hole in passregister?

[Matthew Jacob]

...
         mtx_unlock(periph->sim->mtx);
 	...
         mtx_lock(periph->sim->mtx);
         softc->dev->si_drv1 = periph;

         /*
          * Add an async callback so that we get
          * notified if this device goes away.
          */
         xpt_register_async(AC_LOST_DEVICE, passasync, periph, periph->path);
....
the device can go away prior to xpt_register_async being called I think.