Re: [PATCH v2 2/3] sched/dl: Cleanup prio_changed_dl()

Kirill Tkhai
2014-10-21T16:33:50Z

В Вт, 21/10/2014 в 17:24 +0100, Juri Lelli пишет:
> Hi Kirill,
>
> On 02/10/14 10:52, Kirill Tkhai wrote:
> > В Чт, 02/10/2014 в 11:36 +0200, Peter Zijlstra пишет:
> >> On Wed, Oct 01, 2014 at 01:04:35AM +0400, Kirill Tkhai wrote:
> >>> From: Kirill Tkhai <ktkhai@parallels.com>
> >>>
> >>> rq->curr task can't be in "dequeued" state in prio_changed_dl().
> >>> (The only place we can have that is __schedule()). So, we delete
> >>> rq->curr check.
> >>
> >> the CBS timer can throttle it right?
> >
> > Yeah, it's better to check for on_dl_rq():
> >
> > [PATCH]sched/dl: 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()). So, we delete
> > rq->curr check.
> >
> > We shouldn't do balancing if deadline task is throttled too.
> >
> > Also delete "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).
> >
>
> So, I agree that calling switched_to_dl() makes little sense,
> but don't we have to deal with updates to not running tasks as
> in rt.c? Something like this maybe?

Looks good. No objections from me.

>
> From 75ee75a5fd76526baaed3ba8a58f3ff7daa89cd6 Mon Sep 17 00:00:00 2001
> From: Juri Lelli <juri.lelli@arm.com>
> Date: Tue, 21 Oct 2014 17:15:15 +0100
> Subject: [PATCH] sched/deadline: cleanup prio_changed_dl()
>
> ---
> 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 28d6088..1e62e31 100644
> --- a/kernel/sched/deadline.c
> +++ b/kernel/sched/deadline.c
> @@ -1661,7 +1661,10 @@ 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
> @@ -1688,8 +1691,15 @@ 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 = {