linux-kernel - Re: [PATCH] sched/deadline: fix switching to -deadline

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Message-ID: <20170724094929.216193e1@luca>
Date:   Mon, 24 Jul 2017 09:49:29 +0200
From:   Luca Abeni <luca.abeni@...tannapisa.it>
To:     linux-kernel@...r.kernel.org
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Juri Lelli <juri.lelli@....com>,
        Claudio Scordino <claudio@...dence.eu.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Tommaso Cucinotta <tommaso.cucinotta@...up.it>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        Mathieu Poirier <mathieu.poirier@...aro.org>
Subject: Re: [PATCH] sched/deadline: fix switching to -deadline

Hi all,

I have this patch in a local tree, together with other fixes / cleanups
I plan to submit in the next weeks...

Since I see that the patch has not been applied, I wonder if some
changes are needed before submitting it another time.
If anyone has requests for changes in the patch, let me know.



			Thanks,
				Luca

On Thu, 20 Apr 2017 21:30:56 +0200
luca abeni <luca.abeni@...tannapisa.it> wrote:

> From: Luca Abeni <luca.abeni@...tannapisa.it>
> 
> When switching to -deadline, if the scheduling deadline of a task is
> in the past then switched_to_dl() calls setup_new_entity() to properly
> initialize the scheduling deadline and runtime.
> 
> The problem is that the task is enqueued _before_ having its parameters
> initialized by setup_new_entity(), and this can cause problems.
> For example, a task with its out-of-date deadline in the past will
> potentially be enqueued as the highest priority one; however, its
> adjusted deadline may not be the earliest one.
> 
> This patch fixes the problem by initializing the task's parameters before
> enqueuing it.
> 
> Signed-off-by: Luca Abeni <luca.abeni@...tannapisa.it>
> Reviewed-by: Daniel Bristot de Oliveira <bristot@...hat.com>
> ---
>  kernel/sched/deadline.c | 12 ++++--------
>  1 file changed, 4 insertions(+), 8 deletions(-)
> 
> diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
> index a2ce590..ec53d24 100644
> --- a/kernel/sched/deadline.c
> +++ b/kernel/sched/deadline.c
> @@ -950,6 +950,10 @@ enqueue_dl_entity(struct sched_dl_entity *dl_se,
>  		update_dl_entity(dl_se, pi_se);
>  	else if (flags & ENQUEUE_REPLENISH)
>  		replenish_dl_entity(dl_se, pi_se);
> +	else if ((flags & ENQUEUE_RESTORE) &&
> +		  dl_time_before(dl_se->deadline,
> +				 rq_clock(rq_of_dl_rq(dl_rq_of_se(dl_se)))))
> +		setup_new_dl_entity(dl_se);
>  
>  	__enqueue_dl_entity(dl_se);
>  }
> @@ -1767,14 +1771,6 @@ static void switched_to_dl(struct rq *rq, struct task_struct *p)
>  	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) {
>  #ifdef CONFIG_SMP
>  		if (p->nr_cpus_allowed > 1 && rq->dl.overloaded)