net: remove dev_base_lock from register_netdevice() and friends.

RTNL already protects writes to dev->reg_state, we no longer need to hold
dev_base_lock to protect the readers.

unlist_netdevice() second argument can be removed.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/core/dev.c

@@ -414,7 +414,7 @@ static void list_netdevice(struct net_device *dev)
 /* Device list removal
  * caller must respect a RCU grace period before freeing/reusing dev
  */
-static void unlist_netdevice(struct net_device *dev, bool lock)
+static void unlist_netdevice(struct net_device *dev)
 {
 	struct netdev_name_node *name_node;
 	struct net *net = dev_net(dev);
@@ -427,12 +427,10 @@ static void unlist_netdevice(struct net_device *dev, bool lock)
 		netdev_name_node_del(name_node);
 
 	/* Unlink dev from the device chain */
-	if (lock)
 	write_lock(&dev_base_lock);
 	list_del_rcu(&dev->dev_list);
 	netdev_name_node_del(dev->name_node);
 	hlist_del_rcu(&dev->index_hlist);
-	if (lock)
 	write_unlock(&dev_base_lock);
 
 	dev_base_seq_inc(dev_net(dev));
@@ -10338,9 +10336,9 @@ int register_netdevice(struct net_device *dev)
 		goto err_ifindex_release;
 
 	ret = netdev_register_kobject(dev);
-	write_lock(&dev_base_lock);
+
 	WRITE_ONCE(dev->reg_state, ret ? NETREG_UNREGISTERED : NETREG_REGISTERED);
-	write_unlock(&dev_base_lock);
+
 	if (ret)
 		goto err_uninit_notify;
 
@@ -10629,9 +10627,7 @@ void netdev_run_todo(void)
 			continue;
 		}
 
-		write_lock(&dev_base_lock);
 		WRITE_ONCE(dev->reg_state, NETREG_UNREGISTERED);
-		write_unlock(&dev_base_lock);
 		linkwatch_sync_dev(dev);
 	}
 
@@ -11138,10 +11134,8 @@ void unregister_netdevice_many_notify(struct list_head *head,
 
 	list_for_each_entry(dev, head, unreg_list) {
 		/* And unlink it from device chain. */
-		write_lock(&dev_base_lock);
-		unlist_netdevice(dev, false);
+		unlist_netdevice(dev);
 		WRITE_ONCE(dev->reg_state, NETREG_UNREGISTERING);
-		write_unlock(&dev_base_lock);
 	}
 	flush_all_backlogs();
 
@@ -11323,7 +11317,7 @@ int __dev_change_net_namespace(struct net_device *dev, struct net *net,
 	dev_close(dev);
 
 	/* And unlink it from device chain */
-	unlist_netdevice(dev, true);
+	unlist_netdevice(dev);
 
 	synchronize_net();