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 13:43:24 +0100
From:	Juri Lelli <juri.lelli@....com>
To:	Daniel Wagner <daniel.wagner@...-carit.de>,
	"peterz@...radead.org" <peterz@...radead.org>
CC:	"mingo@...hat.com" <mingo@...hat.com>,
	"juri.lelli@...il.com" <juri.lelli@...il.com>,
	"raistlin@...ux.it" <raistlin@...ux.it>,
	"michael@...rulasolutions.com" <michael@...rulasolutions.com>,
	"fchecconi@...il.com" <fchecconi@...il.com>,
	"vincent@...out.info" <vincent@...out.info>,
	"luca.abeni@...tn.it" <luca.abeni@...tn.it>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/3] sched/deadline: clear dl_entity params when setscheduling
 to different class

Hi Daniel,

On 19/09/14 12:44, Daniel Wagner wrote:
> 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.
> 

Great! Thanks for testing it.

Best,

- Juri

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