sched: More sched_domain iterations fixes

sched_domain iterations needs to be protected by rcu_read_lock() now,
this patch adds another two places which needs the rcu lock, which is
spotted by following suspicious rcu_dereference_check() usage warnings.

kernel/sched_rt.c:1244 invoked rcu_dereference_check() without protection!
kernel/sched_stats.h:41 invoked rcu_dereference_check() without protection!

Signed-off-by: Xiaotian Feng <dfeng@redhat.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1303469634-11678-1-git-send-email-dfeng@redhat.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/kernel/sched_stats.h b/kernel/sched_stats.h
index 48ddf43..331e01b 100644
--- a/kernel/sched_stats.h
+++ b/kernel/sched_stats.h
@@ -37,7 +37,7 @@
 
 #ifdef CONFIG_SMP
 		/* domain-specific stats */
-		preempt_disable();
+		rcu_read_lock();
 		for_each_domain(cpu, sd) {
 			enum cpu_idle_type itype;
 
@@ -64,7 +64,7 @@
 			    sd->ttwu_wake_remote, sd->ttwu_move_affine,
 			    sd->ttwu_move_balance);
 		}
-		preempt_enable();
+		rcu_read_unlock();
 #endif
 	}
 	kfree(mask_str);