sched: deadline: Fix confusing comments about selection of top pi-waiter

PATCH Superseded Joel Fernandes 3 participants 3 messages Feb 23, 2017 – Feb 28, 2017 Scheduler

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Joel Fernandes

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2017-02-23 04:10 UTC #0 lore raw

PATCH 1/1 sched: deadline: Fix confusing comments about selection of top pi-waiter

This comment in the code is incomplete, and I believe it begs a definition of dl_boosted to make sense of the condition that follows. Rewrite the comment and also rearrange the condition that follows to reflect the first condition "we have a top pi-waiter which is a SCHED_DEADLINE task" in that order. Also fix a typo that follows.

Cc Juri Lelli <[email protected]>

Signed-off-by Joel Fernandes <[email protected]>

---
 kernel/sched/deadline.c | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

kernel/sched/deadline.c +8 -6

index 70ef2b1901e4..4b86abcef135 100644
@@ -928,17 +928,19 @@ static void enqueue_task_dl(struct rq *rq, struct task_struct *p, int flags)
 	struct sched_dl_entity *pi_se = &p->dl;
 
 	/*
-	 * Use the scheduling parameters of the top pi-waiter
-	 * task if we have one and its (absolute) deadline is
-	 * smaller than our one... OTW we keep our runtime and
-	 * deadline.
+	 * Use the scheduling parameters of the top pi-waiter task if:
+	 * - we have a top pi-waiter which is a SCHED_DEADLINE task AND
+	 * - our dl_boosted is set (i.e. the pi-waiter's (absolute) deadline is
+	 *   smaller than our deadline OR we are a !SCHED_DEADLINE task getting
+	 *   boosted due to a SCHED_DEADLINE pi-waiter).
+	 * Otherwise we keep our runtime and deadline.
 	 */
-	if (pi_task && p->dl.dl_boosted && dl_prio(pi_task->normal_prio)) {
+	if (pi_task && dl_prio(pi_task->normal_prio) && p->dl.dl_boosted) {
 		pi_se = &pi_task->dl;
 	} else if (!dl_prio(p->normal_prio)) {
 		/*
 		 * Special case in which we have a !SCHED_DEADLINE task
-		 * that is going to be deboosted, but exceedes its
+		 * that is going to be deboosted, but exceeds its
 		 * runtime while doing so. No point in replenishing
 		 * it, as it's going to return back to its original
 		 * scheduling class after this.

Signature · 1 line

2.11.0.483.g087da7b7c-goog

Juri Lelli

Acked-by on v1 1/1

2017-02-28 11:39 UTC #1 lore raw

Hi,

Quoted 8 lines · Joel Fernandes

This comment in the code is incomplete, and I believe it begs a definition of dl_boosted to make sense of the condition that follows. Rewrite the comment and also rearrange the condition that follows to reflect the first condition "we have a top pi-waiter which is a SCHED_DEADLINE task" in that order. Also fix a typo that follows.
Cc Juri Lelli <[email protected]>
Signed-off-by Joel Fernandes <[email protected]>

Looks good to me.

Acked-by Juri Lelli <[email protected]>

Thanks,

- Juri

Daniel Bristot de Oliveira

Reviewed-by on v1 1/1

2017-02-28 13:12 UTC #2 lore raw

In reply to Joel Fernandes

Quoted 8 lines · Joel Fernandes

This comment in the code is incomplete, and I believe it begs a definition of dl_boosted to make sense of the condition that follows. Rewrite the comment and also rearrange the condition that follows to reflect the first condition "we have a top pi-waiter which is a SCHED_DEADLINE task" in that order. Also fix a typo that follows.
Cc Juri Lelli <[email protected]>
Signed-off-by Joel Fernandes <[email protected]>

Reviewed-by Daniel Bristot de Oliveira <[email protected]>

-- Daniel