From 1123e17b16f1f2048dc581ae8da2c4943ad4c45d Mon Sep 17 00:00:00 2001
From: Tejun Heo <tj@kernel.org>
Date: Thu, 18 Oct 2012 17:40:30 -0700
Subject: [PATCH] --- yaml --- r: 334800 b: refs/heads/master c:
 d87838321124061f6c935069d97f37010fa417e6 h: refs/heads/master v: v3

---
 [refs]                |  2 +-
 trunk/kernel/cgroup.c | 15 +++------------
 2 files changed, 4 insertions(+), 13 deletions(-)

diff --git a/[refs] b/[refs]
index a9ba5db0be6b..212701a256cb 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 9bb71308b8133d643648776243e4d5599b1c193d
+refs/heads/master: d87838321124061f6c935069d97f37010fa417e6
diff --git a/trunk/kernel/cgroup.c b/trunk/kernel/cgroup.c
index 75aec12c78a0..f24f724620dd 100644
--- a/trunk/kernel/cgroup.c
+++ b/trunk/kernel/cgroup.c
@@ -4883,19 +4883,10 @@ void cgroup_post_fork(struct task_struct *child)
 	 */
 	if (use_task_css_set_links) {
 		write_lock(&css_set_lock);
-		if (list_empty(&child->cg_list)) {
-			/*
-			 * It's safe to use child->cgroups without task_lock()
-			 * here because we are protected through
-			 * threadgroup_change_begin() against concurrent
-			 * css_set change in cgroup_task_migrate(). Also
-			 * the task can't exit at that point until
-			 * wake_up_new_task() is called, so we are protected
-			 * against cgroup_exit() setting child->cgroup to
-			 * init_css_set.
-			 */
+		task_lock(child);
+		if (list_empty(&child->cg_list))
 			list_add(&child->cg_list, &child->cgroups->tasks);
-		}
+		task_unlock(child);
 		write_unlock(&css_set_lock);
 	}
 }