Help debugging a hang?

[Dave Alden <alden@xxxxxxxxxxxxxxxxxxx>]

Hi,
  I recently replaced an aging Solaris NFS server with a Linux NFS server
(running XFS of course :-).  After a couple of weeks without any problems
the server decided to lockup.  I was able to send a break (through a serial
console), so I did a Sync followed by a reBoot.  Now, in case this happens
again, does anyone have any pointers on where to read up on how to figure
out where it's locking up?
...thnx,
...dave