witness warnings in NFS

[Doug White]

Hey folks,

If you are seeing lock warnings like this one, with the same (or close)
file location and traceback, with WITNESS enabled, please let me know what
the server and client OS versions and hardware are.  I have one report
that was a Solaris 10 server against a FreeBSD-CURRENT system running in
vmware. I have a patch that quiets the warning and papers over the bug
somewhat by faking an mbuf allocation failure as a packet parsing error.

exclusive sleep mutex nfsd_mtx r = 0 (0xc08efb40) locked @ /usr/src/sys/nfsserver/nfs_serv.c:1103
[...]
uma_zalloc_arg(c101f9a0,cc364a3c,2) at uma_zalloc_arg+0x41
nfsm_disct(cc364ac4,cc364ac8,14,e,46) at nfsm_disct+0xa2
nfsm_dissect_xx(14,cc364ac4,cc364ac8) at nfsm_dissect_xx+0x31
nfsrv_write(c14ff900,c19d8480,c13ec000,cc364ca8,cc364ca4) at nfsrv_write+0x1e2

The patch is at:

http://people.freebsd.org/~dwhite/nfs_common.c.20040908.patch

I'd be interested in knowing if someone with a way of creating an mbuf
shortage condition can test this and see if they get EBADRPC errors.

Thanks for any feedback!

-- 
Doug White                    |  FreeBSD: The Power to Serve
dwhite at gumbysoft.com          |  www.FreeBSD.org