rcu: Enable synchronize_sched_expedited() fastpath

This patch adds a counter increment to enable tasks to actually
take the synchronize_sched_expedited() function's fastpath.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: laijs@cn.fujitsu.com
Cc: dipankar@in.ibm.com
Cc: mathieu.desnoyers@polymtl.ca
Cc: josh@joshtriplett.org
Cc: dvhltc@us.ibm.com
Cc: niv@us.ibm.com
Cc: peterz@infradead.org
Cc: rostedt@goodmis.org
Cc: Valdis.Kletnieks@vt.edu
Cc: dhowells@redhat.com
LKML-Reference: <1257889042435-git-send-email->
Signed-off-by: Ingo Molnar <mingo@elte.hu>

kernel/sched.c

@@ -10865,6 +10865,7 @@ void synchronize_sched_expedited(void)
 		spin_unlock_irqrestore(&rq->lock, flags);
 	}
 	rcu_expedited_state = RCU_EXPEDITED_STATE_IDLE;
+	synchronize_sched_expedited_count++;
 	mutex_unlock(&rcu_sched_expedited_mutex);
 	put_online_cpus();
 	if (need_full_sync)