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

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Date:   Sun, 20 Jun 2021 00:30:32 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Mark Rutland <mark.rutland@....com>, linux-kernel@...r.kernel.org
Cc:     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,
        mark.rutland@....com, 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 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.

Other than that.

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