[PATCH v2] kunit: added lockdep support

[Uriel Guajardo]

KUnit will fail tests upon observing a lockdep failure. Because lockdep
turns itself off after its first failure, only fail the first test and
warn users to not expect any future failures from lockdep.

Similar to lib/locking-selftest [1], we check if the status of
debug_locks has changed after the execution of a test case. However, we
do not reset lockdep afterwards.

Like the locking selftests, we also fix possible preemption count
corruption from lock bugs.

Depends on kunit: support failure from dynamic analysis tools [2]

[1] https://elixir.bootlin.com/linux/v5.7.12/source/lib/locking-selftest.c#L1137

[2] https://lore.kernel.org/linux-kselftest/20200806174326.3577537-1-urielguajardojr@xxxxxxxxx/

Signed-off-by: Uriel Guajardo <urielguajardo@xxxxxxxxxx>
---
v2 Changes:
- Removed lockdep_reset

- Added warning to users about lockdep shutting off
---
 lib/kunit/test.c | 27 ++++++++++++++++++++++++++-
 1 file changed, 26 insertions(+), 1 deletion(-)

diff --git a/lib/kunit/test.c b/lib/kunit/test.c
index d8189d827368..7e477482457b 100644
--- a/lib/kunit/test.c
+++ b/lib/kunit/test.c
@@ -11,6 +11,7 @@
 #include <linux/kref.h>
 #include <linux/sched/debug.h>
 #include <linux/sched.h>
+#include <linux/debug_locks.h>
 
 #include "debugfs.h"
 #include "string-stream.h"
@@ -22,6 +23,26 @@ void kunit_fail_current_test(void)
 		kunit_set_failure(current->kunit_test);
 }
 
+static void kunit_check_locking_bugs(struct kunit *test,
+				     unsigned long saved_preempt_count,
+				     bool saved_debug_locks)
+{
+	preempt_count_set(saved_preempt_count);
+#ifdef CONFIG_TRACE_IRQFLAGS
+	if (softirq_count())
+		current->softirqs_enabled = 0;
+	else
+		current->softirqs_enabled = 1;
+#endif
+#if IS_ENABLED(CONFIG_LOCKDEP)
+	if (saved_debug_locks && !debug_locks) {
+		kunit_set_failure(test);
+		kunit_warn(test, "Dynamic analysis tool failure from LOCKDEP.");
+		kunit_warn(test, "Further tests will have LOCKDEP disabled.");
+	}
+#endif
+}
+
 static void kunit_print_tap_version(void)
 {
 	static bool kunit_has_printed_tap_version;
@@ -290,6 +311,9 @@ static void kunit_try_run_case(void *data)
 	struct kunit_suite *suite = ctx->suite;
 	struct kunit_case *test_case = ctx->test_case;
 
+	unsigned long saved_preempt_count = preempt_count();
+	bool saved_debug_locks = debug_locks;
+
 	current->kunit_test = test;
 
 	/*
@@ -298,7 +322,8 @@ 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. */
+	/* These lines may never be reached. */
+	kunit_check_locking_bugs(test, saved_preempt_count, saved_debug_locks);
 	kunit_run_case_cleanup(test, suite);
 }
 
-- 
2.28.0.236.gb10cc79966-goog