sched: fix goto retry in pick_next_task_rt()

looking at it one more time:

(1) it looks to me that there is no need to call
sched_rt_ratio_exceeded() from pick_next_rt_entity()

- [ for CONFIG_FAIR_GROUP_SCHED ] queues with rt_rq->rt_throttled are
not within this 'tree-like hierarchy' (or whatever we should call it
:-)

- there is also no need to re-check 'rt_rq->rt_time > ratio' at this
point as 'rt_rq->rt_time' couldn't have been increased since the last
call to update_curr_rt() (which obviously calls
sched_rt_ratio_esceeded())
well, it might be that 'ratio' for this rt_rq has been re-configured
(and the period over which this rt_rq was active has not yet been
finished)... but I don't think we should really take this into
account.

(2) now pick_next_rt_entity() must never return NULL, so let's change
pick_next_task_rt() accordingly.
Signed-off-by: NDmitry Adamushko <dmitry.adamushko@gmail.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

kernel/sched_rt.c

@@ -476,15 +476,12 @@ static struct sched_rt_entity *pick_next_rt_entity(struct rq *rq,
 	struct list_head *queue;
 	int idx;
 
-	if (sched_rt_ratio_exceeded(rt_rq))
-		goto out;
-
 	idx = sched_find_first_bit(array->bitmap);
 	BUG_ON(idx >= MAX_RT_PRIO);
 
 	queue = array->queue + idx;
 	next = list_entry(queue->next, struct sched_rt_entity, run_list);
- out:
+
 	return next;
 }
 
@@ -494,7 +491,6 @@ static struct task_struct *pick_next_task_rt(struct rq *rq)
 	struct task_struct *p;
 	struct rt_rq *rt_rq;
 
- retry:
 	rt_rq = &rq->rt;
 
 	if (unlikely(!rt_rq->rt_nr_running))
@@ -505,8 +501,7 @@ static struct task_struct *pick_next_task_rt(struct rq *rq)
 
 	do {
 		rt_se = pick_next_rt_entity(rq, rt_rq);
-		if (unlikely(!rt_se))
-			goto retry;
+		BUG_ON(!rt_se);
 		rt_rq = group_rt_rq(rt_se);
 	} while (rt_rq);