lockd using up 60% CPU and won't let go

[Just Marc <marc-ZTWYIuj8JqNeoWH0uzbU5w@public.gmane.org>]

Hi everyone,

Doing a seemingly innocent operation such as opening a file with vim on 
a CFS (yes, that old crypto file system) NFS mount, lockd would wake up 
and take 60% of my CPU away - probably doing nothing important but 
certainly keeping the CPU busy, forever.

I use kernel 2.6.26 and kernel NFS.   Some detail is available below:
 
$ grep nfs /proc/mounts
nfsd /proc/fs/nfsd nfsd rw 0 0localhost:/var/lib/cfs/.cfsfs /var/cfs nfs 
rw,vers=2,rsize=8192,wsize=8192,namlen=255,hard,intr,proto=udp,timeo=11,retrans=3,sec=sys,addr=127.0.0.1 
0 0
localhost:/var/lib/cfs/.cfsfs/x /var/cfs/x nfs 
rw,vers=2,rsize=8192,wsize=8192,namlen=255,hard,intr,proto=udp,timeo=11,retrans=3,sec=sys,addr=127.0.0.1 
0 0

$ egrep 'NFS|_LOCKD' .config
CONFIG_LOCKDEP_SUPPORT=y
CONFIG_NFS_FS=y
CONFIG_NFS_V3=y
CONFIG_NFS_V3_ACL=y
CONFIG_NFS_V4=y
CONFIG_NFSD=y
CONFIG_NFSD_V2_ACL=y
CONFIG_NFSD_V3=y
CONFIG_NFSD_V3_ACL=y
CONFIG_NFSD_V4=y
CONFIG_ROOT_NFS=y
CONFIG_LOCKD=y
CONFIG_LOCKD_V4=y
CONFIG_NFS_ACL_SUPPORT=y
CONFIG_NFS_COMMON=y

I noticed this a few weeks ago but I don't quite know what causes it but 
I certainly know how to trigger it.   Stopping CFS and NFS completely 
doesn't help - as soon as NFS is restarted lockd starts eating CPU again 
just like before.

I'd appreciate any hints on what I can do to find the root cause of the 
problem and help get this bug out of the way.

Best,
Marc