linux-kernel - Re: [PATCH RESEND] sched/deadline: fix pull if dl task who's prio changed is not on queue

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Date:	Tue, 03 Mar 2015 09:32:29 +0000
From:	Juri Lelli <juri.lelli@....com>
To:	Wanpeng Li <wanpeng.li@...ux.intel.com>,
	Ingo Molnar <mingo@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Kirill Tkhai <tkhai@...dex.ru>
Subject: Re: [PATCH RESEND] sched/deadline: fix pull if dl task who's prio
 changed is not on queue

Hi,

[+Kirill]

On 26/02/2015 02:38, Wanpeng Li wrote:
> Dl task who is not on queue and it is also the curr task simultaneously
> can not happen. In addition, pull since the priority of a not on queue
> dl task doesn't make any sense.
> 
> This patch fix it by don't pull if dl task who's prio changed is not on
> queue.
> 

So, this is something that was already raised by Kirill, but I always
forgot to fix :/. Thanks for reminding me!

I have this fix:

>From 8fcb04eee2d76042970e9561d253d1bc1fe4cc2b Mon Sep 17 00:00:00 2001
From: Juri Lelli <juri.lelli@....com>
Date: Tue, 3 Mar 2015 07:51:56 +0000
Subject: [PATCH] sched/deadline: cleanup prio_changed_dl()

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@....com>
Suggested-by: Kirill Tkhai <ktkhai@...allels.com>
Suggested-by: Wanpeng Li <wanpeng.li@...ux.intel.com>
Cc: Ingo Molnar <mingo@...hat.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Juri Lelli <juri.lelli@...il.com>
Cc: linux-kernel@...r.kernel.org
---
 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@...ux.intel.com>
> ---
>  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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