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From: Honnappa Nagarahalli <Honnappa.Nagarahalli@arm.com>
To: Joyce Kong <Joyce.Kong@arm.com>,
	"thomas@monjalon.net" <thomas@monjalon.net>,
	"stephen@networkplumber.org" <stephen@networkplumber.org>,
	Ruifeng Wang <Ruifeng.Wang@arm.com>,
	"mdr@ashroe.eu" <mdr@ashroe.eu>
Cc: "dev@dpdk.org" <dev@dpdk.org>, nd <nd@arm.com>,
	"stable@dpdk.org" <stable@dpdk.org>,
	Honnappa Nagarahalli <Honnappa.Nagarahalli@arm.com>,
	nd <nd@arm.com>
Subject: Re: [dpdk-dev] [PATCH v1] doc: update atomic operation deprecation
Date: Sat, 17 Jul 2021 18:47:47 +0000	[thread overview]
Message-ID: <DBAPR08MB58147A30B8428AA7D534070C98109@DBAPR08MB5814.eurprd08.prod.outlook.com> (raw)
In-Reply-To: <20210712080237.19920-1-joyce.kong@arm.com>

<snip>

> 
> Update the incorrect description about atomic operations with provided
> wrappers in deprecation doc[1].
> 
> [1]https://mails.dpdk.org/archives/dev/2021-July/213333.html
> 
> Fixes: 7518c5c4ae6a ("doc: announce adoption of C11 atomic operations
> semantics")
> Cc: stable@dpdk.org
> 
> Signed-off-by: Joyce Kong <joyce.kong@arm.com>
> Reviewed-by: Ruifeng Wang <ruifeng.wang@arm.com>
> ---
>  doc/guides/rel_notes/deprecation.rst | 16 ++++++++--------
>  1 file changed, 8 insertions(+), 8 deletions(-)
> 
> diff --git a/doc/guides/rel_notes/deprecation.rst
> b/doc/guides/rel_notes/deprecation.rst
> index 9584d6bfd7..4142315842 100644
> --- a/doc/guides/rel_notes/deprecation.rst
> +++ b/doc/guides/rel_notes/deprecation.rst
> @@ -19,16 +19,16 @@ Deprecation Notices
> 
>  * rte_atomicNN_xxx: These APIs do not take memory order parameter. This
> does
>    not allow for writing optimized code for all the CPU architectures supported
> -  in DPDK. DPDK will adopt C11 atomic operations semantics and provide
> wrappers
> -  using C11 atomic built-ins. These wrappers must be used for patches that
> -  need to be merged in 20.08 onwards. This change will not introduce any
> -  performance degradation.
> +  in DPDK. DPDK has adopted atomic operations semantics. GCC atomic
> + built-ins  must be used for patches that need to be merged in 20.08
> + onwards. This change  will not introduce any performance degradation.
Since there have been objections to the language used to refer to GCC C11 atomic built-ins, may be we add a reference to the GCC pages?

DPDK has adopted the atomic operations from https://gcc.gnu.org/onlinedocs/gcc/_005f_005fatomic-Builtins.html. These operations must be used for patches that need to be merged in 20.08 onwards. This change  will not introduce any performance degradation.

> 
>  * rte_smp_*mb: These APIs provide full barrier functionality. However, many
> -  use cases do not require full barriers. To support such use cases, DPDK will
> -  adopt C11 barrier semantics and provide wrappers using C11 atomic built-
> ins.
> -  These wrappers must be used for patches that need to be merged in 20.08
> -  onwards. This change will not introduce any performance degradation.
> +  use cases do not require full barriers. To support such use cases,
> + DPDK has  adopted atomic barrier semantics. GCC atomic built-ins and a
> + new wrapper  ``rte_atomic_thread_fence`` instead of
> + ``__atomic_thread_fence`` must be  used for patches that need to be
> + merged in 20.08 onwards. This change will  not introduce any performance
> degradation.
Same here.
To support such use cases, DPDK has  adopted atomic operations from https://gcc.gnu.org/onlinedocs/gcc/_005f_005fatomic-Builtins.html. A new wrapper  ``rte_atomic_thread_fence`` instead of ``__atomic_thread_fence`` must be  used for patches that need to be merged in 20.08 onwards. This change will  not introduce any performance degradation.

> 
>  * lib: will fix extending some enum/define breaking the ABI. There are
> multiple
>    samples in DPDK that enum/define terminated with a ``.*MAX.*`` value
> which is
> --
> 2.17.1


  reply	other threads:[~2021-07-17 18:48 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-12  8:02 Joyce Kong
2021-07-17 18:47 ` Honnappa Nagarahalli [this message]
2021-07-23  9:49 ` [dpdk-dev] [PATCH v2] " Joyce Kong
2021-07-31 20:26   ` Thomas Monjalon
2021-08-02 17:22     ` Honnappa Nagarahalli
2021-08-02 17:26       ` Thomas Monjalon

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