assert_return(EVENT_SOURCE_IS_TIME(s->type), -EDOM);
assert_return(s->event->state != SD_EVENT_FINISHED, -ESTALE);
assert_return(!event_pid_changed(s->event), -ECHILD);
assert_return(EVENT_SOURCE_IS_TIME(s->type), -EDOM);
assert_return(s->event->state != SD_EVENT_FINISHED, -ESTALE);
assert_return(!event_pid_changed(s->event), -ECHILD);