linux-kernel - Re: [PATCH linux-next] mark access to tick_do_timer_cpu with READ_ONCE/WRITE

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Message-ID: <87tu0xiguq.ffs@tglx>
Date:   Wed, 11 Jan 2023 10:02:37 +0100
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Frederic Weisbecker <frederic@...nel.org>,
        Zhouyi Zhou <zhouzhouyi@...il.com>
Cc:     fweisbec@...il.com, mingo@...nel.org, paulmck@...nel.org,
        rcu@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH linux-next] mark access to tick_do_timer_cpu with
 READ_ONCE/WRITE_ONCE

On Mon, Jan 09 2023 at 13:51, Frederic Weisbecker wrote:
> On Mon, Dec 19, 2022 at 01:21:28PM +0800, Zhouyi Zhou wrote:
>> fix above bug by marking access to tick_do_timer_cpu with READ_ONCE/WRITE_ONCE
>
> This has been discussed before with passion:
>
> http://archive.lwn.net:8080/linux-kernel/1C65422C-FFA4-4651-893B-300FAF9C49DE@....pw/T/
>
> To me data_race() would be more appropriate but that would need a changelog with
> proper analysis of the tick_do_timer_cpu state machine.

Proper analysis and comments in the code are required independent of
READ/WRITE_ONCE() or data_race().

Thanks,

        tglx