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kunit: Add documentation for warning backtrace suppression API

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Document API functions for suppressing warning backtraces.

Link: https://lore.kernel.org/r/20260514-kunit_add_support-v11-4-b36a530a6d8f@redhat.com
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>
Signed-off-by: Alessandro Carminati <acarmina@redhat.com>
Reviewed-by: David Gow <david@davidgow.net>
Signed-off-by: Albert Esteve <aesteve@redhat.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>
This commit is contained in:
Guenter Roeck 2026-05-14 13:06:40 +02:00 committed by Shuah Khan
parent a5eefd0726
commit 5c1553dd5d
1 changed files with 45 additions and 1 deletions
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46
Documentation/dev-tools/kunit/usage.rst
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@ -157,6 +157,50 @@ 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 a 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.
Backtraces can be suppressed with **task-scoped suppression**: while
suppression is active on the current task, the backtrace and stack dump from
``WARN*()``, ``WARN_ON*()``, and related macros on that task are suppressed.
Two API forms are available.
- Scoped suppression is the simplest form. Wrap the code that triggers
warnings in a ``kunit_warning_suppress()`` block:
.. code-block:: c
static void some_test(struct kunit *test)
{
kunit_warning_suppress(test) {
trigger_backtrace();
KUNIT_EXPECT_SUPPRESSED_WARNING_COUNT(test, 1);
}
}
.. note::
The warning count must be checked inside the block; the suppression handle
is not accessible after the block exits.
- Direct functions return an explicit handle pointer. Use them when the handle
needs to be retained or passed across helper functions:
.. code-block:: c
static void some_test(struct kunit *test)
{
struct kunit_suppressed_warning *w;
w = kunit_start_suppress_warning(test);
trigger_backtrace();
kunit_end_suppress_warning(test, w);
KUNIT_EXPECT_EQ(test, kunit_suppressed_warning_count(w), 1);
}
Test Suites
~~~~~~~~~~~
@ -1211,4 +1255,4 @@ For example:
dev_managed_string = devm_kstrdup(fake_device, "Hello, World!");
// Everything is cleaned up automatically when the test ends.
}
}