linux-kernel - Re: [PATCH] sched: ensure a task has a non-normalized vruntime when returning back to cfs

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Message-ID: <20150810121407.GB16853@twins.programming.kicks-ass.net>
Date:	Mon, 10 Aug 2015 14:14:07 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	byungchul.park@....com
Cc:	mingo@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] sched: ensure a task has a non-normalized vruntime when
 returning back to cfs

On Mon, Aug 10, 2015 at 06:02:55PM +0900, byungchul.park@....com wrote:
> From: Byungchul Park <byungchul.park@....com>
> 
> current code ensures a task has a normalized vruntime when switching off
> from fair class, but it does not ensure the task has a non-normalized
> vruntime when switching back to the fair class.
> 
> this is an example breaking this consistency.
> 
> 1. a task is in fair class and !queue
> 2. change its class to rt class (still !queue)
> 3. change its class to fair class again (stll !queue)

Just curious, did you manage to trigger this in practise or did you find
it through code inspection only?
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