The driver periodically traverses the linked list of multicast routes
and updates the kernel about packets and bytes statistics from each
multicast route. These statistics are read from a counter associated
with the route when it is written to the device.

Currently, multicast routes are published via this linked list before
they are associated with a counter. Despite that, it is not possible for
the driver to access an invalid counter because the delayed work that
reads the statistics and multicast route addition / deletion are
mutually exclusive using RTNL.

In order to be able to remove RTNL, the list needs to be protected by a
dedicated lock, but any route published via the list must have an
associated counter, otherwise the driver will access an invalid counter.

Solve this by re-ordering the operations during multicast route addition
so that the route is only added to the linked list after it was written
to the device. Similarly, during deletion the route is first removed
from the linked list before its deletion from the device.
Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Acked-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>