Skip to content
Snippets Groups Projects
Select Git revision
  • 4d7b3394f76ed72cfdec23ca5571dbab6ec41793
  • vme-testing default
  • ci-test
  • master
  • remoteproc
  • am625-sk-ov5640
  • pcal6534-upstreaming
  • lps22df-upstreaming
  • msc-upstreaming
  • imx8mp
  • iio/noa1305
  • vme-next
  • vme-next-4.14-rc4
  • v4.14-rc4
  • v4.14-rc3
  • v4.14-rc2
  • v4.14-rc1
  • v4.13
  • vme-next-4.13-rc7
  • v4.13-rc7
  • v4.13-rc6
  • v4.13-rc5
  • v4.13-rc4
  • v4.13-rc3
  • v4.13-rc2
  • v4.13-rc1
  • v4.12
  • v4.12-rc7
  • v4.12-rc6
  • v4.12-rc5
  • v4.12-rc4
  • v4.12-rc3
32 results

oom_kill.c

Blame
  • oom_kill.c 20.54 KiB
    /*
     *  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>
    
    #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;
    }
    
    /* 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;
    
    	adj = (long)p->signal->oom_score_adj;
    	if (adj == OOM_SCORE_ADJ_MIN) {
    		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;
    }
    
    /*
     * Determine the type of allocation constraint.
     */
    #ifdef CONFIG_NUMA
    static enum oom_constraint constrained_alloc(struct oom_control *oc,
    					     unsigned long *totalpages)
    {
    	struct zone *zone;
    	struct zoneref *z;
    	enum zone_type high_zoneidx = gfp_zone(oc->gfp_mask);
    	bool cpuset_limited = false;
    	int nid;
    
    	/* Default to all available memory */
    	*totalpages = totalram_pages + total_swap_pages;
    
    	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)) {
    		*totalpages = total_swap_pages;
    		for_each_node_mask(nid, *oc->nodemask)
    			*totalpages += node_spanned_pages(nid);
    		return CONSTRAINT_MEMORY_POLICY;
    	}
    
    	/* Check this allocation failure is caused by cpuset's wall function */
    	for_each_zone_zonelist_nodemask(zone, z, oc->zonelist,
    			high_zoneidx, oc->nodemask)
    		if (!cpuset_zone_allowed(zone, oc->gfp_mask))
    			cpuset_limited = true;
    
    	if (cpuset_limited) {
    		*totalpages = total_swap_pages;
    		for_each_node_mask(nid, cpuset_current_mems_allowed)
    			*totalpages += node_spanned_pages(nid);
    		return CONSTRAINT_CPUSET;
    	}
    	return CONSTRAINT_NONE;
    }
    #else
    static enum oom_constraint constrained_alloc(struct oom_control *oc,
    					     unsigned long *totalpages)
    {
    	*totalpages = totalram_pages + total_swap_pages;
    	return CONSTRAINT_NONE;
    }
    #endif
    
    enum oom_scan_t oom_scan_process_thread(struct oom_control *oc,
    			struct task_struct *task, unsigned long totalpages)
    {
    	if (oom_unkillable_task(task, NULL, oc->nodemask))
    		return OOM_SCAN_CONTINUE;
    
    	/*
    	 * This task already has access to memory reserves and is being killed.
    	 * Don't allow any other task to have access to the reserves.
    	 */
    	if (test_tsk_thread_flag(task, TIF_MEMDIE)) {
    		if (oc->order != -1)
    			return OOM_SCAN_ABORT;
    	}
    	if (!task->mm)
    		return OOM_SCAN_CONTINUE;
    
    	/*
    	 * 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))
    		return OOM_SCAN_SELECT;
    
    	if (task_will_free_mem(task) && oc->order != -1)
    		return OOM_SCAN_ABORT;
    
    	return OOM_SCAN_OK;
    }
    
    /*
     * Simple selection loop. We chose the process with the highest
     * number of 'points'.  Returns -1 on scan abort.
     */
    static struct task_struct *select_bad_process(struct oom_control *oc,
    		unsigned int *ppoints, unsigned long totalpages)
    {
    	struct task_struct *g, *p;
    	struct task_struct *chosen = NULL;
    	unsigned long chosen_points = 0;
    
    	rcu_read_lock();
    	for_each_process_thread(g, p) {
    		unsigned int points;
    
    		switch (oom_scan_process_thread(oc, p, totalpages)) {
    		case OOM_SCAN_SELECT:
    			chosen = p;
    			chosen_points = ULONG_MAX;
    			/* fall through */
    		case OOM_SCAN_CONTINUE:
    			continue;
    		case OOM_SCAN_ABORT:
    			rcu_read_unlock();
    			return (struct task_struct *)(-1UL);
    		case OOM_SCAN_OK:
    			break;
    		};
    		points = oom_badness(p, NULL, oc->nodemask, totalpages);
    		if (!points || points < chosen_points)
    			continue;
    		/* Prefer thread group leaders for display purposes */
    		if (points == chosen_points && thread_group_leader(chosen))
    			continue;
    
    		chosen = p;
    		chosen_points = points;
    	}
    	if (chosen)
    		get_task_struct(chosen);
    	rcu_read_unlock();
    
    	*ppoints = chosen_points * 1000 / totalpages;
    	return chosen;
    }
    
    /**
     * 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,
    			struct mem_cgroup *memcg)
    {
    	pr_warning("%s invoked oom-killer: gfp_mask=0x%x, order=%d, "
    		"oom_score_adj=%hd\n",
    		current->comm, oc->gfp_mask, oc->order,
    		current->signal->oom_score_adj);
    	cpuset_print_current_mems_allowed();
    	dump_stack();
    	if (memcg)
    		mem_cgroup_print_oom_info(memcg, p);
    	else
    		show_mem(SHOW_MEM_FILTER_NODES);
    	if (sysctl_oom_dump_tasks)
    		dump_tasks(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);
    
    bool oom_killer_disabled __read_mostly;
    
    /**
     * 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.
     */
    void mark_oom_victim(struct task_struct *tsk)
    {
    	WARN_ON(oom_killer_disabled);
    	/* OOM killer might race with memcg OOM */
    	if (test_and_set_tsk_thread_flag(tsk, TIF_MEMDIE))
    		return;
    	/*
    	 * 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_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
    	 * and that the current is not the victim.
    	 */
    	mutex_lock(&oom_lock);
    	if (test_thread_flag(TIF_MEMDIE)) {
    		mutex_unlock(&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;
    }
    
    /*
     * 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.
     */
    static 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;
    }
    
    #define K(x) ((x) << (PAGE_SHIFT-10))
    /*
     * Must be called while holding a reference to p, which will be released upon
     * returning.
     */
    void oom_kill_process(struct oom_control *oc, struct task_struct *p,
    		      unsigned int points, unsigned long totalpages,
    		      struct mem_cgroup *memcg, const char *message)
    {
    	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);
    
    	/*
    	 * 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 (p->mm && task_will_free_mem(p)) {
    		mark_oom_victim(p);
    		task_unlock(p);
    		put_task_struct(p);
    		return;
    	}
    	task_unlock(p);
    
    	if (__ratelimit(&oom_rs))
    		dump_header(oc, p, memcg);
    
    	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, memcg, oc->nodemask,
    								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\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)));
    	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))
    			continue;
    		if (p->signal->oom_score_adj == OOM_SCORE_ADJ_MIN)
    			continue;
    
    		do_send_sig_info(SIGKILL, SEND_SIG_FORCED, p, true);
    	}
    	rcu_read_unlock();
    
    	mmdrop(mm);
    	put_task_struct(victim);
    }
    #undef K
    
    /*
     * Determines whether the kernel must panic because of the panic_on_oom sysctl.
     */
    void check_panic_on_oom(struct oom_control *oc, enum oom_constraint constraint,
    			struct mem_cgroup *memcg)
    {
    	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 (oc->order == -1)
    		return;
    	dump_header(oc, NULL, memcg);
    	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)
    {
    	struct task_struct *p;
    	unsigned long totalpages;
    	unsigned long freed = 0;
    	unsigned int uninitialized_var(points);
    	enum oom_constraint constraint = CONSTRAINT_NONE;
    
    	if (oom_killer_disabled)
    		return false;
    
    	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.
    	 *
    	 * But don't select if current has already released its mm and cleared
    	 * TIF_MEMDIE flag at exit_mm(), otherwise an OOM livelock may occur.
    	 */
    	if (current->mm &&
    	    (fatal_signal_pending(current) || task_will_free_mem(current))) {
    		mark_oom_victim(current);
    		return true;
    	}
    
    	/*
    	 * Check if there were limitations on the allocation (only relevant for
    	 * NUMA) that may require different handling.
    	 */
    	constraint = constrained_alloc(oc, &totalpages);
    	if (constraint != CONSTRAINT_MEMORY_POLICY)
    		oc->nodemask = NULL;
    	check_panic_on_oom(oc, constraint, NULL);
    
    	if (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);
    		oom_kill_process(oc, current, 0, totalpages, NULL,
    				 "Out of memory (oom_kill_allocating_task)");
    		return true;
    	}
    
    	p = select_bad_process(oc, &points, totalpages);
    	/* Found nothing?!?! Either we hang forever, or we panic. */
    	if (!p && oc->order != -1) {
    		dump_header(oc, NULL, NULL);
    		panic("Out of memory and no killable processes...\n");
    	}
    	if (p && p != (void *)-1UL) {
    		oom_kill_process(oc, p, points, totalpages, NULL,
    				 "Out of memory");
    		/*
    		 * Give the killed process a good chance to exit before trying
    		 * to allocate memory again.
    		 */
    		schedule_timeout_killable(1);
    	}
    	return true;
    }
    
    /*
     * The pagefault handler calls here because it is out of memory, so kill a
     * memory-hogging task.  If any populated zone has ZONE_OOM_LOCKED set, 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,
    		.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);
    }