[PATCH] kunit: added lockdep support

[Uriel Guajardo]

From: Uriel Guajardo <urielguajardo@xxxxxxxxxx>

KUnit tests will now fail if lockdep detects an error during a test
case.

The idea comes from how lib/locking-selftest [1] checks for lock errors: we
first if lock debugging is turned on. If not, an error must have
occurred, so we fail the test and restart lockdep for the next test case.

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>
---
 lib/kunit/test.c | 26 +++++++++++++++++++++++++-
 1 file changed, 25 insertions(+), 1 deletion(-)

diff --git a/lib/kunit/test.c b/lib/kunit/test.c
index d8189d827368..0838ececa005 100644
--- a/lib/kunit/test.c
+++ b/lib/kunit/test.c
@@ -11,6 +11,8 @@
 #include <linux/kref.h>
 #include <linux/sched/debug.h>
 #include <linux/sched.h>
+#include <linux/lockdep.h>
+#include <linux/debug_locks.h>
 
 #include "debugfs.h"
 #include "string-stream.h"
@@ -22,6 +24,26 @@ void kunit_fail_current_test(void)
 		kunit_set_failure(current->kunit_test);
 }
 
+static inline void kunit_check_locking_bugs(struct kunit *test,
+					    unsigned long saved_preempt_count)
+{
+	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)
+	local_irq_disable();
+	if (!debug_locks) {
+		kunit_set_failure(test);
+		lockdep_reset();
+	}
+	local_irq_enable();
+#endif
+}
+
 static void kunit_print_tap_version(void)
 {
 	static bool kunit_has_printed_tap_version;
@@ -289,6 +311,7 @@ static void kunit_try_run_case(void *data)
 	struct kunit *test = ctx->test;
 	struct kunit_suite *suite = ctx->suite;
 	struct kunit_case *test_case = ctx->test_case;
+	unsigned long saved_preempt_count = preempt_count();
 
 	current->kunit_test = test;
 
@@ -298,7 +321,8 @@ 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);
 	kunit_run_case_cleanup(test, suite);
 }
 
-- 
2.28.0.236.gb10cc79966-goog