(kgdb) where
#0  doadump (textdump=1) at pcpu.h:222
#1  0xffffffff809b5dd5 in kern_reboot (howto=260) at /home/src/sys/kern/kern_shutdown.c:366
#2  0xffffffff809b63b0 in vpanic (fmt=<value optimized out>, ap=<value optimized out>) at /home/src/sys/kern/kern_shutdown.c:759
#3  0xffffffff809b63f3 in panic (fmt=<value optimized out>) at /home/src/sys/kern/kern_shutdown.c:690
#4  0xffffffff809e41a2 in __stack_chk_fail () at /home/src/sys/kern/stack_protector.c:17
#5  0xffffffff80838b91 in u3g_intr_callback (xfer=<value optimized out>, error=<value optimized out>)
#6  0xffffffff8083514b in usbd_callback_wrapper (pq=<value optimized out>) at /home/src/sys/dev/usb/usb_transfer.c:2408
#7  0xffffffff808362c8 in usb_command_wrapper (pq=0xfffffe000233b060, xfer=<value optimized out>) at /home/src/sys/dev/usb/usb_transfer.c:3062
#8  0xffffffff808352f6 in usb_callback_proc (_pm=<value optimized out>) at /home/src/sys/dev/usb/usb_transfer.c:2269
#9  0xffffffff808300d9 in usb_process (arg=0xfffffe000127f500) at /home/src/sys/dev/usb/usb_process.c:176
#10 0xffffffff809788e4 in fork_exit (callout=0xffffffff80830000 <usb_process>, arg=0xfffffe000127f500, frame=0xfffffe0453fdeac0)
    at /home/src/sys/kern/kern_fork.c:1043
#11 0xffffffff80e337ce in fork_trampoline () at /home/src/sys/amd64/amd64/exception.S:611
#12 0x0000000000000000 in ?? ()