selftests/user_events: Wait for deferred event teardown after unregister

Unregistering a user event now defers the drop of the enabler's event
reference (and the freeing of the enabler) past an RCU grace period. As a
result DIAG_IOCSDEL can transiently fail with -EBUSY while that last
reference is still being dropped, where it previously succeeded
immediately.

Two tests assumed the delete takes effect the instant the unregister
returns:

  - abi_test "flags" deletes the event right after disabling it.
  - perf_test's fixture teardown clear() deletes __test_event before the
    next test registers the same name; a stale event makes the following
    registration fail with -EADDRINUSE.

Retry the delete until it succeeds (or the event is already gone) with a
bounded wait, matching the existing wait_for_delete() idiom in the same
suite, so the tests are robust to the deferred teardown.

Link: https://patch.msgid.link/20260707180240.2887081-1-michael.bommarito@gmail.com
Assisted-by: Claude:claude-opus-4-8
Signed-off-by: Michael Bommarito <michael.bommarito@gmail.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

diff --git a/tools/testing/selftests/user_events/abi_test.c b/tools/testing/selftests/user_events/abi_test.c
index 85892b3b719ccde0768c1095d1f39997a9cb5470..b71813eaf5c04879f727bef9618d2adfb49ec279 100644 (file)
--- a/tools/testing/selftests/user_events/abi_test.c
+++ b/tools/testing/selftests/user_events/abi_test.c
@@ -132,6 +132,33 @@ static int event_delete(void)
        return ret;
 }
 
+/*
+ * Deleting an event drops its last reference, but an unregister may defer
+ * that put (and the freeing of the associated enabler) past an RCU grace
+ * period. The delete can therefore transiently fail with -EBUSY while the
+ * previous reference is still being dropped. Retry only on that transient
+ * failure; treat an already-deleted event (-ENOENT) as success and return
+ * any other error immediately rather than spinning for the full timeout.
+ */
+static int wait_for_event_delete(void)
+{
+       int i, ret;
+
+       for (i = 0; i < 10000; ++i) {
+               ret = event_delete();
+
+               if (ret == 0 || errno == ENOENT)
+                       return 0;
+
+               if (errno != EBUSY)
+                       return ret;
+
+               usleep(1000);
+       }
+
+       return ret;
+}
+
 static int reg_enable_multi(void *enable, int size, int bit, int flags,
                            char *args)
 {
@@ -262,7 +289,7 @@ TEST_F(user, flags) {
        ASSERT_TRUE(event_exists());
 
        /* Ensure we can delete it */
-       ASSERT_EQ(0, event_delete());
+       ASSERT_EQ(0, wait_for_event_delete());
 
        /* USER_EVENT_REG_MAX or above is not allowed */
        ASSERT_EQ(-1, reg_enable_flags(&self->check, sizeof(int), 0,

diff --git a/tools/testing/selftests/user_events/perf_test.c b/tools/testing/selftests/user_events/perf_test.c
index cafec0e52eb31eff048645ee0a1b4aad1e144570..5727cb5b914cf583937029663db93853eb0c5532 100644 (file)
--- a/tools/testing/selftests/user_events/perf_test.c
+++ b/tools/testing/selftests/user_events/perf_test.c
@@ -85,6 +85,7 @@ static int get_offset(void)
 static int clear(int *check)
 {
        struct user_unreg unreg = {0};
+       int i, ret;
 
        unreg.size = sizeof(unreg);
        unreg.disable_bit = 31;
@@ -99,13 +100,32 @@ static int clear(int *check)
                if (errno != ENOENT)
                        return -1;
 
-       if (ioctl(fd, DIAG_IOCSDEL, "__test_event") == -1)
-               if (errno != ENOENT)
+       /*
+        * Deleting the event drops its last reference, but the unregister
+        * above defers that put (and the freeing of the enabler) past an RCU
+        * grace period. The delete can therefore transiently fail with -EBUSY
+        * until that reference is dropped. Retry for up to ~10 seconds so the
+        * event is actually gone before the next test registers the same name.
+        */
+       for (i = 0; i < 10000; ++i) {
+               ret = ioctl(fd, DIAG_IOCSDEL, "__test_event");
+
+               if (ret == 0 || errno == ENOENT) {
+                       ret = 0;
+                       break;
+               }
+
+               if (errno != EBUSY) {
+                       close(fd);
                        return -1;
+               }
+
+               usleep(1000);
+       }
 
        close(fd);
 
-       return 0;
+       return ret;
 }
 
 FIXTURE(user) {