From 158e0a2d1b3cffed8b46cbc56393a1394672ef79 Mon Sep 17 00:00:00 2001
From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Date: Tue, 10 Aug 2010 18:03:00 -0700
Subject: memcg: use find_lock_task_mm() in memory cgroups oom

When the OOM killer scans task, it check a task is under memcg or
not when it's called via memcg's context.

But, as Oleg pointed out, a thread group leader may have NULL ->mm
and task_in_mem_cgroup() may do wrong decision. We have to use
find_lock_task_mm() in memcg as generic OOM-Killer does.

Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Cc: Balbir Singh <balbir@linux.vnet.ibm.com>
Reviewed-by: Minchan Kim <minchan.kim@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
 mm/memcontrol.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

(limited to 'mm/memcontrol.c')

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index ea5f5edf00b..f52b0a1861c 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -47,6 +47,7 @@
 #include <linux/mm_inline.h>
 #include <linux/page_cgroup.h>
 #include <linux/cpu.h>
+#include <linux/oom.h>
 #include "internal.h"
 
 #include <asm/uaccess.h>
@@ -838,10 +839,13 @@ int task_in_mem_cgroup(struct task_struct *task, const struct mem_cgroup *mem)
 {
 	int ret;
 	struct mem_cgroup *curr = NULL;
+	struct task_struct *p;
 
-	task_lock(task);
-	curr = try_get_mem_cgroup_from_mm(task->mm);
-	task_unlock(task);
+	p = find_lock_task_mm(task);
+	if (!p)
+		return 0;
+	curr = try_get_mem_cgroup_from_mm(p->mm);
+	task_unlock(p);
 	if (!curr)
 		return 0;
 	/*
-- 
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