-current dom0 crash

[Jeff Rizzo <riz%tastylime.net@localhost>]

I just updated one of my dom0s from 5.99.59 to 5.99.63, and got this 
crash when destroying a hung domU (an operation that worked fine under 
5.99.59):

Feb  1 13:20:02 xenserver1 xenbackendd[335]: Failed to read 
/local/domain/0/backend/console/2/0/script (No such file or directory)
xbd backend: detach device mirror-wintermu for domain 2
fatal protection fault in supervisor mode
trap type 4 code 0 rip ffffffff804f7425 cs e030 rflags 10286 cr2  
ffffa000117db7dc cpl 6 rsp ffffa00000a5f880
kernel: protection fault trap, code=0
Stopped in pid 0.31 (system) at netbsd:nd6_purge+0xb5:  movl    
14(%r12),%eax
nd6_purge() at netbsd:nd6_purge+0xb5
in6_ifdetach() at netbsd:in6_ifdetach+0x21
udp6_usrreq() at netbsd:udp6_usrreq+0x208
if_detach() at netbsd:if_detach+0x112
xennetback_xenbus_destroy() at netbsd:xennetback_xenbus_destroy+0x8b
otherend_changed() at netbsd:otherend_changed+0xaf
xenwatch_thread() at netbsd:xenwatch_thread+0xa2
ds          5120
es          5339
fs          f8c0
gs          f960
rdi         ffffa000011c0ce0
rsi         0
rbp         ffffa00000a5f8a0
rbx         ffffa00002079030
rdx         ffffffff803cb327    in6_purgeaddr
rcx         ffffa00000c35120
rax         5
r8          ffffa00002079030
r9          ffffa00000c35120
r10         7
r11         0
r12         b31576d83a9cfd5f
r13         0
r14         0
r15         0
rip         ffffffff804f7425    nd6_purge+0xb5
cs          e030
rflags      10286
rsp         ffffa00000a5f880
ss          e02b
netbsd:nd6_purge+0xb5:  movl    14(%r12),%eax
db>