I'd guess this is because of a bug that crept into test9,
where a TD is now leaked ... you can get rid of the slab
BUG warning by commenting out the line at the top of
drivers/usb/usb-ohci.c that #defines OHCI_MEM_SLAB.
That TD leak prevents the kmem_cache from getting freed,
and hence prevents that module from getting reloaded.
It was a mistake to leave that #defined at this time,
though of course it _ought_ to be fine to do that.