On Thu, Aug 6, 2020 at 3:37 PM Uriel Guajardo urielguajardojr@gmail.com wrote:

From: Uriel Guajardo urielguajardo@google.com

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-urielguajar...

Signed-off-by: Uriel Guajardo urielguajardo@google.com

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

I am not entirely sure why lib/locking-selftests enables/disables softirqs, but I suspect it has to do with the fact that preempt_count became corrupted, and somehow softirqs became incorrectly enabled/disabled as a result. The resetting of the preemption count will undo the enabling/disabling accordingly. Any insight on this would be appreciated!

+#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

On Thu, Aug 6, 2020 at 1:43 PM Uriel Guajardo urielguajardo@google.com wrote:

On Thu, Aug 6, 2020 at 3:37 PM Uriel Guajardo urielguajardojr@gmail.com wrote:

...

From: Uriel Guajardo urielguajardo@google.com

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.

Sorry, just noticed: You probably want to send this to some of the lockdep maintainers or the maintainers of the kselftest for lockdep.

...

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-urielguajar...

Signed-off-by: Uriel Guajardo urielguajardo@google.com

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

I am not entirely sure why lib/locking-selftests enables/disables softirqs, but I suspect it has to do with the fact that preempt_count became corrupted, and somehow softirqs became incorrectly enabled/disabled as a result. The resetting of the preemption count will undo the enabling/disabling accordingly. Any insight on this would be appreciated!

...

+#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