[Samba] device busy, I/O error and unable to umount

[Luca Ferrari]

Hi all,
this is the situation: two linux servers mounting a samba share from each 
other. Sometimes one of the two share becomes locked, I mean that everything 
I try to do on it results in an "Input/Output error". I'm then unable to 
umount the share, since either smbumount or umount report "device or resource 
busy". Unluckily I cannot check if this is the case, since the resource is 
not responding and even an lsof does not work. Other commands, like df, block 
on the share.
Any idea about where/how start looking to solve the problem?

Thanks,
Luca