LOR with filedesc structure and Giant

After upgrading last night, one of the package machines found this:

lock order reversal
 1st 0xc6c1c334 filedesc structure (filedesc structure) _at_ /a/asami/portbuild/i386/src-client/sys/kern/sys_generic.c:902
 2nd 0xc04aa120 Giant (Giant) _at_ /a/asami/portbuild/i386/src-client/sys/fs/specfs/spec_vnops.c:372
Stack backtrace:
backtrace(c043d4af,c04aa120,c0439aa4,c0439aa4,c0434e3d) at backtrace+0x17
witness_lock(c04aa120,8,c0434e3d,174,1bc) at witness_lock+0x672
_mtx_lock_flags(c04aa120,0,c0434e3d,174,c043daba) at _mtx_lock_flags+0xba
spec_poll(d8dddaf8,d8dddb18,c02d119c,d8dddaf8,c04939a0) at spec_poll+0x134
spec_vnoperate(d8dddaf8,c04939a0,c520b124,40,c675e300) at spec_vnoperate+0x18
vn_poll(c44c5e14,40,c675e300,c6222d10,c675e300) at vn_poll+0x3c
selscan(c6222d10,d8dddb98,d8dddb88,6,4) at selscan+0x13e
kern_select(c6222d10,6,bfbff5c0,0,0) at kern_select+0x36f
select(c6222d10,d8dddd10,c0455899,3ee,5) at select+0x66
syscall(2f,2f,2f,8055050,bfbff5b8) at syscall+0x273
Xint0x80_syscall() at Xint0x80_syscall+0x1d
--- syscall (93), eip = 0x280ccacc, esp = 0x2832eb68, ebp = 0x2832ebc0 ---
Debugger("witness_lock")
Stopped at      Debugger+0x54:  xchgl   %ebx,in_Debugger.0

Kris