[PATCH 1/2] test-ww_mutex: Allow test to be run (and re-run) from userland

[PATCH 1/2] test-ww_mutex: Allow test to be run (and re-run) from userland

[John Stultz]

In cases where the ww_mutex test was occasionally tripping on
hard to find issues, leaving qemu in a reboot loop was my best
way to reproduce problems. These reboots however wasted time
when I just wanted to run the test-ww_mutex logic.

So tweak the test-ww_mutex test so that it can be re-triggered
via a sysfs file, so the test can be run repeatedly without
doing module loads or restarting.

This has been particularly valuable to stressing and finding
issues with the proxy-exec series.

To use, run as root:
  echo 1 > /sys/kernel/test_ww_mutex/run_tests

Signed-off-by: John Stultz <jstultz@google.com>
---
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Will Deacon <will@kernel.org>
Cc: Waiman Long <longman@redhat.com>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: "Paul E . McKenney" <paulmck@kernel.org>
Cc: Joel Fernandes <joelagnelf@nvidia.com>
Cc: Dietmar Eggemann <dietmar.eggemann@arm.com>
Cc: Suleiman Souhlal <suleiman@google.com>
Cc: kernel-team@android.com
---
 kernel/locking/test-ww_mutex.c | 70 ++++++++++++++++++++++++++++++----
 1 file changed, 63 insertions(+), 7 deletions(-)

diff --git a/kernel/locking/test-ww_mutex.c b/kernel/locking/test-ww_mutex.c
index 10a5736a21c22..cc0d2e59049a8 100644
--- a/kernel/locking/test-ww_mutex.c
+++ b/kernel/locking/test-ww_mutex.c
@@ -636,19 +636,15 @@ static int stress(int nlocks, int nthreads, unsigned int flags)
 	return 0;
 }
 
-static int __init test_ww_mutex_init(void)
+static DEFINE_MUTEX(run_lock);
+
+static int run_tests(void)
 {
 	int ncpus = num_online_cpus();
 	int ret, i;
 
 	printk(KERN_INFO "Beginning ww mutex selftests\n");
 
-	prandom_seed_state(&rng, get_random_u64());
-
-	wq = alloc_workqueue("test-ww_mutex", WQ_UNBOUND, 0);
-	if (!wq)
-		return -ENOMEM;
-
 	ret = test_mutex();
 	if (ret)
 		return ret;
@@ -687,8 +683,68 @@ static int __init test_ww_mutex_init(void)
 	return 0;
 }
 
+static ssize_t run_tests_store(struct kobject *kobj, struct kobj_attribute *attr,
+			       const char *buf, size_t count)
+{
+	if (!mutex_trylock(&run_lock)) {
+		pr_err("Test already running\n");
+		return count;
+	}
+
+	run_tests();
+	mutex_unlock(&run_lock);
+
+	return count;
+}
+
+static struct kobj_attribute run_tests_attribute =
+	__ATTR(run_tests, 0664, NULL, run_tests_store);
+
+static struct attribute *attrs[] = {
+	&run_tests_attribute.attr,
+	NULL,   /* need to NULL terminate the list of attributes */
+};
+
+static struct attribute_group attr_group = {
+	.attrs = attrs,
+};
+
+static struct kobject *test_ww_mutex_kobj;
+
+static int __init test_ww_mutex_init(void)
+{
+	int ret;
+
+	prandom_seed_state(&rng, get_random_u64());
+
+	wq = alloc_workqueue("test-ww_mutex", WQ_UNBOUND, 0);
+	if (!wq)
+		return -ENOMEM;
+
+	test_ww_mutex_kobj = kobject_create_and_add("test_ww_mutex", kernel_kobj);
+	if (!test_ww_mutex_kobj) {
+		destroy_workqueue(wq);
+		return -ENOMEM;
+	}
+
+	/* Create the files associated with this kobject */
+	ret = sysfs_create_group(test_ww_mutex_kobj, &attr_group);
+	if (ret) {
+		kobject_put(test_ww_mutex_kobj);
+		destroy_workqueue(wq);
+		return ret;
+	}
+
+	mutex_lock(&run_lock);
+	ret = run_tests();
+	mutex_unlock(&run_lock);
+
+	return ret;
+}
+
 static void __exit test_ww_mutex_exit(void)
 {
+	kobject_put(test_ww_mutex_kobj);
 	destroy_workqueue(wq);
 }
 
-- 
2.50.0.727.gbf7dc18ff4-goog

[PATCH 2/2] test-ww_mutex: Move work to its own UNBOUND workqueue

[John Stultz]

The test-ww_mutex test already allocates its own workqueue
so be sure to use it for the mtx.work and abba.work rather
then the default system workqueue.

This resolves numerous messages of the sort:
"workqueue: test_abba_work hogged CPU... consider switching to WQ_UNBOUND"
"workqueue: test_mutex_work hogged CPU... consider switching to WQ_UNBOUND"

Signed-off-by: John Stultz <jstultz@google.com>
---
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Will Deacon <will@kernel.org>
Cc: Waiman Long <longman@redhat.com>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: "Paul E . McKenney" <paulmck@kernel.org>
Cc: Joel Fernandes <joelagnelf@nvidia.com>
Cc: Dietmar Eggemann <dietmar.eggemann@arm.com>
Cc: Suleiman Souhlal <suleiman@google.com>
Cc: kernel-team@android.com
---
 kernel/locking/test-ww_mutex.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/locking/test-ww_mutex.c b/kernel/locking/test-ww_mutex.c
index cc0d2e59049a8..d7c3f7f533f42 100644
--- a/kernel/locking/test-ww_mutex.c
+++ b/kernel/locking/test-ww_mutex.c
@@ -70,7 +70,7 @@ static int __test_mutex(unsigned int flags)
 	init_completion(&mtx.done);
 	mtx.flags = flags;
 
-	schedule_work(&mtx.work);
+	queue_work(wq, &mtx.work);
 
 	wait_for_completion(&mtx.ready);
 	ww_mutex_lock(&mtx.mutex, (flags & TEST_MTX_CTX) ? &ctx : NULL);
@@ -229,7 +229,7 @@ static int test_abba(bool trylock, bool resolve)
 	abba.trylock = trylock;
 	abba.resolve = resolve;
 
-	schedule_work(&abba.work);
+	queue_work(wq, &abba.work);
 
 	ww_acquire_init_noinject(&ctx, &ww_class);
 	if (!trylock)
-- 
2.50.0.727.gbf7dc18ff4-goog