On Tue, 3 Feb 1998, Dirk wrote:

> Hi:
> 
> Machine Type:  IIcx, 20MB RAM
> Version of NetBSD: 1.3 release
> 
> I've got a IIcx running headless, with a serial console on tty01.  The
> serial line is sometimes (but not always) connected to my Powerbook.  Most
> of the time when the serial line *is* connected, I run a ppp connection to
> the Powerbook.  The IIcx has a modem on tty00, and does IP-NAT for the
> Powerbook.
> 
> Unfortunately, sometimes when the Powerbook isn't connected, the IIcx
> chokes.  As near as I can tell without hooking something up to it, all
> activity on the IIcx stops.  When I then re-connect the Powerbook, it looks
> to me like getty (or something similar) has dropped into the debugger (I
> get a db> prompt).  Typing "c" at the db> prompt seems to continue
> whatever-it-is that's hung, and the machine goes on its merry way.  (Note
> -- when this happens, it seems to lose clock time from roughly the point at
> which I disconnected the Powerbook.  If I unplugged it at 8:40 AM, say, the
> clock time will still be at about 8:40 AM when I restart it -- which makes
> me think the whole machine is waiting for the crashed process to come back
> from the debbuger).
> 
> This isn't the desired behavior.  I haven't been able to figure out under
> what conditions the halt occurs (I've tried leaving various users logged in
> on that line, having no one logged in, leaving it running a shell script
> which repeats a sleep over and over... none of these help consistently).
> 
> Any ideas on what I can do to stop this?  What further information should I
> provide?

That's enough info.

You've actually run into a feature of the serial console code. Basically,
you hook up a terminal as the console, hit 'break', and you're dropped
into the debugger. The BREAK sequence is a stream of 0's longer than any
properly-framed character would be. I think it's 10 bits of "0", but the
exact number doesn't matter. We do this so you basicly have a debugger
switch even over a serial link.

Unfortunatly this can happen when you unplug the terminal.

You need to build your own kernel, and remove the ZS_CONSOLE_ABORT option
from the config file. Then you'll be fine.

Take care,

Bill