panic: mutex Giant not owned at ../../../kern/vfs_subr.c:1365

Running an up-to-date CVS kernel without debug.mpsafenet enabled

panic: mutex Giant not owned at ../../../kern/vfs_subr.c:1365
at line 729 in file ../../../kern/kern_mutex.c
Debugger("panic")
Stopped at      Debugger+0x54:  xchgl   %ebx,in_Debugger.0
db> trace
Debugger(c0766179,c07d1e80,2d9,c0765560,100) at Debugger+0x54
__panic(c0765560,2d9,c07656c8,c0765803,c076e07d) at __panic+0xf5
_mtx_assert(c07d09e0,1,c076e07d,555,c68544ec) at _mtx_assert+0x11c
gbincore(c6889514,0,0,985,c07d5980) at gbincore+0x36
getblk(c6889514,0,0,800,0) at getblk+0xf8
breadn(c6889514,0,0,800,0) at breadn+0x52
bread(c6889514,0,0,800,0) at bread+0x4c
ffs_blkatoff(c6889514,0,0,0,e0f87998) at ffs_blkatoff+0x105
ufs_lookup(e0f87a50,e0f87a8c,c05c77e1,e0f87a50,e0f87bc0) at ufs_lookup+0x270
ufs_vnoperate(e0f87a50,e0f87bc0,e0f87bd4,c076e07d,c61d62a0) at ufs_vnoperate+0x18
vfs_cache_lookup(e0f87ad0,e0f87aec,c05cca32,e0f87ad0,c61d62a0) at vfs_cache_lookup+0x301
ufs_vnoperate(e0f87ad0,c61d62a0,0,c61d62a0,c61d62a0) at ufs_vnoperate+0x18
lookup(e0f87bac,0,c076dac5,a2,c61d62a0) at lookup+0x312
namei(e0f87bac,c62088b2,d,c62088c0,0) at namei+0x27e
unp_bind(c6a09000,c62088b0,c61d62a0,e0f87ca0,c05b5e23) at unp_bind+0xb1
uipc_bind(c6427a50,c62088b0,c61d62a0,e0f87cc8,c05ba0e7) at uipc_bind+0x2b
sobind(c6427a50,c62088b0,c61d62a0,0,c6427a50) at sobind+0x23
kern_bind(c61d62a0,3,c62088b0,c62088b0,0) at kern_bind+0x87
bind(c61d62a0,e0f87d14,c,434,3) at bind+0x43
syscall(2f,2f,2f,bfbfee10,0) at syscall+0x2a0
Xint0x80_syscall() at Xint0x80_syscall+0x1f
--- syscall (104, FreeBSD ELF32, bind), eip = 0x280d21ff, esp = 0xbfbfe89c, ebp = 0xbfbfee98 ---

Kris