linux-kernel - Re: [PATCH 03/14] sched: SCHED_DEADLINE structures & implementation.

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Message-ID: <20131014113301.GD3081@twins.programming.kicks-ass.net>
Date:	Mon, 14 Oct 2013 13:33:01 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Juri Lelli <juri.lelli@...il.com>
Cc:	tglx@...utronix.de, mingo@...hat.com, rostedt@...dmis.org,
	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@...il.com, liming.wang@...driver.com, jkacur@...hat.com,
	harald.gustafsson@...csson.com, vincent.guittot@...aro.org,
	bruce.ashfield@...driver.com--no-chain-reply-to
Subject: Re: [PATCH 03/14] sched: SCHED_DEADLINE structures & implementation.

On Mon, Oct 14, 2013 at 12:43:35PM +0200, Juri Lelli wrote:
> +static void replenish_dl_entity(struct sched_dl_entity *dl_se)
> +{
> +	struct dl_rq *dl_rq = dl_rq_of_se(dl_se);
> +	struct rq *rq = rq_of_dl_rq(dl_rq);
> +
> +	/*
> +	 * We keep moving the deadline away until we get some
> +	 * available runtime for the entity. This ensures correct
> +	 * handling of situations where the runtime overrun is
> +	 * arbitrary large.
> +	 */
> +	while (dl_se->runtime <= 0) {
> +		dl_se->deadline += dl_se->dl_deadline;
> +		dl_se->runtime += dl_se->dl_runtime;
> +	}

Are we sure GCC won't be 'smart' and bite us; that is do we need
something like:

  asm("" : "+rm" (dl_se->runtime));

in there? See:

0d98bb2656e9 sched: Prevent compiler from optimising the sched_avg_update() loop

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