linux-kernel - Re: [patch 1/3] timekeeping: Annotate ktime_get_boot_fast_ns() with data

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Message-ID: <87pmli9g0s.ffs@tglx>
Date:   Fri, 15 Apr 2022 23:46:11 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        John Stultz <john.stultz@...aro.org>,
        Stephen Boyd <sboyd@...nel.org>
Subject: Re: [patch 1/3] timekeeping: Annotate ktime_get_boot_fast_ns() with
 data_race()

On Fri, Apr 15 2022 at 14:07, Peter Zijlstra wrote:
> On Fri, Apr 15, 2022 at 11:19:35AM +0200, Thomas Gleixner wrote:
>> Accessing timekeeper::offset_boot in ktime_get_boot_fast_ns() is an
>> intended data race as the reader side cannot synchronize with a writer and
>> there is no space in struct tk_read_base of the NMI safe timekeeper.
>> 
>> Mark it so.
>
> If offs_boot actually ever changed?

Yes, during resume to compensate for the time spent in suspend. So, yes
the data_race() is more of documentary value.

Thanks,

        tglx