linux-kernel - Re: [PATCH 05/16] sched: SCHED_DEADLINE policy implementation.

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Date:	Mon, 23 Apr 2012 13:34:09 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Juri Lelli <juri.lelli@...il.com>
Cc:	tglx@...utronix.de, mingo@...hat.com, rostedt@...dmis.org,
	cfriesen@...tel.com, oleg@...hat.com, fweisbec@...il.com,
	darren@...art.com, johan.eker@...csson.com, p.faure@...tech.ch,
	linux-kernel@...r.kernel.org, claudio@...dence.eu.com,
	michael@...rulasolutions.com, fchecconi@...il.com,
	tommaso.cucinotta@...up.it, nicola.manica@...i.unitn.it,
	luca.abeni@...tn.it, dhaval.giani@...il.com, hgu1972@...il.com,
	paulmck@...ux.vnet.ibm.com, raistlin@...ux.it,
	insop.song@...csson.com, liming.wang@...driver.com
Subject: Re: [PATCH 05/16] sched: SCHED_DEADLINE policy implementation.

On Fri, 2012-04-06 at 09:14 +0200, Juri Lelli wrote:
> +       /*
> +        * At this point, the deadline really should be "in
> +        * the future" with respect to rq->clock. If it's
> +        * not, we are, for some reason, lagging too much!
> +        * Anyway, after having warn userspace abut that,
> +        * we still try to keep the things running by
> +        * resetting the deadline and the budget of the
> +        * entity.
> +        */
> +       if (dl_time_before(dl_se->deadline, rq->clock)) {
> +               WARN_ON_ONCE(1);

Doing printk() and friends from scheduler context isn't actually safe
and can lock up your machine.. there's a printk_sched() that
maybe-sorta-kinda can get your complaints out..

> +               dl_se->deadline = rq->clock + dl_se->dl_deadline;
> +               dl_se->runtime = dl_se->dl_runtime;
> +       } 
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