Re: [dpdk-dev] [PATCH v2] meter: provide experimental alias of API for old apps

[Ray Kinsella <mdr@ashroe.eu>]

On 13/05/2020 19:05, Ferruh Yigit 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.
> 
> Updated the 'check-experimental-syms.sh' buildtool, which was
> complaining that the symbol is in EXPERIMENTAL tag in .map file but it
> is not in the .experimental section (__rte_experimental tag is missing).
> Updated tool in a way it won't complain if the symbol in the
> EXPERIMENTAL tag duplicated in some other block in .map file (versioned)
> 
> Enabled function versioning for meson build for the library.
> 
> Fixes: 30512af820fe ("meter: remove experimental flag from RFC4115 trTCM API")
> Cc: stable@dpdk.org
> 
> Signed-off-by: Ferruh Yigit <ferruh.yigit@intel.com>
> ---
> Cc: Neil Horman <nhorman@tuxdriver.com>
> Cc: Thomas Monjalon <thomas@monjalon.net>
> Cc: Luca Boccassi <bluca@debian.org>
> Cc: David Marchand <david.marchand@redhat.com>
> Cc: Bruce Richardson <bruce.richardson@intel.com>
> Cc: Ian Stokes <ian.stokes@intel.com>
> Cc: Eelco Chaudron <echaudro@redhat.com>
> Cc: Andrzej Ostruszka <amo@semihalf.com>
> Cc: Ray Kinsella <mdr@ashroe.eu>
> 
> v2:
> * Commit log updated
> ---
>  buildtools/check-symbols.sh                   |  3 +-
>  .../include/rte_function_versioning.h         |  4 ++
>  lib/librte_meter/meson.build                  |  1 +
>  lib/librte_meter/rte_meter.c                  | 59 ++++++++++++++++++-
>  lib/librte_meter/rte_meter_version.map        |  8 +++
>  5 files changed, 71 insertions(+), 4 deletions(-)
> 
> diff --git a/buildtools/check-symbols.sh b/buildtools/check-symbols.sh
> index 3df57c322c..e407553a34 100755
> --- a/buildtools/check-symbols.sh
> +++ b/buildtools/check-symbols.sh
> @@ -26,7 +26,8 @@ ret=0
>  for SYM in `$LIST_SYMBOL -S EXPERIMENTAL $MAPFILE |cut -d ' ' -f 3`
>  do
>  	if grep -q "\.text.*[[:space:]]$SYM$" $DUMPFILE &&
> -		! grep -q "\.text\.experimental.*[[:space:]]$SYM$" $DUMPFILE
> +		! grep -q "\.text\.experimental.*[[:space:]]$SYM$" $DUMPFILE &&
> +		$LIST_SYMBOL -s $SYM $MAPFILE | grep -q EXPERIMENTAL
>  	then
>  		cat >&2 <<- END_OF_MESSAGE
>  		$SYM is not flagged as experimental
> diff --git a/lib/librte_eal/include/rte_function_versioning.h b/lib/librte_eal/include/rte_function_versioning.h
> index b9f862d295..22ec5f9424 100644
> --- a/lib/librte_eal/include/rte_function_versioning.h
> +++ b/lib/librte_eal/include/rte_function_versioning.h
> @@ -46,6 +46,9 @@
>   */
>  #define VERSION_SYMBOL(b, e, n) __asm__(".symver " RTE_STR(b) RTE_STR(e) ", " RTE_STR(b) "@DPDK_" RTE_STR(n))

Please add

/*
 * 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.
 */

I will take care of the updates to doc/guides/contributing/abi*.rst

> +
> +#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
> @@ -79,6 +82,7 @@
>   * No symbol versioning in use
>   */
>  #define VERSION_SYMBOL(b, e, n)
> +#define VERSION_SYMBOL_EXPERIMENTAL(b, e)
>  #define __vsym
>  #define BIND_DEFAULT_SYMBOL(b, e, n)
>  #define MAP_STATIC_SYMBOL(f, p) f __attribute__((alias(RTE_STR(p))))
> diff --git a/lib/librte_meter/meson.build b/lib/librte_meter/meson.build
> index 646fd4d43f..fce0368437 100644
> --- a/lib/librte_meter/meson.build
> +++ b/lib/librte_meter/meson.build
> @@ -3,3 +3,4 @@
>  
>  sources = files('rte_meter.c')
>  headers = files('rte_meter.h')
> +use_function_versioning = true
> diff --git a/lib/librte_meter/rte_meter.c b/lib/librte_meter/rte_meter.c
> index da01429a8b..c600b05064 100644
> --- a/lib/librte_meter/rte_meter.c
> +++ b/lib/librte_meter/rte_meter.c
> @@ -9,6 +9,7 @@
>  #include <rte_common.h>
>  #include <rte_log.h>
>  #include <rte_cycles.h>
> +#include <rte_function_versioning.h>
>  
>  #include "rte_meter.h"
>  
> @@ -119,8 +120,8 @@ rte_meter_trtcm_config(struct rte_meter_trtcm *m,
>  	return 0;
>  }
>  
> -int
> -rte_meter_trtcm_rfc4115_profile_config(
> +static int
> +rte_meter_trtcm_rfc4115_profile_config_(
>  	struct rte_meter_trtcm_rfc4115_profile *p,
>  	struct rte_meter_trtcm_rfc4115_params *params)
>  {
> @@ -145,7 +146,35 @@ rte_meter_trtcm_rfc4115_profile_config(
>  }
>  
>  int
> -rte_meter_trtcm_rfc4115_config(
> +rte_meter_trtcm_rfc4115_profile_config_s(
> +	struct rte_meter_trtcm_rfc4115_profile *p,
> +	struct rte_meter_trtcm_rfc4115_params *params);
> +int
> +rte_meter_trtcm_rfc4115_profile_config_s(
> +	struct rte_meter_trtcm_rfc4115_profile *p,
> +	struct rte_meter_trtcm_rfc4115_params *params)
> +{
> +	return rte_meter_trtcm_rfc4115_profile_config_(p, params);
> +}
> +BIND_DEFAULT_SYMBOL(rte_meter_trtcm_rfc4115_profile_config, _s, 21);
> +MAP_STATIC_SYMBOL(int rte_meter_trtcm_rfc4115_profile_config(struct rte_meter_trtcm_rfc4115_profile *p,
> +		struct rte_meter_trtcm_rfc4115_params *params), rte_meter_trtcm_rfc4115_profile_config_s);
> +
> +int
> +rte_meter_trtcm_rfc4115_profile_config_e(
> +	struct rte_meter_trtcm_rfc4115_profile *p,
> +	struct rte_meter_trtcm_rfc4115_params *params);
> +int
> +rte_meter_trtcm_rfc4115_profile_config_e(
> +	struct rte_meter_trtcm_rfc4115_profile *p,
> +	struct rte_meter_trtcm_rfc4115_params *params)
> +{
> +	return rte_meter_trtcm_rfc4115_profile_config_(p, params);
> +}
> +VERSION_SYMBOL_EXPERIMENTAL(rte_meter_trtcm_rfc4115_profile_config, _e);
> +
> +static int
> +rte_meter_trtcm_rfc4115_config_(
>  	struct rte_meter_trtcm_rfc4115 *m,
>  	struct rte_meter_trtcm_rfc4115_profile *p)
>  {
> @@ -160,3 +189,27 @@ rte_meter_trtcm_rfc4115_config(
>  
>  	return 0;
>  }
> +
> +int
> +rte_meter_trtcm_rfc4115_config_s(struct rte_meter_trtcm_rfc4115 *m,
> +	struct rte_meter_trtcm_rfc4115_profile *p);
> +int
> +rte_meter_trtcm_rfc4115_config_s(struct rte_meter_trtcm_rfc4115 *m,
> +	struct rte_meter_trtcm_rfc4115_profile *p)
> +{
> +	return rte_meter_trtcm_rfc4115_config_(m, p);
> +}
> +BIND_DEFAULT_SYMBOL(rte_meter_trtcm_rfc4115_config, _s, 21);
> +MAP_STATIC_SYMBOL(int rte_meter_trtcm_rfc4115_config(struct rte_meter_trtcm_rfc4115 *m,
> +		 struct rte_meter_trtcm_rfc4115_profile *p), rte_meter_trtcm_rfc4115_config_s);
> +
> +int
> +rte_meter_trtcm_rfc4115_config_e(struct rte_meter_trtcm_rfc4115 *m,
> +	struct rte_meter_trtcm_rfc4115_profile *p);
> +int
> +rte_meter_trtcm_rfc4115_config_e(struct rte_meter_trtcm_rfc4115 *m,
> +	struct rte_meter_trtcm_rfc4115_profile *p)
> +{
> +	return rte_meter_trtcm_rfc4115_config_(m, p);
> +}
> +VERSION_SYMBOL_EXPERIMENTAL(rte_meter_trtcm_rfc4115_config, _e);
> diff --git a/lib/librte_meter/rte_meter_version.map b/lib/librte_meter/rte_meter_version.map
> index 2c7dadbcac..b493bcebe9 100644
> --- a/lib/librte_meter/rte_meter_version.map
> +++ b/lib/librte_meter/rte_meter_version.map
> @@ -20,4 +20,12 @@ DPDK_21 {
>  	rte_meter_trtcm_rfc4115_color_blind_check;
>  	rte_meter_trtcm_rfc4115_config;
>  	rte_meter_trtcm_rfc4115_profile_config;
> +
>  } DPDK_20.0;
> +
> +EXPERIMENTAL {
> +       global:
> +
> +	rte_meter_trtcm_rfc4115_config;
> +	rte_meter_trtcm_rfc4115_profile_config;
> +};
>