[PATCH v3 1/3] test-ww_mutex: Fix module cleanup

["Håkon Bugge" <haakon.bugge@oracle.com>]

When test-ww_mutex is compiled as a module, there are two bugs. One is
related to the case where the module fails to load. In that case, some
or all of the allocated objects are not released. Also, if loaded OK
and thereafter unloaded, the sysfs file is not removed.

The latter bug gives the following splat (trimmed for better brevity):

sysfs: cannot create duplicate filename '/kernel/test_ww_mutex'
 dump_stack_lvl+0x5d/0x90
 sysfs_warn_dup.cold+0x17/0x23
 sysfs_create_dir_ns+0xe2/0x100
 kobject_add_internal+0xba/0x270
 kobject_add+0x95/0xd0
 kobject_create_and_add+0xa3/0xd0
 test_ww_mutex_init+0x90/0xff0 [test_ww_mutex]
 do_one_initcall+0x5c/0x330
 do_init_module+0x90/0x290
 __do_sys_init_module+0x195/0x1d0
 do_syscall_64+0xe8/0x550
 entry_SYSCALL_64_after_hwframe+0x76/0x7e

Fixes: 2a0c11282881 ("locking/ww_mutex: Add kselftests for ww_mutex stress")
Fixes: de2c5a1523fd ("test-ww_mutex: Allow test to be run (and re-run) from userland")
Signed-off-by: Håkon Bugge <haakon.bugge@oracle.com>
Acked-by: John Stultz <jstultz@google.com>

---

v1 -> v2:
      * Keep the sysfs file if module is built-in even when the test
        fails. This in order to be able to run the test multiple
        times even in case of errors. Suggested by John Stultz
---
 kernel/locking/test-ww_mutex.c | 27 +++++++++++++++++----------
 1 file changed, 17 insertions(+), 10 deletions(-)

diff --git a/kernel/locking/test-ww_mutex.c b/kernel/locking/test-ww_mutex.c
index 838d631544ed2..8311ff38ab683 100644
--- a/kernel/locking/test-ww_mutex.c
+++ b/kernel/locking/test-ww_mutex.c
@@ -734,7 +734,7 @@ static struct kobject *test_ww_mutex_kobj;
 
 static int __init test_ww_mutex_init(void)
 {
-	int ret;
+	int ret = -ENOMEM;
 
 	prandom_seed_state(&rng, get_random_u64());
 
@@ -743,28 +743,35 @@ static int __init test_ww_mutex_init(void)
 		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;
-	}
+	if (!test_ww_mutex_kobj)
+		goto kobj_err;
 
 	/* 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;
-	}
+	if (ret)
+		goto sysfs_err;
 
 	mutex_lock(&run_lock);
 	ret = run_test_classes();
 	mutex_unlock(&run_lock);
 
+	if (!ret || IS_BUILTIN(CONFIG_WW_MUTEX_SELFTEST))
+		return 0;
+
+	sysfs_remove_group(test_ww_mutex_kobj, &attr_group);
+
+sysfs_err:
+	kobject_put(test_ww_mutex_kobj);
+
+kobj_err:
+	destroy_workqueue(wq);
+
 	return ret;
 }
 
 static void __exit test_ww_mutex_exit(void)
 {
+	sysfs_remove_group(test_ww_mutex_kobj, &attr_group);
 	kobject_put(test_ww_mutex_kobj);
 	destroy_workqueue(wq);
 }
-- 
2.43.5