Finder blocked on nfs unmount/eject

I've a issue with mount_nfs (Server connect from Finder to a NFS server share) using wi-fi/lan

If I mount and then (after working) unmount a shared folder on my NFS Linux box Finder can not do unmount it will freeze.

After that all the terminal commands are unsuccessful. Finder could be relaunched.

Terminal commands log

# Unresponsive unmount

silver:~ root# ps -ef | grep mount_nfs

501 653 652 0 10:38PM ?? 0:00.00 mount_nfs -odeadtimeout=45 10.1.1.2:/u01/ /Volumes/u01

0 859 712 0 10:41PM ttys001 0:00.00 grep mount_nfs

#before Finder relaunch

silver:~ root# ps -ef | grep Finder

501 354 1 0 10:36PM ?? 0:24.10 /System/Library/CoreServices/Finder.app/Contents/MacOS/Finder

0 779 712 0 10:40PM ttys001 0:00.00 grep Finder

# After Finder relaunch

silver:~ root# ps -ef | grep Finder

501 354 1 0 10:36PM ?? 0:00.00 (Finder)

0 795 712 0 10:40PM ttys001 0:00.00 grep Finder

I think that Finder waiting to unmount that share. I have waited more than 20 minutes and nothing.

Only way to relaunch Finder is to press power button for 10+ seconds

Is there any way to restart Finder?