v4.19.13 snapshot.
diff --git a/mm/oom_kill.c b/mm/oom_kill.c
new file mode 100644
index 0000000..f10aa53
--- /dev/null
+++ b/mm/oom_kill.c
@@ -0,0 +1,1147 @@
+/*
+ * 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/sched/mm.h>
+#include <linux/sched/coredump.h>
+#include <linux/sched/task.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 <linux/mmu_notifier.h>
+
+#include <asm/tlb.h>
+#include "internal.h"
+#include "slab.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;
+
+/*
+ * Serializes oom killer invocations (out_of_memory()) from all contexts to
+ * prevent from over eager oom killing (e.g. when the oom killer is invoked
+ * from different domains).
+ *
+ * oom_killer_disable() relies on this lock to stabilize oom_killer_disabled
+ * and mark_oom_victim
+ */
+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;
+}
+
+/*
+ * Print out unreclaimble slabs info when unreclaimable slabs amount is greater
+ * than all user memory (LRU pages)
+ */
+static bool is_dump_unreclaim_slabs(void)
+{
+ unsigned long nr_lru;
+
+ nr_lru = global_node_page_state(NR_ACTIVE_ANON) +
+ global_node_page_state(NR_INACTIVE_ANON) +
+ global_node_page_state(NR_ACTIVE_FILE) +
+ global_node_page_state(NR_INACTIVE_FILE) +
+ global_node_page_state(NR_ISOLATED_ANON) +
+ global_node_page_state(NR_ISOLATED_FILE) +
+ global_node_page_state(NR_UNEVICTABLE);
+
+ return (global_node_page_state(NR_SLAB_UNRECLAIMABLE) > nr_lru);
+}
+
+/**
+ * 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
+ * @memcg: task's memory controller, if constrained
+ * @nodemask: nodemask passed to page allocator for mempolicy ooms
+ *
+ * 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_SKIP, &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) +
+ mm_pgtables_bytes(p->mm) / PAGE_SIZE;
+ task_unlock(p);
+
+ /* 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_max(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_SKIP because chances that it would release
+ * any memory is quite low.
+ */
+ if (!is_sysrq_oom(oc) && tsk_is_oom_victim(task)) {
+ if (test_bit(MMF_OOM_SKIP, &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,
+ * pgtables_bytes, 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("Tasks state (memory values in pages):\n");
+ pr_info("[ pid ] uid tgid total_vm rss pgtables_bytes 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("[%7d] %5d %5d %8lu %8lu %8ld %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),
+ mm_pgtables_bytes(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), nodemask=%*pbl, order=%d, oom_score_adj=%hd\n",
+ current->comm, oc->gfp_mask, &oc->gfp_mask,
+ nodemask_pr_args(oc->nodemask), oc->order,
+ current->signal->oom_score_adj);
+ if (!IS_ENABLED(CONFIG_COMPACTION) && oc->order)
+ pr_warn("COMPACTION is disabled!!!\n");
+
+ cpuset_print_current_mems_allowed();
+ dump_stack();
+ if (is_memcg_oom(oc))
+ mem_cgroup_print_oom_info(oc->memcg, p);
+ else {
+ show_mem(SHOW_MEM_FILTER_NODES, oc->nodemask);
+ if (is_dump_unreclaim_slabs())
+ dump_unreclaimable_slab();
+ }
+ 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);
+
+bool __oom_reap_task_mm(struct mm_struct *mm)
+{
+ struct vm_area_struct *vma;
+ bool ret = true;
+
+ /*
+ * Tell all users of get_user/copy_from_user etc... that the content
+ * is no longer stable. No barriers really needed because unmapping
+ * should imply barriers already and the reader would hit a page fault
+ * if it stumbled over a reaped memory.
+ */
+ set_bit(MMF_UNSTABLE, &mm->flags);
+
+ for (vma = mm->mmap ; vma; vma = vma->vm_next) {
+ if (!can_madv_dontneed_vma(vma))
+ 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)) {
+ const unsigned long start = vma->vm_start;
+ const unsigned long end = vma->vm_end;
+ struct mmu_gather tlb;
+
+ tlb_gather_mmu(&tlb, mm, start, end);
+ if (mmu_notifier_invalidate_range_start_nonblock(mm, start, end)) {
+ tlb_finish_mmu(&tlb, start, end);
+ ret = false;
+ continue;
+ }
+ unmap_page_range(&tlb, vma, start, end, NULL);
+ mmu_notifier_invalidate_range_end(mm, start, end);
+ tlb_finish_mmu(&tlb, start, end);
+ }
+ }
+
+ return ret;
+}
+
+/*
+ * Reaps the address space of the give task.
+ *
+ * Returns true on success and false if none or part of the address space
+ * has been reclaimed and the caller should retry later.
+ */
+static bool oom_reap_task_mm(struct task_struct *tsk, struct mm_struct *mm)
+{
+ bool ret = true;
+
+ if (!down_read_trylock(&mm->mmap_sem)) {
+ trace_skip_task_reaping(tsk->pid);
+ return false;
+ }
+
+ /*
+ * MMF_OOM_SKIP is set by exit_mmap when the OOM reaper can't
+ * work on the mm anymore. The check for MMF_OOM_SKIP must run
+ * under mmap_sem for reading because it serializes against the
+ * down_write();up_write() cycle in exit_mmap().
+ */
+ if (test_bit(MMF_OOM_SKIP, &mm->flags)) {
+ trace_skip_task_reaping(tsk->pid);
+ goto out_unlock;
+ }
+
+ trace_start_task_reaping(tsk->pid);
+
+ /* failed to reap part of the address space. Try again later */
+ ret = __oom_reap_task_mm(mm);
+ if (!ret)
+ goto out_finish;
+
+ 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)));
+out_finish:
+ trace_finish_task_reaping(tsk->pid);
+out_unlock:
+ up_read(&mm->mmap_sem);
+
+ 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 ||
+ test_bit(MMF_OOM_SKIP, &mm->flags))
+ goto done;
+
+ pr_info("oom_reaper: unable to reap pid:%d (%s)\n",
+ task_pid_nr(tsk), tsk->comm);
+ debug_show_all_locks();
+
+done:
+ tsk->oom_reaper_list = NULL;
+
+ /*
+ * 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_SKIP, &mm->flags);
+
+ /* Drop a reference taken by wake_oom_reaper */
+ put_task_struct(tsk);
+}
+
+static int oom_reaper(void *unused)
+{
+ 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)
+{
+ /* 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);
+ trace_wake_reaper(tsk->pid);
+ wake_up(&oom_reaper_wait);
+}
+
+static int __init oom_init(void)
+{
+ oom_reaper_th = kthread_run(oom_reaper, NULL, "oom_reaper");
+ 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;
+
+ /* oom_mm is bound to the signal struct life time. */
+ if (!cmpxchg(&tsk->signal->oom_mm, NULL, mm)) {
+ mmgrab(tsk->signal->oom_mm);
+ set_bit(MMF_OOM_VICTIM, &mm->flags);
+ }
+
+ /*
+ * 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);
+ trace_mark_victim(tsk->pid);
+}
+
+/**
+ * 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_enable - enable OOM killer
+ */
+void oom_killer_enable(void)
+{
+ oom_killer_disabled = false;
+ pr_info("OOM killer enabled.\n");
+}
+
+/**
+ * oom_killer_disable - disable OOM killer
+ * @timeout: maximum timeout to wait for oom victims in jiffies
+ *
+ * Forces all page allocations to fail rather than trigger OOM killer.
+ * Will block and wait until all OOM victims are killed or the given
+ * timeout expires.
+ *
+ * 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(signed long timeout)
+{
+ signed long ret;
+
+ /*
+ * 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);
+
+ ret = wait_event_interruptible_timeout(oom_victims_wait,
+ !atomic_read(&oom_victims), timeout);
+ if (ret <= 0) {
+ oom_killer_enable();
+ return false;
+ }
+ pr_info("OOM killer disabled.\n");
+
+ return true;
+}
+
+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_SKIP, &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 task_struct *victim)
+{
+ struct task_struct *p;
+ struct mm_struct *mm;
+ bool can_oom_reap = true;
+
+ 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;
+ mmgrab(mm);
+
+ /* Raise event before sending signal: task reaper must see this */
+ count_vm_event(OOM_KILL);
+ memcg_memory_event_mm(mm, MEMCG_OOM_KILL);
+
+ /*
+ * We should send SIGKILL before granting access to memory reserves
+ * 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, PIDTYPE_TGID);
+ 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 (is_global_init(p)) {
+ can_oom_reap = false;
+ set_bit(MMF_OOM_SKIP, &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;
+ }
+ /*
+ * No use_mm() user needs to read from the userspace so we are
+ * ok to reap it.
+ */
+ if (unlikely(p->flags & PF_KTHREAD))
+ continue;
+ do_send_sig_info(SIGKILL, SEND_SIG_FORCED, p, PIDTYPE_TGID);
+ }
+ rcu_read_unlock();
+
+ if (can_oom_reap)
+ wake_oom_reaper(victim);
+
+ mmdrop(mm);
+ put_task_struct(victim);
+}
+#undef K
+
+/*
+ * Kill provided task unless it's secured by setting
+ * oom_score_adj to OOM_SCORE_ADJ_MIN.
+ */
+static int oom_kill_memcg_member(struct task_struct *task, void *unused)
+{
+ if (task->signal->oom_score_adj != OOM_SCORE_ADJ_MIN) {
+ get_task_struct(task);
+ __oom_kill_process(task);
+ }
+ return 0;
+}
+
+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 mem_cgroup *oom_group;
+ 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 give it access to memory reserves
+ * 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);
+
+ /*
+ * Do we need to kill the entire memory cgroup?
+ * Or even one of the ancestor memory cgroups?
+ * Check this out before killing the victim task.
+ */
+ oom_group = mem_cgroup_get_oom_group(victim, oc->memcg);
+
+ __oom_kill_process(victim);
+
+ /*
+ * If necessary, kill all tasks in the selected memory cgroup.
+ */
+ if (oom_group) {
+ mem_cgroup_print_oom_group(oom_group);
+ mem_cgroup_scan_tasks(oom_group, oom_kill_memcg_member, NULL);
+ mem_cgroup_put(oom_group);
+ }
+}
+
+/*
+ * 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))
+ 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?!?! */
+ if (!oc->chosen) {
+ dump_header(oc, NULL);
+ pr_warn("Out of memory and no killable processes...\n");
+ /*
+ * If we got here due to an actual allocation at the
+ * system level, we cannot survive this and will enter
+ * an endless loop in the allocator. Bail out now.
+ */
+ if (!is_sysrq_oom(oc) && !is_memcg_oom(oc))
+ panic("System is deadlocked on memory\n");
+ }
+ if (oc->chosen && oc->chosen != (void *)-1UL)
+ oom_kill_process(oc, !is_memcg_oom(oc) ? "Out of memory" :
+ "Memory cgroup out of memory");
+ 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;
+ out_of_memory(&oc);
+ mutex_unlock(&oom_lock);
+}