Lock order reversal in RELENG_6

lock order reversal
 1st 0xc0980be0 UMA lock (UMA lock) _at_ vm/uma_core.c:1494
 2nd 0xc1060144 system map (system map) _at_ vm/vm_map.c:2317
KDB: stack backtrace:
kdb_backtrace(0,ffffffff,c0935cf8,c0935e38,c08bbfa4) at kdb_backtrace+0x29
witness_checkorder(c1060144,9,c0872746,90d) at witness_checkorder+0x564
_mtx_lock_flags(c1060144,0,c087273d,90d) at _mtx_lock_flags+0x5b
_vm_map_lock(c10600c0,c087273d,90d) at _vm_map_lock+0x26
vm_map_remove(c10600c0,c2595000,c2596000,de3cac08,c0780751) at 
vm_map_remove+0x1f
kmem_free(c10600c0,c2595000,1000,de3cac38,c07800fe) at kmem_free+0x25
page_free(c2595000,1000,2) at page_free+0x29
zone_drain(c103dd20) at zone_drain+0x26a
zone_foreach(c077fe94,de3cacec,c0791f7f,c1ecc960,de3cac74) at 
zone_foreach+0x37
uma_reclaim(c1ecc960,de3cac74,0,c092c320,de3cac80) at uma_reclaim+0x12
vm_pageout_scan(0,c0981040,0,c0873c16,5c3) at vm_pageout_scan+0x103
vm_pageout(0,de3cad38,0,c0792d38,0) at vm_pageout+0x2c3
fork_exit(c0792d38,0,de3cad38) at fork_exit+0xa0
fork_trampoline() at fork_trampoline+0x8
--- trap 0x1, eip = 0, esp = 0xde3cad6c, ebp = 0 ---


David Xu