From: Oleg Nesterov <oleg@redhat.com>
Date: Tue, 10 Aug 2010 00:18:44 +0000 (-0700)
Subject: oom: PF_EXITING check should take mm into account
X-Git-Tag: upstream/snapshot3+hdmi~13682
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=b52279406e77be711c068f9a8e970ea6471e089c;p=platform%2Fadaptation%2Frenesas_rcar%2Frenesas_kernel.git

oom: PF_EXITING check should take mm into account

select_bad_process() checks PF_EXITING to detect the task which is going
to release its memory, but the logic is very wrong.

	- a single process P with the dead group leader disables
	  select_bad_process() completely, it will always return
	  ERR_PTR() while P can live forever

	- if the PF_EXITING task has already released its ->mm
	  it doesn't make sense to expect it is goiing to free
	  more memory (except task_struct/etc)

Change the code to ignore the PF_EXITING tasks without ->mm.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: David Rientjes <rientjes@google.com>
Cc: Balbir Singh <balbir@in.ibm.com>
Acked-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---

diff --git a/mm/oom_kill.c b/mm/oom_kill.c
index 7c0dc41..0a6e466 100644
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -287,7 +287,7 @@ static struct task_struct *select_bad_process(unsigned long *ppoints,
 		 * the process of exiting and releasing its resources.
 		 * Otherwise we could get an easy OOM deadlock.
 		 */
-		if (p->flags & PF_EXITING) {
+		if ((p->flags & PF_EXITING) && p->mm) {
 			if (p != current)
 				return ERR_PTR(-1UL);