linux-kernel - Re: [PATCH 00/33] locking/atomic: convert all architectures to ARCH

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Message-ID: <20210511092701.GB6152@C02TD0UTHF1T.local>
Date:   Tue, 11 May 2021 10:27:01 +0100
From:   Mark Rutland <mark.rutland@....com>
To:     Arnd Bergmann <arnd@...db.de>,
        Peter Zijlstra <peterz@...radead.org>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Will Deacon <will@...nel.org>,
        Boqun Feng <boqun.feng@...il.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Brian Cain <bcain@...eaurora.org>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Chris Zankel <chris@...kel.net>, Rich Felker <dalias@...c.org>,
        David Miller <davem@...emloft.net>,
        Vincent Chen <deanbo422@...il.com>,
        Helge Deller <deller@....de>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Greentime Hu <green.hu@...il.com>, Guo Ren <guoren@...nel.org>,
        Ivan Kokshaysky <ink@...assic.park.msu.ru>,
        James Bottomley <James.Bottomley@...senpartnership.com>,
        Max Filippov <jcmvbkbc@...il.com>,
        Jonas Bonn <jonas@...thpole.se>,
        Ley Foon Tan <ley.foon.tan@...el.com>,
        Russell King - ARM Linux <linux@...linux.org.uk>,
        Matt Turner <mattst88@...il.com>,
        Michal Simek <monstr@...str.eu>,
        Michael Ellerman <mpe@...erman.id.au>,
        Nick Hu <nickhu@...estech.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Paul Mackerras <paulus@...ba.org>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Richard Henderson <rth@...ddle.net>,
        Stafford Horne <shorne@...il.com>,
        Stefan Kristiansson <stefan.kristiansson@...nalahti.fi>,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        Vineet Gupta <vgupta@...opsys.com>,
        Yoshinori Sato <ysato@...rs.sourceforge.jp>
Subject: Re: [PATCH 00/33] locking/atomic: convert all architectures to
 ARCH_ATOMIC

On Mon, May 10, 2021 at 04:56:03PM +0200, Arnd Bergmann wrote:
> On Mon, May 10, 2021 at 11:39 AM Mark Rutland <mark.rutland@....com> wrote:
> >
> > This series (based on v5.13-rc1) converts all architectures to
> > ARCH_ATOMIC. This will allow the use of instrumented atomics on all
> > architectures (e.g. for KASAN and similar), and simplifies the core
> > atomic code (which should allow for easier rework of the fallbacks and
> > other bits in future).
> >
> > The series is split into three parts:
> >
> > 1) Some preparatory work is done to prepare architectures and common
> >    code for the conversion. In this phase h8300 and microblaze are
> >    converted to use the asm-generic atomics exclusively, and the
> >    asm-generic implementations are made to function with or without
> >    ARCH_ATOMIC.
> >
> > 2) Architectures are converted one-by-one to use the ARCH_ATOMIC
> >    interface. I've converted each architecture with its own patch (even
> >    where the conversion is trivial) to make review and bisection easier.
> >
> > 3) The code handling !ARCH_ATOMIC is removed.
> >
> > Note: I've generated the patches with:
> >
> >   git format-patch -C -M -D
> >
> > ... so the preimage of include/linux/atomic-fallback.h is not included
> > in the diff when it is deleted.
> >
> > The series can also be found in my atomics/arch-atomic branch on
> > kernel.org:
> >
> >   https://git.kernel.org/pub/scm/linux/kernel/git/mark/linux.git/log/?h=atomics/arch-atomic
> >   git://git.kernel.org/pub/scm/linux/kernel/git/mark/linux.git atomics/arch-atomic
> 
> Nice work!
> 
> I had recently tried experimented with cleanups around cmpxchg(),
> adding fixed-length
> versions of that which can be used to implement the atomics with less bloated
> preprocessor output. My patches will clearly conflict with your
> series, but it seems
> that we should do yours first in any case.

Ah; sorry for stepping on your toes with this. Simplifying the
xchg/cmpxchg glue sounds like a nice cleanup too!

> I'm happy to put this into the asm-generic tree once you have
> collected enough Acks.

Great! Going via asm-generic sounds good to me. The kbuild test robot
has found a few issues, so I'll probably have a v2 with those fixed and
some acks accumulated.

Peter, does that make sense to you, or did you have reasons to want this
to go via tip?

Thanks,
Mark.