If you are in the upgrade process (doing the database updates), and another user logs in, it should say the database upgrade is in progress, rather than allowing them to start running the database updates himself. When this happens, the first client that started to run the updates gets kicked out. If you follow the event log, the upgrade completes correctly.
You could display a message for subsequent users saying "User James Arbaugh has already started the database update process." or something like that rather than letting them try to run the updates and have them fail. They may be tempted to restart the server and leave the database in an unstable state if they didn't know it was already doing something.