panic: sleeping thread owns a mutex

[Jeffrey Hsu]

  > Set a flag in your driver before you drop the wi lock that the
  > wiintr() function can check and bail out immediately if it is set.
  > For example:

  > foo_detach()
  > {
  >        ...
  >        sc->sc_dead = 1;
  >        FOO_UNLOCK(sc);
  >        bus_teardown_intr(...)
  >        ...
	   mtx_destroy(&sc->sc_mtx);		<--- note this
  > }

  > foo_intr()
  > {
  >        FOO_LOCK(sc);
  >        if (sc->sc_dead) {
  >                FOO_UNLOCK(sc);
  >                return;
  >        }
  >	   ...
  > }

The sc_dead flag doesn't protect against foo_intr() attempting to
lock a mutex that has been destroyed.  fxp has the same problem
and is one of the reasons, among others,  I wasn't too happy with
the fxp softc locks introduced there.

The solution I have in mind involves using the DEAD flag in the interrupt
handler to defer destroying the mutex if the interrupt handler is active.

							Jeffrey