/* * 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... * * 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/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/security.h>int sysctl_panic_on_oom;int sysctl_oom_kill_allocating_task;int sysctl_oom_dump_tasks;static DEFINE_SPINLOCK(zone_scan_lock);/* #define DEBUG *//* * Is all threads of the target process nodes overlap ours? */static int has_intersects_mems_allowed(struct task_struct *tsk){ struct task_struct *t; t = tsk; do { if (cpuset_mems_allowed_intersects(current, t)) return 1; t = next_thread(t); } while (t != tsk); return 0;}/** * badness - calculate a numeric value for how bad this task has been * @p: task struct of which task we should calculate * @uptime: current uptime in seconds * * The formula used is relatively simple and documented inline in the * function. The main rationale is that we want to select a good task * to kill when we run out of memory. * * Good in this context means that: * 1) we lose the minimum amount of work done * 2) we recover a large amount of memory * 3) we don't kill anything innocent of eating tons of memory * 4) we want to kill the minimum amount of processes (one) * 5) we try to kill the process the user expects us to kill, this * algorithm has been meticulously tuned to meet the principle * of least surprise ... (be careful when you change it) */unsigned long badness(struct task_struct *p, unsigned long uptime){ unsigned long points, cpu_time, run_time; struct mm_struct *mm; struct task_struct *child; int oom_adj = p->signal->oom_adj; struct task_cputime task_time; unsigned long utime; unsigned long stime; if (oom_adj == OOM_DISABLE) return 0; task_lock(p); mm = p->mm; if (!mm) { task_unlock(p); return 0; } /* * The memory size of the process is the basis for the badness. */ points = mm->total_vm; /* * After this unlock we can no longer dereference local variable `mm' */ task_unlock(p); /* * swapoff can easily use up all memory, so kill those first. */ if (p->flags & PF_OOM_ORIGIN) return ULONG_MAX; /* * Processes which fork a lot of child processes are likely * a good choice. We add half the vmsize of the children if they * have an own mm. This prevents forking servers to flood the * machine with an endless amount of children. In case a single * child is eating the vast majority of memory, adding only half * to the parents will make the child our kill candidate of choice. */ list_for_each_entry(child, &p->children, sibling) { task_lock(child); if (child->mm != mm && child->mm) points += child->mm->total_vm/2 + 1; task_unlock(child); } /* * CPU time is in tens of seconds and run time is in thousands * of seconds. There is no particular reason for this other than * that it turned out to work very well in practice. */ thread_group_cputime(p, &task_time); utime = cputime_to_jiffies(task_time.utime); stime = cputime_to_jiffies(task_time.stime); cpu_time = (utime + stime) >> (SHIFT_HZ + 3); if (uptime >= p->start_time.tv_sec) run_time = (uptime - p->start_time.tv_sec) >> 10; else run_time = 0; if (cpu_time) points /= int_sqrt(cpu_time); if (run_time) points /= int_sqrt(int_sqrt(run_time)); /* * Niced processes are most likely less important, so double * their badness points. */ if (task_nice(p) > 0) points *= 2; /* * Superuser processes are usually more important, so we make it * less likely that we kill those. */ if (has_capability_noaudit(p, CAP_SYS_ADMIN) || has_capability_noaudit(p, CAP_SYS_RESOURCE)) points /= 4; /* * We don't want to kill a process with direct hardware access. * Not only could that mess up the hardware, but usually users * tend to only have this flag set on applications they think * of as important. */ if (has_capability_noaudit(p, CAP_SYS_RAWIO)) points /= 4; /* * If p's nodes don't overlap ours, it may still help to kill p * because p may have allocated or otherwise mapped memory on * this node before. However it will be less likely. */ if (!has_intersects_mems_allowed(p)) points /= 8; /* * Adjust the score by oom_adj. */ if (oom_adj) { if (oom_adj > 0) { if (!points) points = 1; points <<= oom_adj; } else points >>= -(oom_adj); }#ifdef DEBUG printk(KERN_DEBUG "OOMkill: task %d (%s) got %lu points\n", p->pid, p->comm, points);#endif return points;}/* * Determine the type of allocation constraint. */static inline enum oom_constraint constrained_alloc(struct zonelist *zonelist, gfp_t gfp_mask){#ifdef CONFIG_NUMA struct zone *zone; struct zoneref *z; enum zone_type high_zoneidx = gfp_zone(gfp_mask); nodemask_t nodes = node_states[N_HIGH_MEMORY]; for_each_zone_zonelist(zone, z, zonelist, high_zoneidx) if (cpuset_zone_allowed_softwall(zone, gfp_mask)) node_clear(zone_to_nid(zone), nodes); else return CONSTRAINT_CPUSET; if (!nodes_empty(nodes)) return CONSTRAINT_MEMORY_POLICY;#endif return CONSTRAINT_NONE;}/* * 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 long *ppoints, struct mem_cgroup *mem){ struct task_struct *p; struct task_struct *chosen = NULL; struct timespec uptime; *ppoints = 0; do_posix_clock_monotonic_gettime(&uptime); for_each_process(p) { unsigned long points; /* * skip kernel threads and tasks which have already released * their mm. */ if (!p->mm) continue; /* skip the init task */ if (is_global_init(p)) continue; if (mem && !task_in_mem_cgroup(p, mem)) 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 (p->flags & PF_EXITING) { if (p != current) return ERR_PTR(-1UL); chosen = p; *ppoints = ULONG_MAX; } if (p->signal->oom_adj == OOM_DISABLE) continue; points = badness(p, uptime.tv_sec); if (points > *ppoints || !chosen) { chosen = p; *ppoints = points; } } return chosen;}/** * dump_tasks - dump current memory state of all system tasks * @mem: target memory controller * * Dumps the current memory state of all system tasks, excluding kernel threads. * State information includes task's pid, uid, tgid, vm size, rss, cpu, oom_adj * score, and name. * * If the actual is non-NULL, only tasks that are a member of the mem_cgroup are * shown. * * Call with tasklist_lock read-locked. */static void dump_tasks(const struct mem_cgroup *mem){ struct task_struct *g, *p; printk(KERN_INFO "[ pid ] uid tgid total_vm rss cpu oom_adj " "name\n"); do_each_thread(g, p) { struct mm_struct *mm; if (mem && !task_in_mem_cgroup(p, mem)) continue; if (!thread_group_leader(p)) continue; task_lock(p); mm = p->mm; if (!mm) { /* * total_vm and rss sizes do not exist for tasks with no * mm so there's no need to report them; they can't be * oom killed anyway. */ task_unlock(p); continue; } printk(KERN_INFO "[%5d] %5d %5d %8lu %8lu %3d %3d %s\n", p->pid, __task_cred(p)->uid, p->tgid, mm->total_vm, get_mm_rss(mm), (int)task_cpu(p), p->signal->oom_adj, p->comm); task_unlock(p); } while_each_thread(g, p);}/* * Send SIGKILL to the selected process irrespective of CAP_SYS_RAW_IO * flag though it's unlikely that we select a process with CAP_SYS_RAW_IO * set. */static void __oom_kill_task(struct task_struct *p, int verbose){ if (is_global_init(p)) { WARN_ON(1); printk(KERN_WARNING "tried to kill init!\n"); return; } if (!p->mm) { WARN_ON(1); printk(KERN_WARNING "tried to kill an mm-less task!\n"); return; } if (verbose) printk(KERN_ERR "Killed process %d (%s)\n", task_pid_nr(p), p->comm); /* * 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... */ p->rt.time_slice = HZ; set_tsk_thread_flag(p, TIF_MEMDIE); force_sig(SIGKILL, p);}static int oom_kill_task(struct task_struct *p){ /* WARNING: mm may not be dereferenced since we did not obtain its * value from get_task_mm(p). This is OK since all we need to do is * compare mm to q->mm below. * * Furthermore, even if mm contains a non-NULL value, p->mm may * change to NULL at any time since we do not hold task_lock(p). * However, this is of no concern to us. */ if (!p->mm || p->signal->oom_adj == OOM_DISABLE) return 1; __oom_kill_task(p, 1); return 0;}static int oom_kill_process(struct task_struct *p, gfp_t gfp_mask, int order, unsigned long points, struct mem_cgroup *mem, const char *message){ struct task_struct *c; if (printk_ratelimit()) { printk(KERN_WARNING "%s invoked oom-killer: " "gfp_mask=0x%x, order=%d, oom_adj=%d\n", current->comm, gfp_mask, order, current->signal->oom_adj); task_lock(current); cpuset_print_task_mems_allowed(current); task_unlock(current); dump_stack(); mem_cgroup_print_oom_info(mem, current); show_mem(); if (sysctl_oom_dump_tasks) dump_tasks(mem); } /* * 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) { __oom_kill_task(p, 0); return 0; } printk(KERN_ERR "%s: kill process %d (%s) score %li or a child\n", message, task_pid_nr(p), p->comm, points); /* Try to kill a child first */ list_for_each_entry(c, &p->children, sibling) { if (c->mm == p->mm) continue; if (!oom_kill_task(c)) return 0; } return oom_kill_task(p);}#ifdef CONFIG_CGROUP_MEM_RES_CTLRvoid mem_cgroup_out_of_memory(struct mem_cgroup *mem, gfp_t gfp_mask){ unsigned long points = 0; struct task_struct *p; read_lock(&tasklist_lock);retry: p = select_bad_process(&points, mem); if (PTR_ERR(p) == -1UL) goto out; if (!p) p = current; if (oom_kill_process(p, gfp_mask, 0, points, mem, "Memory cgroup out of memory")) goto retry;out: read_unlock(&tasklist_lock);}#endifstatic 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_zone_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_zone_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);}/* * Must be called with tasklist_lock held for read. */static void __out_of_memory(gfp_t gfp_mask, int order){ struct task_struct *p; unsigned long points; if (sysctl_oom_kill_allocating_task) if (!oom_kill_process(current, gfp_mask, order, 0, NULL, "Out of memory (oom_kill_allocating_task)")) return;retry: /* * Rambo mode: Shoot down a process and hope it solves whatever * issues we may have. */ p = select_bad_process(&points, NULL); if (PTR_ERR(p) == -1UL) return; /* Found nothing?!?! Either we hang forever, or we panic. */ if (!p) { read_unlock(&tasklist_lock); panic("Out of memory and no killable processes...\n"); } if (oom_kill_process(p, gfp_mask, order, points, NULL, "Out of memory")) goto retry;}/* * pagefault handler calls into here because it is out of memory but * doesn't know exactly how or why. */void pagefault_out_of_memory(void){ unsigned long freed = 0; blocking_notifier_call_chain(&oom_notify_list, 0, &freed); if (freed > 0) /* Got some memory back in the last second. */ return; /* * If this is from memcg, oom-killer is already invoked. * and not worth to go system-wide-oom. */ if (mem_cgroup_oom_called(current)) goto rest_and_return; if (sysctl_panic_on_oom) panic("out of memory from page fault. panic_on_oom is selected.\n"); read_lock(&tasklist_lock); __out_of_memory(0, 0); /* unknown gfp_mask and order */ read_unlock(&tasklist_lock); /* * Give "p" a good chance of killing itself before we * retry to allocate memory. */rest_and_return: if (!test_thread_flag(TIF_MEMDIE)) schedule_timeout_uninterruptible(1);}/** * 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 * * 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){ unsigned long freed = 0; enum oom_constraint constraint; blocking_notifier_call_chain(&oom_notify_list, 0, &freed); if (freed > 0) /* Got some memory back in the last second. */ return; if (sysctl_panic_on_oom == 2) panic("out of memory. Compulsory panic_on_oom is selected.\n"); /* * Check if there were limitations on the allocation (only relevant for * NUMA) that may require different handling. */ constraint = constrained_alloc(zonelist, gfp_mask); read_lock(&tasklist_lock); switch (constraint) { case CONSTRAINT_MEMORY_POLICY: oom_kill_process(current, gfp_mask, order, 0, NULL, "No available memory (MPOL_BIND)"); break; case CONSTRAINT_NONE: if (sysctl_panic_on_oom) panic("out of memory. panic_on_oom is selected\n"); /* Fall-through */ case CONSTRAINT_CPUSET: __out_of_memory(gfp_mask, order); break; } read_unlock(&tasklist_lock); /* * Give "p" a good chance of killing itself before we * retry to allocate memory unless "p" is current */ if (!test_thread_flag(TIF_MEMDIE)) schedule_timeout_uninterruptible(1);}