Inet6addr notifier is atomic and runs in bh context without RTNL when
ipv6 receives router advertisement packet and performs autoconfiguration.

Proper fix still in discussion. Let's at least plug the bug.
v1: http://lkml.kernel.org/r/20150514135618.14062.1969.stgit@buzz
v2: http://lkml.kernel.org/r/20150703125840.24121.91556.stgit@buzzSigned-off-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Signed-off-by: David S. Miller <davem@davemloft.net>