linux-kernel - Re: [RFC v3 2/6] Improve the tracking of active utilisation

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Message-ID: <20161118184957.GV3117@twins.programming.kicks-ass.net>
Date:   Fri, 18 Nov 2016 19:49:57 +0100
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>,
        Claudio Scordino <claudio@...dence.eu.com>,
        Steven Rostedt <rostedt@...dmis.org>
Subject: Re: [RFC v3 2/6] Improve the tracking of active utilisation

On Fri, Nov 18, 2016 at 05:06:50PM +0100, luca abeni wrote:
> 
> > Also, what happens when hrtimer_try_to_cancel() fails?
> 
> This is something I am working on... My original idea was that nothing
> bad happens, because the timer handler will see the task as RUNNING and
> will not decrease the running bw... But this is wrong.
> My new idea is to add a "dl_contending" flag in the scheduling entity,
> that indicates if the running bw has already been subtracted or not.
> With this, the issue should be solved (if anyone sees additional
> issues, or a better solution that does not require an additional flag,
> let me know).

Right. My suggestion would be to make it obvious, use that flag if
that's what it takes. We can always try and be clever later.