ukbd problem..

when i plug and unplug several times, i can get following panic.
(right after unplugging)

ukbd_timeout + 0x18
softclock()
...


i am sure that ukbd_timeout() is untimeout()ed in ukbd_term() 
and then, kbd is free()ed. but ukbed_timeout() is unexpectedly timeout()ed.

where is problem...?

thank you in advance