Getting debug info from a kernel hang on a Mac Mini?

[Wim Lewis <wiml%hhhh.org@localhost>]

Is there a way to extract useful information from a hung kernel on a  
Mac Mini? From what I've read, it has no serial console even as a  
motherboard header, and these kernel hangs are leaving the Mini  
unresponsive to USB and ethernet.

(They're presumably USB-related, since they tend to happen when I  
plug, unplug, or reset an experimental USB device I'm working on.)

I've tried compiling a kernel with DIAGNOSTIC, DEBUG, and  
DDB_ONPANIC=1 options, but other than a few more console messages  
during normal plug/unplug operations they're not providing any more  
information about the crashes.

I'm probably not up for fixing the underlying problem myself but if I  
can get more information I can at least file a useful pr.

I'm running 5.0 on (of course) a ppc mac mini.