linux-kernel - Re: [PATCH 27/33] locking/atomic: powerpc: move to ARCH

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Message-ID: <20210511095737.GC6152@C02TD0UTHF1T.local>
Date:   Tue, 11 May 2021 10:57:37 +0100
From:   Mark Rutland <mark.rutland@....com>
To:     linux-kernel@...r.kernel.org, will@...nel.org,
        boqun.feng@...il.com, peterz@...radead.org
Cc:     aou@...s.berkeley.edu, arnd@...db.de, bcain@...eaurora.org,
        benh@...nel.crashing.org, chris@...kel.net, dalias@...c.org,
        davem@...emloft.net, deanbo422@...il.com, deller@....de,
        geert@...ux-m68k.org, green.hu@...il.com, guoren@...nel.org,
        ink@...assic.park.msu.ru, James.Bottomley@...senPartnership.com,
        jcmvbkbc@...il.com, jonas@...thpole.se, ley.foon.tan@...el.com,
        linux@...linux.org.uk, mattst88@...il.com, monstr@...str.eu,
        mpe@...erman.id.au, nickhu@...estech.com, palmer@...belt.com,
        paulus@...ba.org, paul.walmsley@...ive.com, rth@...ddle.net,
        shorne@...il.com, stefan.kristiansson@...nalahti.fi,
        tsbogend@...ha.franken.de, vgupta@...opsys.com,
        ysato@...rs.sourceforge.jp
Subject: Re: [PATCH 27/33] locking/atomic: powerpc: move to ARCH_ATOMIC

On Tue, May 11, 2021 at 10:16:21AM +0100, Mark Rutland wrote:
> On Mon, May 10, 2021 at 10:37:47AM +0100, Mark Rutland wrote:
> > We'd like all architectures to convert to ARCH_ATOMIC, as once all
> > architectures are converted it will be possible to make significant
> > cleanups to the atomics headers, and this will make it much easier to
> > generically enable atomic functionality (e.g. debug logic in the
> > instrumented wrappers).
> > 
> > As a step towards that, this patch migrates powerpc to ARCH_ATOMIC. The
> > arch code provides arch_{atomic,atomic64,xchg,cmpxchg}*(), and common
> > code wraps these with optional instrumentation to provide the regular
> > functions.
> > 
> > Signed-off-by: Mark Rutland <mark.rutland@....com>
> > Cc: Benjamin Herrenschmidt <benh@...nel.crashing.org>
> > Cc: Boqun Feng <boqun.feng@...il.com>
> > Cc: Michael Ellerman <mpe@...erman.id.au>
> > Cc: Paul Mackerras <paulus@...ba.org>
> > Cc: Peter Zijlstra <peterz@...radead.org>
> > Cc: Will Deacon <will@...nel.org>
> > ---
> >  arch/powerpc/Kconfig               |   1 +
> >  arch/powerpc/include/asm/atomic.h  | 140 +++++++++++++++++++------------------
> >  arch/powerpc/include/asm/cmpxchg.h |  30 ++++----
> >  3 files changed, 89 insertions(+), 82 deletions(-)
> 
> The kbuild test robot spotted a couple of bits I'd got wrong; I've noted
> those below (and both are now fixed in my kernel.org branch).
> 
> >  static __always_inline bool
> > -atomic_try_cmpxchg_lock(atomic_t *v, int *old, int new)
> > +arch_atomic_try_cmpxchg_lock(atomic_t *v, int *old, int new)
> 
> Since this isn't part of the core atomic API, and is used directly by
> powerpc's spinlock implementation, this should have stayed as-is (or we
> should use the `arch_` prefix consitently and update the spinlock code).
> 
> I've dropped the `arch_` prefix for now.

On second thought (and having hit a similar issue on m68k), I've added
the `arch_` prefix and updated the caller, to more clearly separate the
common atomic API and the arch-specific bits.

Thanks,
Mark.