[PATCH v3 2/4] Documentation: kunit: Note that assertions should not be used in cleanup

[David Gow <davidgow@google.com>]

As assertions abort the test cleanup process, they should be avoided
from within a suite's exit function, or from within resource 'free'
functions. Unlike with initialisation or main test execution, no further
cleanup will be performed after a failed assertion, potentially causing
a leak of resources.

Signed-off-by: David Gow <davidgow@google.com>
---

No changes since v2:
https://lore.kernel.org/linux-kselftest/20230419085426.1671703-2-davidgow@google.com/

This patch was introduced in v2.

---
 Documentation/dev-tools/kunit/usage.rst | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/Documentation/dev-tools/kunit/usage.rst b/Documentation/dev-tools/kunit/usage.rst
index 9faf2b4153fc..9f720f1317d3 100644
--- a/Documentation/dev-tools/kunit/usage.rst
+++ b/Documentation/dev-tools/kunit/usage.rst
@@ -121,6 +121,12 @@ there's an allocation error.
    ``return`` so they only work from the test function. In KUnit, we stop the
    current kthread on failure, so you can call them from anywhere.
 
+.. note::
+   Warning: There is an exception to the above rule. You shouldn't use assertions
+   in the suite's exit() function, or in the free function for a resource. These
+   run when a test is shutting down, and an assertion here prevents further
+   cleanup code from running, potentially leading to a memory leak.
+
 Customizing error messages
 --------------------------
 
-- 
2.40.0.634.g4ca3ef3211-goog