Bug 16227

nfs serving dies on one of my servers which is running Red Hat 6.2 up to
date with all the latest errata.  At the moment I cannot tell why or how
nfs died due to a lack of information (including syslog and dmesg). 
However this bug report is that once nfs had died, it was impossible to
kill the nfsd processes to restart nfs or to reboot cleanly.

The steps I tried were:

1) "service nfs stop": this simply hung and I killed it after waiting ten
minutes.
2) I found the nfsd PIDs and ran "kill -9" on them.  This failed to do
anything and the processes continued to appear in the process table.
3) I tried to start a new set of nfs servers but they would not start
(presumably with the old ones still running).
4) I removed all exports from /etc/exports and ran "exportfs -av" to notice
there were no exports and kill the nfs processes.  The nfsd processes did
not die.
5) I noticed that nfs is provided in the Red hat 6.2 shipped kernel by a
kernel module.  I tried "rmmod" to remove all nfs modules but this just
returned some error very much like:
module X in use
6) running out of options I rebooted the server.  However this hung going
into runlevel 6 when it came to stop the nfs services with the SysV init
script, as I had tried manually in step 1.  I waited ten minutes again and
nothing happened.  In the end I had to do a hard reset on the server with
all the possibilities for data loss this created.

Upon the next boot, nfs started perfectly OK.

Although nfsd is a front-end to the kernel nfs server, would it be possible
to patch it in some way such that even when it had died, you could kill it
with "kill -9" so that it could be restarted without hard-resetting the
server?  Or is kernel nfs serving such that if it dies there is no way
out?  In which case, will Red Hat ship with both kernel and user space nfs
servers which customers can choose from out of the box (like vixie-cron vs.
anacron)?

Thanks.