linux-kernel - Re: [PATCH 8/8] locking/atomics: Use read-write instrumentation for atomic RMWs

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Message-ID: <CANpmjNNXXMXMBOqJqQTkDDoavggDVktNL6AZn-hLMbEPYzZ_0w@mail.gmail.com>
Date:   Fri, 14 Aug 2020 13:59:08 +0200
From:   Marco Elver <elver@...gle.com>
To:     Mark Rutland <mark.rutland@....com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        "Paul E. McKenney" <paulmck@...nel.org>,
        Will Deacon <will@...nel.org>, Arnd Bergmann <arnd@...db.de>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Alexander Potapenko <glider@...gle.com>,
        kasan-dev <kasan-dev@...glegroups.com>,
        LKML <linux-kernel@...r.kernel.org>,
        linux-arch <linux-arch@...r.kernel.org>
Subject: Re: [PATCH 8/8] locking/atomics: Use read-write instrumentation for
 atomic RMWs

On Fri, 14 Aug 2020 at 13:31, Mark Rutland <mark.rutland@....com> wrote:
> On Fri, Aug 14, 2020 at 12:28:26PM +0100, Mark Rutland wrote:
> > Hi,
> >
> > Sorry to come to this rather late -- this comment equally applies to v2
> > so I'm replying here to have context.
>
> ... and now I see that was already applied, so please ignore this!

Thank you for the comment anyway. If this is something urgent, we
could send a separate patch to change.

My argument in favour of keeping it as-is was that the alternative
would throw away the "type" and we no longer recognize a difference
between arguments (in fairness, currently not important though). If,
say, we get an RMW that has a constant argument though, the current
version would do the "right thing" as far as I can tell. Maybe I'm
overly conservative here, but it saves us worrying about some future
use-case breaking this more than before.

Thanks,
-- Marco