* [dpdk-dev] [PATCH v3 1/4] doc: separate versioning.rst into version and policy
2019-08-15 10:23 [dpdk-dev] [PATCH v3 0/4] doc: changes to abi policy introducing major abi versions Ray Kinsella
@ 2019-08-15 10:23 ` Ray Kinsella
2019-08-15 10:23 ` [dpdk-dev] [PATCH v3 2/4] doc: changes to abi policy introducing major abi versions Ray Kinsella
` (2 subsequent siblings)
3 siblings, 0 replies; 8+ messages in thread
From: Ray Kinsella @ 2019-08-15 10:23 UTC (permalink / raw)
To: dev
Cc: mdr, thomas, stephen, bruce.richardson, ferruh.yigit,
konstantin.ananyev, jerinj, olivier.matz, nhorman,
maxime.coquelin, john.mcnamara, marko.kovacevic, hemant.agrawal
Separate versioning.rst into abi versioning and abi policy guidance, in
preparation for adding more detail to the abi policy.
Signed-off-by: Ray Kinsella <mdr@ashroe.eu>
---
doc/guides/contributing/abi_policy.rst | 169 +++++++++
doc/guides/contributing/abi_versioning.rst | 427 +++++++++++++++++++++
doc/guides/contributing/index.rst | 3 +-
doc/guides/contributing/versioning.rst | 591 -----------------------------
4 files changed, 598 insertions(+), 592 deletions(-)
create mode 100644 doc/guides/contributing/abi_policy.rst
create mode 100644 doc/guides/contributing/abi_versioning.rst
delete mode 100644 doc/guides/contributing/versioning.rst
diff --git a/doc/guides/contributing/abi_policy.rst b/doc/guides/contributing/abi_policy.rst
new file mode 100644
index 0000000..55bacb4
--- /dev/null
+++ b/doc/guides/contributing/abi_policy.rst
@@ -0,0 +1,169 @@
+.. SPDX-License-Identifier: BSD-3-Clause
+ Copyright 2018 The DPDK contributors
+
+.. abi_api_policy:
+
+DPDK ABI/API policy
+===================
+
+Description
+-----------
+
+This document details some methods for handling ABI management in the DPDK.
+
+General Guidelines
+------------------
+
+#. Whenever possible, ABI should be preserved
+#. ABI/API may be changed with a deprecation process
+#. The modification of symbols can generally be managed with versioning
+#. Libraries or APIs marked in ``experimental`` state may change without constraint
+#. New APIs will be marked as ``experimental`` for at least one release to allow
+ any issues found by users of the new API to be fixed quickly
+#. The addition of symbols is generally not problematic
+#. The removal of symbols generally is an ABI break and requires bumping of the
+ LIBABIVER macro
+#. Updates to the minimum hardware requirements, which drop support for hardware which
+ was previously supported, should be treated as an ABI change.
+
+What is an ABI
+~~~~~~~~~~~~~~
+
+An ABI (Application Binary Interface) is the set of runtime interfaces exposed
+by a library. It is similar to an API (Application Programming Interface) but
+is the result of compilation. It is also effectively cloned when applications
+link to dynamic libraries. That is to say when an application is compiled to
+link against dynamic libraries, it is assumed that the ABI remains constant
+between the time the application is compiled/linked, and the time that it runs.
+Therefore, in the case of dynamic linking, it is critical that an ABI is
+preserved, or (when modified), done in such a way that the application is unable
+to behave improperly or in an unexpected fashion.
+
+
+ABI/API Deprecation
+-------------------
+
+The DPDK ABI policy
+~~~~~~~~~~~~~~~~~~~
+
+ABI versions are set at the time of major release labeling, and the ABI may
+change multiple times, without warning, between the last release label and the
+HEAD label of the git tree.
+
+ABI versions, once released, are available until such time as their
+deprecation has been noted in the Release Notes for at least one major release
+cycle. For example consider the case where the ABI for DPDK 2.0 has been
+shipped and then a decision is made to modify it during the development of
+DPDK 2.1. The decision will be recorded in the Release Notes for the DPDK 2.1
+release and the modification will be made available in the DPDK 2.2 release.
+
+ABI versions may be deprecated in whole or in part as needed by a given
+update.
+
+Some ABI changes may be too significant to reasonably maintain multiple
+versions. In those cases ABI's may be updated without backward compatibility
+being provided. The requirements for doing so are:
+
+#. At least 3 acknowledgments of the need to do so must be made on the
+ dpdk.org mailing list.
+
+ - The acknowledgment of the maintainer of the component is mandatory, or if
+ no maintainer is available for the component, the tree/sub-tree maintainer
+ for that component must acknowledge the ABI change instead.
+
+ - It is also recommended that acknowledgments from different "areas of
+ interest" be sought for each deprecation, for example: from NIC vendors,
+ CPU vendors, end-users, etc.
+
+#. The changes (including an alternative map file) can be included with
+ deprecation notice, in wrapped way by the ``RTE_NEXT_ABI`` option,
+ to provide more details about oncoming changes.
+ ``RTE_NEXT_ABI`` wrapper will be removed when it become the default ABI.
+ More preferred way to provide this information is sending the feature
+ as a separate patch and reference it in deprecation notice.
+
+#. A full deprecation cycle, as explained above, must be made to offer
+ downstream consumers sufficient warning of the change.
+
+Note that the above process for ABI deprecation should not be undertaken
+lightly. ABI stability is extremely important for downstream consumers of the
+DPDK, especially when distributed in shared object form. Every effort should
+be made to preserve the ABI whenever possible. The ABI should only be changed
+for significant reasons, such as performance enhancements. ABI breakage due to
+changes such as reorganizing public structure fields for aesthetic or
+readability purposes should be avoided.
+
+.. note::
+
+ Updates to the minimum hardware requirements, which drop support for hardware
+ which was previously supported, should be treated as an ABI change, and
+ follow the relevant deprecation policy procedures as above: 3 acks and
+ announcement at least one release in advance.
+
+Examples of Deprecation Notices
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+The following are some examples of ABI deprecation notices which would be
+added to the Release Notes:
+
+* The Macro ``#RTE_FOO`` is deprecated and will be removed with version 2.0,
+ to be replaced with the inline function ``rte_foo()``.
+
+* The function ``rte_mbuf_grok()`` has been updated to include a new parameter
+ in version 2.0. Backwards compatibility will be maintained for this function
+ until the release of version 2.1
+
+* The members of ``struct rte_foo`` have been reorganized in release 2.0 for
+ performance reasons. Existing binary applications will have backwards
+ compatibility in release 2.0, while newly built binaries will need to
+ reference the new structure variant ``struct rte_foo2``. Compatibility will
+ be removed in release 2.2, and all applications will require updating and
+ rebuilding to the new structure at that time, which will be renamed to the
+ original ``struct rte_foo``.
+
+* Significant ABI changes are planned for the ``librte_dostuff`` library. The
+ upcoming release 2.0 will not contain these changes, but release 2.1 will,
+ and no backwards compatibility is planned due to the extensive nature of
+ these changes. Binaries using this library built prior to version 2.1 will
+ require updating and recompilation.
+
+New API replacing previous one
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+If a new API proposed functionally replaces an existing one, when the new API
+becomes non-experimental then the old one is marked with ``__rte_deprecated``.
+Deprecated APIs are removed completely just after the next LTS.
+
+Reminder that old API should follow deprecation process to be removed.
+
+
+Experimental APIs
+-----------------
+
+APIs marked as ``experimental`` are not considered part of the ABI and may
+change without warning at any time. Since changes to APIs are most likely
+immediately after their introduction, as users begin to take advantage of
+those new APIs and start finding issues with them, new DPDK APIs will be
+automatically marked as ``experimental`` to allow for a period of stabilization
+before they become part of a tracked ABI.
+
+Note that marking an API as experimental is a multi step process.
+To mark an API as experimental, the symbols which are desired to be exported
+must be placed in an EXPERIMENTAL version block in the corresponding libraries'
+version map script.
+Secondly, the corresponding prototypes of those exported functions (in the
+development header files), must be marked with the ``__rte_experimental`` tag
+(see ``rte_compat.h``).
+The DPDK build makefiles perform a check to ensure that the map file and the
+C code reflect the same list of symbols.
+This check can be circumvented by defining ``ALLOW_EXPERIMENTAL_API``
+during compilation in the corresponding library Makefile.
+
+In addition to tagging the code with ``__rte_experimental``,
+the doxygen markup must also contain the EXPERIMENTAL string,
+and the MAINTAINERS file should note the EXPERIMENTAL libraries.
+
+For removing the experimental tag associated with an API, deprecation notice
+is not required. Though, an API should remain in experimental state for at least
+one release. Thereafter, normal process of posting patch for review to mailing
+list can be followed.
diff --git a/doc/guides/contributing/abi_versioning.rst b/doc/guides/contributing/abi_versioning.rst
new file mode 100644
index 0000000..53e6ac0
--- /dev/null
+++ b/doc/guides/contributing/abi_versioning.rst
@@ -0,0 +1,427 @@
+.. SPDX-License-Identifier: BSD-3-Clause
+ Copyright 2018 The DPDK contributors
+
+.. library_versioning:
+
+Library versioning
+------------------
+
+Downstreams might want to provide different DPDK releases at the same time to
+support multiple consumers of DPDK linked against older and newer sonames.
+
+Also due to the interdependencies that DPDK libraries can have applications
+might end up with an executable space in which multiple versions of a library
+are mapped by ld.so.
+
+Think of LibA that got an ABI bump and LibB that did not get an ABI bump but is
+depending on LibA.
+
+.. note::
+
+ Application
+ \-> LibA.old
+ \-> LibB.new -> LibA.new
+
+That is a conflict which can be avoided by setting ``CONFIG_RTE_MAJOR_ABI``.
+If set, the value of ``CONFIG_RTE_MAJOR_ABI`` overwrites all - otherwise per
+library - versions defined in the libraries ``LIBABIVER``.
+An example might be ``CONFIG_RTE_MAJOR_ABI=16.11`` which will make all libraries
+``librte<?>.so.16.11`` instead of ``librte<?>.so.<LIBABIVER>``.
+
+
+ABI versioning
+--------------
+
+Versioning Macros
+~~~~~~~~~~~~~~~~~
+
+When a symbol is exported from a library to provide an API, it also provides a
+calling convention (ABI) that is embodied in its name, return type and
+arguments. Occasionally that function may need to change to accommodate new
+functionality or behavior. When that occurs, it is desirable to allow for
+backward compatibility for a time with older binaries that are dynamically
+linked to the DPDK.
+
+To support backward compatibility the ``rte_compat.h``
+header file provides macros to use when updating exported functions. These
+macros are used in conjunction with the ``rte_<library>_version.map`` file for
+a given library to allow multiple versions of a symbol to exist in a shared
+library so that older binaries need not be immediately recompiled.
+
+The macros exported are:
+
+* ``VERSION_SYMBOL(b, e, n)``: Creates a symbol version table entry binding
+ versioned symbol ``b@DPDK_n`` to the internal function ``b_e``.
+
+* ``BIND_DEFAULT_SYMBOL(b, e, n)``: Creates a symbol version entry instructing
+ the linker to bind references to symbol ``b`` to the internal symbol
+ ``b_e``.
+
+* ``MAP_STATIC_SYMBOL(f, p)``: Declare the prototype ``f``, and map it to the
+ fully qualified function ``p``, so that if a symbol becomes versioned, it
+ can still be mapped back to the public symbol name.
+
+Examples of ABI Macro use
+^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Updating a public API
+_____________________
+
+Assume we have a function as follows
+
+.. code-block:: c
+
+ /*
+ * Create an acl context object for apps to
+ * manipulate
+ */
+ struct rte_acl_ctx *
+ rte_acl_create(const struct rte_acl_param *param)
+ {
+ ...
+ }
+
+
+Assume that struct rte_acl_ctx is a private structure, and that a developer
+wishes to enhance the acl api so that a debugging flag can be enabled on a
+per-context basis. This requires an addition to the structure (which, being
+private, is safe), but it also requires modifying the code as follows
+
+.. code-block:: c
+
+ /*
+ * Create an acl context object for apps to
+ * manipulate
+ */
+ struct rte_acl_ctx *
+ rte_acl_create(const struct rte_acl_param *param, int debug)
+ {
+ ...
+ }
+
+
+Note also that, being a public function, the header file prototype must also be
+changed, as must all the call sites, to reflect the new ABI footprint. We will
+maintain previous ABI versions that are accessible only to previously compiled
+binaries
+
+The addition of a parameter to the function is ABI breaking as the function is
+public, and existing application may use it in its current form. However, the
+compatibility macros in DPDK allow a developer to use symbol versioning so that
+multiple functions can be mapped to the same public symbol based on when an
+application was linked to it. To see how this is done, we start with the
+requisite libraries version map file. Initially the version map file for the
+acl library looks like this
+
+.. code-block:: none
+
+ DPDK_2.0 {
+ global:
+
+ rte_acl_add_rules;
+ rte_acl_build;
+ rte_acl_classify;
+ rte_acl_classify_alg;
+ rte_acl_classify_scalar;
+ rte_acl_create;
+ rte_acl_dump;
+ rte_acl_find_existing;
+ rte_acl_free;
+ rte_acl_ipv4vlan_add_rules;
+ rte_acl_ipv4vlan_build;
+ rte_acl_list_dump;
+ rte_acl_reset;
+ rte_acl_reset_rules;
+ rte_acl_set_ctx_classify;
+
+ local: *;
+ };
+
+This file needs to be modified as follows
+
+.. code-block:: none
+
+ DPDK_2.0 {
+ global:
+
+ rte_acl_add_rules;
+ rte_acl_build;
+ rte_acl_classify;
+ rte_acl_classify_alg;
+ rte_acl_classify_scalar;
+ rte_acl_create;
+ rte_acl_dump;
+ rte_acl_find_existing;
+ rte_acl_free;
+ rte_acl_ipv4vlan_add_rules;
+ rte_acl_ipv4vlan_build;
+ rte_acl_list_dump;
+ rte_acl_reset;
+ rte_acl_reset_rules;
+ rte_acl_set_ctx_classify;
+
+ local: *;
+ };
+
+ DPDK_2.1 {
+ global:
+ rte_acl_create;
+
+ } DPDK_2.0;
+
+The addition of the new block tells the linker that a new version node is
+available (DPDK_2.1), which contains the symbol rte_acl_create, and inherits the
+symbols from the DPDK_2.0 node. This list is directly translated into a list of
+exported symbols when DPDK is compiled as a shared library
+
+Next, we need to specify in the code which function map to the rte_acl_create
+symbol at which versions. First, at the site of the initial symbol definition,
+we need to update the function so that it is uniquely named, and not in conflict
+with the public symbol name
+
+.. code-block:: c
+
+ struct rte_acl_ctx *
+ -rte_acl_create(const struct rte_acl_param *param)
+ +rte_acl_create_v20(const struct rte_acl_param *param)
+ {
+ size_t sz;
+ struct rte_acl_ctx *ctx;
+ ...
+
+Note that the base name of the symbol was kept intact, as this is conducive to
+the macros used for versioning symbols. That is our next step, mapping this new
+symbol name to the initial symbol name at version node 2.0. Immediately after
+the function, we add this line of code
+
+.. code-block:: c
+
+ VERSION_SYMBOL(rte_acl_create, _v20, 2.0);
+
+Remembering to also add the rte_compat.h header to the requisite c file where
+these changes are being made. The above macro instructs the linker to create a
+new symbol ``rte_acl_create@DPDK_2.0``, which matches the symbol created in older
+builds, but now points to the above newly named function. We have now mapped
+the original rte_acl_create symbol to the original function (but with a new
+name)
+
+Next, we need to create the 2.1 version of the symbol. We create a new function
+name, with a different suffix, and implement it appropriately
+
+.. code-block:: c
+
+ struct rte_acl_ctx *
+ rte_acl_create_v21(const struct rte_acl_param *param, int debug);
+ {
+ struct rte_acl_ctx *ctx = rte_acl_create_v20(param);
+
+ ctx->debug = debug;
+
+ return ctx;
+ }
+
+This code serves as our new API call. Its the same as our old call, but adds
+the new parameter in place. Next we need to map this function to the symbol
+``rte_acl_create@DPDK_2.1``. To do this, we modify the public prototype of the call
+in the header file, adding the macro there to inform all including applications,
+that on re-link, the default rte_acl_create symbol should point to this
+function. Note that we could do this by simply naming the function above
+rte_acl_create, and the linker would chose the most recent version tag to apply
+in the version script, but we can also do this in the header file
+
+.. code-block:: c
+
+ struct rte_acl_ctx *
+ -rte_acl_create(const struct rte_acl_param *param);
+ +rte_acl_create(const struct rte_acl_param *param, int debug);
+ +BIND_DEFAULT_SYMBOL(rte_acl_create, _v21, 2.1);
+
+The BIND_DEFAULT_SYMBOL macro explicitly tells applications that include this
+header, to link to the rte_acl_create_v21 function and apply the DPDK_2.1
+version node to it. This method is more explicit and flexible than just
+re-implementing the exact symbol name, and allows for other features (such as
+linking to the old symbol version by default, when the new ABI is to be opt-in
+for a period.
+
+One last thing we need to do. Note that we've taken what was a public symbol,
+and duplicated it into two uniquely and differently named symbols. We've then
+mapped each of those back to the public symbol ``rte_acl_create`` with different
+version tags. This only applies to dynamic linking, as static linking has no
+notion of versioning. That leaves this code in a position of no longer having a
+symbol simply named ``rte_acl_create`` and a static build will fail on that
+missing symbol.
+
+To correct this, we can simply map a function of our choosing back to the public
+symbol in the static build with the ``MAP_STATIC_SYMBOL`` macro. Generally the
+assumption is that the most recent version of the symbol is the one you want to
+map. So, back in the C file where, immediately after ``rte_acl_create_v21`` is
+defined, we add this
+
+.. code-block:: c
+
+ struct rte_acl_ctx *
+ rte_acl_create_v21(const struct rte_acl_param *param, int debug)
+ {
+ ...
+ }
+ MAP_STATIC_SYMBOL(struct rte_acl_ctx *rte_acl_create(const struct rte_acl_param *param, int debug), rte_acl_create_v21);
+
+That tells the compiler that, when building a static library, any calls to the
+symbol ``rte_acl_create`` should be linked to ``rte_acl_create_v21``
+
+That's it, on the next shared library rebuild, there will be two versions of
+rte_acl_create, an old DPDK_2.0 version, used by previously built applications,
+and a new DPDK_2.1 version, used by future built applications.
+
+
+Deprecating part of a public API
+________________________________
+
+Lets assume that you've done the above update, and after a few releases have
+passed you decide you would like to retire the old version of the function.
+After having gone through the ABI deprecation announcement process, removal is
+easy. Start by removing the symbol from the requisite version map file:
+
+.. code-block:: none
+
+ DPDK_2.0 {
+ global:
+
+ rte_acl_add_rules;
+ rte_acl_build;
+ rte_acl_classify;
+ rte_acl_classify_alg;
+ rte_acl_classify_scalar;
+ rte_acl_dump;
+ - rte_acl_create
+ rte_acl_find_existing;
+ rte_acl_free;
+ rte_acl_ipv4vlan_add_rules;
+ rte_acl_ipv4vlan_build;
+ rte_acl_list_dump;
+ rte_acl_reset;
+ rte_acl_reset_rules;
+ rte_acl_set_ctx_classify;
+
+ local: *;
+ };
+
+ DPDK_2.1 {
+ global:
+ rte_acl_create;
+ } DPDK_2.0;
+
+
+Next remove the corresponding versioned export.
+
+.. code-block:: c
+
+ -VERSION_SYMBOL(rte_acl_create, _v20, 2.0);
+
+
+Note that the internal function definition could also be removed, but its used
+in our example by the newer version _v21, so we leave it in place. This is a
+coding style choice.
+
+Lastly, we need to bump the LIBABIVER number for this library in the Makefile to
+indicate to applications doing dynamic linking that this is a later, and
+possibly incompatible library version:
+
+.. code-block:: c
+
+ -LIBABIVER := 1
+ +LIBABIVER := 2
+
+Deprecating an entire ABI version
+_________________________________
+
+While removing a symbol from and ABI may be useful, it is often more practical
+to remove an entire version node at once. If a version node completely
+specifies an API, then removing part of it, typically makes it incomplete. In
+those cases it is better to remove the entire node
+
+To do this, start by modifying the version map file, such that all symbols from
+the node to be removed are merged into the next node in the map
+
+In the case of our map above, it would transform to look as follows
+
+.. code-block:: none
+
+ DPDK_2.1 {
+ global:
+
+ rte_acl_add_rules;
+ rte_acl_build;
+ rte_acl_classify;
+ rte_acl_classify_alg;
+ rte_acl_classify_scalar;
+ rte_acl_dump;
+ rte_acl_create
+ rte_acl_find_existing;
+ rte_acl_free;
+ rte_acl_ipv4vlan_add_rules;
+ rte_acl_ipv4vlan_build;
+ rte_acl_list_dump;
+ rte_acl_reset;
+ rte_acl_reset_rules;
+ rte_acl_set_ctx_classify;
+
+ local: *;
+ };
+
+Then any uses of BIND_DEFAULT_SYMBOL that pointed to the old node should be
+updated to point to the new version node in any header files for all affected
+symbols.
+
+.. code-block:: c
+
+ -BIND_DEFAULT_SYMBOL(rte_acl_create, _v20, 2.0);
+ +BIND_DEFAULT_SYMBOL(rte_acl_create, _v21, 2.1);
+
+Lastly, any VERSION_SYMBOL macros that point to the old version node should be
+removed, taking care to keep, where need old code in place to support newer
+versions of the symbol.
+
+
+Running the ABI Validator
+-------------------------
+
+The ``devtools`` directory in the DPDK source tree contains a utility program,
+``validate-abi.sh``, for validating the DPDK ABI based on the Linux `ABI
+Compliance Checker
+<http://ispras.linuxbase.org/index.php/ABI_compliance_checker>`_.
+
+This has a dependency on the ``abi-compliance-checker`` and ``and abi-dumper``
+utilities which can be installed via a package manager. For example::
+
+ sudo yum install abi-compliance-checker
+ sudo yum install abi-dumper
+
+The syntax of the ``validate-abi.sh`` utility is::
+
+ ./devtools/validate-abi.sh <REV1> <REV2>
+
+Where ``REV1`` and ``REV2`` are valid gitrevisions(7)
+https://www.kernel.org/pub/software/scm/git/docs/gitrevisions.html
+on the local repo.
+
+For example::
+
+ # Check between the previous and latest commit:
+ ./devtools/validate-abi.sh HEAD~1 HEAD
+
+ # Check on a specific compilation target:
+ ./devtools/validate-abi.sh -t x86_64-native-linux-gcc HEAD~1 HEAD
+
+ # Check between two tags:
+ ./devtools/validate-abi.sh v2.0.0 v2.1.0
+
+ # Check between git master and local topic-branch "vhost-hacking":
+ ./devtools/validate-abi.sh master vhost-hacking
+
+After the validation script completes (it can take a while since it need to
+compile both tags) it will create compatibility reports in the
+``./abi-check/compat_report`` directory. Listed incompatibilities can be found
+as follows::
+
+ grep -lr Incompatible abi-check/compat_reports/
diff --git a/doc/guides/contributing/index.rst b/doc/guides/contributing/index.rst
index e2608d3..2fefd91 100644
--- a/doc/guides/contributing/index.rst
+++ b/doc/guides/contributing/index.rst
@@ -10,7 +10,8 @@ Contributor's Guidelines
coding_style
design
- versioning
+ abi_policy
+ abi_versioning
documentation
patches
vulnerability
diff --git a/doc/guides/contributing/versioning.rst b/doc/guides/contributing/versioning.rst
deleted file mode 100644
index 3ab2c43..0000000
--- a/doc/guides/contributing/versioning.rst
+++ /dev/null
@@ -1,591 +0,0 @@
-.. SPDX-License-Identifier: BSD-3-Clause
- Copyright 2018 The DPDK contributors
-
-DPDK ABI/API policy
-===================
-
-Description
------------
-
-This document details some methods for handling ABI management in the DPDK.
-
-General Guidelines
-------------------
-
-#. Whenever possible, ABI should be preserved
-#. ABI/API may be changed with a deprecation process
-#. The modification of symbols can generally be managed with versioning
-#. Libraries or APIs marked in ``experimental`` state may change without constraint
-#. New APIs will be marked as ``experimental`` for at least one release to allow
- any issues found by users of the new API to be fixed quickly
-#. The addition of symbols is generally not problematic
-#. The removal of symbols generally is an ABI break and requires bumping of the
- LIBABIVER macro
-#. Updates to the minimum hardware requirements, which drop support for hardware which
- was previously supported, should be treated as an ABI change.
-
-What is an ABI
-~~~~~~~~~~~~~~
-
-An ABI (Application Binary Interface) is the set of runtime interfaces exposed
-by a library. It is similar to an API (Application Programming Interface) but
-is the result of compilation. It is also effectively cloned when applications
-link to dynamic libraries. That is to say when an application is compiled to
-link against dynamic libraries, it is assumed that the ABI remains constant
-between the time the application is compiled/linked, and the time that it runs.
-Therefore, in the case of dynamic linking, it is critical that an ABI is
-preserved, or (when modified), done in such a way that the application is unable
-to behave improperly or in an unexpected fashion.
-
-
-ABI/API Deprecation
--------------------
-
-The DPDK ABI policy
-~~~~~~~~~~~~~~~~~~~
-
-ABI versions are set at the time of major release labeling, and the ABI may
-change multiple times, without warning, between the last release label and the
-HEAD label of the git tree.
-
-ABI versions, once released, are available until such time as their
-deprecation has been noted in the Release Notes for at least one major release
-cycle. For example consider the case where the ABI for DPDK 2.0 has been
-shipped and then a decision is made to modify it during the development of
-DPDK 2.1. The decision will be recorded in the Release Notes for the DPDK 2.1
-release and the modification will be made available in the DPDK 2.2 release.
-
-ABI versions may be deprecated in whole or in part as needed by a given
-update.
-
-Some ABI changes may be too significant to reasonably maintain multiple
-versions. In those cases ABI's may be updated without backward compatibility
-being provided. The requirements for doing so are:
-
-#. At least 3 acknowledgments of the need to do so must be made on the
- dpdk.org mailing list.
-
- - The acknowledgment of the maintainer of the component is mandatory, or if
- no maintainer is available for the component, the tree/sub-tree maintainer
- for that component must acknowledge the ABI change instead.
-
- - It is also recommended that acknowledgments from different "areas of
- interest" be sought for each deprecation, for example: from NIC vendors,
- CPU vendors, end-users, etc.
-
-#. The changes (including an alternative map file) can be included with
- deprecation notice, in wrapped way by the ``RTE_NEXT_ABI`` option,
- to provide more details about oncoming changes.
- ``RTE_NEXT_ABI`` wrapper will be removed when it become the default ABI.
- More preferred way to provide this information is sending the feature
- as a separate patch and reference it in deprecation notice.
-
-#. A full deprecation cycle, as explained above, must be made to offer
- downstream consumers sufficient warning of the change.
-
-Note that the above process for ABI deprecation should not be undertaken
-lightly. ABI stability is extremely important for downstream consumers of the
-DPDK, especially when distributed in shared object form. Every effort should
-be made to preserve the ABI whenever possible. The ABI should only be changed
-for significant reasons, such as performance enhancements. ABI breakage due to
-changes such as reorganizing public structure fields for aesthetic or
-readability purposes should be avoided.
-
-.. note::
-
- Updates to the minimum hardware requirements, which drop support for hardware
- which was previously supported, should be treated as an ABI change, and
- follow the relevant deprecation policy procedures as above: 3 acks and
- announcement at least one release in advance.
-
-Examples of Deprecation Notices
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-
-The following are some examples of ABI deprecation notices which would be
-added to the Release Notes:
-
-* The Macro ``#RTE_FOO`` is deprecated and will be removed with version 2.0,
- to be replaced with the inline function ``rte_foo()``.
-
-* The function ``rte_mbuf_grok()`` has been updated to include a new parameter
- in version 2.0. Backwards compatibility will be maintained for this function
- until the release of version 2.1
-
-* The members of ``struct rte_foo`` have been reorganized in release 2.0 for
- performance reasons. Existing binary applications will have backwards
- compatibility in release 2.0, while newly built binaries will need to
- reference the new structure variant ``struct rte_foo2``. Compatibility will
- be removed in release 2.2, and all applications will require updating and
- rebuilding to the new structure at that time, which will be renamed to the
- original ``struct rte_foo``.
-
-* Significant ABI changes are planned for the ``librte_dostuff`` library. The
- upcoming release 2.0 will not contain these changes, but release 2.1 will,
- and no backwards compatibility is planned due to the extensive nature of
- these changes. Binaries using this library built prior to version 2.1 will
- require updating and recompilation.
-
-New API replacing previous one
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-
-If a new API proposed functionally replaces an existing one, when the new API
-becomes non-experimental then the old one is marked with ``__rte_deprecated``.
-Deprecated APIs are removed completely just after the next LTS.
-
-Reminder that old API should follow deprecation process to be removed.
-
-
-Experimental APIs
------------------
-
-APIs marked as ``experimental`` are not considered part of the ABI and may
-change without warning at any time. Since changes to APIs are most likely
-immediately after their introduction, as users begin to take advantage of
-those new APIs and start finding issues with them, new DPDK APIs will be
-automatically marked as ``experimental`` to allow for a period of stabilization
-before they become part of a tracked ABI.
-
-Note that marking an API as experimental is a multi step process.
-To mark an API as experimental, the symbols which are desired to be exported
-must be placed in an EXPERIMENTAL version block in the corresponding libraries'
-version map script.
-Secondly, the corresponding prototypes of those exported functions (in the
-development header files), must be marked with the ``__rte_experimental`` tag
-(see ``rte_compat.h``).
-The DPDK build makefiles perform a check to ensure that the map file and the
-C code reflect the same list of symbols.
-This check can be circumvented by defining ``ALLOW_EXPERIMENTAL_API``
-during compilation in the corresponding library Makefile.
-
-In addition to tagging the code with ``__rte_experimental``,
-the doxygen markup must also contain the EXPERIMENTAL string,
-and the MAINTAINERS file should note the EXPERIMENTAL libraries.
-
-For removing the experimental tag associated with an API, deprecation notice
-is not required. Though, an API should remain in experimental state for at least
-one release. Thereafter, normal process of posting patch for review to mailing
-list can be followed.
-
-
-Library versioning
-------------------
-
-Downstreams might want to provide different DPDK releases at the same time to
-support multiple consumers of DPDK linked against older and newer sonames.
-
-Also due to the interdependencies that DPDK libraries can have applications
-might end up with an executable space in which multiple versions of a library
-are mapped by ld.so.
-
-Think of LibA that got an ABI bump and LibB that did not get an ABI bump but is
-depending on LibA.
-
-.. note::
-
- Application
- \-> LibA.old
- \-> LibB.new -> LibA.new
-
-That is a conflict which can be avoided by setting ``CONFIG_RTE_MAJOR_ABI``.
-If set, the value of ``CONFIG_RTE_MAJOR_ABI`` overwrites all - otherwise per
-library - versions defined in the libraries ``LIBABIVER``.
-An example might be ``CONFIG_RTE_MAJOR_ABI=16.11`` which will make all libraries
-``librte<?>.so.16.11`` instead of ``librte<?>.so.<LIBABIVER>``.
-
-
-ABI versioning
---------------
-
-Versioning Macros
-~~~~~~~~~~~~~~~~~
-
-When a symbol is exported from a library to provide an API, it also provides a
-calling convention (ABI) that is embodied in its name, return type and
-arguments. Occasionally that function may need to change to accommodate new
-functionality or behavior. When that occurs, it is desirable to allow for
-backward compatibility for a time with older binaries that are dynamically
-linked to the DPDK.
-
-To support backward compatibility the ``rte_compat.h``
-header file provides macros to use when updating exported functions. These
-macros are used in conjunction with the ``rte_<library>_version.map`` file for
-a given library to allow multiple versions of a symbol to exist in a shared
-library so that older binaries need not be immediately recompiled.
-
-The macros exported are:
-
-* ``VERSION_SYMBOL(b, e, n)``: Creates a symbol version table entry binding
- versioned symbol ``b@DPDK_n`` to the internal function ``b_e``.
-
-* ``BIND_DEFAULT_SYMBOL(b, e, n)``: Creates a symbol version entry instructing
- the linker to bind references to symbol ``b`` to the internal symbol
- ``b_e``.
-
-* ``MAP_STATIC_SYMBOL(f, p)``: Declare the prototype ``f``, and map it to the
- fully qualified function ``p``, so that if a symbol becomes versioned, it
- can still be mapped back to the public symbol name.
-
-Examples of ABI Macro use
-^^^^^^^^^^^^^^^^^^^^^^^^^
-
-Updating a public API
-_____________________
-
-Assume we have a function as follows
-
-.. code-block:: c
-
- /*
- * Create an acl context object for apps to
- * manipulate
- */
- struct rte_acl_ctx *
- rte_acl_create(const struct rte_acl_param *param)
- {
- ...
- }
-
-
-Assume that struct rte_acl_ctx is a private structure, and that a developer
-wishes to enhance the acl api so that a debugging flag can be enabled on a
-per-context basis. This requires an addition to the structure (which, being
-private, is safe), but it also requires modifying the code as follows
-
-.. code-block:: c
-
- /*
- * Create an acl context object for apps to
- * manipulate
- */
- struct rte_acl_ctx *
- rte_acl_create(const struct rte_acl_param *param, int debug)
- {
- ...
- }
-
-
-Note also that, being a public function, the header file prototype must also be
-changed, as must all the call sites, to reflect the new ABI footprint. We will
-maintain previous ABI versions that are accessible only to previously compiled
-binaries
-
-The addition of a parameter to the function is ABI breaking as the function is
-public, and existing application may use it in its current form. However, the
-compatibility macros in DPDK allow a developer to use symbol versioning so that
-multiple functions can be mapped to the same public symbol based on when an
-application was linked to it. To see how this is done, we start with the
-requisite libraries version map file. Initially the version map file for the
-acl library looks like this
-
-.. code-block:: none
-
- DPDK_2.0 {
- global:
-
- rte_acl_add_rules;
- rte_acl_build;
- rte_acl_classify;
- rte_acl_classify_alg;
- rte_acl_classify_scalar;
- rte_acl_create;
- rte_acl_dump;
- rte_acl_find_existing;
- rte_acl_free;
- rte_acl_ipv4vlan_add_rules;
- rte_acl_ipv4vlan_build;
- rte_acl_list_dump;
- rte_acl_reset;
- rte_acl_reset_rules;
- rte_acl_set_ctx_classify;
-
- local: *;
- };
-
-This file needs to be modified as follows
-
-.. code-block:: none
-
- DPDK_2.0 {
- global:
-
- rte_acl_add_rules;
- rte_acl_build;
- rte_acl_classify;
- rte_acl_classify_alg;
- rte_acl_classify_scalar;
- rte_acl_create;
- rte_acl_dump;
- rte_acl_find_existing;
- rte_acl_free;
- rte_acl_ipv4vlan_add_rules;
- rte_acl_ipv4vlan_build;
- rte_acl_list_dump;
- rte_acl_reset;
- rte_acl_reset_rules;
- rte_acl_set_ctx_classify;
-
- local: *;
- };
-
- DPDK_2.1 {
- global:
- rte_acl_create;
-
- } DPDK_2.0;
-
-The addition of the new block tells the linker that a new version node is
-available (DPDK_2.1), which contains the symbol rte_acl_create, and inherits the
-symbols from the DPDK_2.0 node. This list is directly translated into a list of
-exported symbols when DPDK is compiled as a shared library
-
-Next, we need to specify in the code which function map to the rte_acl_create
-symbol at which versions. First, at the site of the initial symbol definition,
-we need to update the function so that it is uniquely named, and not in conflict
-with the public symbol name
-
-.. code-block:: c
-
- struct rte_acl_ctx *
- -rte_acl_create(const struct rte_acl_param *param)
- +rte_acl_create_v20(const struct rte_acl_param *param)
- {
- size_t sz;
- struct rte_acl_ctx *ctx;
- ...
-
-Note that the base name of the symbol was kept intact, as this is conducive to
-the macros used for versioning symbols. That is our next step, mapping this new
-symbol name to the initial symbol name at version node 2.0. Immediately after
-the function, we add this line of code
-
-.. code-block:: c
-
- VERSION_SYMBOL(rte_acl_create, _v20, 2.0);
-
-Remembering to also add the rte_compat.h header to the requisite c file where
-these changes are being made. The above macro instructs the linker to create a
-new symbol ``rte_acl_create@DPDK_2.0``, which matches the symbol created in older
-builds, but now points to the above newly named function. We have now mapped
-the original rte_acl_create symbol to the original function (but with a new
-name)
-
-Next, we need to create the 2.1 version of the symbol. We create a new function
-name, with a different suffix, and implement it appropriately
-
-.. code-block:: c
-
- struct rte_acl_ctx *
- rte_acl_create_v21(const struct rte_acl_param *param, int debug);
- {
- struct rte_acl_ctx *ctx = rte_acl_create_v20(param);
-
- ctx->debug = debug;
-
- return ctx;
- }
-
-This code serves as our new API call. Its the same as our old call, but adds
-the new parameter in place. Next we need to map this function to the symbol
-``rte_acl_create@DPDK_2.1``. To do this, we modify the public prototype of the call
-in the header file, adding the macro there to inform all including applications,
-that on re-link, the default rte_acl_create symbol should point to this
-function. Note that we could do this by simply naming the function above
-rte_acl_create, and the linker would chose the most recent version tag to apply
-in the version script, but we can also do this in the header file
-
-.. code-block:: c
-
- struct rte_acl_ctx *
- -rte_acl_create(const struct rte_acl_param *param);
- +rte_acl_create(const struct rte_acl_param *param, int debug);
- +BIND_DEFAULT_SYMBOL(rte_acl_create, _v21, 2.1);
-
-The BIND_DEFAULT_SYMBOL macro explicitly tells applications that include this
-header, to link to the rte_acl_create_v21 function and apply the DPDK_2.1
-version node to it. This method is more explicit and flexible than just
-re-implementing the exact symbol name, and allows for other features (such as
-linking to the old symbol version by default, when the new ABI is to be opt-in
-for a period.
-
-One last thing we need to do. Note that we've taken what was a public symbol,
-and duplicated it into two uniquely and differently named symbols. We've then
-mapped each of those back to the public symbol ``rte_acl_create`` with different
-version tags. This only applies to dynamic linking, as static linking has no
-notion of versioning. That leaves this code in a position of no longer having a
-symbol simply named ``rte_acl_create`` and a static build will fail on that
-missing symbol.
-
-To correct this, we can simply map a function of our choosing back to the public
-symbol in the static build with the ``MAP_STATIC_SYMBOL`` macro. Generally the
-assumption is that the most recent version of the symbol is the one you want to
-map. So, back in the C file where, immediately after ``rte_acl_create_v21`` is
-defined, we add this
-
-.. code-block:: c
-
- struct rte_acl_ctx *
- rte_acl_create_v21(const struct rte_acl_param *param, int debug)
- {
- ...
- }
- MAP_STATIC_SYMBOL(struct rte_acl_ctx *rte_acl_create(const struct rte_acl_param *param, int debug), rte_acl_create_v21);
-
-That tells the compiler that, when building a static library, any calls to the
-symbol ``rte_acl_create`` should be linked to ``rte_acl_create_v21``
-
-That's it, on the next shared library rebuild, there will be two versions of
-rte_acl_create, an old DPDK_2.0 version, used by previously built applications,
-and a new DPDK_2.1 version, used by future built applications.
-
-
-Deprecating part of a public API
-________________________________
-
-Lets assume that you've done the above update, and after a few releases have
-passed you decide you would like to retire the old version of the function.
-After having gone through the ABI deprecation announcement process, removal is
-easy. Start by removing the symbol from the requisite version map file:
-
-.. code-block:: none
-
- DPDK_2.0 {
- global:
-
- rte_acl_add_rules;
- rte_acl_build;
- rte_acl_classify;
- rte_acl_classify_alg;
- rte_acl_classify_scalar;
- rte_acl_dump;
- - rte_acl_create
- rte_acl_find_existing;
- rte_acl_free;
- rte_acl_ipv4vlan_add_rules;
- rte_acl_ipv4vlan_build;
- rte_acl_list_dump;
- rte_acl_reset;
- rte_acl_reset_rules;
- rte_acl_set_ctx_classify;
-
- local: *;
- };
-
- DPDK_2.1 {
- global:
- rte_acl_create;
- } DPDK_2.0;
-
-
-Next remove the corresponding versioned export.
-
-.. code-block:: c
-
- -VERSION_SYMBOL(rte_acl_create, _v20, 2.0);
-
-
-Note that the internal function definition could also be removed, but its used
-in our example by the newer version _v21, so we leave it in place. This is a
-coding style choice.
-
-Lastly, we need to bump the LIBABIVER number for this library in the Makefile to
-indicate to applications doing dynamic linking that this is a later, and
-possibly incompatible library version:
-
-.. code-block:: c
-
- -LIBABIVER := 1
- +LIBABIVER := 2
-
-Deprecating an entire ABI version
-_________________________________
-
-While removing a symbol from and ABI may be useful, it is often more practical
-to remove an entire version node at once. If a version node completely
-specifies an API, then removing part of it, typically makes it incomplete. In
-those cases it is better to remove the entire node
-
-To do this, start by modifying the version map file, such that all symbols from
-the node to be removed are merged into the next node in the map
-
-In the case of our map above, it would transform to look as follows
-
-.. code-block:: none
-
- DPDK_2.1 {
- global:
-
- rte_acl_add_rules;
- rte_acl_build;
- rte_acl_classify;
- rte_acl_classify_alg;
- rte_acl_classify_scalar;
- rte_acl_dump;
- rte_acl_create
- rte_acl_find_existing;
- rte_acl_free;
- rte_acl_ipv4vlan_add_rules;
- rte_acl_ipv4vlan_build;
- rte_acl_list_dump;
- rte_acl_reset;
- rte_acl_reset_rules;
- rte_acl_set_ctx_classify;
-
- local: *;
- };
-
-Then any uses of BIND_DEFAULT_SYMBOL that pointed to the old node should be
-updated to point to the new version node in any header files for all affected
-symbols.
-
-.. code-block:: c
-
- -BIND_DEFAULT_SYMBOL(rte_acl_create, _v20, 2.0);
- +BIND_DEFAULT_SYMBOL(rte_acl_create, _v21, 2.1);
-
-Lastly, any VERSION_SYMBOL macros that point to the old version node should be
-removed, taking care to keep, where need old code in place to support newer
-versions of the symbol.
-
-
-Running the ABI Validator
--------------------------
-
-The ``devtools`` directory in the DPDK source tree contains a utility program,
-``validate-abi.sh``, for validating the DPDK ABI based on the Linux `ABI
-Compliance Checker
-<http://ispras.linuxbase.org/index.php/ABI_compliance_checker>`_.
-
-This has a dependency on the ``abi-compliance-checker`` and ``and abi-dumper``
-utilities which can be installed via a package manager. For example::
-
- sudo yum install abi-compliance-checker
- sudo yum install abi-dumper
-
-The syntax of the ``validate-abi.sh`` utility is::
-
- ./devtools/validate-abi.sh <REV1> <REV2>
-
-Where ``REV1`` and ``REV2`` are valid gitrevisions(7)
-https://www.kernel.org/pub/software/scm/git/docs/gitrevisions.html
-on the local repo.
-
-For example::
-
- # Check between the previous and latest commit:
- ./devtools/validate-abi.sh HEAD~1 HEAD
-
- # Check on a specific compilation target:
- ./devtools/validate-abi.sh -t x86_64-native-linux-gcc HEAD~1 HEAD
-
- # Check between two tags:
- ./devtools/validate-abi.sh v2.0.0 v2.1.0
-
- # Check between git master and local topic-branch "vhost-hacking":
- ./devtools/validate-abi.sh master vhost-hacking
-
-After the validation script completes (it can take a while since it need to
-compile both tags) it will create compatibility reports in the
-``./abi-check/compat_report`` directory. Listed incompatibilities can be found
-as follows::
-
- grep -lr Incompatible abi-check/compat_reports/
--
2.7.4
^ permalink raw reply [flat|nested] 8+ messages in thread* [dpdk-dev] [PATCH v3 2/4] doc: changes to abi policy introducing major abi versions
2019-08-15 10:23 [dpdk-dev] [PATCH v3 0/4] doc: changes to abi policy introducing major abi versions Ray Kinsella
2019-08-15 10:23 ` [dpdk-dev] [PATCH v3 1/4] doc: separate versioning.rst into version and policy Ray Kinsella
@ 2019-08-15 10:23 ` Ray Kinsella
2019-08-30 16:20 ` Kevin Traynor
2019-08-15 10:23 ` [dpdk-dev] [PATCH v3 3/4] doc: updates to versioning guide for " Ray Kinsella
2019-08-15 10:23 ` [dpdk-dev] [PATCH v3 4/4] doc: add maintainer for abi policy Ray Kinsella
3 siblings, 1 reply; 8+ messages in thread
From: Ray Kinsella @ 2019-08-15 10:23 UTC (permalink / raw)
To: dev
Cc: mdr, thomas, stephen, bruce.richardson, ferruh.yigit,
konstantin.ananyev, jerinj, olivier.matz, nhorman,
maxime.coquelin, john.mcnamara, marko.kovacevic, hemant.agrawal
This policy change introduces major ABI versions, these are
declared every year, typically aligned with the LTS release
and are supported by subsequent releases in the following year.
This change is intended to improve ABI stabilty for those projects
consuming DPDK.
Signed-off-by: Ray Kinsella <mdr@ashroe.eu>
---
doc/guides/contributing/abi_policy.rst | 308 ++++++++++++++++++++++++---------
doc/guides/contributing/stable.rst | 38 ++--
2 files changed, 245 insertions(+), 101 deletions(-)
diff --git a/doc/guides/contributing/abi_policy.rst b/doc/guides/contributing/abi_policy.rst
index 55bacb4..6190bdc 100644
--- a/doc/guides/contributing/abi_policy.rst
+++ b/doc/guides/contributing/abi_policy.rst
@@ -1,33 +1,46 @@
.. SPDX-License-Identifier: BSD-3-Clause
- Copyright 2018 The DPDK contributors
+ Copyright 2019 The DPDK contributors
-.. abi_api_policy:
+.. _abi_policy:
-DPDK ABI/API policy
-===================
+ABI Policy
+==========
Description
-----------
-This document details some methods for handling ABI management in the DPDK.
+This document details the management policy that ensures the long-term stability
+of the DPDK ABI and API.
General Guidelines
------------------
-#. Whenever possible, ABI should be preserved
-#. ABI/API may be changed with a deprecation process
-#. The modification of symbols can generally be managed with versioning
-#. Libraries or APIs marked in ``experimental`` state may change without constraint
-#. New APIs will be marked as ``experimental`` for at least one release to allow
- any issues found by users of the new API to be fixed quickly
-#. The addition of symbols is generally not problematic
-#. The removal of symbols generally is an ABI break and requires bumping of the
- LIBABIVER macro
-#. Updates to the minimum hardware requirements, which drop support for hardware which
- was previously supported, should be treated as an ABI change.
-
-What is an ABI
-~~~~~~~~~~~~~~
+#. Major ABI versions are declared every **year** and are then supported for one
+ year, typically aligned with the :ref:`LTS release <stable_lts_releases>`.
+#. The ABI version is managed at a project level in DPDK, with the ABI version
+ reflected in all :ref:`library's soname <what_is_soname>`.
+#. The ABI should be preserved and not changed lightly. ABI changes must follow
+ the outlined :ref:`deprecation process <abi_changes>`.
+#. The addition of symbols is generally not problematic. The modification of
+ symbols is managed with :ref:`ABI Versioning <abi_versioning>`.
+#. The removal of symbols is considered an :ref:`ABI breakage <abi_breakages>`,
+ once approved these will form part of the next ABI version.
+#. Libraries or APIs marked as :ref:`Experimental <experimental_apis>` are not
+ considered part of an ABI version and may change without constraint.
+#. Updates to the :ref:`minimum hardware requirements <hw_rqmts>`, which drop
+ support for hardware which was previously supported, should be treated as an
+ ABI change.
+
+.. note::
+
+ In 2019, the DPDK community stated it's intention to move to ABI stable
+ releases, over a number of release cycles. Beginning with maintaining ABI
+ stability through one year of DPDK releases starting from DPDK 19.11. This
+ policy will be reviewed in 2020, with intention of lengthening the stability
+ period.
+
+What is an ABI?
+~~~~~~~~~~~~~~~
An ABI (Application Binary Interface) is the set of runtime interfaces exposed
by a library. It is similar to an API (Application Programming Interface) but
@@ -39,30 +52,67 @@ Therefore, in the case of dynamic linking, it is critical that an ABI is
preserved, or (when modified), done in such a way that the application is unable
to behave improperly or in an unexpected fashion.
+What is an ABI version?
+~~~~~~~~~~~~~~~~~~~~~~~
-ABI/API Deprecation
--------------------
+An ABI version is an instance of a library's ABI at a specific release. Certain
+releases are considered by the community to be milestone releases, the yearly
+LTS for example. Supporting those milestone release's ABI for some number of
+subsequent releases is desirable to facilitate application upgrade. Those ABI
+version's aligned with milestones release are therefore called 'ABI major
+versions' and are supported for some number of releases.
+
+More details on major ABI version can be found in the :ref:`ABI versioning
+<major_abi_versions>` guide.
The DPDK ABI policy
-~~~~~~~~~~~~~~~~~~~
+-------------------
+
+A major ABI version is declared every year, aligned with that year's LTS
+release, e.g. v19.11. This ABI version is then supported for one year by all
+subsequent releases within that time period, until the next LTS release, e.g.
+v20.11.
+
+At the declaration of a major ABI version, major version numbers encoded in
+libraries soname's are bumped to indicate the new version, with the minor
+version reset to ``0``. An example would be ``librte_eal.so.20.3`` would become
+``librte_eal.so.21.0``.
+
+The ABI may then change multiple times, without warning, between the last major
+ABI version increment and the HEAD label of the git tree, with the condition
+that ABI compatibility with the major ABI version is preserved and therefore
+soname's do not change.
+
+Minor versions are incremented to indicate the release of a new ABI compatible
+DPDK release, typically the DPDK quarterly releases. An example of this, might
+be that ``librte_eal.so.20.1`` would indicate the first ABI compatible DPDK
+release, following the declaration of the new major ABI version ``20``.
+
+ABI versions, are supported by each release until such time as the next major
+ABI version is declared. At that time, the deprecation of the previous major ABI
+version will be noted in the Release Notes with guidance on individual symbol
+depreciation and upgrade notes provided.
-ABI versions are set at the time of major release labeling, and the ABI may
-change multiple times, without warning, between the last release label and the
-HEAD label of the git tree.
+.. _abi_changes:
-ABI versions, once released, are available until such time as their
-deprecation has been noted in the Release Notes for at least one major release
-cycle. For example consider the case where the ABI for DPDK 2.0 has been
-shipped and then a decision is made to modify it during the development of
-DPDK 2.1. The decision will be recorded in the Release Notes for the DPDK 2.1
-release and the modification will be made available in the DPDK 2.2 release.
+ABI Changes
+~~~~~~~~~~~
-ABI versions may be deprecated in whole or in part as needed by a given
-update.
+The ABI may still change after the declaration of a major ABI version, that is
+new APIs may be still added or existing APIs may be modified.
-Some ABI changes may be too significant to reasonably maintain multiple
-versions. In those cases ABI's may be updated without backward compatibility
-being provided. The requirements for doing so are:
+.. Warning::
+
+ Note that, the process for ABI deprecation should not be undertaken lightly.
+ ABI stability is extremely important for downstream consumers of the DPDK,
+ especially when distributed in shared object form. Every effort should be
+ made to preserve the ABI whenever possible. The ABI should only be changed
+ for significant reasons, such as performance enhancements. ABI breakage due
+ to changes such as reorganizing public structure fields for aesthetic or
+ readability purposes should be avoided.
+
+
+The requirements for changing the ABI are:
#. At least 3 acknowledgments of the need to do so must be made on the
dpdk.org mailing list.
@@ -71,34 +121,119 @@ being provided. The requirements for doing so are:
no maintainer is available for the component, the tree/sub-tree maintainer
for that component must acknowledge the ABI change instead.
+ - The acknowledgment of a member of the technical board, as a delegate of the
+ `technical board <https://core.dpdk.org/techboard/>`_ acknowledging the
+ need for the ABI change, is also mandatory.
+
- It is also recommended that acknowledgments from different "areas of
interest" be sought for each deprecation, for example: from NIC vendors,
CPU vendors, end-users, etc.
-#. The changes (including an alternative map file) can be included with
- deprecation notice, in wrapped way by the ``RTE_NEXT_ABI`` option,
- to provide more details about oncoming changes.
- ``RTE_NEXT_ABI`` wrapper will be removed when it become the default ABI.
- More preferred way to provide this information is sending the feature
- as a separate patch and reference it in deprecation notice.
+#. Backward compatibly with the major ABI version must be maintained through
+ :ref:`abi_versioning`, with :ref:`forward-only <forward-only>` compatibility
+ offered for any ABI changes that are indicated to be part of the next ABI
+ version.
-#. A full deprecation cycle, as explained above, must be made to offer
- downstream consumers sufficient warning of the change.
+ - In situations were backward compatibility is not possible, read the
+ section on :ref:`abi_breakages`.
-Note that the above process for ABI deprecation should not be undertaken
-lightly. ABI stability is extremely important for downstream consumers of the
-DPDK, especially when distributed in shared object form. Every effort should
-be made to preserve the ABI whenever possible. The ABI should only be changed
-for significant reasons, such as performance enhancements. ABI breakage due to
-changes such as reorganizing public structure fields for aesthetic or
-readability purposes should be avoided.
+ - No backward or forward compatibility is offered for API changes marked as
+ ``experimental``, as described in the section on :ref:`Experimental APIs
+ and Libraries <experimental_apis>`.
-.. note::
+#. If a newly proposed API functionally replaces an existing one, when the new
+ API becomes non-experimental, then the old one is marked with
+ ``__rte_deprecated``.
+
+ - The depreciated API should follow the notification process to be removed,
+ see :ref:`deprecation_notices`.
+
+ - At the declaration of the next major ABI version, those ABI changes then
+ become a formal part of the new ABI and the requirement to preserve ABI
+ compatibility with the last major ABI version is then dropped.
+
+ - The responsibility for removing redundant ABI compatibility code rests
+ with the original contributor of the ABI changes, failing that, then with
+ the contributor's company and then finally with the maintainer.
+
+.. _forward-only:
+
+.. Note::
+
+ Note that forward-only compatibility is offered for those changes made
+ between major ABI versions. As a library's soname can only describe
+ compatibility with the last major ABI version, until the next major ABI
+ version is declared, these changes therefore cannot be resolved as a runtime
+ dependency through the soname. Therefore any application wishing to make use
+ of these ABI changes can only ensure that it's runtime dependencies are met
+ through Operating System package versioning.
+
+.. _hw_rqmts:
+
+.. Note::
Updates to the minimum hardware requirements, which drop support for hardware
which was previously supported, should be treated as an ABI change, and
- follow the relevant deprecation policy procedures as above: 3 acks and
- announcement at least one release in advance.
+ follow the relevant deprecation policy procedures as above: 3 acks, technical
+ board approval and announcement at least one release in advance.
+
+.. _abi_breakages:
+
+ABI Breakages
+~~~~~~~~~~~~~
+
+For those ABI changes that are too significant to reasonably maintain multiple
+symbol versions, there is an amended process. In these cases, ABIs may be
+updated without the requirement of backward compatibility being provided. These
+changes must follow the `same process :ref:`described above <abi_changes>` as non-breaking
+changes, however with the following additional requirements:
+
+#. ABI breaking changes (including an alternative map file) can be included with
+ deprecation notice, in wrapped way by the ``RTE_NEXT_ABI`` option, to provide
+ more details about oncoming changes. ``RTE_NEXT_ABI`` wrapper will be removed
+ at the declaration of the next major ABI version.
+
+#. Once approved, and after the depreciation notice has been observed these
+ changes will form part of the next declared major ABI version.
+
+Examples of ABI Changes
+~~~~~~~~~~~~~~~~~~~~~~~
+
+The following are examples of allowable ABI changes occurring between
+declarations of major ABI versions.
+
+* DPDK 19.11 release, defines the function ``rte_foo()``, and ``rte_foo()``
+ as part of the major ABI version ``20``.
+
+* DPDK 20.02 release defines a new function ``rte_foo(uint8_t bar)``, and
+ this is not a problem as long as the symbol ``rte_foo@DPDK20`` is
+ preserved through :ref:`abi_versioning`.
+
+ - The new function may be marked with the ``__rte_experimental`` tag for a
+ number of releases, as described in the section :ref:`experimental_apis`.
+
+ - Once ``rte_foo(uint8_t bar)`` becomes non-experimental ``rte_foo()`` is then
+ declared as ``__rte_depreciated``, with an associated deprecation notice
+ provided.
+
+* DPDK 19.11 is not re-released to include ``rte_foo(uint8_t bar)``, the new
+ version of ``rte_foo`` only exists from DPDK 20.02 onwards as described in the
+ :ref:`note on forward-only compatibility<forward-only>`.
+
+* DPDK 20.02 release defines the experimental function ``__rte_experimental
+ rte_baz()``. This function may or may not exist in the DPDK 20.05 release.
+
+* An application ``dPacket`` wishes to use ``rte_foo(uint8_t bar)``, before the
+ declaration of the DPDK ``21`` major API version. The application can only
+ ensure it's runtime dependencies are met by specifying ``DPDK (>= 20.2)`` as
+ an explicit package dependency, as the soname only may only indicate the
+ supported major ABI version.
+
+* At the release of DPDK 20.11, the function ``rte_foo(uint8_t bar)`` becomes
+ formally part of then new major ABI version DPDK 21.0 and ``rte_foo()`` may be
+ removed.
+
+.. _deprecation_notices:
Examples of Deprecation Notices
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
@@ -106,46 +241,42 @@ Examples of Deprecation Notices
The following are some examples of ABI deprecation notices which would be
added to the Release Notes:
-* The Macro ``#RTE_FOO`` is deprecated and will be removed with version 2.0,
- to be replaced with the inline function ``rte_foo()``.
+* The Macro ``#RTE_FOO`` is deprecated and will be removed with ABI version
+ 21, to be replaced with the inline function ``rte_foo()``.
* The function ``rte_mbuf_grok()`` has been updated to include a new parameter
- in version 2.0. Backwards compatibility will be maintained for this function
- until the release of version 2.1
+ in version 20.2. Backwards compatibility will be maintained for this function
+ until the release of the new DPDK major ABI version 21, in DPDK version
+ 20.11.
-* The members of ``struct rte_foo`` have been reorganized in release 2.0 for
+* The members of ``struct rte_foo`` have been reorganized in DPDK 20.02 for
performance reasons. Existing binary applications will have backwards
- compatibility in release 2.0, while newly built binaries will need to
- reference the new structure variant ``struct rte_foo2``. Compatibility will
- be removed in release 2.2, and all applications will require updating and
+ compatibility in release 20.02, while newly built binaries will need to
+ reference the new structure variant ``struct rte_foo2``. Compatibility will be
+ removed in release 20.11, and all applications will require updating and
rebuilding to the new structure at that time, which will be renamed to the
original ``struct rte_foo``.
* Significant ABI changes are planned for the ``librte_dostuff`` library. The
- upcoming release 2.0 will not contain these changes, but release 2.1 will,
+ upcoming release 20.02 will not contain these changes, but release 20.11 will,
and no backwards compatibility is planned due to the extensive nature of
- these changes. Binaries using this library built prior to version 2.1 will
+ these changes. Binaries using this library built prior to ABI version 21 will
require updating and recompilation.
-New API replacing previous one
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-
-If a new API proposed functionally replaces an existing one, when the new API
-becomes non-experimental then the old one is marked with ``__rte_deprecated``.
-Deprecated APIs are removed completely just after the next LTS.
-
-Reminder that old API should follow deprecation process to be removed.
+.. _experimental_apis:
+Experimental
+------------
-Experimental APIs
------------------
+APIs
+~~~~
-APIs marked as ``experimental`` are not considered part of the ABI and may
-change without warning at any time. Since changes to APIs are most likely
-immediately after their introduction, as users begin to take advantage of
-those new APIs and start finding issues with them, new DPDK APIs will be
-automatically marked as ``experimental`` to allow for a period of stabilization
-before they become part of a tracked ABI.
+APIs marked as ``experimental`` are not considered part of an ABI version and
+may change without warning at any time. Since changes to APIs are most likely
+immediately after their introduction, as users begin to take advantage of those
+new APIs and start finding issues with them, new DPDK APIs will be automatically
+marked as ``experimental`` to allow for a period of stabilization before they
+become part of a tracked ABI version.
Note that marking an API as experimental is a multi step process.
To mark an API as experimental, the symbols which are desired to be exported
@@ -163,7 +294,16 @@ In addition to tagging the code with ``__rte_experimental``,
the doxygen markup must also contain the EXPERIMENTAL string,
and the MAINTAINERS file should note the EXPERIMENTAL libraries.
-For removing the experimental tag associated with an API, deprecation notice
-is not required. Though, an API should remain in experimental state for at least
-one release. Thereafter, normal process of posting patch for review to mailing
-list can be followed.
+For removing the experimental tag associated with an API, deprecation notice is
+not required. Though, an API should remain in experimental state for at least
+one release. Thereafter, the normal process of posting patch for review to
+mailing list can be followed.
+
+Libraries
+~~~~~~~~~
+
+Libraries marked as ``experimental`` are entirely not considered part of an ABI
+version, and may change without warning at any time. Experimental libraries
+always have a major version of ``0`` to indicate they exist outside of
+:ref:`abi_versioning` , with the minor version incremented with each ABI change
+to library.
diff --git a/doc/guides/contributing/stable.rst b/doc/guides/contributing/stable.rst
index 6a5eee9..d95c200 100644
--- a/doc/guides/contributing/stable.rst
+++ b/doc/guides/contributing/stable.rst
@@ -1,7 +1,7 @@
.. SPDX-License-Identifier: BSD-3-Clause
Copyright 2018 The DPDK contributors
-.. stable_lts_releases:
+.. _stable_lts_releases:
DPDK Stable Releases and Long Term Support
==========================================
@@ -53,6 +53,9 @@ year's November (X.11) release will be maintained as an LTS for 2 years.
After the X.11 release, an LTS branch will be created for it at
http://git.dpdk.org/dpdk-stable where bugfixes will be backported to.
+A LTS release may align with the declaration of a new major ABI version,
+please read the :ref:`abi_policy` for more information.
+
It is anticipated that there will be at least 4 releases per year of the LTS
or approximately 1 every 3 months. However, the cadence can be shorter or
longer depending on the number and criticality of the backported
@@ -68,10 +71,13 @@ point the LTS branch will no longer be maintained with no further releases.
What changes should be backported
---------------------------------
-Backporting should be limited to bug fixes. All patches accepted on the master
-branch with a Fixes: tag should be backported to the relevant stable/LTS
-branches, unless the submitter indicates otherwise. If there are exceptions,
-they will be discussed on the mailing lists.
+Backporting is a naturally conservative activity, and therefore should only
+include bug fixes and support for new hardware, were adding support does not
+necessitate DPDK ABI/API changes.
+
+All patches accepted on the master branch with a Fixes: tag should be backported
+to the relevant stable/LTS branches, unless the submitter indicates otherwise.
+If there are exceptions, they will be discussed on the mailing lists.
Fixes suitable for backport should have a ``Cc: stable@dpdk.org`` tag in the
commit message body as follows::
@@ -86,13 +92,18 @@ commit message body as follows::
Signed-off-by: Alex Smith <alex.smith@example.com>
-Fixes not suitable for backport should not include the ``Cc: stable@dpdk.org`` tag.
+Fixes not suitable for backport should not include the ``Cc: stable@dpdk.org``
+tag.
-Features should not be backported to stable releases. It may be acceptable, in
-limited cases, to back port features for the LTS release where:
+New features, with the exception of new hardware support, should not be
+backported to stable releases. In the case of new hardware support or any other
+exceptional circumstances limited backporting maybe permitted to the LTS release
+where:
-* There is a justifiable use case (for example a new PMD).
-* The change is non-invasive.
+* There is a justifiable use case, for example the change is required to support
+ a new platform or device (for example a new PMD).
+* The change is ABI/API preserving, it does not present an obvious "new feature"
+ to end consumer.
* The work of preparing the backport is done by the proposer.
* There is support within the community.
@@ -119,10 +130,3 @@ A Stable Release will be released by:
list.
Stable releases are available on the `dpdk.org download page <http://core.dpdk.org/download/>`_.
-
-
-ABI
----
-
-The Stable Release should not be seen as a way of breaking or circumventing
-the DPDK ABI policy.
--
2.7.4
^ permalink raw reply [flat|nested] 8+ messages in thread* Re: [dpdk-dev] [PATCH v3 2/4] doc: changes to abi policy introducing major abi versions
2019-08-15 10:23 ` [dpdk-dev] [PATCH v3 2/4] doc: changes to abi policy introducing major abi versions Ray Kinsella
@ 2019-08-30 16:20 ` Kevin Traynor
2019-09-24 11:32 ` Ray Kinsella
0 siblings, 1 reply; 8+ messages in thread
From: Kevin Traynor @ 2019-08-30 16:20 UTC (permalink / raw)
To: Ray Kinsella, dev
Cc: thomas, stephen, bruce.richardson, ferruh.yigit,
konstantin.ananyev, jerinj, olivier.matz, nhorman,
maxime.coquelin, john.mcnamara, marko.kovacevic, hemant.agrawal,
Luca Boccassi, David Marchand
Hi Ray,
On 15/08/2019 11:23, Ray Kinsella wrote:
> This policy change introduces major ABI versions, these are
> declared every year, typically aligned with the LTS release
> and are supported by subsequent releases in the following year.
> This change is intended to improve ABI stabilty for those projects
> consuming DPDK.
>
> Signed-off-by: Ray Kinsella <mdr@ashroe.eu>
> ---
> doc/guides/contributing/abi_policy.rst | 308 ++++++++++++++++++++++++---------
> doc/guides/contributing/stable.rst | 38 ++--
> 2 files changed, 245 insertions(+), 101 deletions(-)
>
> diff --git a/doc/guides/contributing/abi_policy.rst b/doc/guides/contributing/abi_policy.rst
> index 55bacb4..6190bdc 100644
> --- a/doc/guides/contributing/abi_policy.rst
> +++ b/doc/guides/contributing/abi_policy.rst
> @@ -1,33 +1,46 @@
> .. SPDX-License-Identifier: BSD-3-Clause
> - Copyright 2018 The DPDK contributors
> + Copyright 2019 The DPDK contributors
>
> -.. abi_api_policy:
> +.. _abi_policy:
>
> -DPDK ABI/API policy
> -===================
> +ABI Policy
> +==========
>
> Description
> -----------
>
> -This document details some methods for handling ABI management in the DPDK.
> +This document details the management policy that ensures the long-term stability
> +of the DPDK ABI and API.
>
> General Guidelines
> ------------------
>
> -#. Whenever possible, ABI should be preserved
> -#. ABI/API may be changed with a deprecation process
> -#. The modification of symbols can generally be managed with versioning
> -#. Libraries or APIs marked in ``experimental`` state may change without constraint
> -#. New APIs will be marked as ``experimental`` for at least one release to allow
> - any issues found by users of the new API to be fixed quickly
> -#. The addition of symbols is generally not problematic
> -#. The removal of symbols generally is an ABI break and requires bumping of the
> - LIBABIVER macro
> -#. Updates to the minimum hardware requirements, which drop support for hardware which
> - was previously supported, should be treated as an ABI change.
> -
> -What is an ABI
> -~~~~~~~~~~~~~~
> +#. Major ABI versions are declared every **year** and are then supported for one
> + year, typically aligned with the :ref:`LTS release <stable_lts_releases>`.
> +#. The ABI version is managed at a project level in DPDK, with the ABI version
> + reflected in all :ref:`library's soname <what_is_soname>`.
> +#. The ABI should be preserved and not changed lightly. ABI changes must follow
> + the outlined :ref:`deprecation process <abi_changes>`.
> +#. The addition of symbols is generally not problematic. The modification of
> + symbols is managed with :ref:`ABI Versioning <abi_versioning>`.
> +#. The removal of symbols is considered an :ref:`ABI breakage <abi_breakages>`,
> + once approved these will form part of the next ABI version.
> +#. Libraries or APIs marked as :ref:`Experimental <experimental_apis>` are not
> + considered part of an ABI version and may change without constraint.
> +#. Updates to the :ref:`minimum hardware requirements <hw_rqmts>`, which drop
> + support for hardware which was previously supported, should be treated as an
> + ABI change.
> +
> +.. note::
> +
> + In 2019, the DPDK community stated it's intention to move to ABI stable
> + releases, over a number of release cycles. Beginning with maintaining ABI
> + stability through one year of DPDK releases starting from DPDK 19.11. This
> + policy will be reviewed in 2020, with intention of lengthening the stability
> + period.
> +
> +What is an ABI?
> +~~~~~~~~~~~~~~~
>
> An ABI (Application Binary Interface) is the set of runtime interfaces exposed
> by a library. It is similar to an API (Application Programming Interface) but
> @@ -39,30 +52,67 @@ Therefore, in the case of dynamic linking, it is critical that an ABI is
> preserved, or (when modified), done in such a way that the application is unable
> to behave improperly or in an unexpected fashion.
>
> +What is an ABI version?
> +~~~~~~~~~~~~~~~~~~~~~~~
>
> -ABI/API Deprecation
> --------------------
> +An ABI version is an instance of a library's ABI at a specific release. Certain
> +releases are considered by the community to be milestone releases, the yearly
> +LTS for example. Supporting those milestone release's ABI for some number of
> +subsequent releases is desirable to facilitate application upgrade. Those ABI
> +version's aligned with milestones release are therefore called 'ABI major
> +versions' and are supported for some number of releases.
> +
> +More details on major ABI version can be found in the :ref:`ABI versioning
> +<major_abi_versions>` guide.
>
> The DPDK ABI policy
> -~~~~~~~~~~~~~~~~~~~
> +-------------------
> +
> +A major ABI version is declared every year, aligned with that year's LTS
> +release, e.g. v19.11. This ABI version is then supported for one year by all
> +subsequent releases within that time period, until the next LTS release, e.g.
> +v20.11.
> +
> +At the declaration of a major ABI version, major version numbers encoded in
> +libraries soname's are bumped to indicate the new version, with the minor
> +version reset to ``0``. An example would be ``librte_eal.so.20.3`` would become
> +``librte_eal.so.21.0``.
> +
> +The ABI may then change multiple times, without warning, between the last major
> +ABI version increment and the HEAD label of the git tree, with the condition
> +that ABI compatibility with the major ABI version is preserved and therefore
> +soname's do not change.
> +
> +Minor versions are incremented to indicate the release of a new ABI compatible
> +DPDK release, typically the DPDK quarterly releases. An example of this, might
> +be that ``librte_eal.so.20.1`` would indicate the first ABI compatible DPDK
> +release, following the declaration of the new major ABI version ``20``.
> +
> +ABI versions, are supported by each release until such time as the next major
> +ABI version is declared. At that time, the deprecation of the previous major ABI
> +version will be noted in the Release Notes with guidance on individual symbol
> +depreciation and upgrade notes provided.
>
> -ABI versions are set at the time of major release labeling, and the ABI may
> -change multiple times, without warning, between the last release label and the
> -HEAD label of the git tree.
> +.. _abi_changes:
>
> -ABI versions, once released, are available until such time as their
> -deprecation has been noted in the Release Notes for at least one major release
> -cycle. For example consider the case where the ABI for DPDK 2.0 has been
> -shipped and then a decision is made to modify it during the development of
> -DPDK 2.1. The decision will be recorded in the Release Notes for the DPDK 2.1
> -release and the modification will be made available in the DPDK 2.2 release.
> +ABI Changes
> +~~~~~~~~~~~
>
> -ABI versions may be deprecated in whole or in part as needed by a given
> -update.
> +The ABI may still change after the declaration of a major ABI version, that is
> +new APIs may be still added or existing APIs may be modified.
>
> -Some ABI changes may be too significant to reasonably maintain multiple
> -versions. In those cases ABI's may be updated without backward compatibility
> -being provided. The requirements for doing so are:
> +.. Warning::
> +
> + Note that, the process for ABI deprecation should not be undertaken lightly.
> + ABI stability is extremely important for downstream consumers of the DPDK,
> + especially when distributed in shared object form. Every effort should be
> + made to preserve the ABI whenever possible. The ABI should only be changed
> + for significant reasons, such as performance enhancements. ABI breakage due
> + to changes such as reorganizing public structure fields for aesthetic or
> + readability purposes should be avoided.
> +
This text is not changed and it reads like *any* performance enhancement
is a good enough reason for an ABI break. Can't obviously quantify it,
but maybe "major performance enhancement" is closer to the intended
tone? Sorry for nit-picking over one word!
> +
> +The requirements for changing the ABI are:
>
> #. At least 3 acknowledgments of the need to do so must be made on the
> dpdk.org mailing list.
> @@ -71,34 +121,119 @@ being provided. The requirements for doing so are:
> no maintainer is available for the component, the tree/sub-tree maintainer
> for that component must acknowledge the ABI change instead.
>
> + - The acknowledgment of a member of the technical board, as a delegate of the
> + `technical board <https://core.dpdk.org/techboard/>`_ acknowledging the
> + need for the ABI change, is also mandatory.
> +
> - It is also recommended that acknowledgments from different "areas of
> interest" be sought for each deprecation, for example: from NIC vendors,
> CPU vendors, end-users, etc.
>
> -#. The changes (including an alternative map file) can be included with
> - deprecation notice, in wrapped way by the ``RTE_NEXT_ABI`` option,
> - to provide more details about oncoming changes.
> - ``RTE_NEXT_ABI`` wrapper will be removed when it become the default ABI.
> - More preferred way to provide this information is sending the feature
> - as a separate patch and reference it in deprecation notice.
> +#. Backward compatibly with the major ABI version must be maintained through
s/compatibly/compatibility/
> + :ref:`abi_versioning`, with :ref:`forward-only <forward-only>` compatibility
> + offered for any ABI changes that are indicated to be part of the next ABI
> + version.
>
> -#. A full deprecation cycle, as explained above, must be made to offer
> - downstream consumers sufficient warning of the change.
> + - In situations were backward compatibility is not possible, read the
s/were/where/
> + section on :ref:`abi_breakages`.
>
> -Note that the above process for ABI deprecation should not be undertaken
> -lightly. ABI stability is extremely important for downstream consumers of the
> -DPDK, especially when distributed in shared object form. Every effort should
> -be made to preserve the ABI whenever possible. The ABI should only be changed
> -for significant reasons, such as performance enhancements. ABI breakage due to
> -changes such as reorganizing public structure fields for aesthetic or
> -readability purposes should be avoided.
> + - No backward or forward compatibility is offered for API changes marked as
> + ``experimental``, as described in the section on :ref:`Experimental APIs
> + and Libraries <experimental_apis>`.
>
> -.. note::
> +#. If a newly proposed API functionally replaces an existing one, when the new
> + API becomes non-experimental, then the old one is marked with
> + ``__rte_deprecated``.
> +
> + - The depreciated API should follow the notification process to be removed,
> + see :ref:`deprecation_notices`.
> +
> + - At the declaration of the next major ABI version, those ABI changes then
> + become a formal part of the new ABI and the requirement to preserve ABI
> + compatibility with the last major ABI version is then dropped.
> +
> + - The responsibility for removing redundant ABI compatibility code rests
> + with the original contributor of the ABI changes, failing that, then with
> + the contributor's company and then finally with the maintainer.
> +
> +.. _forward-only:
> +
> +.. Note::
> +
> + Note that forward-only compatibility is offered for those changes made
> + between major ABI versions. As a library's soname can only describe
> + compatibility with the last major ABI version, until the next major ABI
> + version is declared, these changes therefore cannot be resolved as a runtime
> + dependency through the soname. Therefore any application wishing to make use
> + of these ABI changes can only ensure that it's runtime dependencies are met
> + through Operating System package versioning.
> +
> +.. _hw_rqmts:
> +
> +.. Note::
>
> Updates to the minimum hardware requirements, which drop support for hardware
> which was previously supported, should be treated as an ABI change, and
> - follow the relevant deprecation policy procedures as above: 3 acks and
> - announcement at least one release in advance.
> + follow the relevant deprecation policy procedures as above: 3 acks, technical
> + board approval and announcement at least one release in advance.
> +
> +.. _abi_breakages:
> +
> +ABI Breakages
> +~~~~~~~~~~~~~
> +
> +For those ABI changes that are too significant to reasonably maintain multiple
> +symbol versions, there is an amended process. In these cases, ABIs may be
> +updated without the requirement of backward compatibility being provided. These
> +changes must follow the `same process :ref:`described above <abi_changes>` as non-breaking
> +changes, however with the following additional requirements:
> +
> +#. ABI breaking changes (including an alternative map file) can be included with
> + deprecation notice, in wrapped way by the ``RTE_NEXT_ABI`` option, to provide
> + more details about oncoming changes. ``RTE_NEXT_ABI`` wrapper will be removed
> + at the declaration of the next major ABI version.
> +
> +#. Once approved, and after the depreciation notice has been observed these
> + changes will form part of the next declared major ABI version.
> +
> +Examples of ABI Changes
> +~~~~~~~~~~~~~~~~~~~~~~~
> +
> +The following are examples of allowable ABI changes occurring between
> +declarations of major ABI versions.
> +
> +* DPDK 19.11 release, defines the function ``rte_foo()``, and ``rte_foo()``
> + as part of the major ABI version ``20``.
> +
> +* DPDK 20.02 release defines a new function ``rte_foo(uint8_t bar)``, and
> + this is not a problem as long as the symbol ``rte_foo@DPDK20`` is
> + preserved through :ref:`abi_versioning`.
> +
> + - The new function may be marked with the ``__rte_experimental`` tag for a
> + number of releases, as described in the section :ref:`experimental_apis`.
> +
> + - Once ``rte_foo(uint8_t bar)`` becomes non-experimental ``rte_foo()`` is then
> + declared as ``__rte_depreciated``, with an associated deprecation notice
> + provided.
> +
> +* DPDK 19.11 is not re-released to include ``rte_foo(uint8_t bar)``, the new
> + version of ``rte_foo`` only exists from DPDK 20.02 onwards as described in the
> + :ref:`note on forward-only compatibility<forward-only>`.
> +
> +* DPDK 20.02 release defines the experimental function ``__rte_experimental
> + rte_baz()``. This function may or may not exist in the DPDK 20.05 release.
> +
> +* An application ``dPacket`` wishes to use ``rte_foo(uint8_t bar)``, before the
> + declaration of the DPDK ``21`` major API version. The application can only
> + ensure it's runtime dependencies are met by specifying ``DPDK (>= 20.2)`` as
> + an explicit package dependency, as the soname only may only indicate the
> + supported major ABI version.
> +
> +* At the release of DPDK 20.11, the function ``rte_foo(uint8_t bar)`` becomes
> + formally part of then new major ABI version DPDK 21.0 and ``rte_foo()`` may be
> + removed.
> +
> +.. _deprecation_notices:
>
> Examples of Deprecation Notices
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> @@ -106,46 +241,42 @@ Examples of Deprecation Notices
> The following are some examples of ABI deprecation notices which would be
> added to the Release Notes:
>
> -* The Macro ``#RTE_FOO`` is deprecated and will be removed with version 2.0,
> - to be replaced with the inline function ``rte_foo()``.
> +* The Macro ``#RTE_FOO`` is deprecated and will be removed with ABI version
> + 21, to be replaced with the inline function ``rte_foo()``.
>
> * The function ``rte_mbuf_grok()`` has been updated to include a new parameter
> - in version 2.0. Backwards compatibility will be maintained for this function
> - until the release of version 2.1
> + in version 20.2. Backwards compatibility will be maintained for this function
> + until the release of the new DPDK major ABI version 21, in DPDK version
> + 20.11.
>
> -* The members of ``struct rte_foo`` have been reorganized in release 2.0 for
> +* The members of ``struct rte_foo`` have been reorganized in DPDK 20.02 for
> performance reasons. Existing binary applications will have backwards
> - compatibility in release 2.0, while newly built binaries will need to
> - reference the new structure variant ``struct rte_foo2``. Compatibility will
> - be removed in release 2.2, and all applications will require updating and
> + compatibility in release 20.02, while newly built binaries will need to
> + reference the new structure variant ``struct rte_foo2``. Compatibility will be
> + removed in release 20.11, and all applications will require updating and
> rebuilding to the new structure at that time, which will be renamed to the
> original ``struct rte_foo``.
>
> * Significant ABI changes are planned for the ``librte_dostuff`` library. The
> - upcoming release 2.0 will not contain these changes, but release 2.1 will,
> + upcoming release 20.02 will not contain these changes, but release 20.11 will,
> and no backwards compatibility is planned due to the extensive nature of
> - these changes. Binaries using this library built prior to version 2.1 will
> + these changes. Binaries using this library built prior to ABI version 21 will
> require updating and recompilation.
>
> -New API replacing previous one
> -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> -
> -If a new API proposed functionally replaces an existing one, when the new API
> -becomes non-experimental then the old one is marked with ``__rte_deprecated``.
> -Deprecated APIs are removed completely just after the next LTS.
> -
> -Reminder that old API should follow deprecation process to be removed.
> +.. _experimental_apis:
>
> +Experimental
> +------------
>
> -Experimental APIs
> ------------------
> +APIs
> +~~~~
>
> -APIs marked as ``experimental`` are not considered part of the ABI and may
> -change without warning at any time. Since changes to APIs are most likely
> -immediately after their introduction, as users begin to take advantage of
> -those new APIs and start finding issues with them, new DPDK APIs will be
> -automatically marked as ``experimental`` to allow for a period of stabilization
> -before they become part of a tracked ABI.
> +APIs marked as ``experimental`` are not considered part of an ABI version and
> +may change without warning at any time. Since changes to APIs are most likely
> +immediately after their introduction, as users begin to take advantage of those
> +new APIs and start finding issues with them, new DPDK APIs will be automatically
> +marked as ``experimental`` to allow for a period of stabilization before they
> +become part of a tracked ABI version.
>
> Note that marking an API as experimental is a multi step process.
> To mark an API as experimental, the symbols which are desired to be exported
> @@ -163,7 +294,16 @@ In addition to tagging the code with ``__rte_experimental``,
> the doxygen markup must also contain the EXPERIMENTAL string,
> and the MAINTAINERS file should note the EXPERIMENTAL libraries.
>
> -For removing the experimental tag associated with an API, deprecation notice
> -is not required. Though, an API should remain in experimental state for at least
> -one release. Thereafter, normal process of posting patch for review to mailing
> -list can be followed.
> +For removing the experimental tag associated with an API, deprecation notice is
> +not required. Though, an API should remain in experimental state for at least
> +one release. Thereafter, the normal process of posting patch for review to
> +mailing list can be followed.
> +
> +Libraries
> +~~~~~~~~~
> +
> +Libraries marked as ``experimental`` are entirely not considered part of an ABI
> +version, and may change without warning at any time. Experimental libraries
> +always have a major version of ``0`` to indicate they exist outside of
> +:ref:`abi_versioning` , with the minor version incremented with each ABI change
> +to library.
> diff --git a/doc/guides/contributing/stable.rst b/doc/guides/contributing/stable.rst
> index 6a5eee9..d95c200 100644
> --- a/doc/guides/contributing/stable.rst
> +++ b/doc/guides/contributing/stable.rst
> @@ -1,7 +1,7 @@
> .. SPDX-License-Identifier: BSD-3-Clause
> Copyright 2018 The DPDK contributors
>
> -.. stable_lts_releases:
> +.. _stable_lts_releases:
>
> DPDK Stable Releases and Long Term Support
> ==========================================
> @@ -53,6 +53,9 @@ year's November (X.11) release will be maintained as an LTS for 2 years.
> After the X.11 release, an LTS branch will be created for it at
> http://git.dpdk.org/dpdk-stable where bugfixes will be backported to.
>
> +A LTS release may align with the declaration of a new major ABI version,
> +please read the :ref:`abi_policy` for more information.
> +
Above is worth to mention, but as discussed on call earlier today, the
changes below should be dropped from this patchset. At present each LTS
minor release (e.g. 18.11.2) maintains the API/ABI of the original LTS
release (e.g. 18.11) and that is not changing.
What type of non-ABI breaking things are backported to LTS branches can
be discussed during the LTS presentation in DPDK userspace.
thanks,
Kevin.
> It is anticipated that there will be at least 4 releases per year of the LTS
> or approximately 1 every 3 months. However, the cadence can be shorter or
> longer depending on the number and criticality of the backported
> @@ -68,10 +71,13 @@ point the LTS branch will no longer be maintained with no further releases.
> What changes should be backported
> ---------------------------------
>
> -Backporting should be limited to bug fixes. All patches accepted on the master
> -branch with a Fixes: tag should be backported to the relevant stable/LTS
> -branches, unless the submitter indicates otherwise. If there are exceptions,
> -they will be discussed on the mailing lists.
> +Backporting is a naturally conservative activity, and therefore should only
> +include bug fixes and support for new hardware, were adding support does not
> +necessitate DPDK ABI/API changes.
> +
> +All patches accepted on the master branch with a Fixes: tag should be backported
> +to the relevant stable/LTS branches, unless the submitter indicates otherwise.
> +If there are exceptions, they will be discussed on the mailing lists.
>
> Fixes suitable for backport should have a ``Cc: stable@dpdk.org`` tag in the
> commit message body as follows::
> @@ -86,13 +92,18 @@ commit message body as follows::
> Signed-off-by: Alex Smith <alex.smith@example.com>
>
>
> -Fixes not suitable for backport should not include the ``Cc: stable@dpdk.org`` tag.
> +Fixes not suitable for backport should not include the ``Cc: stable@dpdk.org``
> +tag.
>
> -Features should not be backported to stable releases. It may be acceptable, in
> -limited cases, to back port features for the LTS release where:
> +New features, with the exception of new hardware support, should not be
> +backported to stable releases. In the case of new hardware support or any other
> +exceptional circumstances limited backporting maybe permitted to the LTS release
> +where:
>
> -* There is a justifiable use case (for example a new PMD).
> -* The change is non-invasive.
> +* There is a justifiable use case, for example the change is required to support
> + a new platform or device (for example a new PMD).
> +* The change is ABI/API preserving, it does not present an obvious "new feature"
> + to end consumer.
> * The work of preparing the backport is done by the proposer.
> * There is support within the community.
>
> @@ -119,10 +130,3 @@ A Stable Release will be released by:
> list.
>
> Stable releases are available on the `dpdk.org download page <http://core.dpdk.org/download/>`_.
> -
> -
> -ABI
> ----
> -
> -The Stable Release should not be seen as a way of breaking or circumventing
> -the DPDK ABI policy.
>
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [dpdk-dev] [PATCH v3 2/4] doc: changes to abi policy introducing major abi versions
2019-08-30 16:20 ` Kevin Traynor
@ 2019-09-24 11:32 ` Ray Kinsella
2019-09-25 12:29 ` Kevin Traynor
0 siblings, 1 reply; 8+ messages in thread
From: Ray Kinsella @ 2019-09-24 11:32 UTC (permalink / raw)
To: Kevin Traynor, dev
Cc: thomas, stephen, bruce.richardson, ferruh.yigit,
konstantin.ananyev, jerinj, olivier.matz, nhorman,
maxime.coquelin, john.mcnamara, marko.kovacevic, hemant.agrawal,
Luca Boccassi, David Marchand
Thanks Kevin for working through all this.
Other comments are inline.
On 30/08/2019 17:20, Kevin Traynor wrote:
> Hi Ray,
>
> On 15/08/2019 11:23, Ray Kinsella wrote:
>> This policy change introduces major ABI versions, these are
>> declared every year, typically aligned with the LTS release
>> and are supported by subsequent releases in the following year.
>> This change is intended to improve ABI stabilty for those projects
>> consuming DPDK.
>>
>> Signed-off-by: Ray Kinsella <mdr@ashroe.eu>
>> ---
>> doc/guides/contributing/abi_policy.rst | 308 ++++++++++++++++++++++++---------
>> doc/guides/contributing/stable.rst | 38 ++--
>> 2 files changed, 245 insertions(+), 101 deletions(-)
>>
>> diff --git a/doc/guides/contributing/abi_policy.rst b/doc/guides/contributing/abi_policy.rst
>> index 55bacb4..6190bdc 100644
>> --- a/doc/guides/contributing/abi_policy.rst
>> +++ b/doc/guides/contributing/abi_policy.rst
>> @@ -1,33 +1,46 @@
>> .. SPDX-License-Identifier: BSD-3-Clause
>> - Copyright 2018 The DPDK contributors
>> + Copyright 2019 The DPDK contributors
>>
>> -.. abi_api_policy:
>> +.. _abi_policy:
>>
>> -DPDK ABI/API policy
>> -===================
>> +ABI Policy
>> +==========
>>
>> Description
>> -----------
>>
>> -This document details some methods for handling ABI management in the DPDK.
>> +This document details the management policy that ensures the long-term stability
>> +of the DPDK ABI and API.
>>
>> General Guidelines
>> ------------------
>>
>> -#. Whenever possible, ABI should be preserved
>> -#. ABI/API may be changed with a deprecation process
>> -#. The modification of symbols can generally be managed with versioning
>> -#. Libraries or APIs marked in ``experimental`` state may change without constraint
>> -#. New APIs will be marked as ``experimental`` for at least one release to allow
>> - any issues found by users of the new API to be fixed quickly
>> -#. The addition of symbols is generally not problematic
>> -#. The removal of symbols generally is an ABI break and requires bumping of the
>> - LIBABIVER macro
>> -#. Updates to the minimum hardware requirements, which drop support for hardware which
>> - was previously supported, should be treated as an ABI change.
>> -
>> -What is an ABI
>> -~~~~~~~~~~~~~~
>> +#. Major ABI versions are declared every **year** and are then supported for one
>> + year, typically aligned with the :ref:`LTS release <stable_lts_releases>`.
>> +#. The ABI version is managed at a project level in DPDK, with the ABI version
>> + reflected in all :ref:`library's soname <what_is_soname>`.
>> +#. The ABI should be preserved and not changed lightly. ABI changes must follow
>> + the outlined :ref:`deprecation process <abi_changes>`.
>> +#. The addition of symbols is generally not problematic. The modification of
>> + symbols is managed with :ref:`ABI Versioning <abi_versioning>`.
>> +#. The removal of symbols is considered an :ref:`ABI breakage <abi_breakages>`,
>> + once approved these will form part of the next ABI version.
>> +#. Libraries or APIs marked as :ref:`Experimental <experimental_apis>` are not
>> + considered part of an ABI version and may change without constraint.
>> +#. Updates to the :ref:`minimum hardware requirements <hw_rqmts>`, which drop
>> + support for hardware which was previously supported, should be treated as an
>> + ABI change.
>> +
>> +.. note::
>> +
>> + In 2019, the DPDK community stated it's intention to move to ABI stable
>> + releases, over a number of release cycles. Beginning with maintaining ABI
>> + stability through one year of DPDK releases starting from DPDK 19.11. This
>> + policy will be reviewed in 2020, with intention of lengthening the stability
>> + period.
>> +
>> +What is an ABI?
>> +~~~~~~~~~~~~~~~
>>
>> An ABI (Application Binary Interface) is the set of runtime interfaces exposed
>> by a library. It is similar to an API (Application Programming Interface) but
>> @@ -39,30 +52,67 @@ Therefore, in the case of dynamic linking, it is critical that an ABI is
>> preserved, or (when modified), done in such a way that the application is unable
>> to behave improperly or in an unexpected fashion.
>>
>> +What is an ABI version?
>> +~~~~~~~~~~~~~~~~~~~~~~~
>>
>> -ABI/API Deprecation
>> --------------------
>> +An ABI version is an instance of a library's ABI at a specific release. Certain
>> +releases are considered by the community to be milestone releases, the yearly
>> +LTS for example. Supporting those milestone release's ABI for some number of
>> +subsequent releases is desirable to facilitate application upgrade. Those ABI
>> +version's aligned with milestones release are therefore called 'ABI major
>> +versions' and are supported for some number of releases.
>> +
>> +More details on major ABI version can be found in the :ref:`ABI versioning
>> +<major_abi_versions>` guide.
>>
>> The DPDK ABI policy
>> -~~~~~~~~~~~~~~~~~~~
>> +-------------------
>> +
>> +A major ABI version is declared every year, aligned with that year's LTS
>> +release, e.g. v19.11. This ABI version is then supported for one year by all
>> +subsequent releases within that time period, until the next LTS release, e.g.
>> +v20.11.
>> +
>> +At the declaration of a major ABI version, major version numbers encoded in
>> +libraries soname's are bumped to indicate the new version, with the minor
>> +version reset to ``0``. An example would be ``librte_eal.so.20.3`` would become
>> +``librte_eal.so.21.0``.
>> +
>> +The ABI may then change multiple times, without warning, between the last major
>> +ABI version increment and the HEAD label of the git tree, with the condition
>> +that ABI compatibility with the major ABI version is preserved and therefore
>> +soname's do not change.
>> +
>> +Minor versions are incremented to indicate the release of a new ABI compatible
>> +DPDK release, typically the DPDK quarterly releases. An example of this, might
>> +be that ``librte_eal.so.20.1`` would indicate the first ABI compatible DPDK
>> +release, following the declaration of the new major ABI version ``20``.
>> +
>> +ABI versions, are supported by each release until such time as the next major
>> +ABI version is declared. At that time, the deprecation of the previous major ABI
>> +version will be noted in the Release Notes with guidance on individual symbol
>> +depreciation and upgrade notes provided.
>>
>> -ABI versions are set at the time of major release labeling, and the ABI may
>> -change multiple times, without warning, between the last release label and the
>> -HEAD label of the git tree.
>> +.. _abi_changes:
>>
>> -ABI versions, once released, are available until such time as their
>> -deprecation has been noted in the Release Notes for at least one major release
>> -cycle. For example consider the case where the ABI for DPDK 2.0 has been
>> -shipped and then a decision is made to modify it during the development of
>> -DPDK 2.1. The decision will be recorded in the Release Notes for the DPDK 2.1
>> -release and the modification will be made available in the DPDK 2.2 release.
>> +ABI Changes
>> +~~~~~~~~~~~
>>
>> -ABI versions may be deprecated in whole or in part as needed by a given
>> -update.
>> +The ABI may still change after the declaration of a major ABI version, that is
>> +new APIs may be still added or existing APIs may be modified.
>>
>> -Some ABI changes may be too significant to reasonably maintain multiple
>> -versions. In those cases ABI's may be updated without backward compatibility
>> -being provided. The requirements for doing so are:
>> +.. Warning::
>> +
>> + Note that, the process for ABI deprecation should not be undertaken lightly.
>> + ABI stability is extremely important for downstream consumers of the DPDK,
>
>> + especially when distributed in shared object form. Every effort should be
>> + made to preserve the ABI whenever possible. The ABI should only be changed
>> + for significant reasons, such as performance enhancements. ABI breakage due
>> + to changes such as reorganizing public structure fields for aesthetic or
>> + readability purposes should be avoided.
>> +
>
> This text is not changed and it reads like *any* performance enhancement
> is a good enough reason for an ABI break. Can't obviously quantify it,
> but maybe "major performance enhancement" is closer to the intended
> tone? Sorry for nit-picking over one word!
I agree, I was in two minds about whether to clarify this section or if
it was fine as-is. I left it there as a general warning to stop and
think before you ask to change the ABI. A performance gain alone doesn't
absolve the contributor from an obligation to preserve ABI compatibility.
Perhaps reword as follows?
.. Warning::
Note that, this policy details the method by which the ABI may be
changed, with due regard to preserving compatibility and observing
depreciation notices. This process however should not be undertaken
lightly, as a general rule ABI stability is extremely important for
downstream consumers of DPDK. The ABI should only be changed for
significant reasons, such as performance enhancements. ABI breakages due
to changes such as reorganizing public structure fields for aesthetic or
readability purposes should be avoided.
>
>> +
>> +The requirements for changing the ABI are:
>>
>> #. At least 3 acknowledgments of the need to do so must be made on the
>> dpdk.org mailing list.
>> @@ -71,34 +121,119 @@ being provided. The requirements for doing so are:
>> no maintainer is available for the component, the tree/sub-tree maintainer
>> for that component must acknowledge the ABI change instead.
>>
>> + - The acknowledgment of a member of the technical board, as a delegate of the
>> + `technical board <https://core.dpdk.org/techboard/>`_ acknowledging the
>> + need for the ABI change, is also mandatory.
>> +
>> - It is also recommended that acknowledgments from different "areas of
>> interest" be sought for each deprecation, for example: from NIC vendors,
>> CPU vendors, end-users, etc.
>>
>> -#. The changes (including an alternative map file) can be included with
>> - deprecation notice, in wrapped way by the ``RTE_NEXT_ABI`` option,
>> - to provide more details about oncoming changes.
>> - ``RTE_NEXT_ABI`` wrapper will be removed when it become the default ABI.
>> - More preferred way to provide this information is sending the feature
>> - as a separate patch and reference it in deprecation notice.
>> +#. Backward compatibly with the major ABI version must be maintained through
>
> s/compatibly/compatibility/
ACK
>
>> + :ref:`abi_versioning`, with :ref:`forward-only <forward-only>` compatibility
>> + offered for any ABI changes that are indicated to be part of the next ABI
>> + version.
>>
>> -#. A full deprecation cycle, as explained above, must be made to offer
>> - downstream consumers sufficient warning of the change.
>> + - In situations were backward compatibility is not possible, read the
>
> s/were/where/
ACK
>
>> + section on :ref:`abi_breakages`.
>>
>> -Note that the above process for ABI deprecation should not be undertaken
>> -lightly. ABI stability is extremely important for downstream consumers of the
>> -DPDK, especially when distributed in shared object form. Every effort should
>> -be made to preserve the ABI whenever possible. The ABI should only be changed
>> -for significant reasons, such as performance enhancements. ABI breakage due to
>> -changes such as reorganizing public structure fields for aesthetic or
>> -readability purposes should be avoided.
>> + - No backward or forward compatibility is offered for API changes marked as
>> + ``experimental``, as described in the section on :ref:`Experimental APIs
>> + and Libraries <experimental_apis>`.
>>
>> -.. note::
>> +#. If a newly proposed API functionally replaces an existing one, when the new
>> + API becomes non-experimental, then the old one is marked with
>> + ``__rte_deprecated``.
>> +
>> + - The depreciated API should follow the notification process to be removed,
>> + see :ref:`deprecation_notices`.
>> +
>> + - At the declaration of the next major ABI version, those ABI changes then
>> + become a formal part of the new ABI and the requirement to preserve ABI
>> + compatibility with the last major ABI version is then dropped.
>> +
>> + - The responsibility for removing redundant ABI compatibility code rests
>> + with the original contributor of the ABI changes, failing that, then with
>> + the contributor's company and then finally with the maintainer.
>> +
>> +.. _forward-only:
>> +
>> +.. Note::
>> +
>> + Note that forward-only compatibility is offered for those changes made
>> + between major ABI versions. As a library's soname can only describe
>> + compatibility with the last major ABI version, until the next major ABI
>> + version is declared, these changes therefore cannot be resolved as a runtime
>> + dependency through the soname. Therefore any application wishing to make use
>> + of these ABI changes can only ensure that it's runtime dependencies are met
>> + through Operating System package versioning.
>> +
>> +.. _hw_rqmts:
>> +
>> +.. Note::
>>
>> Updates to the minimum hardware requirements, which drop support for hardware
>> which was previously supported, should be treated as an ABI change, and
>> - follow the relevant deprecation policy procedures as above: 3 acks and
>> - announcement at least one release in advance.
>> + follow the relevant deprecation policy procedures as above: 3 acks, technical
>> + board approval and announcement at least one release in advance.
>> +
>> +.. _abi_breakages:
>> +
>> +ABI Breakages
>> +~~~~~~~~~~~~~
>> +
>> +For those ABI changes that are too significant to reasonably maintain multiple
>> +symbol versions, there is an amended process. In these cases, ABIs may be
>> +updated without the requirement of backward compatibility being provided. These
>> +changes must follow the `same process :ref:`described above <abi_changes>` as non-breaking
>> +changes, however with the following additional requirements:
>> +
>> +#. ABI breaking changes (including an alternative map file) can be included with
>> + deprecation notice, in wrapped way by the ``RTE_NEXT_ABI`` option, to provide
>> + more details about oncoming changes. ``RTE_NEXT_ABI`` wrapper will be removed
>> + at the declaration of the next major ABI version.
>> +
>> +#. Once approved, and after the depreciation notice has been observed these
>> + changes will form part of the next declared major ABI version.
>> +
>> +Examples of ABI Changes
>> +~~~~~~~~~~~~~~~~~~~~~~~
>> +
>> +The following are examples of allowable ABI changes occurring between
>> +declarations of major ABI versions.
>> +
>> +* DPDK 19.11 release, defines the function ``rte_foo()``, and ``rte_foo()``
>> + as part of the major ABI version ``20``.
>> +
>> +* DPDK 20.02 release defines a new function ``rte_foo(uint8_t bar)``, and
>> + this is not a problem as long as the symbol ``rte_foo@DPDK20`` is
>> + preserved through :ref:`abi_versioning`.
>> +
>> + - The new function may be marked with the ``__rte_experimental`` tag for a
>> + number of releases, as described in the section :ref:`experimental_apis`.
>> +
>> + - Once ``rte_foo(uint8_t bar)`` becomes non-experimental ``rte_foo()`` is then
>> + declared as ``__rte_depreciated``, with an associated deprecation notice
>> + provided.
>> +
>> +* DPDK 19.11 is not re-released to include ``rte_foo(uint8_t bar)``, the new
>> + version of ``rte_foo`` only exists from DPDK 20.02 onwards as described in the
>> + :ref:`note on forward-only compatibility<forward-only>`.
>> +
>> +* DPDK 20.02 release defines the experimental function ``__rte_experimental
>> + rte_baz()``. This function may or may not exist in the DPDK 20.05 release.
>> +
>> +* An application ``dPacket`` wishes to use ``rte_foo(uint8_t bar)``, before the
>> + declaration of the DPDK ``21`` major API version. The application can only
>> + ensure it's runtime dependencies are met by specifying ``DPDK (>= 20.2)`` as
>> + an explicit package dependency, as the soname only may only indicate the
>> + supported major ABI version.
>> +
>> +* At the release of DPDK 20.11, the function ``rte_foo(uint8_t bar)`` becomes
>> + formally part of then new major ABI version DPDK 21.0 and ``rte_foo()`` may be
>> + removed.
>> +
>> +.. _deprecation_notices:
>>
>> Examples of Deprecation Notices
>> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>> @@ -106,46 +241,42 @@ Examples of Deprecation Notices
>> The following are some examples of ABI deprecation notices which would be
>> added to the Release Notes:
>>
>> -* The Macro ``#RTE_FOO`` is deprecated and will be removed with version 2.0,
>> - to be replaced with the inline function ``rte_foo()``.
>> +* The Macro ``#RTE_FOO`` is deprecated and will be removed with ABI version
>> + 21, to be replaced with the inline function ``rte_foo()``.
>>
>> * The function ``rte_mbuf_grok()`` has been updated to include a new parameter
>> - in version 2.0. Backwards compatibility will be maintained for this function
>> - until the release of version 2.1
>> + in version 20.2. Backwards compatibility will be maintained for this function
>> + until the release of the new DPDK major ABI version 21, in DPDK version
>> + 20.11.
>>
>> -* The members of ``struct rte_foo`` have been reorganized in release 2.0 for
>> +* The members of ``struct rte_foo`` have been reorganized in DPDK 20.02 for
>> performance reasons. Existing binary applications will have backwards
>> - compatibility in release 2.0, while newly built binaries will need to
>> - reference the new structure variant ``struct rte_foo2``. Compatibility will
>> - be removed in release 2.2, and all applications will require updating and
>> + compatibility in release 20.02, while newly built binaries will need to
>> + reference the new structure variant ``struct rte_foo2``. Compatibility will be
>> + removed in release 20.11, and all applications will require updating and
>> rebuilding to the new structure at that time, which will be renamed to the
>> original ``struct rte_foo``.
>>
>> * Significant ABI changes are planned for the ``librte_dostuff`` library. The
>> - upcoming release 2.0 will not contain these changes, but release 2.1 will,
>> + upcoming release 20.02 will not contain these changes, but release 20.11 will,
>> and no backwards compatibility is planned due to the extensive nature of
>> - these changes. Binaries using this library built prior to version 2.1 will
>> + these changes. Binaries using this library built prior to ABI version 21 will
>> require updating and recompilation.
>>
>> -New API replacing previous one
>> -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>> -
>> -If a new API proposed functionally replaces an existing one, when the new API
>> -becomes non-experimental then the old one is marked with ``__rte_deprecated``.
>> -Deprecated APIs are removed completely just after the next LTS.
>> -
>> -Reminder that old API should follow deprecation process to be removed.
>> +.. _experimental_apis:
>>
>> +Experimental
>> +------------
>>
>> -Experimental APIs
>> ------------------
>> +APIs
>> +~~~~
>>
>> -APIs marked as ``experimental`` are not considered part of the ABI and may
>> -change without warning at any time. Since changes to APIs are most likely
>> -immediately after their introduction, as users begin to take advantage of
>> -those new APIs and start finding issues with them, new DPDK APIs will be
>> -automatically marked as ``experimental`` to allow for a period of stabilization
>> -before they become part of a tracked ABI.
>> +APIs marked as ``experimental`` are not considered part of an ABI version and
>> +may change without warning at any time. Since changes to APIs are most likely
>> +immediately after their introduction, as users begin to take advantage of those
>> +new APIs and start finding issues with them, new DPDK APIs will be automatically
>> +marked as ``experimental`` to allow for a period of stabilization before they
>> +become part of a tracked ABI version.
>>
>> Note that marking an API as experimental is a multi step process.
>> To mark an API as experimental, the symbols which are desired to be exported
>> @@ -163,7 +294,16 @@ In addition to tagging the code with ``__rte_experimental``,
>> the doxygen markup must also contain the EXPERIMENTAL string,
>> and the MAINTAINERS file should note the EXPERIMENTAL libraries.
>>
>> -For removing the experimental tag associated with an API, deprecation notice
>> -is not required. Though, an API should remain in experimental state for at least
>> -one release. Thereafter, normal process of posting patch for review to mailing
>> -list can be followed.
>> +For removing the experimental tag associated with an API, deprecation notice is
>> +not required. Though, an API should remain in experimental state for at least
>> +one release. Thereafter, the normal process of posting patch for review to
>> +mailing list can be followed.
>> +
>> +Libraries
>> +~~~~~~~~~
>> +
>> +Libraries marked as ``experimental`` are entirely not considered part of an ABI
>> +version, and may change without warning at any time. Experimental libraries
>> +always have a major version of ``0`` to indicate they exist outside of
>> +:ref:`abi_versioning` , with the minor version incremented with each ABI change
>> +to library.
>> diff --git a/doc/guides/contributing/stable.rst b/doc/guides/contributing/stable.rst
>> index 6a5eee9..d95c200 100644
>> --- a/doc/guides/contributing/stable.rst
>> +++ b/doc/guides/contributing/stable.rst
>> @@ -1,7 +1,7 @@
>> .. SPDX-License-Identifier: BSD-3-Clause
>> Copyright 2018 The DPDK contributors
>>
>> -.. stable_lts_releases:
>> +.. _stable_lts_releases:
>>
>> DPDK Stable Releases and Long Term Support
>> ==========================================
>> @@ -53,6 +53,9 @@ year's November (X.11) release will be maintained as an LTS for 2 years.
>> After the X.11 release, an LTS branch will be created for it at
>> http://git.dpdk.org/dpdk-stable where bugfixes will be backported to.
>>
>> +A LTS release may align with the declaration of a new major ABI version,
>> +please read the :ref:`abi_policy` for more information.
>> +
>
> Above is worth to mention, but as discussed on call earlier today, the
> changes below should be dropped from this patchset. At present each LTS
> minor release (e.g. 18.11.2) maintains the API/ABI of the original LTS
> release (e.g. 18.11) and that is not changing.
ACK, I will remove
>
> What type of non-ABI breaking things are backported to LTS branches can
> be discussed during the LTS presentation in DPDK userspace.
Do you anticipate any updates here?
Thanks,
Ray K
>
> thanks,
> Kevin.
>
>> It is anticipated that there will be at least 4 releases per year of the LTS
>> or approximately 1 every 3 months. However, the cadence can be shorter or
>> longer depending on the number and criticality of the backported
>> @@ -68,10 +71,13 @@ point the LTS branch will no longer be maintained with no further releases.
>> What changes should be backported
>> ---------------------------------
>>
>> -Backporting should be limited to bug fixes. All patches accepted on the master
>> -branch with a Fixes: tag should be backported to the relevant stable/LTS
>> -branches, unless the submitter indicates otherwise. If there are exceptions,
>> -they will be discussed on the mailing lists.
>> +Backporting is a naturally conservative activity, and therefore should only
>> +include bug fixes and support for new hardware, were adding support does not
>> +necessitate DPDK ABI/API changes.
>> +
>> +All patches accepted on the master branch with a Fixes: tag should be backported
>> +to the relevant stable/LTS branches, unless the submitter indicates otherwise.
>> +If there are exceptions, they will be discussed on the mailing lists.
>>
>> Fixes suitable for backport should have a ``Cc: stable@dpdk.org`` tag in the
>> commit message body as follows::
>> @@ -86,13 +92,18 @@ commit message body as follows::
>> Signed-off-by: Alex Smith <alex.smith@example.com>
>>
>>
>> -Fixes not suitable for backport should not include the ``Cc: stable@dpdk.org`` tag.
>> +Fixes not suitable for backport should not include the ``Cc: stable@dpdk.org``
>> +tag.
>>
>> -Features should not be backported to stable releases. It may be acceptable, in
>> -limited cases, to back port features for the LTS release where:
>> +New features, with the exception of new hardware support, should not be
>> +backported to stable releases. In the case of new hardware support or any other
>> +exceptional circumstances limited backporting maybe permitted to the LTS release
>> +where:
>>
>> -* There is a justifiable use case (for example a new PMD).
>> -* The change is non-invasive.
>> +* There is a justifiable use case, for example the change is required to support
>> + a new platform or device (for example a new PMD).
>> +* The change is ABI/API preserving, it does not present an obvious "new feature"
>> + to end consumer.
>> * The work of preparing the backport is done by the proposer.
>> * There is support within the community.
>>
>> @@ -119,10 +130,3 @@ A Stable Release will be released by:
>> list.
>>
>> Stable releases are available on the `dpdk.org download page <http://core.dpdk.org/download/>`_.
>> -
>> -
>> -ABI
>> ----
>> -
>> -The Stable Release should not be seen as a way of breaking or circumventing
>> -the DPDK ABI policy.
>>
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [dpdk-dev] [PATCH v3 2/4] doc: changes to abi policy introducing major abi versions
2019-09-24 11:32 ` Ray Kinsella
@ 2019-09-25 12:29 ` Kevin Traynor
0 siblings, 0 replies; 8+ messages in thread
From: Kevin Traynor @ 2019-09-25 12:29 UTC (permalink / raw)
To: Ray Kinsella, dev
Cc: thomas, stephen, bruce.richardson, ferruh.yigit,
konstantin.ananyev, jerinj, olivier.matz, nhorman,
maxime.coquelin, john.mcnamara, marko.kovacevic, hemant.agrawal,
Luca Boccassi, David Marchand
On 24/09/2019 12:32, Ray Kinsella wrote:
>
> Thanks Kevin for working through all this.
> Other comments are inline.
>
> On 30/08/2019 17:20, Kevin Traynor wrote:
>> Hi Ray,
>>
>> On 15/08/2019 11:23, Ray Kinsella wrote:
>>> This policy change introduces major ABI versions, these are
>>> declared every year, typically aligned with the LTS release
>>> and are supported by subsequent releases in the following year.
>>> This change is intended to improve ABI stabilty for those projects
>>> consuming DPDK.
>>>
>>> Signed-off-by: Ray Kinsella <mdr@ashroe.eu>
>>> ---
>>> doc/guides/contributing/abi_policy.rst | 308 ++++++++++++++++++++++++---------
>>> doc/guides/contributing/stable.rst | 38 ++--
>>> 2 files changed, 245 insertions(+), 101 deletions(-)
>>>
>>> diff --git a/doc/guides/contributing/abi_policy.rst b/doc/guides/contributing/abi_policy.rst
>>> index 55bacb4..6190bdc 100644
>>> --- a/doc/guides/contributing/abi_policy.rst
>>> +++ b/doc/guides/contributing/abi_policy.rst
>>> @@ -1,33 +1,46 @@
>>> .. SPDX-License-Identifier: BSD-3-Clause
>>> - Copyright 2018 The DPDK contributors
>>> + Copyright 2019 The DPDK contributors
>>>
>>> -.. abi_api_policy:
>>> +.. _abi_policy:
>>>
>>> -DPDK ABI/API policy
>>> -===================
>>> +ABI Policy
>>> +==========
>>>
>>> Description
>>> -----------
>>>
>>> -This document details some methods for handling ABI management in the DPDK.
>>> +This document details the management policy that ensures the long-term stability
>>> +of the DPDK ABI and API.
>>>
>>> General Guidelines
>>> ------------------
>>>
>>> -#. Whenever possible, ABI should be preserved
>>> -#. ABI/API may be changed with a deprecation process
>>> -#. The modification of symbols can generally be managed with versioning
>>> -#. Libraries or APIs marked in ``experimental`` state may change without constraint
>>> -#. New APIs will be marked as ``experimental`` for at least one release to allow
>>> - any issues found by users of the new API to be fixed quickly
>>> -#. The addition of symbols is generally not problematic
>>> -#. The removal of symbols generally is an ABI break and requires bumping of the
>>> - LIBABIVER macro
>>> -#. Updates to the minimum hardware requirements, which drop support for hardware which
>>> - was previously supported, should be treated as an ABI change.
>>> -
>>> -What is an ABI
>>> -~~~~~~~~~~~~~~
>>> +#. Major ABI versions are declared every **year** and are then supported for one
>>> + year, typically aligned with the :ref:`LTS release <stable_lts_releases>`.
>>> +#. The ABI version is managed at a project level in DPDK, with the ABI version
>>> + reflected in all :ref:`library's soname <what_is_soname>`.
>>> +#. The ABI should be preserved and not changed lightly. ABI changes must follow
>>> + the outlined :ref:`deprecation process <abi_changes>`.
>>> +#. The addition of symbols is generally not problematic. The modification of
>>> + symbols is managed with :ref:`ABI Versioning <abi_versioning>`.
>>> +#. The removal of symbols is considered an :ref:`ABI breakage <abi_breakages>`,
>>> + once approved these will form part of the next ABI version.
>>> +#. Libraries or APIs marked as :ref:`Experimental <experimental_apis>` are not
>>> + considered part of an ABI version and may change without constraint.
>>> +#. Updates to the :ref:`minimum hardware requirements <hw_rqmts>`, which drop
>>> + support for hardware which was previously supported, should be treated as an
>>> + ABI change.
>>> +
>>> +.. note::
>>> +
>>> + In 2019, the DPDK community stated it's intention to move to ABI stable
>>> + releases, over a number of release cycles. Beginning with maintaining ABI
>>> + stability through one year of DPDK releases starting from DPDK 19.11. This
>>> + policy will be reviewed in 2020, with intention of lengthening the stability
>>> + period.
>>> +
>>> +What is an ABI?
>>> +~~~~~~~~~~~~~~~
>>>
>>> An ABI (Application Binary Interface) is the set of runtime interfaces exposed
>>> by a library. It is similar to an API (Application Programming Interface) but
>>> @@ -39,30 +52,67 @@ Therefore, in the case of dynamic linking, it is critical that an ABI is
>>> preserved, or (when modified), done in such a way that the application is unable
>>> to behave improperly or in an unexpected fashion.
>>>
>>> +What is an ABI version?
>>> +~~~~~~~~~~~~~~~~~~~~~~~
>>>
>>> -ABI/API Deprecation
>>> --------------------
>>> +An ABI version is an instance of a library's ABI at a specific release. Certain
>>> +releases are considered by the community to be milestone releases, the yearly
>>> +LTS for example. Supporting those milestone release's ABI for some number of
>>> +subsequent releases is desirable to facilitate application upgrade. Those ABI
>>> +version's aligned with milestones release are therefore called 'ABI major
>>> +versions' and are supported for some number of releases.
>>> +
>>> +More details on major ABI version can be found in the :ref:`ABI versioning
>>> +<major_abi_versions>` guide.
>>>
>>> The DPDK ABI policy
>>> -~~~~~~~~~~~~~~~~~~~
>>> +-------------------
>>> +
>>> +A major ABI version is declared every year, aligned with that year's LTS
>>> +release, e.g. v19.11. This ABI version is then supported for one year by all
>>> +subsequent releases within that time period, until the next LTS release, e.g.
>>> +v20.11.
>>> +
>>> +At the declaration of a major ABI version, major version numbers encoded in
>>> +libraries soname's are bumped to indicate the new version, with the minor
>>> +version reset to ``0``. An example would be ``librte_eal.so.20.3`` would become
>>> +``librte_eal.so.21.0``.
>>> +
>>> +The ABI may then change multiple times, without warning, between the last major
>>> +ABI version increment and the HEAD label of the git tree, with the condition
>>> +that ABI compatibility with the major ABI version is preserved and therefore
>>> +soname's do not change.
>>> +
>>> +Minor versions are incremented to indicate the release of a new ABI compatible
>>> +DPDK release, typically the DPDK quarterly releases. An example of this, might
>>> +be that ``librte_eal.so.20.1`` would indicate the first ABI compatible DPDK
>>> +release, following the declaration of the new major ABI version ``20``.
>>> +
>>> +ABI versions, are supported by each release until such time as the next major
>>> +ABI version is declared. At that time, the deprecation of the previous major ABI
>>> +version will be noted in the Release Notes with guidance on individual symbol
>>> +depreciation and upgrade notes provided.
>>>
>>> -ABI versions are set at the time of major release labeling, and the ABI may
>>> -change multiple times, without warning, between the last release label and the
>>> -HEAD label of the git tree.
>>> +.. _abi_changes:
>>>
>>> -ABI versions, once released, are available until such time as their
>>> -deprecation has been noted in the Release Notes for at least one major release
>>> -cycle. For example consider the case where the ABI for DPDK 2.0 has been
>>> -shipped and then a decision is made to modify it during the development of
>>> -DPDK 2.1. The decision will be recorded in the Release Notes for the DPDK 2.1
>>> -release and the modification will be made available in the DPDK 2.2 release.
>>> +ABI Changes
>>> +~~~~~~~~~~~
>>>
>>> -ABI versions may be deprecated in whole or in part as needed by a given
>>> -update.
>>> +The ABI may still change after the declaration of a major ABI version, that is
>>> +new APIs may be still added or existing APIs may be modified.
>>>
>>> -Some ABI changes may be too significant to reasonably maintain multiple
>>> -versions. In those cases ABI's may be updated without backward compatibility
>>> -being provided. The requirements for doing so are:
>>> +.. Warning::
>>> +
>>> + Note that, the process for ABI deprecation should not be undertaken lightly.
>>> + ABI stability is extremely important for downstream consumers of the DPDK,
>>
>>> + especially when distributed in shared object form. Every effort should be
>>> + made to preserve the ABI whenever possible. The ABI should only be changed
>>> + for significant reasons, such as performance enhancements. ABI breakage due
>>> + to changes such as reorganizing public structure fields for aesthetic or
>>> + readability purposes should be avoided.
>>> +
>>
>> This text is not changed and it reads like *any* performance enhancement
>> is a good enough reason for an ABI break. Can't obviously quantify it,
>> but maybe "major performance enhancement" is closer to the intended
>> tone? Sorry for nit-picking over one word!
>
> I agree, I was in two minds about whether to clarify this section or if
> it was fine as-is. I left it there as a general warning to stop and
> think before you ask to change the ABI. A performance gain alone doesn't
> absolve the contributor from an obligation to preserve ABI compatibility.
>
> Perhaps reword as follows?
>
> .. Warning::
>
> Note that, this policy details the method by which the ABI may be
> changed, with due regard to preserving compatibility and observing
> depreciation notices. This process however should not be undertaken
> lightly, as a general rule ABI stability is extremely important for
> downstream consumers of DPDK. The ABI should only be changed for
> significant reasons, such as performance enhancements. ABI breakages due
> to changes such as reorganizing public structure fields for aesthetic or
> readability purposes should be avoided.
>
Hi Ray,
ok, thanks for checking it.
>>
>>> +
>>> +The requirements for changing the ABI are:
>>>
>>> #. At least 3 acknowledgments of the need to do so must be made on the
>>> dpdk.org mailing list.
>>> @@ -71,34 +121,119 @@ being provided. The requirements for doing so are:
>>> no maintainer is available for the component, the tree/sub-tree maintainer
>>> for that component must acknowledge the ABI change instead.
>>>
>>> + - The acknowledgment of a member of the technical board, as a delegate of the
>>> + `technical board <https://core.dpdk.org/techboard/>`_ acknowledging the
>>> + need for the ABI change, is also mandatory.
>>> +
>>> - It is also recommended that acknowledgments from different "areas of
>>> interest" be sought for each deprecation, for example: from NIC vendors,
>>> CPU vendors, end-users, etc.
>>>
>>> -#. The changes (including an alternative map file) can be included with
>>> - deprecation notice, in wrapped way by the ``RTE_NEXT_ABI`` option,
>>> - to provide more details about oncoming changes.
>>> - ``RTE_NEXT_ABI`` wrapper will be removed when it become the default ABI.
>>> - More preferred way to provide this information is sending the feature
>>> - as a separate patch and reference it in deprecation notice.
>>> +#. Backward compatibly with the major ABI version must be maintained through
>>
>> s/compatibly/compatibility/
>
> ACK
>
>>
>>> + :ref:`abi_versioning`, with :ref:`forward-only <forward-only>` compatibility
>>> + offered for any ABI changes that are indicated to be part of the next ABI
>>> + version.
>>>
>>> -#. A full deprecation cycle, as explained above, must be made to offer
>>> - downstream consumers sufficient warning of the change.
>>> + - In situations were backward compatibility is not possible, read the
>>
>> s/were/where/
>
> ACK
>
>>
>>> + section on :ref:`abi_breakages`.
>>>
>>> -Note that the above process for ABI deprecation should not be undertaken
>>> -lightly. ABI stability is extremely important for downstream consumers of the
>>> -DPDK, especially when distributed in shared object form. Every effort should
>>> -be made to preserve the ABI whenever possible. The ABI should only be changed
>>> -for significant reasons, such as performance enhancements. ABI breakage due to
>>> -changes such as reorganizing public structure fields for aesthetic or
>>> -readability purposes should be avoided.
>>> + - No backward or forward compatibility is offered for API changes marked as
>>> + ``experimental``, as described in the section on :ref:`Experimental APIs
>>> + and Libraries <experimental_apis>`.
>>>
>>> -.. note::
>>> +#. If a newly proposed API functionally replaces an existing one, when the new
>>> + API becomes non-experimental, then the old one is marked with
>>> + ``__rte_deprecated``.
>>> +
>>> + - The depreciated API should follow the notification process to be removed,
>>> + see :ref:`deprecation_notices`.
>>> +
>>> + - At the declaration of the next major ABI version, those ABI changes then
>>> + become a formal part of the new ABI and the requirement to preserve ABI
>>> + compatibility with the last major ABI version is then dropped.
>>> +
>>> + - The responsibility for removing redundant ABI compatibility code rests
>>> + with the original contributor of the ABI changes, failing that, then with
>>> + the contributor's company and then finally with the maintainer.
>>> +
>>> +.. _forward-only:
>>> +
>>> +.. Note::
>>> +
>>> + Note that forward-only compatibility is offered for those changes made
>>> + between major ABI versions. As a library's soname can only describe
>>> + compatibility with the last major ABI version, until the next major ABI
>>> + version is declared, these changes therefore cannot be resolved as a runtime
>>> + dependency through the soname. Therefore any application wishing to make use
>>> + of these ABI changes can only ensure that it's runtime dependencies are met
>>> + through Operating System package versioning.
>>> +
>>> +.. _hw_rqmts:
>>> +
>>> +.. Note::
>>>
>>> Updates to the minimum hardware requirements, which drop support for hardware
>>> which was previously supported, should be treated as an ABI change, and
>>> - follow the relevant deprecation policy procedures as above: 3 acks and
>>> - announcement at least one release in advance.
>>> + follow the relevant deprecation policy procedures as above: 3 acks, technical
>>> + board approval and announcement at least one release in advance.
>>> +
>>> +.. _abi_breakages:
>>> +
>>> +ABI Breakages
>>> +~~~~~~~~~~~~~
>>> +
>>> +For those ABI changes that are too significant to reasonably maintain multiple
>>> +symbol versions, there is an amended process. In these cases, ABIs may be
>>> +updated without the requirement of backward compatibility being provided. These
>>> +changes must follow the `same process :ref:`described above <abi_changes>` as non-breaking
>>> +changes, however with the following additional requirements:
>>> +
>>> +#. ABI breaking changes (including an alternative map file) can be included with
>>> + deprecation notice, in wrapped way by the ``RTE_NEXT_ABI`` option, to provide
>>> + more details about oncoming changes. ``RTE_NEXT_ABI`` wrapper will be removed
>>> + at the declaration of the next major ABI version.
>>> +
>>> +#. Once approved, and after the depreciation notice has been observed these
>>> + changes will form part of the next declared major ABI version.
>>> +
>>> +Examples of ABI Changes
>>> +~~~~~~~~~~~~~~~~~~~~~~~
>>> +
>>> +The following are examples of allowable ABI changes occurring between
>>> +declarations of major ABI versions.
>>> +
>>> +* DPDK 19.11 release, defines the function ``rte_foo()``, and ``rte_foo()``
>>> + as part of the major ABI version ``20``.
>>> +
>>> +* DPDK 20.02 release defines a new function ``rte_foo(uint8_t bar)``, and
>>> + this is not a problem as long as the symbol ``rte_foo@DPDK20`` is
>>> + preserved through :ref:`abi_versioning`.
>>> +
>>> + - The new function may be marked with the ``__rte_experimental`` tag for a
>>> + number of releases, as described in the section :ref:`experimental_apis`.
>>> +
>>> + - Once ``rte_foo(uint8_t bar)`` becomes non-experimental ``rte_foo()`` is then
>>> + declared as ``__rte_depreciated``, with an associated deprecation notice
>>> + provided.
>>> +
>>> +* DPDK 19.11 is not re-released to include ``rte_foo(uint8_t bar)``, the new
>>> + version of ``rte_foo`` only exists from DPDK 20.02 onwards as described in the
>>> + :ref:`note on forward-only compatibility<forward-only>`.
>>> +
>>> +* DPDK 20.02 release defines the experimental function ``__rte_experimental
>>> + rte_baz()``. This function may or may not exist in the DPDK 20.05 release.
>>> +
>>> +* An application ``dPacket`` wishes to use ``rte_foo(uint8_t bar)``, before the
>>> + declaration of the DPDK ``21`` major API version. The application can only
>>> + ensure it's runtime dependencies are met by specifying ``DPDK (>= 20.2)`` as
>>> + an explicit package dependency, as the soname only may only indicate the
>>> + supported major ABI version.
>>> +
>>> +* At the release of DPDK 20.11, the function ``rte_foo(uint8_t bar)`` becomes
>>> + formally part of then new major ABI version DPDK 21.0 and ``rte_foo()`` may be
>>> + removed.
>>> +
>>> +.. _deprecation_notices:
>>>
>>> Examples of Deprecation Notices
>>> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>>> @@ -106,46 +241,42 @@ Examples of Deprecation Notices
>>> The following are some examples of ABI deprecation notices which would be
>>> added to the Release Notes:
>>>
>>> -* The Macro ``#RTE_FOO`` is deprecated and will be removed with version 2.0,
>>> - to be replaced with the inline function ``rte_foo()``.
>>> +* The Macro ``#RTE_FOO`` is deprecated and will be removed with ABI version
>>> + 21, to be replaced with the inline function ``rte_foo()``.
>>>
>>> * The function ``rte_mbuf_grok()`` has been updated to include a new parameter
>>> - in version 2.0. Backwards compatibility will be maintained for this function
>>> - until the release of version 2.1
>>> + in version 20.2. Backwards compatibility will be maintained for this function
>>> + until the release of the new DPDK major ABI version 21, in DPDK version
>>> + 20.11.
>>>
>>> -* The members of ``struct rte_foo`` have been reorganized in release 2.0 for
>>> +* The members of ``struct rte_foo`` have been reorganized in DPDK 20.02 for
>>> performance reasons. Existing binary applications will have backwards
>>> - compatibility in release 2.0, while newly built binaries will need to
>>> - reference the new structure variant ``struct rte_foo2``. Compatibility will
>>> - be removed in release 2.2, and all applications will require updating and
>>> + compatibility in release 20.02, while newly built binaries will need to
>>> + reference the new structure variant ``struct rte_foo2``. Compatibility will be
>>> + removed in release 20.11, and all applications will require updating and
>>> rebuilding to the new structure at that time, which will be renamed to the
>>> original ``struct rte_foo``.
>>>
>>> * Significant ABI changes are planned for the ``librte_dostuff`` library. The
>>> - upcoming release 2.0 will not contain these changes, but release 2.1 will,
>>> + upcoming release 20.02 will not contain these changes, but release 20.11 will,
>>> and no backwards compatibility is planned due to the extensive nature of
>>> - these changes. Binaries using this library built prior to version 2.1 will
>>> + these changes. Binaries using this library built prior to ABI version 21 will
>>> require updating and recompilation.
>>>
>>> -New API replacing previous one
>>> -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>>> -
>>> -If a new API proposed functionally replaces an existing one, when the new API
>>> -becomes non-experimental then the old one is marked with ``__rte_deprecated``.
>>> -Deprecated APIs are removed completely just after the next LTS.
>>> -
>>> -Reminder that old API should follow deprecation process to be removed.
>>> +.. _experimental_apis:
>>>
>>> +Experimental
>>> +------------
>>>
>>> -Experimental APIs
>>> ------------------
>>> +APIs
>>> +~~~~
>>>
>>> -APIs marked as ``experimental`` are not considered part of the ABI and may
>>> -change without warning at any time. Since changes to APIs are most likely
>>> -immediately after their introduction, as users begin to take advantage of
>>> -those new APIs and start finding issues with them, new DPDK APIs will be
>>> -automatically marked as ``experimental`` to allow for a period of stabilization
>>> -before they become part of a tracked ABI.
>>> +APIs marked as ``experimental`` are not considered part of an ABI version and
>>> +may change without warning at any time. Since changes to APIs are most likely
>>> +immediately after their introduction, as users begin to take advantage of those
>>> +new APIs and start finding issues with them, new DPDK APIs will be automatically
>>> +marked as ``experimental`` to allow for a period of stabilization before they
>>> +become part of a tracked ABI version.
>>>
>>> Note that marking an API as experimental is a multi step process.
>>> To mark an API as experimental, the symbols which are desired to be exported
>>> @@ -163,7 +294,16 @@ In addition to tagging the code with ``__rte_experimental``,
>>> the doxygen markup must also contain the EXPERIMENTAL string,
>>> and the MAINTAINERS file should note the EXPERIMENTAL libraries.
>>>
>>> -For removing the experimental tag associated with an API, deprecation notice
>>> -is not required. Though, an API should remain in experimental state for at least
>>> -one release. Thereafter, normal process of posting patch for review to mailing
>>> -list can be followed.
>>> +For removing the experimental tag associated with an API, deprecation notice is
>>> +not required. Though, an API should remain in experimental state for at least
>>> +one release. Thereafter, the normal process of posting patch for review to
>>> +mailing list can be followed.
>>> +
>>> +Libraries
>>> +~~~~~~~~~
>>> +
>>> +Libraries marked as ``experimental`` are entirely not considered part of an ABI
>>> +version, and may change without warning at any time. Experimental libraries
>>> +always have a major version of ``0`` to indicate they exist outside of
>>> +:ref:`abi_versioning` , with the minor version incremented with each ABI change
>>> +to library.
>>> diff --git a/doc/guides/contributing/stable.rst b/doc/guides/contributing/stable.rst
>>> index 6a5eee9..d95c200 100644
>>> --- a/doc/guides/contributing/stable.rst
>>> +++ b/doc/guides/contributing/stable.rst
>>> @@ -1,7 +1,7 @@
>>> .. SPDX-License-Identifier: BSD-3-Clause
>>> Copyright 2018 The DPDK contributors
>>>
>>> -.. stable_lts_releases:
>>> +.. _stable_lts_releases:
>>>
>>> DPDK Stable Releases and Long Term Support
>>> ==========================================
>>> @@ -53,6 +53,9 @@ year's November (X.11) release will be maintained as an LTS for 2 years.
>>> After the X.11 release, an LTS branch will be created for it at
>>> http://git.dpdk.org/dpdk-stable where bugfixes will be backported to.
>>>
>>> +A LTS release may align with the declaration of a new major ABI version,
>>> +please read the :ref:`abi_policy` for more information.
>>> +
>>
>> Above is worth to mention, but as discussed on call earlier today, the
>> changes below should be dropped from this patchset. At present each LTS
>> minor release (e.g. 18.11.2) maintains the API/ABI of the original LTS
>> release (e.g. 18.11) and that is not changing.
>
> ACK, I will remove
>
>>
>> What type of non-ABI breaking things are backported to LTS branches can
>> be discussed during the LTS presentation in DPDK userspace.
>
> Do you anticipate any updates here?
>
I should probably update it to add some more info, similar to one of the
slides from Bordeaux re examples etc.
thanks,
Kevin.
> Thanks,
>
> Ray K
>
>>
>> thanks,
>> Kevin.
>>
>>> It is anticipated that there will be at least 4 releases per year of the LTS
>>> or approximately 1 every 3 months. However, the cadence can be shorter or
>>> longer depending on the number and criticality of the backported
>>> @@ -68,10 +71,13 @@ point the LTS branch will no longer be maintained with no further releases.
>>> What changes should be backported
>>> ---------------------------------
>>>
>>> -Backporting should be limited to bug fixes. All patches accepted on the master
>>> -branch with a Fixes: tag should be backported to the relevant stable/LTS
>>> -branches, unless the submitter indicates otherwise. If there are exceptions,
>>> -they will be discussed on the mailing lists.
>>> +Backporting is a naturally conservative activity, and therefore should only
>>> +include bug fixes and support for new hardware, were adding support does not
>>> +necessitate DPDK ABI/API changes.
>>> +
>>> +All patches accepted on the master branch with a Fixes: tag should be backported
>>> +to the relevant stable/LTS branches, unless the submitter indicates otherwise.
>>> +If there are exceptions, they will be discussed on the mailing lists.
>>>
>>> Fixes suitable for backport should have a ``Cc: stable@dpdk.org`` tag in the
>>> commit message body as follows::
>>> @@ -86,13 +92,18 @@ commit message body as follows::
>>> Signed-off-by: Alex Smith <alex.smith@example.com>
>>>
>>>
>>> -Fixes not suitable for backport should not include the ``Cc: stable@dpdk.org`` tag.
>>> +Fixes not suitable for backport should not include the ``Cc: stable@dpdk.org``
>>> +tag.
>>>
>>> -Features should not be backported to stable releases. It may be acceptable, in
>>> -limited cases, to back port features for the LTS release where:
>>> +New features, with the exception of new hardware support, should not be
>>> +backported to stable releases. In the case of new hardware support or any other
>>> +exceptional circumstances limited backporting maybe permitted to the LTS release
>>> +where:
>>>
>>> -* There is a justifiable use case (for example a new PMD).
>>> -* The change is non-invasive.
>>> +* There is a justifiable use case, for example the change is required to support
>>> + a new platform or device (for example a new PMD).
>>> +* The change is ABI/API preserving, it does not present an obvious "new feature"
>>> + to end consumer.
>>> * The work of preparing the backport is done by the proposer.
>>> * There is support within the community.
>>>
>>> @@ -119,10 +130,3 @@ A Stable Release will be released by:
>>> list.
>>>
>>> Stable releases are available on the `dpdk.org download page <http://core.dpdk.org/download/>`_.
>>> -
>>> -
>>> -ABI
>>> ----
>>> -
>>> -The Stable Release should not be seen as a way of breaking or circumventing
>>> -the DPDK ABI policy.
>>>
^ permalink raw reply [flat|nested] 8+ messages in thread
* [dpdk-dev] [PATCH v3 3/4] doc: updates to versioning guide for abi versions
2019-08-15 10:23 [dpdk-dev] [PATCH v3 0/4] doc: changes to abi policy introducing major abi versions Ray Kinsella
2019-08-15 10:23 ` [dpdk-dev] [PATCH v3 1/4] doc: separate versioning.rst into version and policy Ray Kinsella
2019-08-15 10:23 ` [dpdk-dev] [PATCH v3 2/4] doc: changes to abi policy introducing major abi versions Ray Kinsella
@ 2019-08-15 10:23 ` Ray Kinsella
2019-08-15 10:23 ` [dpdk-dev] [PATCH v3 4/4] doc: add maintainer for abi policy Ray Kinsella
3 siblings, 0 replies; 8+ messages in thread
From: Ray Kinsella @ 2019-08-15 10:23 UTC (permalink / raw)
To: dev
Cc: mdr, thomas, stephen, bruce.richardson, ferruh.yigit,
konstantin.ananyev, jerinj, olivier.matz, nhorman,
maxime.coquelin, john.mcnamara, marko.kovacevic, hemant.agrawal
Updates to the ABI versioning guide, to account for the changes to the DPDK
ABI/API policy. Fixes for references to abi versioning and policy guides.
Signed-off-by: Ray Kinsella <mdr@ashroe.eu>
---
doc/guides/contributing/abi_versioning.rst | 248 +++++++++++++++++++----------
doc/guides/contributing/patches.rst | 6 +-
doc/guides/rel_notes/deprecation.rst | 2 +-
3 files changed, 172 insertions(+), 84 deletions(-)
diff --git a/doc/guides/contributing/abi_versioning.rst b/doc/guides/contributing/abi_versioning.rst
index 53e6ac0..76c63c8 100644
--- a/doc/guides/contributing/abi_versioning.rst
+++ b/doc/guides/contributing/abi_versioning.rst
@@ -1,44 +1,134 @@
.. SPDX-License-Identifier: BSD-3-Clause
Copyright 2018 The DPDK contributors
-.. library_versioning:
+.. _abi_versioning:
-Library versioning
+ABI Versioning
+==============
+
+This document details the mechanics of ABI version management in DPDK.
+
+.. _what_is_soname:
+
+What is a library's soname?
+---------------------------
+
+System libraries usually adopt the familiar major and minor version naming
+convention, where major versions (e.g. ``librte_eal 20.x, 21.x``) are presumed
+to be ABI incompatible with each other and minor versions (e.g. ``librte_eal
+20.1, 20.2``) are presumed to be ABI compatible. A library's `soname
+<https://en.wikipedia.org/wiki/Soname>`_. is typically used to provide backward
+compatibility information about a given library, describing the lowest common
+denominator ABI supported by the library. The soname or logical name for the
+library, is typically comprised of the library's name and major version e.g.
+``librte_eal.so.20``.
+
+During an application's build process, a library's soname is noted as a runtime
+dependency of the application. This information is then used by the `dynamic
+linker <https://en.wikipedia.org/wiki/Dynamic_linker>`_ when resolving the
+applications dependencies at runtime, to load a library supporting the correct
+ABI version. The library loaded at runtime therefore, may be a minor revision
+supporting the same major ABI version (e.g. ``librte_eal.20.2``), as the library
+used to link the application (e.g ``librte_eal.20.0``).
+
+.. _major_abi_versions:
+
+Major ABI versions
------------------
-Downstreams might want to provide different DPDK releases at the same time to
-support multiple consumers of DPDK linked against older and newer sonames.
+An ABI version change to a given library, especially in core libraries such as
+``librte_mbuf``, may cause an implicit ripple effect on the ABI of it's
+consuming libraries, causing ABI breakages. There may however be no explicit
+reason to bump a dependent library's ABI version, as there may have been no
+obvious change to the dependent library's API, even though the library's ABI
+compatibility will have been broken.
+
+This interdependence of DPDK libraries, means that ABI versioning of libraries
+is more manageable at a project level, with all project libraries sharing a
+**single ABI version**. In addition, the need to maintain a stable ABI for some
+number of releases as described in the section :ref:`abi_policy`, means
+that ABI version increments need to carefully planned and managed at a project
+level.
+
+Major ABI versions are therefore declared typically aligned with an LTS release
+and is then supported some number of subsequent releases, shared across all
+libraries. This means that a single project level ABI version, reflected in all
+individual library's soname, library filenames and associated version maps
+persists over multiple releases.
+
+.. code-block:: none
+
+ $ head ./lib/librte_acl/rte_acl_version.map
+ DPDK_20 {
+ global:
+ ...
-Also due to the interdependencies that DPDK libraries can have applications
-might end up with an executable space in which multiple versions of a library
-are mapped by ld.so.
+ $ head ./lib/librte_eal/rte_eal_version.map
+ DPDK_20 {
+ global:
+ ...
-Think of LibA that got an ABI bump and LibB that did not get an ABI bump but is
-depending on LibA.
+When an ABI change is made between major ABI versions to a given library, a new
+section is added to that library's version map describing the impending new ABI
+version, as described in the section :ref:`example_abi_macro_usage`. The
+library's soname and filename however do not change, e.g. ``libacl.so.20``, as
+ABI compatibility with the last major ABI version continues to be preserved for
+that library.
-.. note::
+.. code-block:: none
- Application
- \-> LibA.old
- \-> LibB.new -> LibA.new
+ $ head ./lib/librte_acl/rte_acl_version.map
+ DPDK_20 {
+ global:
+ ...
-That is a conflict which can be avoided by setting ``CONFIG_RTE_MAJOR_ABI``.
-If set, the value of ``CONFIG_RTE_MAJOR_ABI`` overwrites all - otherwise per
-library - versions defined in the libraries ``LIBABIVER``.
-An example might be ``CONFIG_RTE_MAJOR_ABI=16.11`` which will make all libraries
-``librte<?>.so.16.11`` instead of ``librte<?>.so.<LIBABIVER>``.
+ DPDK_21 {
+ global:
+
+ } DPDK_20;
+ ...
+ $ head ./lib/librte_eal/rte_eal_version.map
+ DPDK_20 {
+ global:
+ ...
+
+However when a new ABI version is declared, for example DPDK ``21``, old
+depreciated functions may be safely removed at this point and the entire old
+major ABI version removed, see the section :ref:`deprecating_entire_abi` on
+how this may be done.
+
+.. code-block:: none
+
+ $ head ./lib/librte_acl/rte_acl_version.map
+ DPDK_21 {
+ global:
+ ...
+
+ $ head ./lib/librte_eal/rte_eal_version.map
+ DPDK_21 {
+ global:
+ ...
+
+At the same time, the major ABI version is changed atomically across all
+libraries by incrementing the major version in individual library's soname, e.g.
+``libacl.so.21``. This is done by bumping the LIBABIVER number in the libraries
+Makefile to indicate to dynamic linking applications that this is a later, and
+possibly incompatible library version:
+
+.. code-block:: c
+
+ -LIBABIVER := 20
+ +LIBABIVER := 21
-ABI versioning
---------------
Versioning Macros
-~~~~~~~~~~~~~~~~~
+-----------------
When a symbol is exported from a library to provide an API, it also provides a
calling convention (ABI) that is embodied in its name, return type and
arguments. Occasionally that function may need to change to accommodate new
-functionality or behavior. When that occurs, it is desirable to allow for
+functionality or behavior. When that occurs, it is may be required to allow for
backward compatibility for a time with older binaries that are dynamically
linked to the DPDK.
@@ -61,8 +151,10 @@ The macros exported are:
fully qualified function ``p``, so that if a symbol becomes versioned, it
can still be mapped back to the public symbol name.
+.. _example_abi_macro_usage:
+
Examples of ABI Macro use
-^^^^^^^^^^^^^^^^^^^^^^^^^
+~~~~~~~~~~~~~~~~~~~~~~~~~
Updating a public API
_____________________
@@ -106,16 +198,16 @@ maintain previous ABI versions that are accessible only to previously compiled
binaries
The addition of a parameter to the function is ABI breaking as the function is
-public, and existing application may use it in its current form. However, the
+public, and existing application may use it in its current form. However, the
compatibility macros in DPDK allow a developer to use symbol versioning so that
multiple functions can be mapped to the same public symbol based on when an
-application was linked to it. To see how this is done, we start with the
-requisite libraries version map file. Initially the version map file for the
-acl library looks like this
+application was linked to it. To see how this is done, we start with the
+requisite libraries version map file. Initially the version map file for the acl
+library looks like this
.. code-block:: none
- DPDK_2.0 {
+ DPDK_20 {
global:
rte_acl_add_rules;
@@ -141,7 +233,7 @@ This file needs to be modified as follows
.. code-block:: none
- DPDK_2.0 {
+ DPDK_20 {
global:
rte_acl_add_rules;
@@ -163,16 +255,16 @@ This file needs to be modified as follows
local: *;
};
- DPDK_2.1 {
+ DPDK_21 {
global:
rte_acl_create;
- } DPDK_2.0;
+ } DPDK_20;
The addition of the new block tells the linker that a new version node is
-available (DPDK_2.1), which contains the symbol rte_acl_create, and inherits the
-symbols from the DPDK_2.0 node. This list is directly translated into a list of
-exported symbols when DPDK is compiled as a shared library
+available (DPDK_21), which contains the symbol rte_acl_create, and inherits
+the symbols from the DPDK_20 node. This list is directly translated into a
+list of exported symbols when DPDK is compiled as a shared library
Next, we need to specify in the code which function map to the rte_acl_create
symbol at which versions. First, at the site of the initial symbol definition,
@@ -191,22 +283,22 @@ with the public symbol name
Note that the base name of the symbol was kept intact, as this is conducive to
the macros used for versioning symbols. That is our next step, mapping this new
-symbol name to the initial symbol name at version node 2.0. Immediately after
+symbol name to the initial symbol name at version node 20. Immediately after
the function, we add this line of code
.. code-block:: c
- VERSION_SYMBOL(rte_acl_create, _v20, 2.0);
+ VERSION_SYMBOL(rte_acl_create, _v20, 20);
Remembering to also add the rte_compat.h header to the requisite c file where
-these changes are being made. The above macro instructs the linker to create a
-new symbol ``rte_acl_create@DPDK_2.0``, which matches the symbol created in older
-builds, but now points to the above newly named function. We have now mapped
-the original rte_acl_create symbol to the original function (but with a new
-name)
+these changes are being made. The above macro instructs the linker to create a
+new symbol ``rte_acl_create@DPDK_20``, which matches the symbol created in
+older builds, but now points to the above newly named function. We have now
+mapped the original rte_acl_create symbol to the original function (but with a
+new name)
-Next, we need to create the 2.1 version of the symbol. We create a new function
-name, with a different suffix, and implement it appropriately
+Next, we need to create the 21 version of the symbol. We create a new function
+name, with a different suffix, and implement it appropriately
.. code-block:: c
@@ -220,12 +312,12 @@ name, with a different suffix, and implement it appropriately
return ctx;
}
-This code serves as our new API call. Its the same as our old call, but adds
-the new parameter in place. Next we need to map this function to the symbol
-``rte_acl_create@DPDK_2.1``. To do this, we modify the public prototype of the call
-in the header file, adding the macro there to inform all including applications,
-that on re-link, the default rte_acl_create symbol should point to this
-function. Note that we could do this by simply naming the function above
+This code serves as our new API call. Its the same as our old call, but adds the
+new parameter in place. Next we need to map this function to the symbol
+``rte_acl_create@DPDK_21``. To do this, we modify the public prototype of the
+call in the header file, adding the macro there to inform all including
+applications, that on re-link, the default rte_acl_create symbol should point to
+this function. Note that we could do this by simply naming the function above
rte_acl_create, and the linker would chose the most recent version tag to apply
in the version script, but we can also do this in the header file
@@ -233,11 +325,11 @@ in the version script, but we can also do this in the header file
struct rte_acl_ctx *
-rte_acl_create(const struct rte_acl_param *param);
- +rte_acl_create(const struct rte_acl_param *param, int debug);
- +BIND_DEFAULT_SYMBOL(rte_acl_create, _v21, 2.1);
+ +rte_acl_create_v21(const struct rte_acl_param *param, int debug);
+ +BIND_DEFAULT_SYMBOL(rte_acl_create, _v21, 21);
The BIND_DEFAULT_SYMBOL macro explicitly tells applications that include this
-header, to link to the rte_acl_create_v21 function and apply the DPDK_2.1
+header, to link to the rte_acl_create_v21 function and apply the DPDK_21
version node to it. This method is more explicit and flexible than just
re-implementing the exact symbol name, and allows for other features (such as
linking to the old symbol version by default, when the new ABI is to be opt-in
@@ -257,6 +349,7 @@ assumption is that the most recent version of the symbol is the one you want to
map. So, back in the C file where, immediately after ``rte_acl_create_v21`` is
defined, we add this
+
.. code-block:: c
struct rte_acl_ctx *
@@ -270,21 +363,22 @@ That tells the compiler that, when building a static library, any calls to the
symbol ``rte_acl_create`` should be linked to ``rte_acl_create_v21``
That's it, on the next shared library rebuild, there will be two versions of
-rte_acl_create, an old DPDK_2.0 version, used by previously built applications,
-and a new DPDK_2.1 version, used by future built applications.
+rte_acl_create, an old DPDK_20 version, used by previously built applications,
+and a new DPDK_21 version, used by future built applications.
Deprecating part of a public API
________________________________
-Lets assume that you've done the above update, and after a few releases have
-passed you decide you would like to retire the old version of the function.
-After having gone through the ABI deprecation announcement process, removal is
-easy. Start by removing the symbol from the requisite version map file:
+Lets assume that you've done the above update, and in preparation for the next
+major ABI version you decide you would like to retire the old version of the
+function. After having gone through the ABI deprecation announcement process,
+removal is easy. Start by removing the symbol from the requisite version map
+file:
.. code-block:: none
- DPDK_2.0 {
+ DPDK_20 {
global:
rte_acl_add_rules;
@@ -306,48 +400,42 @@ easy. Start by removing the symbol from the requisite version map file:
local: *;
};
- DPDK_2.1 {
+ DPDK_21 {
global:
rte_acl_create;
- } DPDK_2.0;
+ } DPDK_20;
Next remove the corresponding versioned export.
.. code-block:: c
- -VERSION_SYMBOL(rte_acl_create, _v20, 2.0);
+ -VERSION_SYMBOL(rte_acl_create, _v20, 20);
Note that the internal function definition could also be removed, but its used
-in our example by the newer version _v21, so we leave it in place. This is a
-coding style choice.
-
-Lastly, we need to bump the LIBABIVER number for this library in the Makefile to
-indicate to applications doing dynamic linking that this is a later, and
-possibly incompatible library version:
-
-.. code-block:: c
+in our example by the newer version v21, so we leave it in place and declare it
+as static. This is a coding style choice.
- -LIBABIVER := 1
- +LIBABIVER := 2
+.. _deprecating_entire_abi:
Deprecating an entire ABI version
_________________________________
-While removing a symbol from and ABI may be useful, it is often more practical
-to remove an entire version node at once. If a version node completely
-specifies an API, then removing part of it, typically makes it incomplete. In
-those cases it is better to remove the entire node
+While removing a symbol from an ABI may be useful, it is more practical to
+remove an entire version node at once, as is typically done at the declaration
+of a major ABI version. If a version node completely specifies an API, then
+removing part of it, typically makes it incomplete. In those cases it is better
+to remove the entire node.
To do this, start by modifying the version map file, such that all symbols from
-the node to be removed are merged into the next node in the map
+the node to be removed are merged into the next node in the map.
In the case of our map above, it would transform to look as follows
.. code-block:: none
- DPDK_2.1 {
+ DPDK_21 {
global:
rte_acl_add_rules;
@@ -375,8 +463,8 @@ symbols.
.. code-block:: c
- -BIND_DEFAULT_SYMBOL(rte_acl_create, _v20, 2.0);
- +BIND_DEFAULT_SYMBOL(rte_acl_create, _v21, 2.1);
+ -BIND_DEFAULT_SYMBOL(rte_acl_create, _v20, 20);
+ +BIND_DEFAULT_SYMBOL(rte_acl_create, _v21, 21);
Lastly, any VERSION_SYMBOL macros that point to the old version node should be
removed, taking care to keep, where need old code in place to support newer
diff --git a/doc/guides/contributing/patches.rst b/doc/guides/contributing/patches.rst
index 9e1013b..d63c9f5 100644
--- a/doc/guides/contributing/patches.rst
+++ b/doc/guides/contributing/patches.rst
@@ -156,9 +156,9 @@ Make your planned changes in the cloned ``dpdk`` repo. Here are some guidelines
* For other PMDs and more info, refer to the ``MAINTAINERS`` file.
-* New external functions should be added to the local ``version.map`` file.
- See the :doc:`Guidelines for ABI policy and versioning </contributing/versioning>`.
- New external functions should also be added in alphabetical order.
+* New external functions should be added to the local ``version.map`` file. See
+ the :ref:`ABI policy <abi_policy>` and :ref:`ABI versioning <abi_versioning>`
+ guides. New external functions should also be added in alphabetical order.
* Important changes will require an addition to the release notes in ``doc/guides/rel_notes/``.
See the :ref:`Release Notes section of the Documentation Guidelines <doc_guidelines>` for details.
diff --git a/doc/guides/rel_notes/deprecation.rst b/doc/guides/rel_notes/deprecation.rst
index 0ee8533..2e163a5 100644
--- a/doc/guides/rel_notes/deprecation.rst
+++ b/doc/guides/rel_notes/deprecation.rst
@@ -4,7 +4,7 @@
ABI and API Deprecation
=======================
-See the :doc:`guidelines document for details of the ABI policy </contributing/versioning>`.
+See the :ref:`guidelines document for details of the ABI policy <abi_policy>`.
API and ABI deprecation notices are to be posted here.
--
2.7.4
^ permalink raw reply [flat|nested] 8+ messages in thread* [dpdk-dev] [PATCH v3 4/4] doc: add maintainer for abi policy
2019-08-15 10:23 [dpdk-dev] [PATCH v3 0/4] doc: changes to abi policy introducing major abi versions Ray Kinsella
` (2 preceding siblings ...)
2019-08-15 10:23 ` [dpdk-dev] [PATCH v3 3/4] doc: updates to versioning guide for " Ray Kinsella
@ 2019-08-15 10:23 ` Ray Kinsella
3 siblings, 0 replies; 8+ messages in thread
From: Ray Kinsella @ 2019-08-15 10:23 UTC (permalink / raw)
To: dev
Cc: mdr, thomas, stephen, bruce.richardson, ferruh.yigit,
konstantin.ananyev, jerinj, olivier.matz, nhorman,
maxime.coquelin, john.mcnamara, marko.kovacevic, hemant.agrawal
Add an entry to the maintainer file for the abi policy.
Signed-off-by: Ray Kinsella <mdr@ashroe.eu>
---
MAINTAINERS | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/MAINTAINERS b/MAINTAINERS
index 4100260..a36afc1 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -81,6 +81,10 @@ M: Marko Kovacevic <marko.kovacevic@intel.com>
F: README
F: doc/
+ABI Policy
+M: Ray Kinsella <mdr@ashroe.eu>
+F: doc/guides/contributing/abi_*.rst
+
Developers and Maintainers Tools
M: Thomas Monjalon <thomas@monjalon.net>
F: MAINTAINERS
--
2.7.4
^ permalink raw reply [flat|nested] 8+ messages in thread