| /* |
| * 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/export.h> |
| #include <linux/notifier.h> |
| #include <linux/memcontrol.h> |
| #include <linux/mempolicy.h> |
| #include <linux/security.h> |
| #include <linux/ptrace.h> |
| #include <linux/freezer.h> |
| #include <linux/ftrace.h> |
| #include <linux/ratelimit.h> |
| #include <linux/kthread.h> |
| #include <linux/init.h> |
| |
| #include <asm/tlb.h> |
| #include "internal.h" |
| |
| #define CREATE_TRACE_POINTS |
| #include <trace/events/oom.h> |
| |
| 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; |
| } |
| |
| static inline bool is_memcg_oom(struct oom_control *oc) |
| { |
| return oc->memcg != NULL; |
| } |
| |
| /* 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; |
| |
| /* |
| * Do not even consider tasks which are explicitly marked oom |
| * unkillable or have been already oom reaped or the are in |
| * the middle of vfork |
| */ |
| adj = (long)p->signal->oom_score_adj; |
| if (adj == OOM_SCORE_ADJ_MIN || |
| test_bit(MMF_OOM_REAPED, &p->mm->flags) || |
| in_vfork(p)) { |
| 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; |
| } |
| |
| enum oom_constraint { |
| CONSTRAINT_NONE, |
| CONSTRAINT_CPUSET, |
| CONSTRAINT_MEMORY_POLICY, |
| CONSTRAINT_MEMCG, |
| }; |
| |
| /* |
| * Determine the type of allocation constraint. |
| */ |
| static enum oom_constraint constrained_alloc(struct oom_control *oc) |
| { |
| struct zone *zone; |
| struct zoneref *z; |
| enum zone_type high_zoneidx = gfp_zone(oc->gfp_mask); |
| bool cpuset_limited = false; |
| int nid; |
| |
| if (is_memcg_oom(oc)) { |
| oc->totalpages = mem_cgroup_get_limit(oc->memcg) ?: 1; |
| return CONSTRAINT_MEMCG; |
| } |
| |
| /* Default to all available memory */ |
| oc->totalpages = totalram_pages + total_swap_pages; |
| |
| if (!IS_ENABLED(CONFIG_NUMA)) |
| return CONSTRAINT_NONE; |
| |
| 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)) { |
| oc->totalpages = total_swap_pages; |
| for_each_node_mask(nid, *oc->nodemask) |
| oc->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) { |
| oc->totalpages = total_swap_pages; |
| for_each_node_mask(nid, cpuset_current_mems_allowed) |
| oc->totalpages += node_spanned_pages(nid); |
| return CONSTRAINT_CPUSET; |
| } |
| return CONSTRAINT_NONE; |
| } |
| |
| static int oom_evaluate_task(struct task_struct *task, void *arg) |
| { |
| struct oom_control *oc = arg; |
| unsigned long points; |
| |
| if (oom_unkillable_task(task, NULL, oc->nodemask)) |
| goto next; |
| |
| /* |
| * This task already has access to memory reserves and is being killed. |
| * Don't allow any other task to have access to the reserves unless |
| * the task has MMF_OOM_REAPED because chances that it would release |
| * any memory is quite low. |
| */ |
| if (!is_sysrq_oom(oc) && atomic_read(&task->signal->oom_victims)) { |
| if (test_bit(MMF_OOM_REAPED, &task->signal->oom_mm->flags)) |
| goto next; |
| goto abort; |
| } |
| |
| /* |
| * 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)) { |
| points = ULONG_MAX; |
| goto select; |
| } |
| |
| points = oom_badness(task, NULL, oc->nodemask, oc->totalpages); |
| if (!points || points < oc->chosen_points) |
| goto next; |
| |
| /* Prefer thread group leaders for display purposes */ |
| if (points == oc->chosen_points && thread_group_leader(oc->chosen)) |
| goto next; |
| select: |
| if (oc->chosen) |
| put_task_struct(oc->chosen); |
| get_task_struct(task); |
| oc->chosen = task; |
| oc->chosen_points = points; |
| next: |
| return 0; |
| abort: |
| if (oc->chosen) |
| put_task_struct(oc->chosen); |
| oc->chosen = (void *)-1UL; |
| return 1; |
| } |
| |
| /* |
| * Simple selection loop. We choose the process with the highest number of |
| * 'points'. In case scan was aborted, oc->chosen is set to -1. |
| */ |
| static void select_bad_process(struct oom_control *oc) |
| { |
| if (is_memcg_oom(oc)) |
| mem_cgroup_scan_tasks(oc->memcg, oom_evaluate_task, oc); |
| else { |
| struct task_struct *p; |
| |
| rcu_read_lock(); |
| for_each_process(p) |
| if (oom_evaluate_task(p, oc)) |
| break; |
| rcu_read_unlock(); |
| } |
| |
| oc->chosen_points = oc->chosen_points * 1000 / oc->totalpages; |
| } |
| |
| /** |
| * 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) |
| { |
| pr_warn("%s invoked oom-killer: gfp_mask=%#x(%pGg), order=%d, oom_score_adj=%hd\n", |
| current->comm, oc->gfp_mask, &oc->gfp_mask, oc->order, |
| current->signal->oom_score_adj); |
| |
| cpuset_print_current_mems_allowed(); |
| dump_stack(); |
| if (oc->memcg) |
| mem_cgroup_print_oom_info(oc->memcg, p); |
| else |
| show_mem(SHOW_MEM_FILTER_NODES); |
| if (sysctl_oom_dump_tasks) |
| dump_tasks(oc->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); |
| |
| static bool oom_killer_disabled __read_mostly; |
| |
| #define K(x) ((x) << (PAGE_SHIFT-10)) |
| |
| /* |
| * 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. |
| */ |
| 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; |
| } |
| |
| |
| #ifdef CONFIG_MMU |
| /* |
| * OOM Reaper kernel thread which tries to reap the memory used by the OOM |
| * victim (if that is possible) to help the OOM killer to move on. |
| */ |
| static struct task_struct *oom_reaper_th; |
| static DECLARE_WAIT_QUEUE_HEAD(oom_reaper_wait); |
| static struct task_struct *oom_reaper_list; |
| static DEFINE_SPINLOCK(oom_reaper_lock); |
| |
| static bool __oom_reap_task_mm(struct task_struct *tsk, struct mm_struct *mm) |
| { |
| struct mmu_gather tlb; |
| struct vm_area_struct *vma; |
| struct zap_details details = {.check_swap_entries = true, |
| .ignore_dirty = true}; |
| bool ret = true; |
| |
| /* |
| * We have to make sure to not race with the victim exit path |
| * and cause premature new oom victim selection: |
| * __oom_reap_task_mm exit_mm |
| * mmget_not_zero |
| * mmput |
| * atomic_dec_and_test |
| * exit_oom_victim |
| * [...] |
| * out_of_memory |
| * select_bad_process |
| * # no TIF_MEMDIE task selects new victim |
| * unmap_page_range # frees some memory |
| */ |
| mutex_lock(&oom_lock); |
| |
| if (!down_read_trylock(&mm->mmap_sem)) { |
| ret = false; |
| goto unlock_oom; |
| } |
| |
| /* |
| * increase mm_users only after we know we will reap something so |
| * that the mmput_async is called only when we have reaped something |
| * and delayed __mmput doesn't matter that much |
| */ |
| if (!mmget_not_zero(mm)) { |
| up_read(&mm->mmap_sem); |
| goto unlock_oom; |
| } |
| |
| tlb_gather_mmu(&tlb, mm, 0, -1); |
| for (vma = mm->mmap ; vma; vma = vma->vm_next) { |
| if (is_vm_hugetlb_page(vma)) |
| continue; |
| |
| /* |
| * mlocked VMAs require explicit munlocking before unmap. |
| * Let's keep it simple here and skip such VMAs. |
| */ |
| if (vma->vm_flags & VM_LOCKED) |
| continue; |
| |
| /* |
| * Only anonymous pages have a good chance to be dropped |
| * without additional steps which we cannot afford as we |
| * are OOM already. |
| * |
| * We do not even care about fs backed pages because all |
| * which are reclaimable have already been reclaimed and |
| * we do not want to block exit_mmap by keeping mm ref |
| * count elevated without a good reason. |
| */ |
| if (vma_is_anonymous(vma) || !(vma->vm_flags & VM_SHARED)) |
| unmap_page_range(&tlb, vma, vma->vm_start, vma->vm_end, |
| &details); |
| } |
| tlb_finish_mmu(&tlb, 0, -1); |
| pr_info("oom_reaper: reaped process %d (%s), now anon-rss:%lukB, file-rss:%lukB, shmem-rss:%lukB\n", |
| task_pid_nr(tsk), tsk->comm, |
| K(get_mm_counter(mm, MM_ANONPAGES)), |
| K(get_mm_counter(mm, MM_FILEPAGES)), |
| K(get_mm_counter(mm, MM_SHMEMPAGES))); |
| up_read(&mm->mmap_sem); |
| |
| /* |
| * Drop our reference but make sure the mmput slow path is called from a |
| * different context because we shouldn't risk we get stuck there and |
| * put the oom_reaper out of the way. |
| */ |
| mmput_async(mm); |
| unlock_oom: |
| mutex_unlock(&oom_lock); |
| return ret; |
| } |
| |
| #define MAX_OOM_REAP_RETRIES 10 |
| static void oom_reap_task(struct task_struct *tsk) |
| { |
| int attempts = 0; |
| struct mm_struct *mm = tsk->signal->oom_mm; |
| |
| /* Retry the down_read_trylock(mmap_sem) a few times */ |
| while (attempts++ < MAX_OOM_REAP_RETRIES && !__oom_reap_task_mm(tsk, mm)) |
| schedule_timeout_idle(HZ/10); |
| |
| if (attempts <= MAX_OOM_REAP_RETRIES) |
| goto done; |
| |
| |
| pr_info("oom_reaper: unable to reap pid:%d (%s)\n", |
| task_pid_nr(tsk), tsk->comm); |
| debug_show_all_locks(); |
| |
| done: |
| /* |
| * Clear TIF_MEMDIE because the task shouldn't be sitting on a |
| * reasonably reclaimable memory anymore or it is not a good candidate |
| * for the oom victim right now because it cannot release its memory |
| * itself nor by the oom reaper. |
| */ |
| tsk->oom_reaper_list = NULL; |
| exit_oom_victim(tsk); |
| |
| /* |
| * Hide this mm from OOM killer because it has been either reaped or |
| * somebody can't call up_write(mmap_sem). |
| */ |
| set_bit(MMF_OOM_REAPED, &mm->flags); |
| |
| /* Drop a reference taken by wake_oom_reaper */ |
| put_task_struct(tsk); |
| } |
| |
| static int oom_reaper(void *unused) |
| { |
| set_freezable(); |
| |
| while (true) { |
| struct task_struct *tsk = NULL; |
| |
| wait_event_freezable(oom_reaper_wait, oom_reaper_list != NULL); |
| spin_lock(&oom_reaper_lock); |
| if (oom_reaper_list != NULL) { |
| tsk = oom_reaper_list; |
| oom_reaper_list = tsk->oom_reaper_list; |
| } |
| spin_unlock(&oom_reaper_lock); |
| |
| if (tsk) |
| oom_reap_task(tsk); |
| } |
| |
| return 0; |
| } |
| |
| static void wake_oom_reaper(struct task_struct *tsk) |
| { |
| if (!oom_reaper_th) |
| return; |
| |
| /* tsk is already queued? */ |
| if (tsk == oom_reaper_list || tsk->oom_reaper_list) |
| return; |
| |
| get_task_struct(tsk); |
| |
| spin_lock(&oom_reaper_lock); |
| tsk->oom_reaper_list = oom_reaper_list; |
| oom_reaper_list = tsk; |
| spin_unlock(&oom_reaper_lock); |
| wake_up(&oom_reaper_wait); |
| } |
| |
| static int __init oom_init(void) |
| { |
| oom_reaper_th = kthread_run(oom_reaper, NULL, "oom_reaper"); |
| if (IS_ERR(oom_reaper_th)) { |
| pr_err("Unable to start OOM reaper %ld. Continuing regardless\n", |
| PTR_ERR(oom_reaper_th)); |
| oom_reaper_th = NULL; |
| } |
| return 0; |
| } |
| subsys_initcall(oom_init) |
| #else |
| static inline void wake_oom_reaper(struct task_struct *tsk) |
| { |
| } |
| #endif /* CONFIG_MMU */ |
| |
| /** |
| * 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. |
| * |
| * tsk->mm has to be non NULL and caller has to guarantee it is stable (either |
| * under task_lock or operate on the current). |
| */ |
| static void mark_oom_victim(struct task_struct *tsk) |
| { |
| struct mm_struct *mm = tsk->mm; |
| |
| WARN_ON(oom_killer_disabled); |
| /* OOM killer might race with memcg OOM */ |
| if (test_and_set_tsk_thread_flag(tsk, TIF_MEMDIE)) |
| return; |
| |
| atomic_inc(&tsk->signal->oom_victims); |
| |
| /* oom_mm is bound to the signal struct life time. */ |
| if (!cmpxchg(&tsk->signal->oom_mm, NULL, mm)) |
| atomic_inc(&tsk->signal->oom_mm->mm_count); |
| |
| /* |
| * 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(struct task_struct *tsk) |
| { |
| if (!test_and_clear_tsk_thread_flag(tsk, TIF_MEMDIE)) |
| return; |
| atomic_dec(&tsk->signal->oom_victims); |
| |
| 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. Check that the |
| * current is not killed (possibly due to sharing the victim's memory). |
| */ |
| if (mutex_lock_killable(&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; |
| } |
| |
| static inline bool __task_will_free_mem(struct task_struct *task) |
| { |
| struct signal_struct *sig = task->signal; |
| |
| /* |
| * A coredumping process may sleep for an extended period in exit_mm(), |
| * so the oom killer cannot assume that the process will promptly exit |
| * and release memory. |
| */ |
| if (sig->flags & SIGNAL_GROUP_COREDUMP) |
| return false; |
| |
| if (sig->flags & SIGNAL_GROUP_EXIT) |
| return true; |
| |
| if (thread_group_empty(task) && (task->flags & PF_EXITING)) |
| return true; |
| |
| return false; |
| } |
| |
| /* |
| * Checks whether the given task is dying or exiting and likely to |
| * release its address space. This means that all threads and processes |
| * sharing the same mm have to be killed or exiting. |
| * Caller has to make sure that task->mm is stable (hold task_lock or |
| * it operates on the current). |
| */ |
| static bool task_will_free_mem(struct task_struct *task) |
| { |
| struct mm_struct *mm = task->mm; |
| struct task_struct *p; |
| bool ret = true; |
| |
| /* |
| * Skip tasks without mm because it might have passed its exit_mm and |
| * exit_oom_victim. oom_reaper could have rescued that but do not rely |
| * on that for now. We can consider find_lock_task_mm in future. |
| */ |
| if (!mm) |
| return false; |
| |
| if (!__task_will_free_mem(task)) |
| return false; |
| |
| /* |
| * This task has already been drained by the oom reaper so there are |
| * only small chances it will free some more |
| */ |
| if (test_bit(MMF_OOM_REAPED, &mm->flags)) |
| return false; |
| |
| if (atomic_read(&mm->mm_users) <= 1) |
| return true; |
| |
| /* |
| * Make sure that all tasks which share the mm with the given tasks |
| * are dying as well to make sure that a) nobody pins its mm and |
| * b) the task is also reapable by the oom reaper. |
| */ |
| rcu_read_lock(); |
| for_each_process(p) { |
| if (!process_shares_mm(p, mm)) |
| continue; |
| if (same_thread_group(task, p)) |
| continue; |
| ret = __task_will_free_mem(p); |
| if (!ret) |
| break; |
| } |
| rcu_read_unlock(); |
| |
| return ret; |
| } |
| |
| static void oom_kill_process(struct oom_control *oc, const char *message) |
| { |
| struct task_struct *p = oc->chosen; |
| unsigned int points = oc->chosen_points; |
| 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); |
| bool can_oom_reap = true; |
| |
| /* |
| * 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 (task_will_free_mem(p)) { |
| mark_oom_victim(p); |
| wake_oom_reaper(p); |
| task_unlock(p); |
| put_task_struct(p); |
| return; |
| } |
| task_unlock(p); |
| |
| if (__ratelimit(&oom_rs)) |
| dump_header(oc, p); |
| |
| 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); |
| 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, |
| oc->memcg, oc->nodemask, oc->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; |
| } |
| |
| /* 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, shmem-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)), |
| K(get_mm_counter(victim->mm, MM_SHMEMPAGES))); |
| 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) || is_global_init(p)) { |
| /* |
| * We cannot use oom_reaper for the mm shared by this |
| * process because it wouldn't get killed and so the |
| * memory might be still used. Hide the mm from the oom |
| * killer to guarantee OOM forward progress. |
| */ |
| can_oom_reap = false; |
| set_bit(MMF_OOM_REAPED, &mm->flags); |
| pr_info("oom killer %d (%s) has mm pinned by %d (%s)\n", |
| task_pid_nr(victim), victim->comm, |
| task_pid_nr(p), p->comm); |
| continue; |
| } |
| do_send_sig_info(SIGKILL, SEND_SIG_FORCED, p, true); |
| } |
| rcu_read_unlock(); |
| |
| if (can_oom_reap) |
| wake_oom_reaper(victim); |
| |
| mmdrop(mm); |
| put_task_struct(victim); |
| } |
| #undef K |
| |
| /* |
| * Determines whether the kernel must panic because of the panic_on_oom sysctl. |
| */ |
| static void check_panic_on_oom(struct oom_control *oc, |
| enum oom_constraint constraint) |
| { |
| 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); |
| 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) |
| { |
| unsigned long freed = 0; |
| enum oom_constraint constraint = CONSTRAINT_NONE; |
| |
| if (oom_killer_disabled) |
| return false; |
| |
| if (!is_memcg_oom(oc)) { |
| 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. |
| */ |
| if (task_will_free_mem(current)) { |
| mark_oom_victim(current); |
| wake_oom_reaper(current); |
| return true; |
| } |
| |
| /* |
| * The OOM killer does not compensate for IO-less reclaim. |
| * pagefault_out_of_memory lost its gfp context so we have to |
| * make sure exclude 0 mask - all other users should have at least |
| * ___GFP_DIRECT_RECLAIM to get here. |
| */ |
| if (oc->gfp_mask && !(oc->gfp_mask & (__GFP_FS|__GFP_NOFAIL))) |
| return true; |
| |
| /* |
| * Check if there were limitations on the allocation (only relevant for |
| * NUMA and memcg) that may require different handling. |
| */ |
| constraint = constrained_alloc(oc); |
| if (constraint != CONSTRAINT_MEMORY_POLICY) |
| oc->nodemask = NULL; |
| check_panic_on_oom(oc, constraint); |
| |
| if (!is_memcg_oom(oc) && 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); |
| oc->chosen = current; |
| oom_kill_process(oc, "Out of memory (oom_kill_allocating_task)"); |
| return true; |
| } |
| |
| select_bad_process(oc); |
| /* Found nothing?!?! Either we hang forever, or we panic. */ |
| if (!oc->chosen && !is_sysrq_oom(oc) && !is_memcg_oom(oc)) { |
| dump_header(oc, NULL); |
| panic("Out of memory and no killable processes...\n"); |
| } |
| if (oc->chosen && oc->chosen != (void *)-1UL) { |
| oom_kill_process(oc, !is_memcg_oom(oc) ? "Out of memory" : |
| "Memory cgroup out of memory"); |
| /* |
| * Give the killed process a good chance to exit before trying |
| * to allocate memory again. |
| */ |
| schedule_timeout_killable(1); |
| } |
| return !!oc->chosen; |
| } |
| |
| /* |
| * The pagefault handler calls here because it is out of memory, so kill a |
| * memory-hogging task. If oom_lock is held by somebody else, 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, |
| .memcg = NULL, |
| .gfp_mask = 0, |
| .order = 0, |
| }; |
| |
| if (mem_cgroup_oom_synchronize(true)) |
| 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); |
| } |