Losing a modem port under Ultrix 2.0-1

[Russell Crook]

( This is also posted to comp.unix.ultrix. My news (2.10.1) does
  not appear to allow posting to moderated and unmoderated groups
  simultaneously. This could simply be MY problem though ...)

Our site has a problem with "losing" a modem port when using uucp.
Fairly often (say, once every twenty calls or so), the port "hangs"
at the end of the uucico session - the line has been dropped, but
the modem indicates receive and transmit both active (but no data
is flowing in or out), and the host uucico is unkillable. Indeed,
a kill -9 on it will eventually cause the system to hang! (this seems
to be hastened by doing a ps after this). It appears to be hung
in dhu11 (according to ps's WCHAN and nm); possibly, a close
(or something similar) got lost. The modem is not (entirely) at fault,
as power cycling the modem doesn't help, but a reboot does.

Questions:
    Is this a known bug in the driver?
    Is there a cure (we do not have source)?
    The modem port is the last port of the eight (it used to be tty07).
Would the problem be less likely to occur if I used a different port
(due to driver timing considerations)?

Other configuration details: we are running a uVax II with DECnet; there
are eight serial ports (one dhu11), 9Mb of memory, and a 140 Mb disk.
We run DECnet/Ultrix over Ethernet to talk to several other (VMS)
microVAXen.
The uucp is the uucp that comes with Ultrix 2.0-1 (which we are running).
None of the direct-connect ports have exhibited any problems. The modem is a
Capetronics 1200 baud modem (Hayes compatible). The problem occurs upon
connecting to both Hayes and Trailblazer Plus modems.

Any help would be much appreciated.

Russell Crook (UUCP: ...!uunet!mnetor!motto!russ, or ...!motto!tardis.dnet!russ)
Disclaimer: "...we're all mad here. I'm mad. You're mad."
            "How do you know I'm mad?" said Alice.
            "You must be", said the Cat, "or you wouldn't have come here."
-- 
Russell Crook (UUCP: ...!uunet!mnetor!motto!russ)
Disclaimer: "...we're all mad here. I'm mad. You're mad."
            "How do you know I'm mad?" said Alice.
            "You must be", said the Cat, "or you wouldn't have come here."