Add some basic documentation for kunit_add_action() and related deferred action functions. Reviewed-by: Rae Moar <rmoar@xxxxxxxxxx> Signed-off-by: David Gow <davidgow@xxxxxxxxxx> --- Changes since v2: https://lore.kernel.org/linux-kselftest/20230518083849.2631178-4-davidgow@xxxxxxxxxx/ - Fix a couple of typos (Thanks Bagas, Rae) - Add Rae's Reviewed-by. This patch is new in v2. --- Documentation/dev-tools/kunit/usage.rst | 51 +++++++++++++++++++++++++ 1 file changed, 51 insertions(+) diff --git a/Documentation/dev-tools/kunit/usage.rst b/Documentation/dev-tools/kunit/usage.rst index 46957d1cbcbb..c27e1646ecd9 100644 --- a/Documentation/dev-tools/kunit/usage.rst +++ b/Documentation/dev-tools/kunit/usage.rst @@ -615,6 +615,57 @@ For example: KUNIT_ASSERT_STREQ(test, buffer, ""); } +Registering Cleanup Actions +--------------------------- + +If you need to perform some cleanup beyond simple use of ``kunit_kzalloc``, +you can register a custom "deferred action", which is a cleanup function +run when the test exits (whether cleanly, or via a failed assertion). + +Actions are simple functions with no return value, and a single ``void*`` +context argument, and fulfill the same role as "cleanup" functions in Python +and Go tests, "defer" statements in languages which support them, and +(in some cases) destructors in RAII languages. + +These are very useful for unregistering things from global lists, closing +files or other resources, or freeing resources. + +For example: + +.. code-block:: C + + static void cleanup_device(void *ctx) + { + struct device *dev = (struct device *)ctx; + + device_unregister(dev); + } + + void example_device_test(struct kunit *test) + { + struct my_device dev; + + device_register(&dev); + + kunit_add_action(test, &cleanup_device, &dev); + } + +Note that, for functions like device_unregister which only accept a single +pointer-sized argument, it's possible to directly cast that function to +a ``kunit_action_t`` rather than writing a wrapper function, for example: + +.. code-block:: C + + kunit_add_action(test, (kunit_action_t *)&device_unregister, &dev); + +``kunit_add_action`` can fail if, for example, the system is out of memory. +You can use ``kunit_add_action_or_reset`` instead which runs the action +immediately if it cannot be deferred. + +If you need more control over when the cleanup function is called, you +can trigger it early using ``kunit_release_action``, or cancel it entirely +with ``kunit_remove_action``. + Testing Static Functions ------------------------ -- 2.41.0.rc0.172.g3f132b7071-goog
