[PATCH v3 04/15] kunit: Add documentation for warning backtrace suppression API

[David Gow]

On Wed, 3 Apr 2024 at 21:19, Guenter Roeck <linux at roeck-us.net> wrote:
>
> Document API functions for suppressing warning backtraces.
>
> Tested-by: Linux Kernel Functional Testing <lkft at linaro.org>
> Acked-by: Dan Carpenter <dan.carpenter at linaro.org>
> Reviewed-by: Kees Cook <keescook at chromium.org>
> Signed-off-by: Guenter Roeck <linux at roeck-us.net>
> ---

This looks good to me: thanks for adding the documentation!

If we add integration between this and the KUnit resource system,
we'll need to add that to this documentation.

I wonder if it would make sense to have an example where the
DEFINE_SUPPRESSED_WARNING() is global, e.g., in the test init/exit
functions. That might overcomplicate it a bit.

It also might be nice to document the individual macros with kerneldoc
comments. (Though, that could equally fit in patch #1).

Still, this is the most important bit, so I'm happy to have it as-is.

Reviewed-by: David Gow <davidgow at google.com>

Cheers,
-- David


> v2:
> - Rebased to v6.9-rc1
> - Added Tested-by:, Acked-by:, and Reviewed-by: tags
> v3:
> - Rebased to v6.9-rc2
>
>  Documentation/dev-tools/kunit/usage.rst | 30 ++++++++++++++++++++++++-
>  1 file changed, 29 insertions(+), 1 deletion(-)
>
> diff --git a/Documentation/dev-tools/kunit/usage.rst b/Documentation/dev-tools/kunit/usage.rst
> index 22955d56b379..8d3d36d4103d 100644
> --- a/Documentation/dev-tools/kunit/usage.rst
> +++ b/Documentation/dev-tools/kunit/usage.rst
> @@ -157,6 +157,34 @@ Alternatively, one can take full control over the error message by using
>         if (some_setup_function())
>                 KUNIT_FAIL(test, "Failed to setup thing for testing");
>
> +Suppressing warning backtraces
> +------------------------------
> +
> +Some unit tests trigger warning backtraces either intentionally or as side
> +effect. Such backtraces are normally undesirable since they distract from
> +the actual test and may result in the impression that there is a problem.
> +
> +Such backtraces can be suppressed. To suppress a backtrace in some_function(),
> +use the following code.
> +
> +.. code-block:: c
> +
> +       static void some_test(struct kunit *test)
> +       {
> +               DEFINE_SUPPRESSED_WARNING(some_function);
> +
> +               START_SUPPRESSED_WARNING(some_function);
> +               trigger_backtrace();
> +               END_SUPPRESSED_WARNING(some_function);
> +       }
> +
> +SUPPRESSED_WARNING_COUNT() returns the number of suppressed backtraces. If the
> +suppressed backtrace was triggered on purpose, this can be used to check if
> +the backtrace was actually triggered.
> +
> +.. code-block:: c
> +
> +       KUNIT_EXPECT_EQ(test, SUPPRESSED_WARNING_COUNT(some_function), 1);
>
>  Test Suites
>  ~~~~~~~~~~~
> @@ -857,4 +885,4 @@ For example:
>                 dev_managed_string = devm_kstrdup(fake_device, "Hello, World!");
>
>                 // Everything is cleaned up automatically when the test ends.
> -       }
> \ No newline at end of file
> +       }
> --
> 2.39.2
>
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