linux-kernel - Re: [PATCH v2] sched/pelt: fix false running accounting

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Message-ID: <20170704110722.jjne2fio5f4gtnwm@hirez.programming.kicks-ass.net>
Date:   Tue, 4 Jul 2017 13:07:22 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Vincent Guittot <vincent.guittot@...aro.org>
Cc:     Ingo Molnar <mingo@...nel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Morten Rasmussen <Morten.Rasmussen@....com>
Subject: Re: [PATCH v2] sched/pelt: fix false running accounting

On Tue, Jul 04, 2017 at 11:57:12AM +0200, Vincent Guittot wrote:
> On 4 July 2017 at 11:44, Peter Zijlstra <peterz@...radead.org> wrote:

> > But but but, how can that happen? Should it not all be under the same
> > rq->lock and thus have only a single update_rq_clock() and thus be at
> > the same 'instant' ?
> 
> idle_balance() unlock rq->lock before calling  update_blocked_averages
> And update_blocked_averages() starts by calling update_rq_clock()

Ah indeed. Might want to clarify that point.