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>

3 files changed, 16 insertions, 5 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.
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 4f14a656a720..7570dd969c28 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -6728,7 +6728,8 @@ static int idle_balance(struct rq *this_rq)
 out:
         /* Is there a task of a high priority class? */
         if (this_rq->nr_running != this_rq->cfs.h_nr_running &&
-            (this_rq->dl.dl_nr_running ||
+            ((this_rq->stop && this_rq->stop->on_rq) ||
+             this_rq->dl.dl_nr_running ||
              (this_rq->rt.rt_nr_running && !rt_rq_throttled(&this_rq->rt))))
                 pulled_task = -1;
 
diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
index d8cdf1618551..bd2267ad404f 100644
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -1362,10 +1362,11 @@ pick_next_task_rt(struct rq *rq, struct task_struct *prev)
                 pull_rt_task(rq);
                 /*
                  * pull_rt_task() can drop (and re-acquire) rq->lock; this
-                 * means a dl task can slip in, in which case we need to
-                 * re-start task selection.
+                 * means a dl or stop task can slip in, in which case we need
+                 * to re-start task selection.
                  */
-                if (unlikely(rq->dl.dl_nr_running))
+                if (unlikely((rq->stop && rq->stop->on_rq) ||
+                             rq->dl.dl_nr_running))
                         return RETRY_TASK;
         }