Smbfs hang when connection broken

[Jonathan Wallace]

Processes that access a share from a remote machine hang if the connection
goes away.  I'm using FBSD V5.4 and mount_smbfs.  This can be replicated
by the following sequence:

1) Share a file system from a remote Windows machine.
2) Mount the share using mount_smbfs
3) Start a tar() command to copy the data from the windows share.
4) Unplug the network cable from the windows box

The ps() command shows that smbiod has a stat of SL (sleeping and waiting to
acquire a lock) and the tar() process stat is D (uniterruptable wait).  If
you kill smbiod, the FBSD system hangs and has to be rebooted.

Is there any workaround to this issue?

Thanks,
Jon