linux-kernel - Re: [PATCH 1/3] sched/deadline: clear dl_entity params when setscheduling to different class

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Date:	Mon, 22 Sep 2014 14:50:33 -0400
From:	Vincent Legout <vincent@...out.info>
To:	Juri Lelli <juri.lelli@....com>
Cc:	peterz@...radead.org, mingo@...hat.com, juri.lelli@...il.com,
	raistlin@...ux.it, michael@...rulasolutions.com,
	fchecconi@...il.com, daniel.wagner@...-carit.de,
	luca.abeni@...tn.it, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] sched/deadline: clear dl_entity params when setscheduling to different class

Hello,

Juri Lelli <juri.lelli@....com> writes:

> When a task is using SCHED_DEADLINE and the user setschedules it to a different
> class its sched_dl_entity static parameters are not cleaned up. This causes a
> bug if the user sets it back to SCHED_DEADLINE with the same parameters again.
> The problem resides in the check we perform at the very beginning of
> dl_overflow():
>
> 	if (new_bw == p->dl.dl_bw)
> 		return 0;
>
> This condition is met in the case depicted above, so the function returns and
> dl_b->total_bw is not updated (the p->dl.dl_bw is not added to it). After this,
> admission control is broken.
>
> This patch fixes the thing, properly clearing static parameters for a task
> that ceases to use SCHED_DEADLINE.

Thanks, this fixes the issue I had:

Tested-by: Vincent Legout <vincent@...out.info>

Thanks,
Vincent
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