sched: break out early if RT task cannot be migrated

We don't need to bother searching if the task cannot be migrated

Signed-off-by: Gregory Haskins <ghaskins@novell.com>
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

kernel/sched_rt.c

@@ -176,7 +176,8 @@ static int select_task_rq_rt(struct task_struct *p, int sync)
 	 * that is just being woken and probably will have
 	 * cold cache anyway.
 	 */
-	if (unlikely(rt_task(rq->curr))) {
+	if (unlikely(rt_task(rq->curr)) &&
+	    (p->nr_cpus_allowed > 1)) {
 		int cpu = find_lowest_rq(p);
 
 		return (cpu == -1) ? task_cpu(p) : cpu;