panic: mutex Giant owned at nfs_syscalls.c:556

I got this assertion while attempting to remove file on nfs mounted
ffs filesystem.
NFS client on 7.0-PRERELEASE and NFS server on 8-CURRENT.

FreeBSD 7.0-PRERELEASE #1: Wed Feb  6 18:09:18 MSK 2008
FreeBSD 8.0-CURRENT #9: Fri Feb 15 14:31:07 MSK 2008

Unread portion of the kernel message buffer:
panic: mutex Giant owned at
/usr/src/sys/modules/nfsserver/../../nfsserver/nfs_syscalls.c:556
KDB: enter: panic
exclusive sleep mutex nfsd_mtx r = 0 (0xc41d1660) locked _at_
/usr/src/sys/modules/nfsserver/../../nfsserver/nfs_syscalls.c:501
exclusive sleep mutex Giant r = 0 (0xc07e6410) locked _at_
/usr/src/sys/kern/vfs_lookup.c:663
...
#9  0xc053959d in panic (fmt=0xc076181d "mutex %s owned at %s:%d")
    at /usr/src/sys/kern/kern_shutdown.c:555
#10 0xc052adf7 in _mtx_assert (m=0xc07e6410, what=0,
    file=0xc41cb7b2
"/usr/src/sys/modules/nfsserver/../../nfsserver/nfs_syscalls.c",
line=556) at /usr/src/sys/kern/kern_mutex.c:652
#11 0xc41c9e82 in nfssvc (td=0xc2e68000, uap=0xd600dcfc)
    at /usr/src/sys/modules/nfsserver/../../nfsserver/nfs_syscalls.c:556
#12 0xc0727903 in syscall (frame=0xd600dd38)
    at /usr/src/sys/i386/i386/trap.c:1034
#13 0xc0711630 in Xint0x80_syscall () at /usr/src/sys/i386/i386/exception.s:203
---Type <return> to continue, or q <return> to quit---
#14 0x00000033 in ?? ()

Looks somewhat strange because nfs_syscalls.c:556 is not in nfssvc(),
it's in nfssvc_nfsd().
Kernel and world synchronized on 8-CUR though.

wbr,
pluknet