[PATCH v4 1/4] kunit: Always run cleanup from a test kthread

[David Gow]

KUnit tests run in a kthread, with the current->kunit_test pointer set
to the test's context. This allows the kunit_get_current_test() and
kunit_fail_current_test() macros to work. Normally, this pointer is
still valid during test shutdown (i.e., the suite->exit function, and
any resource cleanup). However, if the test has exited early (e.g., due
to a failed assertion), the cleanup is done in the parent KUnit thread,
which does not have an active context.

Instead, in the event test terminates early, run the test exit and
cleanup from a new 'cleanup' kthread, which sets current->kunit_test,
and better isolates the rest of KUnit from issues which arise in test
cleanup.

If a test cleanup function itself aborts (e.g., due to an assertion
failing), there will be no further attempts to clean up: an error will
be logged and the test failed. For example:
# example_simple_test: test aborted during cleanup. continuing without cleaning up

This should also make it easier to get access to the KUnit context,
particularly from within resource cleanup functions, which may, for
example, need access to data in test->priv.

Reviewed-by: Benjamin Berg <benjam...@intel.com>
Reviewed-by: Maxime Ripard <max...@cerno.tech>
Tested-by: Maxime Ripard <max...@cerno.tech>
Signed-off-by: David Gow <davi...@google.com>
---

This is an updated version of / replacement for "kunit: Set the current
KUnit context when cleaning up", which instead creates a new kthread
for cleanup tasks if the original test kthread is aborted. This protects
us from failed assertions during cleanup, if the test exited early.

Changes since v3:
https://lore.kernel.org/all/20230421040218.2...@google.com/
- Get rid of a unused 'suite' variable (kernel test robot)
- Add Benjamin and Maxime's Reviewed-by tags.

Changes since v2:
https://lore.kernel.org/linux-kselftest/20230419085426.1...@google.com/
- Always run cleanup in its own kthread
- Therefore, never attempt to re-run it if it exits
- Thanks, Benjamin.

Changes since v1:
https://lore.kernel.org/linux-kselftest/20230415091401.6...@google.com/
- Move cleanup execution to another kthread
- (Thanks, Benjamin, for pointing out the assertion issues)

---
lib/kunit/test.c | 56 +++++++++++++++++++++++++++++++++++++++++-------
1 file changed, 48 insertions(+), 8 deletions(-)

diff --git a/lib/kunit/test.c b/lib/kunit/test.c
index e2910b261112..f5e4ceffd282 100644
--- a/lib/kunit/test.c
+++ b/lib/kunit/test.c
@@ -419,15 +419,54 @@ static void kunit_try_run_case(void *data)
* thread will resume control and handle any necessary clean up.
*/
kunit_run_case_internal(test, suite, test_case);
- /* This line may never be reached. */
+}
+
+static void kunit_try_run_case_cleanup(void *data)
+{
+ struct kunit_try_catch_context *ctx = data;
+ struct kunit *test = ctx->test;
+ struct kunit_suite *suite = ctx->suite;
+
+ current->kunit_test = test;
+
kunit_run_case_cleanup(test, suite);
}

+static void kunit_catch_run_case_cleanup(void *data)
+{
+ struct kunit_try_catch_context *ctx = data;
+ struct kunit *test = ctx->test;
+ int try_exit_code = kunit_try_catch_get_result(&test->try_catch);
+
+ /* It is always a failure if cleanup aborts. */
+ kunit_set_failure(test);
+
+ if (try_exit_code) {
+ /*
+ * Test case could not finish, we have no idea what state it is
+ * in, so don't do clean up.
+ */
+ if (try_exit_code == -ETIMEDOUT) {
+ kunit_err(test, "test case cleanup timed out\n");
+ /*
+ * Unknown internal error occurred preventing test case from
+ * running, so there is nothing to clean up.
+ */
+ } else {
+ kunit_err(test, "internal error occurred during test case cleanup: %d\n",
+ try_exit_code);
+ }
+ return;
+ }
+
+ kunit_err(test, "test aborted during cleanup. continuing without cleaning up\n");
+}
+
+
static void kunit_catch_run_case(void *data)
{
struct kunit_try_catch_context *ctx = data;
struct kunit *test = ctx->test;
- struct kunit_suite *suite = ctx->suite;
int try_exit_code = kunit_try_catch_get_result(&test->try_catch);

if (try_exit_code) {
@@ -448,12 +487,6 @@ static void kunit_catch_run_case(void *data)
}
return;
}
-
- /*
- * Test case was run, but aborted. It is the test case's business as to
- * whether it failed or not, we just need to clean up.
- */
- kunit_run_case_cleanup(test, suite);
}

/*
@@ -478,6 +511,13 @@ static void kunit_run_case_catch_errors(struct kunit_suite *suite,
context.test_case = test_case;
kunit_try_catch_run(try_catch, &context);

+ /* Now run the cleanup */
+ kunit_try_catch_init(try_catch,
+ test,
+ kunit_try_run_case_cleanup,
+ kunit_catch_run_case_cleanup);
+ kunit_try_catch_run(try_catch, &context);
+
/* Propagate the parameter result to the test case. */
if (test->status == KUNIT_FAILURE)
test_case->status = KUNIT_FAILURE;
--
2.40.1.521.gf1e218fcd8-goog

[David Gow]

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.

Reviewed-by: Sadiya Kazi <sadiy...@google.com>

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

Changes since v3:
https://lore.kernel.org/linux-kselftest/20230421040218.2...@google.com/
- Add Sadiya's Reviewed-by tag.

No changes since v2:
https://lore.kernel.org/linux-kselftest/20230419085426.1...@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
--------------------------

--
2.40.1.521.gf1e218fcd8-goog

[David Gow]

KUnit's exit functions will run even if the corresponding init function
fails. It's easy, when writing an exit function, to assume the init
function succeeded, and (for example) access uninitialised memory or
dereference NULL pointers.

Note that this case exists and should be handled in the documentation.

Suggested-by: Benjamin Berg <benj...@sipsolutions.net>
Link: https://lore.kernel.org/linux-kselftest/a39af0400abedb2e9b31d84...@sipsolutions.net/
Reviewed-by: Sadiya Kazi <sadiy...@google.com>

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

Changes since v3:
https://lore.kernel.org/linux-kselftest/20230421040218.2...@google.com/

- Fix a spelling error (thanks, Sadiya)
- Add Reviewed-by tag.

No changes since v2:
https://lore.kernel.org/linux-kselftest/20230419085426.1...@google.com/

This patch was introduced in v2.

---

Documentation/dev-tools/kunit/usage.rst | 12 ++++++++++--
include/kunit/test.h | 3 +++
2 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/Documentation/dev-tools/kunit/usage.rst b/Documentation/dev-tools/kunit/usage.rst
index 9f720f1317d3..46957d1cbcbb 100644
--- a/Documentation/dev-tools/kunit/usage.rst
+++ b/Documentation/dev-tools/kunit/usage.rst
@@ -166,7 +166,12 @@ many similar tests. In order to reduce duplication in these closely related
tests, most unit testing frameworks (including KUnit) provide the concept of a
*test suite*. A test suite is a collection of test cases for a unit of code
with optional setup and teardown functions that run before/after the whole
-suite and/or every test case. For example:
+suite and/or every test case.
+
+.. note::
+ A test case will only run if it is associated with a test suite.
+
+For example:

.. code-block:: c

@@ -196,7 +201,10 @@ after everything else. ``kunit_test_suite(example_test_suite)`` registers the
test suite with the KUnit test framework.

.. note::
- A test case will only run if it is associated with a test suite.
+ The ``exit`` and ``suite_exit`` functions will run even if ``init`` or
+ ``suite_init`` fail. Make sure that they can handle any inconsistent
+ state which may result from ``init`` or ``suite_init`` encountering errors
+ or exiting early.

``kunit_test_suite(...)`` is a macro which tells the linker to put the
specified test suite in a special linker section so that it can be run by KUnit
diff --git a/include/kunit/test.h b/include/kunit/test.h
index 57b309c6ca27..3028a1a3fcad 100644
--- a/include/kunit/test.h
+++ b/include/kunit/test.h
@@ -168,6 +168,9 @@ static inline char *kunit_status_to_ok_not_ok(enum kunit_status status)
* test case, similar to the notion of a *test fixture* or a *test class*
* in other unit testing frameworks like JUnit or Googletest.
*
+ * Note that @exit and @suite_exit will run even if @init or @suite_init
+ * fail: make sure they can handle any inconsistent state which may result.
+ *
* Every &struct kunit_case must be associated with a kunit_suite for KUnit
* to run it.
*/
--
2.40.1.521.gf1e218fcd8-goog

[David Gow]

Add an example .exit and .suite_exit function to the KUnit example
suite. Given exit functions are a bit more subtle than init functions
(due to running in a different kthread, and running even after tests or
test init functions fail), providing an easy place to experiment with
them is useful.

Reviewed-by: Rae Moar <rm...@google.com>

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

Changes since v3:
https://lore.kernel.org/linux-kselftest/20230421040218.2...@google.com/

- Rebased on top of latest kselftest/kunit branch.
- Added Reviewed-by tag.

This patch was introduced in v3.

---
lib/kunit/kunit-example-test.c | 22 ++++++++++++++++++++++
1 file changed, 22 insertions(+)

diff --git a/lib/kunit/kunit-example-test.c b/lib/kunit/kunit-example-test.c
index cd8b7e51d02b..24315c882b31 100644
--- a/lib/kunit/kunit-example-test.c
+++ b/lib/kunit/kunit-example-test.c
@@ -41,6 +41,16 @@ static int example_test_init(struct kunit *test)
return 0;
}

+/*
+ * This is run once after each test case, see the comment on
+ * example_test_suite for more information.
+ */
+static void example_test_exit(struct kunit *test)
+{
+ kunit_info(test, "cleaning up\n");
+}
+
+
/*
* This is run once before all test cases in the suite.
* See the comment on example_test_suite for more information.
@@ -52,6 +62,16 @@ static int example_test_init_suite(struct kunit_suite *suite)
return 0;
}

+/*
+ * This is run once after all test cases in the suite.
+ * See the comment on example_test_suite for more information.
+ */
+static void example_test_exit_suite(struct kunit_suite *suite)
+{
+ kunit_info(suite, "exiting suite\n");
+}
+
+
/*
* This test should always be skipped.
*/
@@ -211,7 +231,9 @@ static struct kunit_case example_test_cases[] = {
static struct kunit_suite example_test_suite = {
.name = "example",
.init = example_test_init,
+ .exit = example_test_exit,
.suite_init = example_test_init_suite,
+ .suite_exit = example_test_exit_suite,
.test_cases = example_test_cases,
};

--
2.40.1.521.gf1e218fcd8-goog