un-dedicating a line to a dialer

[Chris Maltby]

 > If someone dials in and releases a long-running background job the
 > special file will be held open until the background job finishes (which
 > happens quite often on our system).  This will prevent locking mechanisms
 > like the above from working.  

A sensible system will send a HUP signal to the process group when its
leader dies, and unless the long-runner has been 'nohup'ed (and its
references to the terminal closed), it will die.