Race between NFS server thread increase / decrease

Hi NFSD developers,

I've found what I think is an interesting problem that occurs on single-CPU machines as far as I can tell.

Basically the following snippet will occasionally loop forever printing that one thread is still running. Further attempts to run "/usr/sbin/rpc.nfsd 0" don't help.

/usr/sbin/rpc.nfsd 1
/usr/sbin/rpc.nfsd 0
while [ ! $[cat /proc/fs/nfsd/threads] -eq 0 ]; do
echo $[cat /proc/fs/nfsd/threads] still running sleep .1
done

I've not looked a whole lot at it. It appears that although the paths calling svc_set_num_threads synchronize on nfsd_mutex, the code doesn't seem to try waiting on the number of threads to reach the desired count.

What do you guys think?

Thanks.

A

Yeah, I guess it just signals and returns, I agree that's not ideal.

Though in your case fixing that may just mean the "rpc.nfsd 0" would hang.

That is odd. I'm not sure to suggest without spending a bunch of time on it.

Presumably ps will still show an nfsd thread running?

Might be interesting to see its stack (cat /proc/<pid>/stack) or look at a full sysrq-t dump (sysrq-t, then check the logs).

Is it stuck spinning in some kind of loop? (E.g. does "top" show anything interesting?)

If none of that provides any hints, I dunno, my caveman approach would be to just stare really hard and the relevant code and start sprinkling printk's around as necessary.

--b.