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 <pbonz...@redhat.com>
> ---
> 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 <c...@braap.org>
Emilio
