linux-kernel - Re: [PATCH V2 0/3] riscv: atomic: Optimize AMO instructions usage

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Date:   Wed, 13 Apr 2022 23:46:00 +0800
From:   Boqun Feng <boqun.feng@...il.com>
To:     guoren@...nel.org
Cc:     arnd@...db.de, palmer@...belt.com, mark.rutland@....com,
        will@...nel.org, peterz@...radead.org, linux-arch@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-riscv@...ts.infradead.org,
        Guo Ren <guoren@...ux.alibaba.com>,
        Andrea Parri <parri.andrea@...il.com>
Subject: Re: [PATCH V2 0/3] riscv: atomic: Optimize AMO instructions usage

[Cc Andrea]

On Tue, Apr 12, 2022 at 11:49:54AM +0800, guoren@...nel.org wrote:
> From: Guo Ren <guoren@...ux.alibaba.com>
> 
> These patch series contain one cleanup and some optimizations for
> atomic operations.
> 

Seems to me that you are basically reverting 5ce6c1f3535f
("riscv/atomic: Strengthen implementations with fences"). That commit
fixed an memory ordering issue, could you explain why the issue no
longer needs a fix?

Regards,
Boqun

> Changes in V2:
>  - Fixup LR/SC memory barrier semantic problems which pointed by
>    Rutland
>  - Combine patches into one patchset series
>  - Separate AMO optimization & LRSC optimization for convenience
>    patch review
> 
> Guo Ren (3):
>   riscv: atomic: Cleanup unnecessary definition
>   riscv: atomic: Optimize acquire and release for AMO operations
>   riscv: atomic: Optimize memory barrier semantics of LRSC-pairs
> 
>  arch/riscv/include/asm/atomic.h  | 70 ++++++++++++++++++++++++++++++--
>  arch/riscv/include/asm/cmpxchg.h | 42 +++++--------------
>  2 files changed, 76 insertions(+), 36 deletions(-)
> 
> -- 
> 2.25.1
> 

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