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, 3 insertions, 3 deletions

diff --git a/net/decnet/dn_route.c b/net/decnet/dn_route.c
index 57662cabaf9b..860286a3921b 100644
--- a/net/decnet/dn_route.c
+++ b/net/decnet/dn_route.c
@@ -908,8 +908,8 @@ static int dn_route_output_slow(struct dst_entry **pprt, const struct flowi *old
                         dev_put(dev_out);
                         goto out;
                 }
-                read_lock(&dev_base_lock);
-                for_each_netdev(&init_net, dev) {
+                rcu_read_lock();
+                for_each_netdev_rcu(&init_net, dev) {
                         if (!dev->dn_ptr)
                                 continue;
                         if (!dn_dev_islocal(dev, oldflp->fld_src))
@@ -922,7 +922,7 @@ static int dn_route_output_slow(struct dst_entry **pprt, const struct flowi *old
                         dev_out = dev;
                         break;
                 }
-                read_unlock(&dev_base_lock);
+                rcu_read_unlock();
                 if (dev_out == NULL)
                         goto out;
                 dev_hold(dev_out);