Re: [PATCH v3] eal: add notes to SMP memory barrier APIs

[Thomas Monjalon <thomas@monjalon.net>]

03/07/2023 11:56, Ruifeng Wang:
> The rte_smp_xx() APIs are deprecated. But it is not mentioned
> in the function header.
> Added notes in function header for clarification.
> 
> Signed-off-by: Ruifeng Wang <ruifeng.wang@arm.com>
> ---
> v3: Added suggested memory ordering semantic for replacement.
>     Refined deprecation explanation.
> v2: Made the notes more specific.
> 
>  lib/eal/include/generic/rte_atomic.h | 30 ++++++++++++++++++++++++++++
>  1 file changed, 30 insertions(+)
> 
> diff --git a/lib/eal/include/generic/rte_atomic.h b/lib/eal/include/generic/rte_atomic.h
> index 58df843c54..aef44e2455 100644
> --- a/lib/eal/include/generic/rte_atomic.h
> +++ b/lib/eal/include/generic/rte_atomic.h
> @@ -55,6 +55,14 @@ static inline void rte_rmb(void);
>   * Guarantees that the LOAD and STORE operations that precede the
>   * rte_smp_mb() call are globally visible across the lcores
>   * before the LOAD and STORE operations that follows it.
> + *
> + * @note
> + *  This function is deprecated.
> + *  It provides similar synchronization primitive as atomic fence,
> + *  but has different syntax and memory ordering semantic. Hence
> + *  deprecated for the simplicity of memory ordering semantics in use.
> + *
> + *  rte_atomic_thread_fence(__ATOMIC_ACQ_REL) should be used instead.
>   */
>  static inline void rte_smp_mb(void);
>  
> @@ -64,6 +72,17 @@ static inline void rte_smp_mb(void);
>   * Guarantees that the STORE operations that precede the
>   * rte_smp_wmb() call are globally visible across the lcores
>   * before the STORE operations that follows it.
> + *
> + * @note
> + *  This function is deprecated.
> + *  It provides similar synchronization primitive as atomic fence,
> + *  but has different syntax and memory ordering semantic. Hence
> + *  deprecated for the simplicity of memory ordering semantics in use.
> + *
> + *  rte_atomic_thread_fence(__ATOMIC_RELEASE) should be used instead.
> + *  The fence also guarantees LOAD operations that precede the call
> + *  are globally visible across the lcores before the STORE operations
> + *  that follows it.
>   */
>  static inline void rte_smp_wmb(void);
>  
> @@ -73,6 +92,17 @@ static inline void rte_smp_wmb(void);
>   * Guarantees that the LOAD operations that precede the
>   * rte_smp_rmb() call are globally visible across the lcores
>   * before the LOAD operations that follows it.
> + *
> + * @note
> + *  This function is deprecated.
> + *  It provides similar synchronization primitive as atomic fence,
> + *  but has different syntax and memory ordering semantic. Hence
> + *  deprecated for the simplicity of memory ordering semantics in use.
> + *
> + *  rte_atomic_thread_fence(__ATOMIC_ACQUIRE) should be used instead.
> + *  The fence also guarantees LOAD operations that precede the call
> + *  are globally visible across the lcores before the STORE operations
> + *  that follows it.
>   */
>  static inline void rte_smp_rmb(void);
>  ///@}

There was no more comment.

Applied, thanks.