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Date: Thu, 7 Jun 2018 10:32:29 +0200
From: Peter Zijlstra <peterz@infradead.org>
To: Daniel Lezcano <daniel.lezcano@linaro.org>
Cc: rjw@rjwysocki.net, linux-kernel@vger.kernel.org,
        Viresh Kumar <viresh.kumar@linaro.org>,
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        "open list:POWER MANAGEMENT CORE" <linux-pm@vger.kernel.org>
Subject: Re: [PATCH V5] powercap/drivers/idle_injection: Add an idle
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On Thu, Jun 07, 2018 at 10:18:27AM +0200, Daniel Lezcano wrote:
> So IIUC, neither atomic or WRITE|READ_ONCE are necessary in this code
> because of the wake_up_process() barrier is enough, right ?

I didn't look hard enough; if there ever is a time where the loads and
stores happen concurrently, you need READ/WRITE_ONCE(). If there is no
concurrency on the variables, you don't need anything.

Neither atomic_read/set() nor REAd/WRITE_ONCE() will help with ordering,
which is what the wake_up_process() would provide here, different things
entirely.