linux-kernel - Re: [RFC PATCH v1 0/2] Deduplicating RISCV cmpxchg.h macros

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Date:   Thu, 6 Apr 2023 19:19:43 +0200
From:   Andrea Parri <parri.andrea@...il.com>
To:     Leonardo Bras <leobras@...hat.com>
Cc:     Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>, Guo Ren <guoren@...nel.org>,
        Conor Dooley <conor.dooley@...rochip.com>,
        linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH v1 0/2] Deduplicating RISCV cmpxchg.h macros

On Thu, Apr 06, 2023 at 05:20:17AM -0300, Leonardo Bras wrote:
> While studying riscv's cmpxchg.h file, I got really interested in
> understanding how RISCV asm implemented the different versions of
> {cmp,}xchg.
> 
> When I understood the pattern, it made sense for me to remove the
> duplications and create macros to make it easier to understand what exactly
> changes between the versions: Instruction sufixes & barriers.
> 
> Thanks!
> Leo
> 
> Changes since RFCv3:
> - Squashed the 6 original patches in 2: one for cmpxchg and one for xchg
> https://lore.kernel.org/all/20230404163741.2762165-1-leobras@redhat.com/
> 
> Changes since RFCv2:
> - Fixed  macros that depend on having a local variable with a magic name
> - Previous cast to (long) is now only applied on 4-bytes cmpxchg
> https://lore.kernel.org/all/20230321074249.2221674-1-leobras@redhat.com/
> 
> Changes since RFCv1:
> - Fixed patch 4/6 suffix from 'w.aqrl' to '.w.aqrl', to avoid build error
> https://lore.kernel.org/all/20230318080059.1109286-1-leobras@redhat.com/
> 
> Leonardo Bras (2):
>   riscv/cmpxchg: Deduplicate cmpxchg() asm and macros
>   riscv/cmpxchg: Deduplicate xchg() asm functions
> 
>  arch/riscv/include/asm/cmpxchg.h | 319 +++++++------------------------
>  1 file changed, 67 insertions(+), 252 deletions(-)

LGTM.  AFAICT, this would need to be rebased, cf. e.g.

  a8596dda1fbf7e ("arch: rename all internal names __xchg to __arch_xchg")

from the tip tree.

  Andrea