LOR involving igmp on 11.0-ALPHA5

[Michael Plass]

FreeBSD xx 11.0-ALPHA5 FreeBSD 11.0-ALPHA5 #0 r302164: Fri Jun 24 02:51:52 UTC 2016     root at releng2.nyi.freebsd.org:/usr/obj/usr/src/sys/GENERIC  amd64

lock order reversal:
1st 0xfffff80003cff990 if_addr_lock (if_addr_lock) @ /usr/src/sys/netinet/igmp.c:1716
2nd 0xffffffff81d7b660 ifnet_rw (ifnet_rw) @ /usr/src/sys/net/if.c:258

More details (with stack) are at
    https://gist.github.com/mfplass/aa7c78640af1309699e908c4d73c0d40

I've seen this twice.

Thanks,
- Michael