[PATCH] sched/deadline: cleanup prio_changed_dl()

[Juri Lelli]

rq->curr task can't be in "dequeued" state in prio_changed_dl()
(The only place we can have that is __schedule()), but it can
be throttled, in which case we shouldn't do balancing.

Also modify the "else" branch, which is dead code (switched_to_dl()
is not interested in dequeued tasks and we are not interested
in balancing in this case), to take into account updates to not
running tasks.

Signed-off-by: Juri Lelli <juri.lelli@xxxxxxx>
Suggested-by: Kirill Tkhai <ktkhai@xxxxxxxxxxxxx>
Suggested-by: Wanpeng Li <wanpeng.li@xxxxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Juri Lelli <juri.lelli@xxxxxxxxx>
Cc: linux-kernel@xxxxxxxxxxxxxxx
---
 kernel/sched/deadline.c | 16 +++++++++++++---
 1 file changed, 13 insertions(+), 3 deletions(-)

diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index cfa45c1..9d83748 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -1759,7 +1759,10 @@ static void switched_to_dl(struct rq *rq, struct task_struct *p)
 static void prio_changed_dl(struct rq *rq, struct task_struct *p,
 			    int oldprio)
 {
-	if (task_on_rq_queued(p) || rq->curr == p) {
+	if (!on_dl_rq(&p->dl))
+		return;
+
+	if (rq->curr == p) {
 #ifdef CONFIG_SMP
 		/*
 		 * This might be too much, but unfortunately
@@ -1786,8 +1789,15 @@ static void prio_changed_dl(struct rq *rq, struct task_struct *p,
 		 */
 		resched_curr(rq);
 #endif /* CONFIG_SMP */
-	} else
-		switched_to_dl(rq, p);
+	} else {
+		/*
+		 * This task is not running, so if its deadline is
+		 * now more imminent than that of the current running
+		 * task then reschedule.
+		 */
+		if (dl_time_before(p->dl.deadline, rq->curr->dl.deadline))
+			resched_curr(rq);
+	}
 }
 
 const struct sched_class dl_sched_class = {
-- 
2.3.0

> Signed-off-by: Wanpeng Li <wanpeng.li@xxxxxxxxxxxxxxx>
> ---
>  kernel/sched/deadline.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
> index 49f92c8..ca391c0 100644
> --- a/kernel/sched/deadline.c
> +++ b/kernel/sched/deadline.c
> @@ -1728,7 +1728,10 @@ static void switched_to_dl(struct rq *rq, struct task_struct *p)
>  static void prio_changed_dl(struct rq *rq, struct task_struct *p,
>  			    int oldprio)
>  {
> -	if (task_on_rq_queued(p) || rq->curr == p) {
> +	if (!task_on_rq_queued(p))
> +		return;
> +
> +	if (rq->curr == p) {
>  #ifdef CONFIG_SMP
>  		/*
>  		 * This might be too much, but unfortunately
> 

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