Re: [PATCH v7 5/5] kunit: Add documentation for warning backtrace suppression API

[David Gow <david@davidgow.net>]

Le 20/04/2026 à 8:28 PM, Albert Esteve a écrit :
> From: Guenter Roeck <linux@roeck-us.net>
> 
> Document API functions for suppressing warning backtraces.
> 
> Tested-by: Linux Kernel Functional Testing <lkft@linaro.org>
> Acked-by: Dan Carpenter <dan.carpenter@linaro.org>
> Reviewed-by: Kees Cook <keescook@chromium.org>
> Signed-off-by: Guenter Roeck <linux@roeck-us.net>
> Reviewed-by: David Gow <davidgow@google.com>
> Signed-off-by: Alessandro Carminati <acarmina@redhat.com>
> Signed-off-by: Albert Esteve <aesteve@redhat.com>
> ---

Thanks -- it's always good to have documentation.

Apart from one note below, this looks good to me.

Reviewed-by: David Gow <david@davidgow.net>

Cheers,
-- David

>   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 ebd06f5ea4550..76e85412f240e 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 with **task scope suppression**: while
> +``START`` / ``END`` is active on the current task, the backtrace and stack
> +dump from warnings on that task are suppressed. Wrap the call from your test
> +in that window, like shown in the following code.
> +
> +.. code-block:: c
> +
> +	static void some_test(struct kunit *test)
> +	{
> +		KUNIT_START_SUPPRESSED_WARNING(test);
> +		trigger_backtrace();
> +		KUNIT_END_SUPPRESSED_WARNING(test);
> +	}
> +
> +``KUNIT_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, KUNIT_SUPPRESSED_WARNING_COUNT(), 1);


It might be worth noting that all of these must be in the same function, 
and the KUNIT_START_SUPPRESSED_WARNING() must be first. (And, in 
addition, there can't be more than one START/END pair per-function).

Of course, if the implementation is changed, that wouldn't be necessary. :-)
>   
>   Test Suites
>   ~~~~~~~~~~~
> @@ -1211,4 +1239,4 @@ 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
> +	}
>