linux-kernel - Re: [PATCH v5] sched/deadline: remove useless param from setup_new_dl

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Date:	Fri, 5 Aug 2016 15:34:44 +0100
From:	Juri Lelli <juri.lelli@....com>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	peterz@...radead.org, linux-kernel@...r.kernel.org,
	mingo@...hat.com, luca.abeni@...tn.it, xpang@...hat.com
Subject: Re: [PATCH v5] sched/deadline: remove useless param from
 setup_new_dl_entity

On 05/08/16 09:56, Steven Rostedt wrote:
> On Fri,  5 Aug 2016 11:09:59 +0100
> Juri Lelli <juri.lelli@....com> wrote:
> 
> > @@ -1720,19 +1720,28 @@ static void switched_from_dl(struct rq *rq, struct task_struct *p)
> >   */
> >  static void switched_to_dl(struct rq *rq, struct task_struct *p)
> >  {
> > -	if (dl_time_before(p->dl.deadline, rq_clock(rq)))
> > -		setup_new_dl_entity(&p->dl, &p->dl);
> >  
> > -	if (task_on_rq_queued(p) && rq->curr != p) {
> > +	if (task_on_rq_queued(p)) {
> 
> I always hated functions totally encapsulated by an if statement. This
> can be a bit simpler (and less indented) if you have:
> 
> 	/* If p is not queued, its parameters will be updated at wakeup */
> 	if (!task_on_rq_queued(p))
> 		return;
> 
> 	[...]
> 

You mean like what follows?

I'll post a v6 if OK.

Thanks,

- Juri

--->8---
 kernel/sched/deadline.c | 35 ++++++++++++++++++-----------------
 1 file changed, 18 insertions(+), 17 deletions(-)

diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index 9491dbe039e8..03f35f66cf1f 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -1721,27 +1721,28 @@ static void switched_from_dl(struct rq *rq, struct task_struct *p)
 static void switched_to_dl(struct rq *rq, struct task_struct *p)
 {
 
-	if (task_on_rq_queued(p)) {
-		/*
-		 * If p is not queued we will update its parameters at next
-		 * wakeup. If p is dl_boosted we already updated its params in
-		 * rt_mutex_setprio()->enqueue_task(..., ENQUEUE_REPLENISH),
-		 * p's deadline being now already after rq_clock(rq).
-		 */
-		if (dl_time_before(p->dl.deadline, rq_clock(rq)))
-			setup_new_dl_entity(&p->dl);
+	/* If p is not queued we will update its parameters at next wakeup. */
+	if (!task_on_rq_queued(p))
+		return;
+
+	/*
+	 * If p is boosted we already updated its params in
+	 * rt_mutex_setprio()->enqueue_task(..., ENQUEUE_REPLENISH),
+	 * p's deadline being now already after rq_clock(rq).
+	 */
+	if (dl_time_before(p->dl.deadline, rq_clock(rq)))
+		setup_new_dl_entity(&p->dl);
 
-		if (rq->curr != p) {
+	if (rq->curr != p) {
 #ifdef CONFIG_SMP
-			if (tsk_nr_cpus_allowed(p) > 1 && rq->dl.overloaded)
-				queue_push_tasks(rq);
+		if (tsk_nr_cpus_allowed(p) > 1 && rq->dl.overloaded)
+			queue_push_tasks(rq);
 #else
-			if (dl_task(rq->curr))
-				check_preempt_curr_dl(rq, p, 0);
-			else
-				resched_curr(rq);
+		if (dl_task(rq->curr))
+			check_preempt_curr_dl(rq, p, 0);
+		else
+			resched_curr(rq);
 #endif
-		}
 	}
 }