Just had a panic while rebooting new kernel => lost corresponding gdb file..
So here's a fairly useless trace (don't have correponding kernel either:( ):

panic: uvm_fault_unwire_locked: unwiring non-wired memory
Stopped in pid 195 (ntpd) at cpu_Debugger+0x4: leave

cpu_Debugger
panic
uvm_fault_unwire_locked
uvm_unmap_remove
uvm_unmap
uvm_deallocate
exit1
sys_exit
syscall_plain

after shutdown -r now on i386 with approx 3 day old kernel.

Cheers,

Patrick