linux-kernel - Re: [PATCH v2 1/1] psi: stop relying on timer_pending for poll

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Message-ID: <YN2DsLlE+WtxK6K9@hirez.programming.kicks-ass.net>
Date:   Thu, 1 Jul 2021 10:58:24 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Suren Baghdasaryan <surenb@...gle.com>
Cc:     hannes@...xchg.org, mingo@...hat.com, juri.lelli@...hat.com,
        vincent.guittot@...aro.org, dietmar.eggemann@....com,
        rostedt@...dmis.org, bsegall@...gle.com, mgorman@...e.de,
        bristot@...hat.com, matthias.bgg@...il.com, minchan@...gle.com,
        timmurray@...gle.com, yt.chang@...iatek.com, wenju.xu@...iatek.com,
        jonathan.jmchen@...iatek.com, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org, kernel-team@...roid.com,
        SH Chen <show-hong.chen@...iatek.com>
Subject: Re: [PATCH v2 1/1] psi: stop relying on timer_pending for poll_work
 rescheduling

On Wed, Jun 30, 2021 at 01:51:51PM -0700, Suren Baghdasaryan wrote:
> +	/* cmpxchg should be called even when !force to set poll_scheduled */
> +	if (atomic_cmpxchg(&group->poll_scheduled, 0, 1) && !force)
>  		return;

Why is that a cmpxchg() ?