[PATCH]rcu: avoid unnecessary thread wakeup

[Shaohua Li <shaohua.li@intel.com>]

invoke_rcu_cpu_kthread could be called in the thread itself. In this case,
we don't need call wakeup, which is just wasting CPU.

Signed-off-by: Shaohua Li <shaohua.li@intel.com>

diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index 89419ff..f9bd051 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -1475,7 +1475,8 @@ static void invoke_rcu_cpu_kthread(void)
 		local_irq_restore(flags);
 		return;
 	}
-	wake_up_process(__this_cpu_read(rcu_cpu_kthread_task));
+	if (current != __this_cpu_read(rcu_cpu_kthread_task))
+		wake_up_process(__this_cpu_read(rcu_cpu_kthread_task));
 	local_irq_restore(flags);
 }