Closing a Notification Port
Applications close a notification port by calling CloseClusterNotifyPort.
Note the potential for a race condition if multiple threads access the same notification port. For example, one thread could be calling CloseClusterNotifyPort to close the notification port while another thread, which has called GetClusterNotify, is waiting to retrieve information from the same port.
Prevent this problem by having the thread that is calling GetClusterNotify check for a CLUSTER_CHANGE_HANDLE_CLOSE event.