[PATCH tip/core/urgent 1/3] rcu: fix lockdep splat in wake_affine()

["Paul E. McKenney" <paulmck@linux.vnet.ibm.com>]

From: Daniel J Blueman <daniel.blueman@gmail.com>

With 2.6.35-rc1 and your patch in the context below, we still see
"include/linux/cgroup.h:534 invoked rcu_dereference_check() without
protection!", so need this additional patch:

Acquire read-side RCU lock around task_group() calls, addressing
"include/linux/cgroup.h:534 invoked rcu_dereference_check() without
protection!" warning.

Signed-off-by: Daniel J Blueman <daniel.blueman@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
---
 kernel/sched_fair.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)

diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index eed35ed..ca56133 100644
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -1240,6 +1240,7 @@ static int wake_affine(struct sched_domain *sd, struct task_struct *p, int sync)
 	 * effect of the currently running task from the load
 	 * of the current CPU:
 	 */
+	rcu_read_lock();
 	if (sync) {
 		tg = task_group(current);
 		weight = current->se.load.weight;
@@ -1249,6 +1250,7 @@ static int wake_affine(struct sched_domain *sd, struct task_struct *p, int sync)
 	}
 
 	tg = task_group(p);
+	rcu_read_unlock();
 	weight = p->se.load.weight;
 
 	/*
-- 
1.7.0.6