"Losing" a modem port under Ultrix 2.0-1

[Russell Crook]

.
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 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 ttyd7).
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.
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)
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."