rcu: Make RCU use the new is_idle_task() API

Change from direct comparison of ->pid with zero to is_idle_task().

Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
diff --git a/kernel/rcutiny.c b/kernel/rcutiny.c
index 4e16ce3..e5bd949 100644
--- a/kernel/rcutiny.c
+++ b/kernel/rcutiny.c
@@ -64,7 +64,7 @@
 		return;
 	}
 	RCU_TRACE(trace_rcu_dyntick("Start", oldval, rcu_dynticks_nesting));
-	if (current->pid != 0) {
+	if (!is_idle_task(current)) {
 		struct task_struct *idle = idle_task(smp_processor_id());
 
 		RCU_TRACE(trace_rcu_dyntick("Error on entry: not idle task",
@@ -118,7 +118,7 @@
 		return;
 	}
 	RCU_TRACE(trace_rcu_dyntick("End", oldval, rcu_dynticks_nesting));
-	if (current->pid != 0) {
+	if (!is_idle_task(current)) {
 		struct task_struct *idle = idle_task(smp_processor_id());
 
 		RCU_TRACE(trace_rcu_dyntick("Error on exit: not idle task",