sched: rt: dont stop the period timer when there are tasks wanting to run

So if the group ever gets throttled, it will never wake up again.
Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: "Daniel K." <dk@uw.no>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Reported-by: N"Daniel K." <dk@uw.no>

kernel/sched_rt.c

@@ -412,7 +412,8 @@ static int do_sched_rt_period_timer(struct rt_bandwidth *rt_b, int overrun)
 			if (rt_rq->rt_time || rt_rq->rt_nr_running)
 				idle = 0;
 			spin_unlock(&rt_rq->rt_runtime_lock);
-		}
+		} else if (rt_rq->rt_nr_running)
+			idle = 0;
 
 		if (enqueue)
 			sched_rt_rq_enqueue(rt_rq);