[PATCH v2 2/4] locktorture: Add nested locking to mutex torture tests

[John Stultz <jstultz@google.com>]

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

This was inspired by locktorture extensions originally implemented
by Connor O'Brien, for stress testing the proxy-execution series:
  https://lore.kernel.org/lkml/20221003214501.2050087-12-connoro@google.com/

Comments or feedback would be greatly appreciated!

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>
Signed-off-by: John Stultz <jstultz@google.com>
---
v2:
* Add LOCK08 config file suggested by Paul McKenney
---
 kernel/locking/locktorture.c                  | 35 +++++++++++++++++++
 .../selftests/rcutorture/configs/lock/CFLIST  |  1 +
 .../selftests/rcutorture/configs/lock/LOCK08  |  6 ++++
 .../rcutorture/configs/lock/LOCK08.boot       |  1 +
 4 files changed, 43 insertions(+)
 create mode 100644 tools/testing/selftests/rcutorture/configs/lock/LOCK08
 create mode 100644 tools/testing/selftests/rcutorture/configs/lock/LOCK08.boot

diff --git a/kernel/locking/locktorture.c b/kernel/locking/locktorture.c
index f4fbd3194654..27d92ce36836 100644
--- a/kernel/locking/locktorture.c
+++ b/kernel/locking/locktorture.c
@@ -332,6 +332,28 @@ static struct lock_torture_ops rw_lock_irq_ops = {
 };
 
 static DEFINE_MUTEX(torture_mutex);
+static struct mutex torture_nested_mutexes[MAX_LOCKS];
+static struct lock_class_key nested_mutex_keys[MAX_LOCKS];
+
+static void torture_mutex_init(void)
+{
+	int i;
+
+	for (i = 0; i < MAX_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 < nlocks; 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)
@@ -360,11 +382,24 @@ __releases(torture_mutex)
 	mutex_unlock(&torture_mutex);
 }
 
+static void torture_mutex_nested_unlock(int tid __maybe_unused,
+					u32 lockset)
+{
+	int i;
+
+	for (i = nlocks - 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_boost_dummy,
 	.writeunlock	= torture_mutex_unlock,
+	.nested_unlock	= torture_mutex_nested_unlock,
 	.readlock       = NULL,
 	.read_delay     = NULL,
 	.readunlock     = NULL,
diff --git a/tools/testing/selftests/rcutorture/configs/lock/CFLIST b/tools/testing/selftests/rcutorture/configs/lock/CFLIST
index 41bae5824339..a48bba0d35a6 100644
--- a/tools/testing/selftests/rcutorture/configs/lock/CFLIST
+++ b/tools/testing/selftests/rcutorture/configs/lock/CFLIST
@@ -5,3 +5,4 @@ LOCK04
 LOCK05
 LOCK06
 LOCK07
+LOCK08
diff --git a/tools/testing/selftests/rcutorture/configs/lock/LOCK08 b/tools/testing/selftests/rcutorture/configs/lock/LOCK08
new file mode 100644
index 000000000000..1d1da1477fc3
--- /dev/null
+++ b/tools/testing/selftests/rcutorture/configs/lock/LOCK08
@@ -0,0 +1,6 @@
+CONFIG_SMP=y
+CONFIG_NR_CPUS=4
+CONFIG_HOTPLUG_CPU=y
+CONFIG_PREEMPT_NONE=n
+CONFIG_PREEMPT_VOLUNTARY=n
+CONFIG_PREEMPT=y
diff --git a/tools/testing/selftests/rcutorture/configs/lock/LOCK08.boot b/tools/testing/selftests/rcutorture/configs/lock/LOCK08.boot
new file mode 100644
index 000000000000..e59a369b470e
--- /dev/null
+++ b/tools/testing/selftests/rcutorture/configs/lock/LOCK08.boot
@@ -0,0 +1 @@
+locktorture.torture_type=mutex_lock locktorture.nlocks=8
-- 
2.39.1.519.gcb327c4b5f-goog