#0  dumpsys () at thread.h:83
#1  0xc019f9f6 in boot (howto=260) at /usr/src/sys/kern/kern_shutdown.c:370
#2  0xc01a0146 in panic (fmt=0xc02e3fc6 "from debugger")
    at /usr/src/sys/kern/kern_shutdown.c:767
#3  0xc0145f02 in db_panic (addr=-1070943602, have_addr=0, count=-1,
    modif=0xce6766d8 "") at /usr/src/sys/ddb/db_command.c:447
#4  0xc0145e97 in db_command (last_cmdp=0xc033fb70, cmd_table=0x0,
    aux_cmd_tablep=0xc03125a4, aux_cmd_tablep_end=0xc03125a8)
    at /usr/src/sys/ddb/db_command.c:343
#5  0xc0145f77 in db_command_loop () at /usr/src/sys/ddb/db_command.c:469
#6  0xc0148afc in db_trap (type=3, code=0) at /usr/src/sys/ddb/db_trap.c:71
#7  0xc02aaeb3 in kdb_trap (type=3, code=0, regs=0xce676804)
    at /usr/src/sys/platform/pc32/i386/db_interface.c:148
#8  0xc02c0274 in trap (frame=0xce676804)
    at /usr/src/sys/platform/pc32/i386/trap.c:797
#9  0xc02abf76 in calltrap ()
    at /usr/src/sys/platform/pc32/i386/exception.s:783
#10 0xc02ab28e in Debugger (msg=0x12 <Address 0x12 out of bounds>)
    at cpufunc.h:73
#11 0xc01a013e in panic (
    fmt=0xc02ff3a4 "lwkt_switch: still holding %d exclusive spinlocks!")
    at /usr/src/sys/kern/kern_shutdown.c:765
#12 0xc01a779c in lwkt_switch () at /usr/src/sys/kern/lwkt_thread.c:529
#13 0xc01ac9d9 in tsleep (ident=0xcccc2428, flags=0,
    wmesg=0xc02ef4dc "usbsyn", timo=0) at /usr/src/sys/kern/kern_synch.c:452
#14 0xc027f7bf in usbd_transfer (xfer=0xcccc2428)
    at /usr/src/sys/bus/usb/usbdi.c:341
#15 0xc027f812 in usbd_sync_transfer (xfer=0x12)
    at /usr/src/sys/bus/usb/usbdi.c:352
#16 0xc0280175 in usbd_do_request_flags_pipe (dev=0xc7f89e90, pipe=0x12,
    req=0xce6769f4, data=0x12, flags=0, actlen=0x0, timeout=18)
    at /usr/src/sys/bus/usb/usbdi.c:976
#17 0xc02800f6 in usbd_do_request_flags (dev=0x20, req=0x12, data=0x12,
    flags=0, actlen=0x12, timo=18) at /usr/src/sys/bus/usb/usbdi.c:942
#18 0xc02800b8 in usbd_do_request (dev=0x12, req=0x12, data=0x12)
    at /usr/src/sys/bus/usb/usbdi.c:934
#19 0xc027fd26 in usbd_set_interface (iface=0xccd08d00, altidx=18)
    at /usr/src/sys/bus/usb/usbdi.c:697
#20 0xc042cfe3 in ?? ()