linux-kernel - Re: [RFC][PATCH] sched: SCHED

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Date:	Mon, 15 Oct 2007 15:26:42 +0200
From:	"Dmitry Adamushko" <dmitry.adamushko@...il.com>
To:	"Peter Zijlstra" <a.p.zijlstra@...llo.nl>
Cc:	linux-kernel <linux-kernel@...r.kernel.org>,
	"Ingo Molnar" <mingo@...e.hu>,
	"Thomas Gleixner" <tglx@...utronix.de>,
	"Mike Galbraith" <efault@....de>,
	"Lennart Poettering" <mztabzr@...inter.de>
Subject: Re: [RFC][PATCH] sched: SCHED_FIFO watchdog timer

On 14/10/2007, Peter Zijlstra <a.p.zijlstra@...llo.nl> wrote:
> The below patch is an idea proposed by tglx and depends on sched-devel +
> the hrtick patch previously posted.
>
> The current watchdog action is to demote the task to SCHED_NORMAL,
> however it might be wanted to deliver a signal instead (or have more per
> task configuration state). Which is why I added Lennart to the CC list
> as I gathered he would like something like this for PulseAudio.
>
> ---
> Subject: sched: SCHED_FIFO watchdog timer

Why only SHCED_FIFO and not SCHED_RR?
Their (mis)behavior is similar wrt SCHED_NORMAL tasks.


> +#ifdef CONFIG_SCHED_HRT_TICK
> +static int fifo_watchdog(struct rq *rq, struct task_struct *p, int queued)
> +{
> +       if (likely(!queued || p->policy != SCHED_FIFO))
> +               return 0;
> +
> +       /*
> +        * task has been naughty, turn into SCHED_NORMAL
> +        */
> +       printk(KERN_INFO "SCHED_FIFO task %s/%d exceeded his runtime quota,"
> +                       " demoting to regular task\n", p->comm, task_pid_nr(p));
> +       deactivate_task(rq, p, 0);
> +       __setscheduler(rq, p, SCHED_NORMAL, 0);
> +       activate_task(rq, p, 0);
> +       resched_task(p);

I guess, put_prev_task() / set_curr_task() should be called (for the
case of task_running(p)) to make it group-scheduler-friendly (as it's
done e.g. in sched_setscheduler()).

(normilize_task() should probably do the same)


-- 
Best regards,
Dmitry Adamushko
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