linux-kernel - [PATCH v5 5/5] kunit: Add documentation for warning backtrace suppression API

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Message-Id: <20250526132755.166150-6-acarmina@redhat.com>
Date: Mon, 26 May 2025 13:27:55 +0000
From: Alessandro Carminati <acarmina@...hat.com>
To: linux-kselftest@...r.kernel.org
Cc: Dan Carpenter <dan.carpenter@...aro.org>,
	Kees Cook <keescook@...omium.org>,
	Daniel Diaz <daniel.diaz@...aro.org>,
	David Gow <davidgow@...gle.com>,
	Arthur Grillo <arthurgrillo@...eup.net>,
	Brendan Higgins <brendan.higgins@...ux.dev>,
	Naresh Kamboju <naresh.kamboju@...aro.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Maxime Ripard <mripard@...nel.org>,
	Ville Syrjala <ville.syrjala@...ux.intel.com>,
	Daniel Vetter <daniel@...ll.ch>,
	Guenter Roeck <linux@...ck-us.net>,
	Alessandro Carminati <alessandro.carminati@...il.com>,
	Jani Nikula <jani.nikula@...el.com>,
	Jeff Johnson <jeff.johnson@....qualcomm.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Josh Poimboeuf <jpoimboe@...nel.org>,
	Shuah Khan <skhan@...uxfoundation.org>,
	Linux Kernel Functional Testing <lkft@...aro.org>,
	dri-devel@...ts.freedesktop.org,
	kunit-dev@...glegroups.com,
	linux-kernel@...r.kernel.org,
	Alessandro Carminati <acarmina@...hat.com>
Subject: [PATCH v5 5/5] kunit: Add documentation for warning backtrace suppression API

From: Guenter Roeck <linux@...ck-us.net>

Document API functions for suppressing warning backtraces.

Tested-by: Linux Kernel Functional Testing <lkft@...aro.org>
Acked-by: Dan Carpenter <dan.carpenter@...aro.org>
Reviewed-by: Kees Cook <keescook@...omium.org>
Signed-off-by: Guenter Roeck <linux@...ck-us.net>
Reviewed-by: David Gow <davidgow@...gle.com>
Signed-off-by: Alessandro Carminati <acarmina@...hat.com>
---
 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..b2f1e56d53b4 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);
+
+		KUNIT_START_SUPPRESSED_WARNING(some_function);
+		trigger_backtrace();
+		KUNIT_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
+	}
-- 
2.34.1