linux-kernel - Re: [RFC PATCH 10/10] x86: snapshot thread flags

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Message-ID: <20210621083518.GD37068@C02TD0UTHF1T.local>
Date:   Mon, 21 Jun 2021 09:35:18 +0100
From:   Mark Rutland <mark.rutland@....com>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     linux-kernel@...r.kernel.org, benh@...nel.crashing.org,
        boqun.feng@...il.com, bp@...en8.de, catalin.marinas@....com,
        dvyukov@...gle.com, elver@...gle.com, ink@...assic.park.msu.ru,
        jonas@...thpole.se, juri.lelli@...hat.com, linux@...linux.org.uk,
        luto@...nel.org, mattst88@...il.com, mingo@...hat.com,
        monstr@...str.eu, mpe@...erman.id.au, paulmck@...nel.org,
        paulus@...ba.org, peterz@...radead.org, rth@...ddle.net,
        shorne@...il.com, stefan.kristiansson@...nalahti.fi,
        vincent.guittot@...aro.org, will@...nel.org
Subject: Re: [RFC PATCH 10/10] x86: snapshot thread flags

On Sun, Jun 20, 2021 at 12:30:32AM +0200, Thomas Gleixner wrote:
> On Wed, Jun 09 2021 at 13:20, Mark Rutland wrote:
> > Some thread flags can be set remotely, and so even when IRQs are
> > disabled, the flags can change under our feet. Generally this is
> > unlikely to cause a problem in practice, but it is somewhat unsound, and
> > KCSAN will legitimately warn that there is a data race.
> >
> > To avoid such issues, we should snapshot the flags prior to using them.
> > Let's use the new helpers to do so on x86.
> 
>  To avoid such issues, a snapshot of the flags has to be taken prior to
>  using them. Some places already use READ_ONCE() for that, others do
>  not.
> 
>  Convert them all to the new flag accessor helpers.

I'll use that wording consistently throughout the series.

> Other than that.
> 
>  Reviewed-by: Thomas Gleixner <tglx@...utronix.de>

Thanks!

Mark.