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References: <20230518083849.2631178-1-davidgow@google.com> <20230518083849.2631178-4-davidgow@google.com>
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From:   Rae Moar <rmoar@google.com>
Date:   Wed, 24 May 2023 17:22:49 -0400
Message-ID: <CA+GJov6nq+RHsc5wU_WJw8nfMO=YEW=f2OsHM+_=hZP7xf92wQ@mail.gmail.com>
Subject: Re: [PATCH v2 4/4] Documentation: kunit: Add usage notes for kunit_add_action()
To:     David Gow <davidgow@google.com>
Cc:     Matti Vaittinen <mazziesaccount@gmail.com>,
        Daniel Latypov <dlatypov@google.com>,
        Maxime Ripard <maxime@cerno.tech>,
        Benjamin Berg <benjamin@sipsolutions.net>,
        Brendan Higgins <brendan.higgins@linux.dev>,
        Stephen Boyd <sboyd@kernel.org>,
        Shuah Khan <skhan@linuxfoundation.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        "Rafael J . Wysocki" <rafael@kernel.org>,
        Heikki Krogerus <heikki.krogerus@linux.intel.com>,
        Jonathan Cameron <jic23@kernel.org>,
        Sadiya Kazi <sadiyakazi@google.com>,
        Jonathan Corbet <corbet@lwn.net>, linux-doc@vger.kernel.org,
        kunit-dev@googlegroups.com, linux-kselftest@vger.kernel.org,
        linux-kernel@vger.kernel.org
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On Thu, May 18, 2023 at 4:39=E2=80=AFAM David Gow <davidgow@google.com> wro=
te:
>
> Add some basic documentation for kunit_add_action() and related
> deferred action functions.

Hi David!

This looks good to me. Just two typos below. Thanks!

Reviewed-by: Rae Moar <rmoar@google.com>

>
> Signed-off-by: David Gow <davidgow@google.com>
> ---
>
> 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..c2f0ed648385 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 cusom "deferred action", which is a cleanup function

Looks like a typo here: "custom"

> +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 forfil the same role as "cleanup" functions in Pyt=
hon

Another small typo here as Bagas noted.

> +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, closin=
g
> +files or other resources, or freeing resources.
> +
> +For example:
> +
> +.. code-block:: C
> +
> +       static void cleanup_device(void *ctx)
> +       {
> +               struct device *dev =3D (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 sing=
le
> +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 memo=
ry.
> +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 entire=
ly
> +with ``kunit_remove_action``.
> +
>
>  Testing Static Functions
>  ------------------------
> --
> 2.40.1.698.g37aff9b760-goog
>