linux-kernel - Re: [PATCH 1/3] asm-generic/atomic64: Add support for ARCH

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Date:   Wed, 11 Nov 2020 14:44:12 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Christophe Leroy <christophe.leroy@...roup.eu>
Cc:     Nicholas Piggin <npiggin@...il.com>, linuxppc-dev@...ts.ozlabs.org,
        Will Deacon <will@...nel.org>,
        Boqun Feng <boqun.feng@...il.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Arnd Bergmann <arnd@...db.de>,
        Christophe Leroy <christophe.leroy@....fr>,
        Alexey Kardashevskiy <aik@...abs.ru>,
        linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org
Subject: Re: [PATCH 1/3] asm-generic/atomic64: Add support for ARCH_ATOMIC

On Wed, Nov 11, 2020 at 02:39:01PM +0100, Christophe Leroy wrote:
> Hello,
> 
> Le 11/11/2020 à 12:07, Nicholas Piggin a écrit :
> > This passes atomic64 selftest on ppc32 on qemu (uniprocessor only)
> > both before and after powerpc is converted to use ARCH_ATOMIC.
> 
> Can you explain what this change does and why it is needed ?

That certainly should've been in the Changelog. This enables atomic
instrumentation, see asm-generic/atomic-instrumented.h. IOW, it makes
atomic ops visible to K*SAN.