linux-kernel - Re: [PATCH 2/4] base/drivers/arch_topology: Replace mutex with READ_ONCE / WRITE

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Message-ID: <CAOh2x=my6pusOOgKNhk4O3iE3TaTLjeZ6q86MdH4q10BB6dnEg@mail.gmail.com>
Date:   Tue, 30 Oct 2018 11:27:38 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     Daniel Lezcano <daniel.lezcano@...aro.org>
Cc:     "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        kstewart@...uxfoundation.org, Juri Lelli <juri.lelli@....com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH 2/4] base/drivers/arch_topology: Replace mutex with
 READ_ONCE / WRITE_ONCE

On Mon, Oct 29, 2018 at 9:54 PM Daniel Lezcano
<daniel.lezcano@...aro.org> wrote:
>
> The mutex protects a per_cpu variable access. The potential race can
> happen only when the cpufreq governor module is loaded and at the same
> time the cpu capacity is changed in the sysfs.
>
> There is no real interest of using a mutex to protect a variable
> assignation when there is no situation where a task can take the lock
> and block.
>
> Replace the mutex by READ_ONCE / WRITE_ONCE.
>
> Signed-off-by: Daniel Lezcano <daniel.lezcano@...aro.org>
> ---
>  drivers/base/arch_topology.c  | 7 +------
>  include/linux/arch_topology.h | 2 +-
>  2 files changed, 2 insertions(+), 7 deletions(-)

Reviewed-by: Viresh Kumar <viresh.kumar@...aro.org>