Reader / writer lock error: rw_vector_enter: locking against myself

[Sarton O'Brien <bsd-xen%roguewrt.org@localhost>]

kernel only a hour old produces the following and then locks up:

                    Loaded initial symtab at 0xffffffff8063dba4, strtab at 
0xffffffff80688b08, # entries 12714
Reader / writer lock error: rw_vector_enter: locking against myself

lock address : 0xffffffff805afe48
current cpu  :                  0
current lwp  : 0xffffffff805739a0
owner/count  : 0xffffffff805739a0 flags    : 0x0000000000000004

panic: lock error
fatal breakpoint trap in supervisor mode
trap type 1 code 0 rip ffffffff803648f5 cs e030 rflags 246 cr2  
ffffa00000f520b4 cpl 8 rsp ffffffff807cd720
Stopped in pid 0.1 (system) at  netbsd:breakpoint+0x5:  leave
breakpoint() at netbsd:breakpoint+0x5
panic() at netbsd:panic+0x255
lockdebug_abort() at netbsd:lockdebug_abort+0x42
rw_vector_enter() at netbsd:rw_vector_enter+0x213
uvm_fault_internal() at netbsd:uvm_fault_internal+0xc8
trap() at netbsd:trap+0x805
--- trap (number 0) ---
0:
ds          0xd730
es          0xd32a
fs          0xd730
gs          0xd32a
rdi         0x8
rsi         0xd
rbp         0xffffffff807cd720
rbx         0xffffffff807cd730
rdx         0
rcx         0
rax         0x1
r8          0xffffffff807cd640
r9          0
r10         0xffffffff807cd640
--db_more--xenconscn_getc(): not console

Sarton