Re: [dpdk-dev] [PATCH v3] meter: provide experimental alias of API for old apps

From: Ferruh Yigit <ferruh.yigit@intel.com>
To: David Marchand <david.marchand@redhat.com>, Ray Kinsella <mdr@ashroe.eu>
Cc: Neil Horman <nhorman@tuxdriver.com>,
	Cristian Dumitrescu <cristian.dumitrescu@intel.com>,
	Eelco Chaudron <echaudro@redhat.com>, dev <dev@dpdk.org>,
	Thomas Monjalon <thomas@monjalon.net>,
	dpdk stable <stable@dpdk.org>, Luca Boccassi <bluca@debian.org>,
	Bruce Richardson <bruce.richardson@intel.com>,
	Ian Stokes <ian.stokes@intel.com>,
	Andrzej Ostruszka <amo@semihalf.com>
Subject: Re: [dpdk-dev] [PATCH v3] meter: provide experimental alias of API for old apps
Date: Thu, 14 May 2020 17:07:36 +0100	[thread overview]
Message-ID: <29137948-49d4-0dfd-a030-3f084dafd99b@intel.com> (raw)
In-Reply-To: <CAJFAV8xen_oSUDyOMA+_EDg773-+pPnCWxb=f7vRcXiVb-HE-Q@mail.gmail.com>

On 5/14/2020 4:32 PM, David Marchand wrote:
> On Thu, May 14, 2020 at 1:52 PM Ferruh Yigit <ferruh.yigit@intel.com> wrote:
>>
>> On v20.02 some meter APIs have been matured and symbols moved from
>> EXPERIMENTAL to DPDK_20.0.1 block.
>>
>> This can break the applications that were using these mentioned APIs on
>> v19.11. Although there is no modification on the APIs and the action is
>> positive and matures the APIs, the affect can be negative to
>> applications.
>>
>> Since experimental APIs can change or go away without notice as part of
>> contract, to prevent this negative affect that may occur by maturing
>> experimental API, a process update already suggested, which enables
>> aliasing without forcing it:
>> https://patches.dpdk.org/patch/65863/
>>
>> This patch provides aliasing by duplicating the existing and versioned
>> symbols as experimental.
>>
>> Since symbols moved from DPDK_20.0.1 to DPDK_21 block in the v20.05, the
>> aliasing done between EXPERIMENTAL and DPDK_21.
>>
>> Also following changes done to enabling aliasing:
>>
>> Created VERSION_SYMBOL_EXPERIMENTAL helper macro.
> 
> This helper (+ script update) must come with the process update: the
> macro is referenced in its v5 revision.

The macro is implementation detail, and this patch does the implementation.
There is a dependency to process update patch, but that doesn't need to define
how the macro should be.

Let me send a new version with below updates, we can discuss this more if required.

> 
> 
>>
>> Updated the 'check-experimental-syms.sh' buildtool, which was
> 
> Nit: the script name changed.
> 
> 
>> diff --git a/lib/librte_eal/include/rte_function_versioning.h b/lib/librte_eal/include/rte_function_versioning.h
>> index b9f862d295..534a8bff95 100644
>> --- a/lib/librte_eal/include/rte_function_versioning.h
>> +++ b/lib/librte_eal/include/rte_function_versioning.h
>> @@ -46,6 +46,15 @@
>>   */
>>  #define VERSION_SYMBOL(b, e, n) __asm__(".symver " RTE_STR(b) RTE_STR(e) ", " RTE_STR(b) "@DPDK_" RTE_STR(n))
>>
>> +
> 
> No need for this newline.
> 
>> +/*
>> + * VERSION_SYMBOL_EXPERIMENTAL
>> + * Creates a symbol version table entry binding the symbol <b>@EXPERIMENTAL to the internal
>> + * function name <b><e>. The macro is used when a symbol matures to become part of the stable ABI,
>> + * to provide an alias to experimental for some time.
>> + */
>> +#define VERSION_SYMBOL_EXPERIMENTAL(b, e) __asm__(".symver " RTE_STR(b) RTE_STR(e) ", " RTE_STR(b) "@EXPERIMENTAL")
>> +
>>  /*
>>   * BIND_DEFAULT_SYMBOL
>>   * Creates a symbol version entry instructing the linker to bind references to
> 
> 