netdev: add netdev_continue_rcu

This adds an RCU macro for continuing search, useful for some
network devices like vlan.

Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>
Acked-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 465add6..083b598 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -1079,6 +1079,8 @@
 		list_for_each_entry_safe(d, n, &(net)->dev_base_head, dev_list)
 #define for_each_netdev_continue(net, d)		\
 		list_for_each_entry_continue(d, &(net)->dev_base_head, dev_list)
+#define for_each_netdev_continue_rcu(net, d)		\
+	list_for_each_entry_continue_rcu(d, &(net)->dev_base_head, dev_list)
 #define net_device_entry(lh)	list_entry(lh, struct net_device, dev_list)
 
 static inline struct net_device *next_net_device(struct net_device *dev)