On Mon, Oct 26, 2015 at 11:07 AM, Petri Savolainen <
petri.savolai...@nokia.com> wrote:
> Updated odp_sync_stores() specification and added odp_sync_loads
> to pair it. Used GCC __atomic_thread_fence to implement both of
> those.
>
> Signed-off-by: Petri Savolainen <petri.savolai...@nokia.com>
>
Reviewed-by: Bill Fischofer <bill.fischo...@linaro.org>
> ---
> include/odp/api/sync.h | 53
> +++++++++++++++----------------
> platform/linux-generic/include/odp/sync.h | 18 +++++++++++
> 2 files changed, 43 insertions(+), 28 deletions(-)
>
> diff --git a/include/odp/api/sync.h b/include/odp/api/sync.h
> index 6477e74..8456f68 100644
> --- a/include/odp/api/sync.h
> +++ b/include/odp/api/sync.h
> @@ -23,37 +23,34 @@ extern "C" {
> */
>
> /**
> - * Synchronise stores
> + * Synchronize stores
> *
> - * Ensures that all CPU store operations that precede the
> odp_sync_stores()
> - * call are globally visible before any store operation that follows it.
> + * This call implements a write memory barrier between threads. It
> ensures that
> + * all (non-atomic or relaxed atomic) stores (from the calling thread)
> that
> + * precede this call are globally visible before any store operation that
> + * follows it. It prevents stores moving from before the call to after it.
> + *
> + * ODP synchronization mechanisms (e.g. barrier, unlocks, queue enqueues)
> + * include write barrier, so this call is not needed when using those.
> + *
> + * @see odp_sync_loads()
> */
> -static inline void odp_sync_stores(void)
> -{
> -#if defined __x86_64__ || defined __i386__
> -
> - __asm__ __volatile__ ("sfence\n" : : : "memory");
> -
> -#elif defined(__arm__)
> -#if __ARM_ARCH == 6
> - __asm__ __volatile__ ("mcr p15, 0, %0, c7, c10, 5" \
> - : : "r" (0) : "memory");
> -#elif __ARM_ARCH >= 7 || defined __aarch64__
> -
> - __asm__ __volatile__ ("dmb st" : : : "memory");
> -#else
> - __asm__ __volatile__ ("" : : : "memory");
> -#endif
> -
> -#elif defined __OCTEON__
> -
> - __asm__ __volatile__ ("syncws\n" : : : "memory");
> -
> -#else
> - __sync_synchronize();
> -#endif
> -}
> +void odp_sync_stores(void);
>
> +/**
> + * Synchronize loads
> + *
> + * This call implements a read memory barrier. It ensures that all
> (non-atomic
> + * or relaxed atomic) loads that precede this call happen before any load
> + * operation that follows it. It prevents loads moving from after the
> call to
> + * before it.
> + *
> + * ODP synchronization mechanisms (e.g. barrier, locks, queue dequeues)
> + * include read barrier, so this call is not needed when using those.
> + *
> + * @see odp_sync_stores()
> + */
> +void odp_sync_loads(void);
>
> /**
> * @}
> diff --git a/platform/linux-generic/include/odp/sync.h
> b/platform/linux-generic/include/odp/sync.h
> index bc73083..09b3939 100644
> --- a/platform/linux-generic/include/odp/sync.h
> +++ b/platform/linux-generic/include/odp/sync.h
> @@ -17,6 +17,24 @@
> extern "C" {
> #endif
>
> +/** @ingroup odp_barrier
> + * @{
> + */
> +
> +static inline void odp_sync_stores(void)
> +{
> + __atomic_thread_fence(__ATOMIC_RELEASE);
> +}
> +
> +static inline void odp_sync_loads(void)
> +{
> + __atomic_thread_fence(__ATOMIC_ACQUIRE);
> +}
> +
> +/**
> + * @}
> + */
> +
> #include <odp/api/sync.h>
>
> #ifdef __cplusplus
> --
> 2.6.2
>
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> lng-odp@lists.linaro.org
> https://lists.linaro.org/mailman/listinfo/lng-odp
>
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