linux-kernel - Re: [PATCH] nohz: Fix collision between tick and other hrtimers

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Message-ID: <1482721017.11006.83.camel@redhat.com>
Date:   Sun, 25 Dec 2016 21:56:57 -0500
From:   Rik van Riel <riel@...hat.com>
To:     Frederic Weisbecker <fweisbec@...il.com>,
        Thomas Gleixner <tglx@...utronix.de>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        James Hartsock <hartsjc@...hat.com>,
        Ingo Molnar <mingo@...nel.org>
Subject: Re: [PATCH] nohz: Fix collision between tick and other hrtimers

On Sat, 2016-12-24 at 17:15 +0100, Frederic Weisbecker wrote:
> When the tick is stopped and an interrupt occurs afterward, we check
> on
> that interrupt exit if the next tick needs to be rescheduled. If it
> doesn't need any update, we don't want to do anything.
> 
> In order to check if the tick needs an update, we compare it against
> the
> clockevent device deadline. Now that's a problem because the
> clockevent
> device is at a lower level than the tick itself if it is implemented
> on top of hrtimer.

Ohhhhh, good find. That is one subtle bug.

Acked-by: Rik van Riel <riel@...hat.com>

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