netstat fails with memory allocation error and error in kvm_read

[J. Martin Petersen]

> I just got another "netstat: kvm_read: Bad address". 
> vm.kvm_free was 675278848 two seconds earlier and a couple of 
> seconds later (and also currently).

We just had another hard hang, and this time I managed to break to the
debugger on the serial console. I got this stack trace
<http://www.aub.dk/~jmp/fw/trace>, which seems to indicate that pf is
messing up somehow. 

I of course didn't have the ddb man or the handbook section on kernel
debugging at hand, so I've just printed it for the next time it happens.

Both 'show witness' and 'show locks' came up empty. What's the most
effective way to hunt down these deadlocks with the online kernel debugger? 

Best regards
Martin