panic: _mtx_lock_sleep: recursed on non-recursive mutex if_addr_mtx

GENERIC CURRENT as of this morning.

panic: _mtx_lock_sleep: recursed on non-recursive mutex if_addr_mtx _at_ /d2/emaste/HEAD/src/sys/netinet6/ip6_output.c:719

db> bt
Tracing pid 12 tid 100013 td 0xffffff00010fa000
kdb_enter() at kdb_enter+0x3d
panic() at panic+0x176
_mtx_lock_sleep() at _mtx_lock_sleep+0x181
_mtx_lock_flags() at _mtx_lock_flags+0xe1
ip6_output() at ip6_output+0xe98
mld6_sendpkt() at mld6_sendpkt+0x204
mld6_input() at mld6_input+0x55c
icmp6_input() at icmp6_input+0xf0b
ip6_input() at ip6_input+0xa6d
netisr_processqueue() at netisr_processqueue+0x44
swi_net() at swi_net+0xce
ithread_loop() at ithread_loop+0xe0
fork_exit() at fork_exit+0x12a
fork_trampoline() at fork_trampoline+0xe

db> show alllocks
Process 12 (swi1: net) thread 0xffffff00010fa000 (100013)
exclusive sleep mutex if_addr_mtx r = 0 (0xffffff00010d1c50) locked _at_ /d2/emaste/HEAD/src/sys/netinet6/mld6.c:371
exclusive sleep mutex Giant r = 0 (0xffffffff80a99060) locked _at_ /d2/emaste/HEAD/src/sys/net/netisr.c:246

I haven't looked into it at all yet.

-Ed