linux-kernel - Re: [RFC 0/12][PATCH] SCHED_DEADLINE: core of the scheduling class

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Message-ID: <1262089538.7135.139.camel@laptop>
Date:	Tue, 29 Dec 2009 13:25:38 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Raistlin <raistlin@...ux.it>
Cc:	linux-kernel <linux-kernel@...r.kernel.org>,
	michael trimarchi <michael@...dence.eu.com>,
	Fabio Checconi <fabio@...dalf.sssup.it>,
	Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>,
	Dhaval Giani <dhaval.giani@...il.com>,
	Johan Eker <johan.eker@...csson.com>,
	"p.faure" <p.faure@...tech.ch>,
	Chris Friesen <cfriesen@...tel.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Henrik Austad <henrik@...tad.us>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Darren Hart <darren@...art.com>,
	Sven-Thorsten Dietrich <sven@...bigcorporation.com>,
	Bjoern Brandenburg <bbb@...unc.edu>,
	Tommaso Cucinotta <tommaso.cucinotta@...up.it>,
	"giuseppe.lipari" <giuseppe.lipari@...up.it>,
	Juri Lelli <juri.lelli@...il.com>
Subject: Re: [RFC 0/12][PATCH] SCHED_DEADLINE: core of the scheduling class

On Fri, 2009-10-16 at 17:40 +0200, Raistlin wrote:
> @@ -5966,10 +5982,14 @@ void rt_mutex_setprio(struct task_struct *p, int prio)
>         if (running)
>                 p->sched_class->put_prev_task(rq, p);
>  
> -       if (rt_prio(prio))
> -               p->sched_class = &rt_sched_class;
> -       else
> -               p->sched_class = &fair_sched_class;
> +       if (deadline_task(p))
> +               p->sched_class = &deadline_sched_class;
> +       else {
> +               if (rt_prio(prio))
> +                       p->sched_class = &rt_sched_class;
> +               else
> +                       p->sched_class = &fair_sched_class;
> +       } 

This looks wrong.

This is PI code, so the effective class should be determined based on
the 'priority' not on the 'policy'.

I understand we don't yet have deadline inheritance like things in
place, but this would be where we should make use of the simple ceiling
protocol to boost things for now.


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