Re: [PATCH] atomic.h: Reword confusing comment for qatomic_cmpxchg

[Zhao Liu]

On Fri, Feb 23, 2024 at 06:20:35PM +0000, Peter Maydell wrote:
> Date: Fri, 23 Feb 2024 18:20:35 +0000
> From: Peter Maydell <peter.maydell@linaro.org>
> Subject: [PATCH] atomic.h: Reword confusing comment for qatomic_cmpxchg
> X-Mailer: git-send-email 2.34.1
> 
> The qatomic_cmpxchg() and qatomic_cmpxchg__nocheck() macros have
> a comment that reads:
>  Returns the eventual value, failed or not
> 
> This is somewhere between cryptic and wrong, since the value actually
> returned is the value that was in memory before the cmpxchg.  Reword
> to match how we describe these macros in atomics.rst.
> 
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
> ---
>  include/qemu/atomic.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)

Reviewed-by: Zhao Liu <zhao1.liu@intel.com>

> 
> diff --git a/include/qemu/atomic.h b/include/qemu/atomic.h
> index f1d3d1702a9..99110abefb3 100644
> --- a/include/qemu/atomic.h
> +++ b/include/qemu/atomic.h
> @@ -202,7 +202,7 @@
>      qatomic_xchg__nocheck(ptr, i);                          \
>  })
>  
> -/* Returns the eventual value, failed or not */
> +/* Returns the old value of '*ptr' (whether the cmpxchg failed or not) */
>  #define qatomic_cmpxchg__nocheck(ptr, old, new)    ({                   \
>      typeof_strip_qual(*ptr) _old = (old);                               \
>      (void)__atomic_compare_exchange_n(ptr, &_old, new, false,           \
> -- 
> 2.34.1
> 
>