From:	MERC::"uunet!WKUVX1.BITNET!goathunter" 16-JUL-1992 15:56:29.85
To:	supser-l@WKUVX1.BITNET
CC:	
Subj:	A couple of bugs....

Hello, all.  I hope the Supervisor Series is working well for most
everyone!  The list has been quiet, so I assume....

There are two problems I'd like to warn you about.  These situations
are rare, but *can* crash your system.

  o  SUPERVISOR: when supervising a terminal that becomes "hung" (or
     is "hung" when you start supervising it), the SUPERVISOR process
     may also hang.  If this happens, you should STOP/ID the process
     running SUPERVISOR *before* you STOP/ID the hung process.  At
     least, I *think* this will prevent a system crash.

     What's happening is that somehow the target terminal's UCB is
     getting deleted and SUPERVISOR isn't told that it was deleted.
     It happily tries to keep accessing a UCB that has been
     deallocated and is no longer valid, thus the crash.  I've
     come up with a method for trying to catch this case, but I
     still haven't figured out why SUPERVISOR isn't getting that
     notification like it should (when the target process is killed,
     you should get a "Data set hangup" message).

  o  PHOTO: do *not* specify an invalid log file name when using
     PHOTO.  Something is going wrong in the initialization that
     PHOTO doesn't recover from gracefully.  If you do specify
     an invalid file name (for example, a directory that doesn't
     exist), PHOTO will continue to work OK for that process, but
     when it logs out, some PHOTO code goes into an infinite loop
     that will either hang the system (uniprocessor) or crash it
     with a CPUSPINWAIT bugcheck (SMP).  I know, that makes it
     difficult to use in an academic environment.

I'm trying to track these down and fix them, but my time for
Supervisor is very short at the moment (real work beckons).  I'll do
my best to come up with fixes ASAP.  Thanks.

Hunter
------
Hunter Goatley, VMS Systems Programmer, Western Kentucky University
goathunter@WKUVX1.BITNET, 502-745-5251