nfs_lookup() panic, again

[Hubert Feyrer <hubert%feyrer.de@localhost>]

Hallo David,

we've been talking about a NFS panic in nfs_lookop() some time ago:

panic: kernel diagnostic assertion "dvp != *vpp" failed: file
        ".../sys/nfs/nfs_vnopds.c", line 826

The setup of this is NetBSD-current/i386 in VMware Fusion with sources 
mounted via NFS from a Mac OS X NFS server. The panic occurs repeatly when 
doing a full build.

I've had a look at ddb and gdb, but can't really make a lot of sense from 
that:

http://www.feyrer.de/Misc/priv/nfs-panic/nfs_lookup-panic-msg+vnode.png 
has the panic message (from ddb "dmesg"), and an attempt to dig into the 
vnode pointed to by dvp and *vpp. The source of nfs_vnops.c was modified 
for those printfs, it's at
www.feyrer.de/Misc/priv/nfs-panic/nfs_vnops.c

I also have a stack backtrace from ddb, which is at
http://www.feyrer.de/Misc/priv/nfs-panic/nfs_lookup-panic-bt.png

I've tried to look into the kernel crash dump with gdb, but that has the 
stack messed up, see screenshot at 
http://www.feyrer.de/Misc/priv/nfs-panic/nfs_lookup-panic-gdb.png

Do you (or anyone else on tech-kern?) have an idea on where to go next? 
I'm not familiar with vnodes... Thanks!


 - Hubert