lpd causes crash with CPU PANIC !!

[Dietmar Weis]

On a DECSystem3100 running Ultrix 4.0 sometimes occur inconsistencies
in the lpd system (printing to lat printers), followed by a system crash!!

lpc status said for example "no progress since 3 days" ,
"waiting to connect" or "no daemon active", the error log says "output
filter to lat malfunctioned (0)", "cannot open /dev/tty??, no such file or
directory" or "job aborted".

But there *was* a lpd daemon, there *is* a /dev/tty??, but there were also
an idle /usr/lib/lpdfilters/xf with PPID 1 and the forked /bin/cat-process.
The user did not miss his last printouts.

So, cleaning up the queue, restarting and killing the idle print-processes
(I can't remember in which order, doesn't matter) resulted in an immediate
system crash:

cpu0 panic: unaligned access
locks held by cpu0
print locks held by non-active processes

Rebooted to Multiusermode the system crashed again and again, sometimes
at the starting up of lpd in rc.local, sometimes after login and doing
lpc status. At this time there were of course no more print processes
and no print jobs.

Only powering off the terminal server resolved this.

This is the 6. time something like this happend and it's very serious.

Other messages in the lpd error log were: "sleeping, retrying in xx seconds",
(already discussed here, with no solution I think) and "socket already in use".

So, what is going on here, does anyone know?

Specification: DS3100 with 20 MB, Ultrix 4.0, Emulex Terminal Server P4000,
Kyocera F-800 printers.

Thank you very much, 

Dietmar