1103 lines
30 KiB
C
1103 lines
30 KiB
C
/*
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* linux/mm/oom_kill.c
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*
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* Copyright (C) 1998,2000 Rik van Riel
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* Thanks go out to Claus Fischer for some serious inspiration and
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* for goading me into coding this file...
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* Copyright (C) 2010 Google, Inc.
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* Rewritten by David Rientjes
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*
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* The routines in this file are used to kill a process when
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* we're seriously out of memory. This gets called from __alloc_pages()
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* in mm/page_alloc.c when we really run out of memory.
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*
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* Since we won't call these routines often (on a well-configured
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* machine) this file will double as a 'coding guide' and a signpost
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* for newbie kernel hackers. It features several pointers to major
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* kernel subsystems and hints as to where to find out what things do.
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*/
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#include <linux/oom.h>
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#include <linux/mm.h>
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#include <linux/err.h>
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#include <linux/gfp.h>
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#include <linux/sched.h>
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#include <linux/swap.h>
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#include <linux/timex.h>
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#include <linux/jiffies.h>
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#include <linux/cpuset.h>
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#include <linux/export.h>
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#include <linux/notifier.h>
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#include <linux/memcontrol.h>
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#include <linux/mempolicy.h>
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#include <linux/security.h>
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#include <linux/ptrace.h>
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#include <linux/freezer.h>
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#include <linux/ftrace.h>
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#include <linux/ratelimit.h>
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#include <linux/kthread.h>
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#include <linux/init.h>
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#include <linux/mmu_notifier.h>
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#include <asm/tlb.h>
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#include "internal.h"
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#define CREATE_TRACE_POINTS
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#include <trace/events/oom.h>
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int sysctl_panic_on_oom;
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int sysctl_oom_kill_allocating_task;
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int sysctl_oom_dump_tasks = 1;
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DEFINE_MUTEX(oom_lock);
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#ifdef CONFIG_NUMA
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/**
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* has_intersects_mems_allowed() - check task eligiblity for kill
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* @start: task struct of which task to consider
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* @mask: nodemask passed to page allocator for mempolicy ooms
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*
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* Task eligibility is determined by whether or not a candidate task, @tsk,
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* shares the same mempolicy nodes as current if it is bound by such a policy
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* and whether or not it has the same set of allowed cpuset nodes.
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*/
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static bool has_intersects_mems_allowed(struct task_struct *start,
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const nodemask_t *mask)
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{
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struct task_struct *tsk;
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bool ret = false;
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rcu_read_lock();
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for_each_thread(start, tsk) {
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if (mask) {
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/*
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* If this is a mempolicy constrained oom, tsk's
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* cpuset is irrelevant. Only return true if its
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* mempolicy intersects current, otherwise it may be
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* needlessly killed.
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*/
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ret = mempolicy_nodemask_intersects(tsk, mask);
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} else {
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/*
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* This is not a mempolicy constrained oom, so only
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* check the mems of tsk's cpuset.
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*/
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ret = cpuset_mems_allowed_intersects(current, tsk);
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}
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if (ret)
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break;
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}
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rcu_read_unlock();
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return ret;
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}
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#else
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static bool has_intersects_mems_allowed(struct task_struct *tsk,
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const nodemask_t *mask)
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{
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return true;
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}
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#endif /* CONFIG_NUMA */
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/*
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* The process p may have detached its own ->mm while exiting or through
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* use_mm(), but one or more of its subthreads may still have a valid
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* pointer. Return p, or any of its subthreads with a valid ->mm, with
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* task_lock() held.
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*/
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struct task_struct *find_lock_task_mm(struct task_struct *p)
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{
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struct task_struct *t;
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rcu_read_lock();
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for_each_thread(p, t) {
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task_lock(t);
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if (likely(t->mm))
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goto found;
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task_unlock(t);
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}
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t = NULL;
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found:
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rcu_read_unlock();
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return t;
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}
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/*
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* order == -1 means the oom kill is required by sysrq, otherwise only
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* for display purposes.
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*/
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static inline bool is_sysrq_oom(struct oom_control *oc)
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{
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return oc->order == -1;
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}
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static inline bool is_memcg_oom(struct oom_control *oc)
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{
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return oc->memcg != NULL;
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}
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/* return true if the task is not adequate as candidate victim task. */
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static bool oom_unkillable_task(struct task_struct *p,
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struct mem_cgroup *memcg, const nodemask_t *nodemask)
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{
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if (is_global_init(p))
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return true;
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if (p->flags & PF_KTHREAD)
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return true;
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/* When mem_cgroup_out_of_memory() and p is not member of the group */
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if (memcg && !task_in_mem_cgroup(p, memcg))
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return true;
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/* p may not have freeable memory in nodemask */
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if (!has_intersects_mems_allowed(p, nodemask))
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return true;
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return false;
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}
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/**
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* oom_badness - heuristic function to determine which candidate task to kill
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* @p: task struct of which task we should calculate
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* @totalpages: total present RAM allowed for page allocation
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*
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* The heuristic for determining which task to kill is made to be as simple and
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* predictable as possible. The goal is to return the highest value for the
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* task consuming the most memory to avoid subsequent oom failures.
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*/
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unsigned long oom_badness(struct task_struct *p, struct mem_cgroup *memcg,
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const nodemask_t *nodemask, unsigned long totalpages)
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{
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long points;
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long adj;
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if (oom_unkillable_task(p, memcg, nodemask))
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return 0;
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p = find_lock_task_mm(p);
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if (!p)
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return 0;
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/*
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* Do not even consider tasks which are explicitly marked oom
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* unkillable or have been already oom reaped or the are in
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* the middle of vfork
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*/
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adj = (long)p->signal->oom_score_adj;
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if (adj == OOM_SCORE_ADJ_MIN ||
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test_bit(MMF_OOM_SKIP, &p->mm->flags) ||
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in_vfork(p)) {
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task_unlock(p);
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return 0;
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}
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/*
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* The baseline for the badness score is the proportion of RAM that each
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* task's rss, pagetable and swap space use.
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*/
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points = get_mm_rss(p->mm) + get_mm_counter(p->mm, MM_SWAPENTS) +
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atomic_long_read(&p->mm->nr_ptes) + mm_nr_pmds(p->mm);
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task_unlock(p);
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/*
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* Root processes get 3% bonus, just like the __vm_enough_memory()
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* implementation used by LSMs.
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*/
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if (has_capability_noaudit(p, CAP_SYS_ADMIN))
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points -= (points * 3) / 100;
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/* Normalize to oom_score_adj units */
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adj *= totalpages / 1000;
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points += adj;
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/*
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* Never return 0 for an eligible task regardless of the root bonus and
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* oom_score_adj (oom_score_adj can't be OOM_SCORE_ADJ_MIN here).
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*/
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return points > 0 ? points : 1;
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}
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enum oom_constraint {
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CONSTRAINT_NONE,
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CONSTRAINT_CPUSET,
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CONSTRAINT_MEMORY_POLICY,
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CONSTRAINT_MEMCG,
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};
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/*
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* Determine the type of allocation constraint.
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*/
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static enum oom_constraint constrained_alloc(struct oom_control *oc)
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{
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struct zone *zone;
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struct zoneref *z;
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enum zone_type high_zoneidx = gfp_zone(oc->gfp_mask);
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bool cpuset_limited = false;
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int nid;
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if (is_memcg_oom(oc)) {
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oc->totalpages = mem_cgroup_get_limit(oc->memcg) ?: 1;
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return CONSTRAINT_MEMCG;
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}
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/* Default to all available memory */
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oc->totalpages = totalram_pages + total_swap_pages;
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if (!IS_ENABLED(CONFIG_NUMA))
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return CONSTRAINT_NONE;
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if (!oc->zonelist)
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return CONSTRAINT_NONE;
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/*
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* Reach here only when __GFP_NOFAIL is used. So, we should avoid
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* to kill current.We have to random task kill in this case.
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* Hopefully, CONSTRAINT_THISNODE...but no way to handle it, now.
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*/
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if (oc->gfp_mask & __GFP_THISNODE)
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return CONSTRAINT_NONE;
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/*
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* This is not a __GFP_THISNODE allocation, so a truncated nodemask in
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* the page allocator means a mempolicy is in effect. Cpuset policy
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* is enforced in get_page_from_freelist().
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*/
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if (oc->nodemask &&
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!nodes_subset(node_states[N_MEMORY], *oc->nodemask)) {
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oc->totalpages = total_swap_pages;
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for_each_node_mask(nid, *oc->nodemask)
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oc->totalpages += node_spanned_pages(nid);
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return CONSTRAINT_MEMORY_POLICY;
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}
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/* Check this allocation failure is caused by cpuset's wall function */
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for_each_zone_zonelist_nodemask(zone, z, oc->zonelist,
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high_zoneidx, oc->nodemask)
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if (!cpuset_zone_allowed(zone, oc->gfp_mask))
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cpuset_limited = true;
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if (cpuset_limited) {
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oc->totalpages = total_swap_pages;
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for_each_node_mask(nid, cpuset_current_mems_allowed)
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oc->totalpages += node_spanned_pages(nid);
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return CONSTRAINT_CPUSET;
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}
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return CONSTRAINT_NONE;
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}
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static int oom_evaluate_task(struct task_struct *task, void *arg)
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{
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struct oom_control *oc = arg;
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unsigned long points;
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if (oom_unkillable_task(task, NULL, oc->nodemask))
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goto next;
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/*
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* This task already has access to memory reserves and is being killed.
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* Don't allow any other task to have access to the reserves unless
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* the task has MMF_OOM_SKIP because chances that it would release
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* any memory is quite low.
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*/
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if (!is_sysrq_oom(oc) && tsk_is_oom_victim(task)) {
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if (test_bit(MMF_OOM_SKIP, &task->signal->oom_mm->flags))
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goto next;
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goto abort;
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}
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/*
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* If task is allocating a lot of memory and has been marked to be
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* killed first if it triggers an oom, then select it.
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*/
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if (oom_task_origin(task)) {
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points = ULONG_MAX;
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goto select;
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}
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points = oom_badness(task, NULL, oc->nodemask, oc->totalpages);
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if (!points || points < oc->chosen_points)
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goto next;
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/* Prefer thread group leaders for display purposes */
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if (points == oc->chosen_points && thread_group_leader(oc->chosen))
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goto next;
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select:
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if (oc->chosen)
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put_task_struct(oc->chosen);
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get_task_struct(task);
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oc->chosen = task;
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oc->chosen_points = points;
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next:
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return 0;
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abort:
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if (oc->chosen)
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put_task_struct(oc->chosen);
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oc->chosen = (void *)-1UL;
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return 1;
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}
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/*
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* Simple selection loop. We choose the process with the highest number of
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* 'points'. In case scan was aborted, oc->chosen is set to -1.
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*/
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static void select_bad_process(struct oom_control *oc)
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{
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if (is_memcg_oom(oc))
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mem_cgroup_scan_tasks(oc->memcg, oom_evaluate_task, oc);
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else {
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struct task_struct *p;
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rcu_read_lock();
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for_each_process(p)
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if (oom_evaluate_task(p, oc))
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break;
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rcu_read_unlock();
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}
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oc->chosen_points = oc->chosen_points * 1000 / oc->totalpages;
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}
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/**
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* dump_tasks - dump current memory state of all system tasks
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* @memcg: current's memory controller, if constrained
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* @nodemask: nodemask passed to page allocator for mempolicy ooms
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*
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* Dumps the current memory state of all eligible tasks. Tasks not in the same
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* memcg, not in the same cpuset, or bound to a disjoint set of mempolicy nodes
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* are not shown.
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* State information includes task's pid, uid, tgid, vm size, rss, nr_ptes,
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* swapents, oom_score_adj value, and name.
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*/
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static void dump_tasks(struct mem_cgroup *memcg, const nodemask_t *nodemask)
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{
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struct task_struct *p;
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struct task_struct *task;
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pr_info("[ pid ] uid tgid total_vm rss nr_ptes nr_pmds swapents oom_score_adj name\n");
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rcu_read_lock();
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for_each_process(p) {
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if (oom_unkillable_task(p, memcg, nodemask))
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continue;
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task = find_lock_task_mm(p);
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if (!task) {
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/*
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* This is a kthread or all of p's threads have already
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* detached their mm's. There's no need to report
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* them; they can't be oom killed anyway.
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*/
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continue;
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}
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pr_info("[%5d] %5d %5d %8lu %8lu %7ld %7ld %8lu %5hd %s\n",
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task->pid, from_kuid(&init_user_ns, task_uid(task)),
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task->tgid, task->mm->total_vm, get_mm_rss(task->mm),
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atomic_long_read(&task->mm->nr_ptes),
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mm_nr_pmds(task->mm),
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get_mm_counter(task->mm, MM_SWAPENTS),
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task->signal->oom_score_adj, task->comm);
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task_unlock(task);
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}
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rcu_read_unlock();
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}
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static void dump_header(struct oom_control *oc, struct task_struct *p)
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{
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nodemask_t *nm = (oc->nodemask) ? oc->nodemask : &cpuset_current_mems_allowed;
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pr_warn("%s invoked oom-killer: gfp_mask=%#x(%pGg), nodemask=%*pbl, order=%d, oom_score_adj=%hd\n",
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current->comm, oc->gfp_mask, &oc->gfp_mask,
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nodemask_pr_args(nm), oc->order,
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current->signal->oom_score_adj);
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if (!IS_ENABLED(CONFIG_COMPACTION) && oc->order)
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pr_warn("COMPACTION is disabled!!!\n");
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cpuset_print_current_mems_allowed();
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dump_stack();
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if (oc->memcg)
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mem_cgroup_print_oom_info(oc->memcg, p);
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else
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show_mem(SHOW_MEM_FILTER_NODES);
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if (sysctl_oom_dump_tasks)
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dump_tasks(oc->memcg, oc->nodemask);
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}
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/*
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* Number of OOM victims in flight
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*/
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static atomic_t oom_victims = ATOMIC_INIT(0);
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static DECLARE_WAIT_QUEUE_HEAD(oom_victims_wait);
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static bool oom_killer_disabled __read_mostly;
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#define K(x) ((x) << (PAGE_SHIFT-10))
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/*
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* task->mm can be NULL if the task is the exited group leader. So to
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* determine whether the task is using a particular mm, we examine all the
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* task's threads: if one of those is using this mm then this task was also
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* using it.
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*/
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bool process_shares_mm(struct task_struct *p, struct mm_struct *mm)
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{
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struct task_struct *t;
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for_each_thread(p, t) {
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struct mm_struct *t_mm = READ_ONCE(t->mm);
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if (t_mm)
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return t_mm == mm;
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}
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return false;
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}
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#ifdef CONFIG_MMU
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/*
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* OOM Reaper kernel thread which tries to reap the memory used by the OOM
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* victim (if that is possible) to help the OOM killer to move on.
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*/
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static struct task_struct *oom_reaper_th;
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static DECLARE_WAIT_QUEUE_HEAD(oom_reaper_wait);
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static struct task_struct *oom_reaper_list;
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static DEFINE_SPINLOCK(oom_reaper_lock);
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static bool __oom_reap_task_mm(struct task_struct *tsk, struct mm_struct *mm)
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{
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struct mmu_gather tlb;
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struct vm_area_struct *vma;
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struct zap_details details = {.check_swap_entries = true,
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.ignore_dirty = true};
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bool ret = true;
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/*
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* We have to make sure to not race with the victim exit path
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* and cause premature new oom victim selection:
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* __oom_reap_task_mm exit_mm
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* mmget_not_zero
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* mmput
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* atomic_dec_and_test
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* exit_oom_victim
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* [...]
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* out_of_memory
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* select_bad_process
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* # no TIF_MEMDIE task selects new victim
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* unmap_page_range # frees some memory
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*/
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mutex_lock(&oom_lock);
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if (!down_read_trylock(&mm->mmap_sem)) {
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ret = false;
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goto unlock_oom;
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}
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/*
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* If the mm has notifiers then we would need to invalidate them around
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* unmap_page_range and that is risky because notifiers can sleep and
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* what they do is basically undeterministic. So let's have a short
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* sleep to give the oom victim some more time.
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* TODO: we really want to get rid of this ugly hack and make sure that
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* notifiers cannot block for unbounded amount of time and add
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* mmu_notifier_invalidate_range_{start,end} around unmap_page_range
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*/
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if (mm_has_notifiers(mm)) {
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up_read(&mm->mmap_sem);
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schedule_timeout_idle(HZ);
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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;
|
|
}
|
|
|
|
/*
|
|
* 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 (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)) {
|
|
tlb_gather_mmu(&tlb, mm, vma->vm_start, vma->vm_end);
|
|
unmap_page_range(&tlb, vma, vma->vm_start, vma->vm_end,
|
|
&details);
|
|
tlb_finish_mmu(&tlb, vma->vm_start, vma->vm_end);
|
|
}
|
|
}
|
|
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:
|
|
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)
|
|
{
|
|
if (!oom_reaper_th)
|
|
return;
|
|
|
|
/* mm is already queued? */
|
|
if (test_and_set_bit(MMF_OOM_REAP_QUEUED, &tsk->signal->oom_mm->flags))
|
|
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;
|
|
|
|
/* 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(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;
|
|
}
|
|
|
|
/**
|
|
* 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;
|
|
}
|
|
|
|
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 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);
|
|
|
|
/*
|
|
* The task 'p' might have already exited before reaching here. The
|
|
* put_task_struct() will free task_struct 'p' while the loop still try
|
|
* to access the field of 'p', so, get an extra reference.
|
|
*/
|
|
get_task_struct(p);
|
|
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);
|
|
}
|
|
}
|
|
}
|
|
put_task_struct(p);
|
|
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 (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, 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;
|
|
out_of_memory(&oc);
|
|
mutex_unlock(&oom_lock);
|
|
}
|