panic: lockmgr: upgrade without shared

im getting this, so i guess i can reproduce it:

panic: lockmgr: upgrade without shared
cpuid = 0
KDB: enter: panic
[thread pid 806 tid 100167 ]
Stopped at      kdb_enter+0x2b: nop     
db> tr
Tracing pid 806 tid 100167 td 0xc9881000
kdb_enter(c087b148) at kdb_enter+0x2b
panic(c0879c7b,c9881000,0,c08ddd00,eb9edc08) at panic+0x127
lockmgr(c9706388,2014,c97063ac,c9881000,eb9edbf8) at lockmgr+0x26b
vop_stdlock(eb9edc08,c9706330,c9881000,eb9edc34,c069b937) at vop_stdlock+0x1e
VOP_LOCK_APV(c961e240,eb9edc08) at VOP_LOCK_APV+0x43
vput(c9706330,1,c9ac9b00,eb9edc30,1) at vput+0xff
NDFREE(eb9edc80,0,c9881000,c9706000,0,8057400) at NDFREE+0x104
__acl_get_file(c9881000,eb9edd04,3,89d,206) at __acl_get_file+0x67
syscall(3b,bfbe003b,eb9e003b,805c03c,8057400) at syscall+0x2bf
Xint0x80_syscall() at Xint0x80_syscall+0x1f
--- syscall (347, FreeBSD ELF32, __acl_get_file), eip = 0x880f8517, esp = 
0xbfbec5bc, ebp = 0xbfbec5d8 ---

it's 6.0-STABLE from this morning (it also happens with an older one)

newfs -U /dev/ad4s1g
mount /dev/ad4s1g /mnt
cd /mnt
tar cf - -C /dist | tar xpf -
(/dist is nfs mounted).

and after some time it panics.

danny