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

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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>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://patch.msgid.link/20251205013515.759030-4-jstultz@google.com
This commit is contained in:
John Stultz 2025-12-05 01:35:11 +00:00 committed by Peter Zijlstra
parent d327e7166e
commit de2c5a1523
1 changed files with 49 additions and 2 deletions
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51
kernel/locking/test-ww_mutex.c
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@ -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);
}