sched: Check for stop task appearance when balancing happens

We need to do it like we do for the other higher priority classes..

Signed-off-by: Kirill Tkhai <tkhai@yandex.ru>
Cc: Michael wang <wangyun@linux.vnet.ibm.com>
Cc: Sasha Levin <sasha.levin@oracle.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/336561397137116@web27h.yandex.ru
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 10 insertions, 1 deletions

diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index 27ef40925525..b08095786cb8 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -1021,8 +1021,17 @@ struct task_struct *pick_next_task_dl(struct rq *rq, struct task_struct *prev)
 
         dl_rq = &rq->dl;
 
-        if (need_pull_dl_task(rq, prev))
+        if (need_pull_dl_task(rq, prev)) {
                 pull_dl_task(rq);
+                /*
+                 * pull_rt_task() can drop (and re-acquire) rq->lock; this
+                 * means a stop task can slip in, in which case we need to
+                 * re-start task selection.
+                 */
+                if (rq->stop && rq->stop->on_rq)
+                        return RETRY_TASK;
+        }
+
         /*
          * When prev is DL, we may throttle it in put_prev_task().
          * So, we update time before we check for dl_nr_running.