panic: __lockmgr_args: unknown lockmgr request 0x0

Hi,

I'm getting a kernel panic, whenever I try to work with an XFS file 
system with todays sources.

I created the filesystem, mounted it and created a directory on it. The 
crash occurred when I tried to chown the directory.

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Unread portion of the kernel message buffer:
panic: __lockmgr_args: unknown lockmgr request 0x0

cpuid = 1
Uptime: 25m36s
Physical memory: 3314 MB
Dumping 95 MB: 80 (CTRL-C to abort)  64 48 32 16

Reading symbols from /boot/kernel/acpi.ko...Reading symbols from 
/boot/kernel/acpi.ko.symbols...done.
done.
Loaded symbols for /boot/kernel/acpi.ko
Reading symbols from /boot/kernel/xfs.ko...Reading symbols from 
/boot/kernel/xfs.ko.symbols...done.
done.
Loaded symbols for /boot/kernel/xfs.ko
#0  doadump () at pcpu.h:196
196		__asm __volatile("movl %%fs:0,%0" : "=r" (td));
(kgdb) bt
#0  doadump () at pcpu.h:196
#1  0xc078f1cc in boot (howto=260) at /usr/src/sys/kern/kern_shutdown.c:418
#2  0xc078f489 in panic (fmt=Variable "fmt" is not available.
) at /usr/src/sys/kern/kern_shutdown.c:572
#3  0xc077b83c in __lockmgr_args (lk=0xc6eecce8, flags=256, ilk=0xc6eecd04,
     wmesg=0x0, pri=0, timo=0, file=0xc0b2b883 
"/usr/src/sys/kern/vfs_subr.c",
     line=2044) at /usr/src/sys/kern/kern_lock.c:848
#4  0xc0801cf2 in vop_stdlock (ap=0xe8fa7810) at lockmgr.h:93
#5  0xc0aac906 in VOP_LOCK1_APV (vop=0xc0bf5400, a=0xe8fa7810)
     at vnode_if.c:1618
#6  0xc081e64d in _vn_lock (vp=0xc6eecc90, flags=256,
     file=0xc0b2b883 "/usr/src/sys/kern/vfs_subr.c", line=2044)
     at vnode_if.h:845
#7  0xc080ea29 in vget (vp=0xc6eecc90, flags=0, td=0xc6a50460)
     at /usr/src/sys/kern/vfs_subr.c:2044
#8  0xc6e2f6a6 in vn_get (xfs_vp=0xc692d780, vmap=0xe8fa78c0)
     at /usr/src/sys/modules/xfs/../../gnu/fs/xfs/FreeBSD/xfs_vnode.c:107
#9  0xc6df4cb2 in xfs_iget (mp=0xc6776800, tp=0x0, ino=Unhandled dwarf 
expression opcode 0x93
)
     at 
/usr/src/sys/modules/xfs/../../gnu/fs/xfs/FreeBSD/xfs_freebsd_iget.c:164
#10 0xc6e160fc in xfs_dir_lookup_int (dir_bdp=0xc6ee9020, lock_mode=8,
     dentry=0xe8fa7bb0, inum=0xe8fa7938, ipp=0xe8fa7940)
     at /usr/src/sys/modules/xfs/../../gnu/fs/xfs/xfs_utils.c:97
#11 0xc6e1a75e in xfs_lookup (dir_bdp=0xc6ee9020, dentry=0xe8fa7bb0,
     vpp=0xe8fa79a8, flags=0, rdir=0x0, credp=0xc698e500)
     at /usr/src/sys/modules/xfs/../../gnu/fs/xfs/xfs_vnodeops.c:1828
#12 0xc6e2a973 in _xfs_cachedlookup (ap=0xe8fa79e0)
     at /usr/src/sys/modules/xfs/../../gnu/fs/xfs/FreeBSD/xfs_vnops.c:1275
#13 0xc0aab322 in VOP_CACHEDLOOKUP_APV (vop=0xc6e367e0, a=0xe8fa79e0)
     at vnode_if.c:153
#14 0xc07ff8c0 in vfs_cache_lookup (ap=0xe8fa7a64) at vnode_if.h:80
#15 0xc0aacfe6 in VOP_LOOKUP_APV (vop=0xc6e367e0, a=0xe8fa7a64)
     at vnode_if.c:99
#16 0xc0806371 in lookup (ndp=0xe8fa7b84) at vnode_if.h:54
#17 0xc08071bb in namei (ndp=0xe8fa7b84) at 
/usr/src/sys/kern/vfs_lookup.c:239
#18 0xc0814a64 in kern_statat (td=0xc6a50460, flag=0, fd=-100,
     path=0x8104928 <Address 0x8104928 out of bounds>, 
pathseg=UIO_USERSPACE,
     sbp=0xe8fa7c18) at /usr/src/sys/kern/vfs_syscalls.c:2331
#19 0xc0814cf6 in kern_stat (td=0xc6a50460,
     path=0x8104928 <Address 0x8104928 out of bounds>, 
pathseg=UIO_USERSPACE,
     sbp=0xe8fa7c18) at /usr/src/sys/kern/vfs_syscalls.c:2313
#20 0xc0814d9f in stat (td=0xc6a50460, uap=0xe8fa7cf8)
     at /usr/src/sys/kern/vfs_syscalls.c:2282
#21 0xc0aa1075 in syscall (frame=0xe8fa7d38)
     at /usr/src/sys/i386/i386/trap.c:1081
#22 0xc0a86a90 in Xint0x80_syscall ()
     at /usr/src/sys/i386/i386/exception.s:261
#23 0x00000033 in ?? ()
Previous frame inner to this frame (corrupt stack?)

Can I provide any additional information that could help to debug the 
problem?

Best regards,
   Lothar