) { /* * oom_kill_process() needs tasklist_lock held. If it returns * non-zero, current could not be killed so we must fallback to * the tasklist scan. */ if (!oom_kill_process(current, gfp_mask, order, 0, totalpages, NULL, nodemask, "Out of memory (oom_kill_allocating_task)")) goto out; } retry: p = select_bad_process(&points, totalpages, NULL, mpol_mask); if (PTR_ERR(p) == -1UL) goto out; /* 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 (oom_kill_process(p, gfp_mask, order, points, totalpages, NULL, nodemask, "Out of memory")) goto retry; killed = 1; out: read_unlock(&tasklist_lock); /* * Give "p" a good chance of killing itself before we * retry to allocate memory unless "p" is current */ if (killed && !test_thread_flag(TIF_MEMDIE)) schedule_timeout_uninterruptible(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); clear_system_oom(); } if (!test_thread_flag(TIF_MEMDIE)) schedule_timeout_uninterruptible(1); }