linux-kernel - Re: [RFC v2 4/7] Fix the update of the total -deadline utilization

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Message-ID: <20160405125859.GY3430@twins.programming.kicks-ass.net>
Date:	Tue, 5 Apr 2016 14:58:59 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Luca Abeni <luca.abeni@...tn.it>
Cc:	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...hat.com>,
	Juri Lelli <juri.lelli@....com>
Subject: Re: [RFC v2 4/7] Fix the update of the total -deadline utilization

On Fri, Apr 01, 2016 at 05:12:30PM +0200, Luca Abeni wrote:
> +		/*
> +		 * XXX this is slightly incorrect: when the task
> +		 * utilization decreases, we should delay the total
> +		 * utilization change until the task's 0-lag point.
> +		 * But this would require to set the task's "inactive
> +		 * timer" when the task is not inactive.
> +		 */

Could you quickly remind me why this is a problem? The timeline does
continue running right? So even if the task isn't active now, it will
still reach its 0-lag point.

>  		__dl_clear(dl_b, p->dl.dl_bw);
>  		__dl_add(dl_b, new_bw);
>  		err = 0;