panic in usbdi.c

[Patrick Welche <prlw1%cam.ac.uk@localhost>]

I just built yesterday's -current/amd64 into a releasedir which is
nfs exported, and prepared it for netbooting. Trying "boot netbsd -a"
at the network boot prompt gets me

boot device: wm0
root device (default wm0): panic:kernel diagnostic assertion 
"KERNEL_LOCKED_P()" failed: file "/usr/src/sys/dev/usb/usbdi.c", line 755
fatal breakpoint trap in supervisor mode
trap type 1 code 0 rip ffffffff802544c5 cs 8 rflags 246 cr2  0 cpl 4 rsp 
ffffffff810489f0
Stopped in pid 0.1 (system) at  netbsd:breakpoint+0x5:  leave

Sure enough, these modern computers don't have PS2 ports, so it is a USB
keyboard which explains the usbdi.c just before keyboard input is necessary,
and also why I can't type bt. (Time for DDB_COMMANDONENTER !)

Cheers,

Patrick