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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <1335194148.28150.175.camel@twins>
Date:	Mon, 23 Apr 2012 17:15:48 +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:
> +static
> +int dl_runtime_exceeded(struct rq *rq, struct sched_dl_entity *dl_se)
> +{
> +       int dmiss = dl_time_before(dl_se->deadline, rq->clock);
> +       int rorun = dl_se->runtime <= 0;
>+
> +       if (!rorun && !dmiss)
> +               return 0;
> +
> +       /*
> +        * If we are beyond our current deadline and we are still
> +        * executing, then we have already used some of the runtime of
> +        * the next instance. Thus, if we do not account that, we are
> +        * stealing bandwidth from the system at each deadline miss!
> +        */
> +       if (dmiss) {
> +               dl_se->runtime = rorun ? dl_se->runtime : 0;
> +               dl_se->runtime -= rq->clock - dl_se->deadline;
> +       }

So ideally this can't happen, but since we already leak time from the
system through means of hardirq / kstop / context-switch-overhead /
clock-jitter etc.. we avoid the error accumulating?

> +
> +       return 1;
> +} 


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/