[PATCH v2 4/7] sched/deadline: reschedule if stop task slip in after pull operations

[Wanpeng Li <wanpeng.li@linux.intel.com>]

pull_dl_task can drop (and re-acquire) rq->lock, this means a stop task
can slip in, in which case we need to reschedule. This patch add the
reschedule when the scenario occurs.

Signed-off-by: Wanpeng Li <wanpeng.li@linux.intel.com>
---
 kernel/sched/deadline.c | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index e49b1e6..7d4c4fc 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -1750,7 +1750,13 @@ static void switched_from_dl(struct rq *rq, struct task_struct *p)
 	if (!task_on_rq_queued(p) || rq->dl.dl_nr_running)
 		return;
 
-	if (pull_dl_task(rq))
+	/*
+	 * pull_dl_task() can drop (and re-acquire) rq->lock; this
+	 * means a stop task can slip in, in which case we need to
+	 * reschedule.
+	 */
+	if (pull_dl_task(rq) ||
+		(rq->stop && task_on_rq_queued(rq->stop)))
 		resched_curr(rq);
 }
 
@@ -1797,6 +1803,14 @@ static void prio_changed_dl(struct rq *rq, struct task_struct *p,
 			pull_dl_task(rq);
 
 		/*
+		 * pull_dl_task() can drop (and re-acquire) rq->lock; this
+		 * means a stop task can slip in, in which case we need to
+		 * reschedule.
+		 */
+		if (rq->stop && task_on_rq_queued(rq->stop))
+			resched_curr(rq);
+
+		/*
 		 * If we now have a earlier deadline task than p,
 		 * then reschedule, provided p is still on this
 		 * runqueue.
-- 
1.9.1