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

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Date:	Fri, 19 Sep 2014 13:44:30 +0200
From:	Daniel Wagner <daniel.wagner@...-carit.de>
To:	Juri Lelli <juri.lelli@....com>, <peterz@...radead.org>
CC:	<mingo@...hat.com>, <juri.lelli@...il.com>, <raistlin@...ux.it>,
	<michael@...rulasolutions.com>, <fchecconi@...il.com>,
	<vincent@...out.info>, <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

Hi,

On 09/19/2014 11:22 AM, Juri Lelli wrote:
> 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.
> 
> Reported-by: Daniele Alessandrelli <daniele.alessandrelli@...il.com>
> Reported-by: Daniel Wagner <daniel.wagner@...-carit.de>

Tested-by: Daniel Wagner <daniel.wagner@...-carit.de>

Fixes my problem.

Thanks,
Daniel
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