Commit e18641e1 authored Oct 26, 2010 by David Rientjes Committed by Linus Torvalds Oct 26, 2010

oom: avoid killing a task if a thread sharing its mm cannot be killed



The oom killer's goal is to kill a memory-hogging task so that it may
exit, free its memory, and allow the current context to allocate the
memory that triggered it in the first place.  Thus, killing a task is
pointless if other threads sharing its mm cannot be killed because of its
/proc/pid/oom_adj or /proc/pid/oom_score_adj value.

This patch checks whether any other thread sharing p->mm has an
oom_score_adj of OOM_SCORE_ADJ_MIN.  If so, the thread cannot be killed
and oom_badness(p) returns 0, meaning it's unkillable.

Signed-off-by: David Rientjes <rientjes@google.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Ying Han <yinghan@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 3d5992d2

mm/oom_kill.c

+5 −4

Original line number	Diff line number	Diff line
		@@ -162,10 +162,11 @@ unsigned int oom_badness(struct task_struct p, struct mem_cgroup mem,
		return 0;

		/*
		* Shortcut check for OOM_SCORE_ADJ_MIN so the entire heuristic doesn't
		* need to be executed for something that cannot be killed.
		* Shortcut check for a thread sharing p->mm that is OOM_SCORE_ADJ_MIN
		* so the entire heuristic doesn't need to be executed for something
		* that cannot be killed.
		*/
		if (p->signal->oom_score_adj == OOM_SCORE_ADJ_MIN) {
		if (atomic_read(&p->mm->oom_disable_count)) {
		task_unlock(p);
		return 0;
		}
		@@ -680,7 +681,7 @@ void out_of_memory(struct zonelist *zonelist, gfp_t gfp_mask,
		read_lock(&tasklist_lock);
		if (sysctl_oom_kill_allocating_task &&
		!oom_unkillable_task(current, NULL, nodemask) &&
		(current->signal->oom_adj != OOM_DISABLE)) {
		current->mm && !atomic_read(&current->mm->oom_disable_count)) {
		/*
		* oom_kill_process() needs tasklist_lock held. If it returns
		* non-zero, current could not be killed so we must fallback to

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