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Message-ID: <20250801023358.562525-4-jstultz@google.com>
Date: Fri, 1 Aug 2025 02:33:49 +0000
From: John Stultz <jstultz@...gle.com>
To: LKML <linux-kernel@...r.kernel.org>
Cc: John Stultz <jstultz@...gle.com>, Peter Zijlstra <peterz@...radead.org>,
Ingo Molnar <mingo@...hat.com>, Will Deacon <will@...nel.org>, Waiman Long <longman@...hat.com>,
Boqun Feng <boqun.feng@...il.com>, "Paul E . McKenney" <paulmck@...nel.org>,
Joel Fernandes <joelagnelf@...dia.com>, Dietmar Eggemann <dietmar.eggemann@....com>,
Suleiman Souhlal <suleiman@...gle.com>, kernel-team@...roid.com
Subject: [PATCH 3/3] 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: John Stultz <jstultz@...gle.com>
---
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Ingo Molnar <mingo@...hat.com>
Cc: Will Deacon <will@...nel.org>
Cc: Waiman Long <longman@...hat.com>
Cc: Boqun Feng <boqun.feng@...il.com>
Cc: "Paul E . McKenney" <paulmck@...nel.org>
Cc: Joel Fernandes <joelagnelf@...dia.com>
Cc: Dietmar Eggemann <dietmar.eggemann@....com>
Cc: Suleiman Souhlal <suleiman@...gle.com>
Cc: kernel-team@...roid.com
---
kernel/locking/test-ww_mutex.c | 51 ++++++++++++++++++++++++++++++++--
1 file changed, 49 insertions(+), 2 deletions(-)
diff --git a/kernel/locking/test-ww_mutex.c b/kernel/locking/test-ww_mutex.c
index 11bc467c286aa..e7b7211d25768 100644
--- a/kernel/locking/test-ww_mutex.c
+++ b/kernel/locking/test-ww_mutex.c
@@ -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);
}
--
2.50.1.565.gc32cd1483b-goog
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