Yet another LOR

Stumbled across another LOR today:

May  3 20:01:32 lothlorien kernel: lock order reversal:
May  3 20:01:32 lothlorien kernel: 1st 0xc3ea6890 user map (user map) _at_ /usr/src/sys/vm/vm_map.c:2203
May  3 20:01:32 lothlorien kernel: 2nd 0xc5d19d78 ufs (ufs) _at_ /usr/src/sys/vm/vm_object.c:1039
May  3 20:01:32 lothlorien kernel: KDB: stack backtrace:
May  3 20:01:32 lothlorien kernel: db_trace_self_wrapper(c0873465,e67ccaa8,c065781a,c0875b35,c5d19d78,...) at db_trace_self_wrapper+0x26
May  3 20:01:32 lothlorien kernel: kdb_backtrace(c0875b35,c5d19d78,c086a7e7,c086a7e7,c0891dd7,...) at kdb_backtrace+0x29
May  3 20:01:32 lothlorien kernel: witness_checkorder(c5d19d78,9,c0891dd7,40f,0,...) at witness_checkorder+0x6b0
May  3 20:01:32 lothlorien kernel: __lockmgr_args(c5d19d78,80400,c5d19d98,0,0,...) at __lockmgr_args+0x738
May  3 20:01:32 lothlorien kernel: ffs_lock(e67ccb98,0,9f,80400,c5d19d20,...) at ffs_lock+0x7d
May  3 20:01:32 lothlorien kernel: VOP_LOCK1_APV(c08ddfe0,e67ccb98,c08f4a00,c5d19d20,80400,...) at VOP_LOCK1_APV+0xab
May  3 20:01:32 lothlorien kernel: _vn_lock(c5d19d20,80400,c0891dd7,40f,2869a000,...) at _vn_lock+0x5e
May  3 20:01:32 lothlorien kernel: vm_object_sync(c59ac380,42c0000,0,40000,0,...) at vm_object_sync+0x17a
May  3 20:01:32 lothlorien kernel: vm_map_sync(c3ea684c,2869a000,286da000,0,0,...) at vm_map_sync+0x256
May  3 20:01:32 lothlorien kernel: msync(c442d660,e67cccfc,c,c08a0413,c06113f4,...) at msync+0x6c
May  3 20:01:32 lothlorien kernel: syscall(e67ccd38) at syscall+0x279
May  3 20:01:32 lothlorien kernel: Xint0x80_syscall() at Xint0x80_syscall+0x20
May  3 20:01:32 lothlorien kernel: --- syscall (65, FreeBSD ELF32, msync), eip = 0x28556ddb, esp = 0xbfbfe51c, ebp = 0xbfbfe548 ---

Not really sure how to debug these...

Brix
-- 
Henrik Brix Andersen <brix_at_FreeBSD.org>