locktorture: Add nested locking to mutex torture tests

This patch adds randomized nested locking to the mutex torture
tests, as well as new LOCK08 config files for testing mutexes
with nested locking

Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: "Paul E. McKenney" <paulmck@kernel.org>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Joel Fernandes <joel@joelfernandes.org>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Valentin Schneider <vschneid@redhat.com>
Cc: Dietmar Eggemann <dietmar.eggemann@arm.com>
Cc: kernel-team@android.com
Reviewed-by: Davidlohr Bueso <dave@stgolabs.net>
Co-developed-by: Connor O'Brien <connoro@google.com>
Signed-off-by: Connor O'Brien <connoro@google.com>
Signed-off-by: John Stultz <jstultz@google.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

kernel/locking/locktorture.c

@@ -370,6 +370,28 @@ static struct lock_torture_ops rw_lock_irq_ops = {
 };
 
 static DEFINE_MUTEX(torture_mutex);
+static struct mutex torture_nested_mutexes[MAX_NESTED_LOCKS];
+static struct lock_class_key nested_mutex_keys[MAX_NESTED_LOCKS];
+
+static void torture_mutex_init(void)
+{
+	int i;
+
+	for (i = 0; i < MAX_NESTED_LOCKS; i++)
+		__mutex_init(&torture_nested_mutexes[i], __func__,
+			     &nested_mutex_keys[i]);
+}
+
+static int torture_mutex_nested_lock(int tid __maybe_unused,
+				     u32 lockset)
+{
+	int i;
+
+	for (i = 0; i < nested_locks; i++)
+		if (lockset & (1 << i))
+			mutex_lock(&torture_nested_mutexes[i]);
+	return 0;
+}
 
 static int torture_mutex_lock(int tid __maybe_unused)
 __acquires(torture_mutex)
@@ -398,11 +420,24 @@ __releases(torture_mutex)
 	mutex_unlock(&torture_mutex);
 }
 
+static void torture_mutex_nested_unlock(int tid __maybe_unused,
+					u32 lockset)
+{
+	int i;
+
+	for (i = nested_locks - 1; i >= 0; i--)
+		if (lockset & (1 << i))
+			mutex_unlock(&torture_nested_mutexes[i]);
+}
+
 static struct lock_torture_ops mutex_lock_ops = {
+	.init		= torture_mutex_init,
+	.nested_lock	= torture_mutex_nested_lock,
 	.writelock	= torture_mutex_lock,
 	.write_delay	= torture_mutex_delay,
 	.task_boost     = torture_rt_boost,
 	.writeunlock	= torture_mutex_unlock,
+	.nested_unlock	= torture_mutex_nested_unlock,
 	.readlock       = NULL,
 	.read_delay     = NULL,
 	.readunlock     = NULL,

tools/testing/selftests/rcutorture/configs/lock/CFLIST

@@ -5,3 +5,4 @@ LOCK04
 LOCK05
 LOCK06
 LOCK07
+LOCK08

tools/testing/selftests/rcutorture/configs/lock/LOCK08

+CONFIG_SMP=y
+CONFIG_NR_CPUS=4
+CONFIG_HOTPLUG_CPU=y
+CONFIG_PREEMPT_NONE=n
+CONFIG_PREEMPT_VOLUNTARY=n
+CONFIG_PREEMPT=y

tools/testing/selftests/rcutorture/configs/lock/LOCK08.boot

+locktorture.torture_type=mutex_lock locktorture.nested_locks=8