Commit de2c5a15 authored by John Stultz's avatar John Stultz Committed by Peter Zijlstra
Browse files

test-ww_mutex: Allow test to be run (and re-run) from userland 



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: default avatarJohn Stultz <jstultz@google.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Link: https://patch.msgid.link/20251205013515.759030-4-jstultz@google.com
parent d327e716

kernel/locking/test-ww_mutex.c

+49 −2
Original line number Diff line number Diff line
@@ -642,7 +642,7 @@ static int stress(struct ww_class *class, int nlocks, int nthreads, unsigned int 
	return 0;

}



static int __init run_tests(struct ww_class *class)

static int run_tests(struct ww_class *class)

{

	int ncpus = num_online_cpus();

	int ret, i;
@@ -684,7 +684,7 @@ static int __init run_tests(struct ww_class *class) 
	return 0;

}



static int __init run_test_classes(void)

static int run_test_classes(void)

{

	int ret;
@@ -703,6 +703,36 @@ static int __init run_test_classes(void) 
	return 0;

}



static DEFINE_MUTEX(run_lock);



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_test_classes();

	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;
@@ -713,13 +743,30 @@ static int __init test_ww_mutex_init(void) 
	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_test_classes();

	mutex_unlock(&run_lock);



	return ret;

}



static void __exit test_ww_mutex_exit(void)

{

	kobject_put(test_ww_mutex_kobj);

	destroy_workqueue(wq);

}