Unable to clear a stuck device

[Joe Moog]

We have a FreeBSD host (FreeBSD 9.1-PRERELEASE #0 r244125) configured with a few ZFS storage volumes. Recently we attached an external volume to the host, created a GELI-encrypted ZFS volume, and copied some data to it. When completed, the device was not disconnected properly. Now, any ZFS/zpool commands that attempt to touch that missing device are left hanging in perpetuity on the host because it seems to think it can still access the volume when in fact it cannot. This is not affecting any other functions of the host besides a few scripts that are intended to check the health of the attached volumes.

Is there any way to clear the apparent presence of this missing device? We tried to re-attach the volume and perform the necessary ZFS export/import, but these commands now hang as well (the -f option has no effect). No doubt a reboot would take care of it, but there are some functions running on this host that we do not wish to interrupt, if at all possible. Can anybody make a recommendation?

Thanks

Joe