So fib_seq_sum() can't use rtnl_lock() only for protection.
The possible solution could be to use rtnl_lock()
in fib_notifier_ops_unregister(), but this adds
a possible delay during net namespace creation,
so we better use rcu_read_lock() till someone
really needs the mutex (if that happens).
Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com> Signed-off-by: David S. Miller <davem@davemloft.net>