misc/62026: COM-ports disabled in BIOS = FreeBSD Freeze

[Elof]

>Number:         62026
>Category:       misc
>Synopsis:       COM-ports disabled in BIOS = FreeBSD Freeze
>Confidential:   no
>Severity:       critical
>Priority:       low
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Wed Jan 28 04:00:34 PST 2004
>Closed-Date:
>Last-Modified:
>Originator:     Elof
>Release:        4.9-STABLE
>Organization:
BTL
>Environment:
FreeBSD foo.bar.se 4.9-STABLE FreeBSD 4.9-STABLE #0: Tue Jan 27 16:00:26 CET 2004    root at foo.bar.se:/usr/obj/usr/src/sys/FOO-KERNEL-4-9  i386
Run on a Dell Optiplex machine with a PIII 600MHz.
>Description:
(I'm running on a cvsup:ed RELENG_4 world)

I have enabled a login on a serial port via /etc/ttys:
  ttyd0  "/usr/libexec/getty std.9600"  vt100  on secure

Yesterday I added some NICs and got some PnP configuration errors in BIOS. While troubleshooting this, I disabled everything I didn't use; all serial (COM) ports, the parallell port, the builtin NIC, etc.

When I finally got a working config I forgot to enable the stuff I had disabled. I started FreeBSD and it booted fine.

Everything looked as it should on the screen. The last line was the login-prompt. The problem was that the machine had freezed. No response to keystrokes and no network traffic, not even responses to ARP-requests.

Nothing on the screen indicates what's wrong.
I rebooted the machine and booted on a LiveCD, ran fsck on my /var partition, only to see that nothing revealing was logged to /var/log.

Suddenly I remembered my dialin line in /etc/ttys. I disabled it and now there were no freeze.
>How-To-Repeat:
Disable all COM-ports in BIOS. Enable a dialin getty in /etc/ttys that use a (nonexistent) serial port.
>Fix:
This is a problem that is manually introduced. My hopes are that you could add some funtions that test wether any serial port exist before trying to use it. Then you could avoid the freeze and print/log a warning.
>Release-Note:
>Audit-Trail:
>Unformatted: