Interesting. It looks like some kind of RPC failure. During the hang, I cannot contact the nfs service via RPC:
# rpcinfo -t <server> nfs rpcinfo: RPC: Timed out program 100003 version 0 is not available
even though it is supposedly available:
# rpcinfo -p <server> program vers proto port 100000 2 tcp 111 portmapper 100000 2 udp 111 portmapper 100024 1 udp 1007 status 100024 1 tcp 1010 status 100021 1 udp 35077 nlockmgr 100021 3 udp 35077 nlockmgr 100021 4 udp 35077 nlockmgr 100021 1 tcp 56622 nlockmgr 100021 3 tcp 56622 nlockmgr 100021 4 tcp 56622 nlockmgr 100011 1 udp 1009 rquotad 100011 2 udp 1009 rquotad 100011 1 tcp 1012 rquotad 100011 2 tcp 1012 rquotad 100003 2 udp 2049 nfs 100003 3 udp 2049 nfs 100003 4 udp 2049 nfs 100003 2 tcp 2049 nfs 100003 3 tcp 2049 nfs 100003 4 tcp 2049 nfs 100005 1 udp 605 mountd 100005 1 tcp 608 mountd 100005 2 udp 605 mountd 100005 2 tcp 608 mountd 100005 3 udp 605 mountd 100005 3 tcp 608 mountd
However, I can connect to the service via telnet:
# telnet <server> nfs Trying <ipaddr>... Connected to <server> (<ipaddr>). Escape character is '^]'.
so the service is running but internally borked in some way.
Steve