Re: [Qemu-devel] [PATCH] docs/atomics: update comparison with Linux

[Emilio G. Cota]

On Wed, May 25, 2016 at 14:26:06 +0200, Paolo Bonzini wrote:
> Over time, some differences between QEMU and Linux atomics are getting
> smoothed.  In particular, Linux grew atomic_fetch_or (and in general
> the differences regarding RMW operations were not described accurately)
> and smp_load_acquire/smp_store_release.  Also, set_mb was renamed to
> smp_store_mb().  Include these changes in the documentation.
> 
> Signed-off-by: Paolo Bonzini <address@hidden>
> ---
>  docs/atomics.txt | 20 +++++++++++++++-----
>  1 file changed, 15 insertions(+), 5 deletions(-)
> 
> diff --git a/docs/atomics.txt b/docs/atomics.txt
> index 67a27ad..3f8b770 100644
> --- a/docs/atomics.txt
> +++ b/docs/atomics.txt
> @@ -340,17 +340,27 @@ and memory barriers, and the equivalents in QEMU:
>    properly aligned.
>    No barriers are implied by atomic_read/set in either Linux or QEMU.
>  
> -- most atomic read-modify-write operations in Linux return void;
> -  in QEMU, all of them return the old value of the variable.
> +- atomic read-modify-write operations in Linux are of three kinds:
> +
> +         atomic_OP          returns void
> +         atomic_OP_return   returns new value of the variable
> +         atomic_fetch_OP    returns the old value of the variable
> +         atomic_cmpxchg     returns the old value of the variable
> +
> +  In QEMU, the second kind does not exist.  Currently Linux has
> +  atomic_fetch_or only; QEMU provides all of inc, dec, and, sub, and, or.

Not clear whether the last 'and' is redundant or is being used as
a conjunction. Either way it would be clearer to just remove it.

Other than that:
  Reviewed-by: Emilio G. Cota <address@hidden>

                Emilio