linux-kernel - Re: [PATCH] locking/atomic: Add acquire and release fence for atomic(64)

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Message-ID: <20231124163220.GU3818@noisy.programming.kicks-ass.net>
Date:   Fri, 24 Nov 2023 17:32:20 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     guoren@...nel.org
Cc:     mark.rutland@....com, keescook@...omium.org, paulmck@...nel.org,
        ubizjak@...il.com, tglx@...utronix.de,
        linux-kernel@...r.kernel.org, Guo Ren <guoren@...ux.alibaba.com>
Subject: Re: [PATCH] locking/atomic: Add acquire and release fence for
 atomic(64)_read(set)

On Fri, Nov 24, 2023 at 11:25:08AM -0500, guoren@...nel.org wrote:
> From: Guo Ren <guoren@...ux.alibaba.com>
> 
> The definitions of atomic(64)_read(set) are relax version, so
> add acquire and release fence for them.
> 
> Signed-off-by: Guo Ren <guoren@...ux.alibaba.com>
> Signed-off-by: Guo Ren <guoren@...nel.org>
> ---

You lost the script change?

>  include/linux/atomic/atomic-arch-fallback.h | 14 +++++++++++---
>  1 file changed, 11 insertions(+), 3 deletions(-)
> 
> diff --git a/include/linux/atomic/atomic-arch-fallback.h b/include/linux/atomic/atomic-arch-fallback.h
> index 18f5744dfb5d..9775900eeefd 100644
> --- a/include/linux/atomic/atomic-arch-fallback.h
> +++ b/include/linux/atomic/atomic-arch-fallback.h
> @@ -460,7 +460,10 @@ raw_atomic_read_acquire(const atomic_t *v)
>  #if defined(arch_atomic_read_acquire)
>  	return arch_atomic_read_acquire(v);
>  #elif defined(arch_atomic_read)
> -	return arch_atomic_read(v);
> +	int ret;
> +	ret = arch_atomic_read(v);
> +	__atomic_acquire_fence();
> +	return ret;
>  #else
>  	int ret;
>  
> @@ -509,6 +512,7 @@ raw_atomic_set_release(atomic_t *v, int i)
>  #if defined(arch_atomic_set_release)
>  	arch_atomic_set_release(v, i);
>  #elif defined(arch_atomic_set)
> +	__atomic_release_fence();
>  	arch_atomic_set(v, i);
>  #else
>  	if (__native_word(atomic_t)) {
> @@ -2576,7 +2580,10 @@ raw_atomic64_read_acquire(const atomic64_t *v)
>  #if defined(arch_atomic64_read_acquire)
>  	return arch_atomic64_read_acquire(v);
>  #elif defined(arch_atomic64_read)
> -	return arch_atomic64_read(v);
> +	s64 ret;
> +	ret = arch_atomic64_read(v);
> +	__atomic_acquire_fence();
> +	return ret;
>  #else
>  	s64 ret;
>  
> @@ -2625,6 +2632,7 @@ raw_atomic64_set_release(atomic64_t *v, s64 i)
>  #if defined(arch_atomic64_set_release)
>  	arch_atomic64_set_release(v, i);
>  #elif defined(arch_atomic64_set)
> +	__atomic_release_fence();
>  	arch_atomic64_set(v, i);
>  #else
>  	if (__native_word(atomic64_t)) {
> @@ -4657,4 +4665,4 @@ raw_atomic64_dec_if_positive(atomic64_t *v)
>  }
>  
>  #endif /* _LINUX_ATOMIC_FALLBACK_H */
> -// 202b45c7db600ce36198eb1f1fc2c2d5268ace2d
> +// 3135f55051cf62b76664e528bf04337c44a14e72
> -- 
> 2.36.1
>