Ah, so both of the "hcd-ized" UHCI drivers have a common bug:
they've got logic to look at the USB_ASYNC_UNLINK flag and
block unless it's clear ... but the hcd framework is already
handling the synchronous behavior, so that's wrong.

Try to repeat that with the patch I've attached, which rips
out that duplicated code ... and so should at least get rid of
that oops, even if it doesn't entirely fix the timeout issue.

(Or: try with either the OHCI driver, or with the EHCI driver
through a USB 2.0 hub, if you have appropriate hardware.)

- Dave

p.s. Disclaimer about this patch:  all it does is rip out
      code and make it compile without warnings, but I've
      not tested it otherwise.  There's a possiblity it'll
      uncover latent issues on the other code path, but then
      that's exactly why we only want one unlink code path
      inside the HCDs!  So Greg, please merge anyway ...