panic: ifc_free_unit: bit is already cleared

Hi,

I have found a repeatable panic with network device cloning, unfortunatly I am
unable to dump on this box. This is sparc64 with a 2 day old current.


[root_at_dev]# kldload if_vlan
[root_at_dev]# for i in `jot 100 1`; do
for> ifconfig xl0.$i create
for> done
[root_at_dev]# kldunload if_vlan
panic: ifc_free_unit: bit is already cleared
cpuid = 0
KDB: enter: panic
[thread pid 4527 tid 100089 ]
Stopped at      kdb_enter+0x3c: ta              %xcc, 1
db> trace
Tracing pid 4527 tid 100089 td 0xfffff8000ab8e4c0
panic() at panic+0x164
ifc_free_unit() at ifc_free_unit+0x50
vlan_clone_destroy() at vlan_clone_destroy+0x8c
vlan_modevent() at vlan_modevent+0x44
module_unload() at module_unload+0x60
linker_file_unload() at linker_file_unload+0x7c
kern_kldunload() at kern_kldunload+0x84
kldunloadf() at kldunloadf+0x1c
syscall() at syscall+0x2dc
-- syscall (444, FreeBSD ELF64, kldunloadf) %o7=0x100b58 --
userland() at 0x40391348
user trace: trap %o7=0x100b58
pc 0x40391348, sp 0x7fdffffdde1
pc 0x100894, sp 0x7fdffffe2c1
pc 0x40209474, sp 0x7fdffffe381
done
db>