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From: Sergey Fedorov <serge.fdrv@gmail.com>
Message-ID: <573B43B8.2000306@gmail.com>
Date: Tue, 17 May 2016 19:15:52 +0300
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Subject: Re: [Qemu-devel] [PATCH v5 05/18] atomics: add
 atomic_test_and_set_acquire
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To: "Emilio G. Cota" <cota@braap.org>, QEMU Developers <qemu-devel@nongnu.org>, MTTCG Devel <mttcg@listserver.greensocs.com>
Cc: =?UTF-8?Q?Alex_Benn=c3=a9e?= <alex.bennee@linaro.org>, Paolo Bonzini <pbonzini@redhat.com>, Peter Crosthwaite <crosthwaite.peter@gmail.com>, Richard Henderson <rth@twiddle.net>

On 14/05/16 06:34, Emilio G. Cota wrote:
> This new helper expands to __atomic_test_and_set with acquire semantics
> where available; otherwise it expands to __sync_test_and_set, which
> has acquire semantics.

Why don't also add atomic_clear_release() for completeness?

Kind regards,
Sergey

>
> Signed-off-by: Emilio G. Cota <cota@braap.org>
> ---
>  include/qemu/atomic.h | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/include/qemu/atomic.h b/include/qemu/atomic.h
> index 5bc4d6c..6061a46 100644
> --- a/include/qemu/atomic.h
> +++ b/include/qemu/atomic.h
> @@ -113,6 +113,7 @@
>  } while(0)
>  #endif
>  
> +#define atomic_test_and_set_acquire(ptr) __atomic_test_and_set(ptr, __ATOMIC_ACQUIRE)
>  
>  /* All the remaining operations are fully sequentially consistent */
>  
> @@ -327,6 +328,8 @@
>  #endif
>  #endif
>  
> +#define atomic_test_and_set_acquire(ptr) __sync_lock_test_and_set(ptr, true)
> +
>  /* Provide shorter names for GCC atomic builtins.  */
>  #define atomic_fetch_inc(ptr)  __sync_fetch_and_add(ptr, 1)
>  #define atomic_fetch_dec(ptr)  __sync_fetch_and_add(ptr, -1)