net: Introduce for_each_netdev_rcu() iterator

Adds RCU management to the list of netdevices.

Convert some for_each_netdev() users to RCU version, if
it can avoid read_lock-ing dev_base_lock

Ie:
	read_lock(&dev_base_loack);
	for_each_netdev(net, dev)
		some_action();
	read_unlock(&dev_base_lock);

becomes :

	rcu_read_lock();
	for_each_netdev_rcu(net, dev)
		some_action();
	rcu_read_unlock();


Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 8 insertions, 7 deletions

diff --git a/net/netrom/nr_route.c b/net/netrom/nr_route.c
index 4eb1ac9..aacba76 100644
--- a/net/netrom/nr_route.c
+++ b/net/netrom/nr_route.c
@@ -597,15 +597,15 @@ struct net_device *nr_dev_first(void)
 {
 	struct net_device *dev, *first = NULL;
 
-	read_lock(&dev_base_lock);
-	for_each_netdev(&init_net, dev) {
+	rcu_read_lock();
+	for_each_netdev_rcu(&init_net, dev) {
 		if ((dev->flags & IFF_UP) && dev->type == ARPHRD_NETROM)
 			if (first == NULL || strncmp(dev->name, first->name, 3) < 0)
 				first = dev;
 	}
 	if (first)
 		dev_hold(first);
-	read_unlock(&dev_base_lock);
+	rcu_read_unlock();
 
 	return first;
 }
@@ -617,16 +617,17 @@ struct net_device *nr_dev_get(ax25_address *addr)
 {
 	struct net_device *dev;
 
-	read_lock(&dev_base_lock);
-	for_each_netdev(&init_net, dev) {
-		if ((dev->flags & IFF_UP) && dev->type == ARPHRD_NETROM && ax25cmp(addr, (ax25_address *)dev->dev_addr) == 0) {
+	rcu_read_lock();
+	for_each_netdev_rcu(&init_net, dev) {
+		if ((dev->flags & IFF_UP) && dev->type == ARPHRD_NETROM &&
+		    ax25cmp(addr, (ax25_address *)dev->dev_addr) == 0) {
 			dev_hold(dev);
 			goto out;
 		}
 	}
 	dev = NULL;
 out:
-	read_unlock(&dev_base_lock);
+	rcu_read_unlock();
 	return dev;
 }