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

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Message-ID: <20150305012832.GA2793@kernel>
Date:	Thu, 5 Mar 2015 09:28:32 +0800
From:	Wanpeng Li <wanpeng.li@...ux.intel.com>
To:	Juri Lelli <juri.lelli@....com>
Cc:	Wanpeng Li <wanpeng.li@...ux.intel.com>,
	Ingo Molnar <mingo@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	"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 Juri,
On Tue, Mar 03, 2015 at 09:32:29AM +0000, Juri Lelli wrote:
>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:

Cool, your patch looks good to me.

Regards,
Wanpeng Li 

>
>>>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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