bridge: add rcu_read_lock on transmit

Long ago, when bridge was converted to RCU, rcu lock was equivalent
to having preempt disabled. RCU has changed a lot since then and
bridge code was still assuming the since transmit was called with
bottom half disabled, it was RCU safe.

Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>
Tested-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/bridge/br_input.c b/net/bridge/br_input.c
index d36e700..114365c 100644
--- a/net/bridge/br_input.c
+++ b/net/bridge/br_input.c
@@ -37,7 +37,7 @@
 		       netif_receive_skb);
 }
 
-/* note: already called with rcu_read_lock (preempt_disabled) */
+/* note: already called with rcu_read_lock */
 int br_handle_frame_finish(struct sk_buff *skb)
 {
 	const unsigned char *dest = eth_hdr(skb)->h_dest;
@@ -108,7 +108,7 @@
 	goto out;
 }
 
-/* note: already called with rcu_read_lock (preempt_disabled) */
+/* note: already called with rcu_read_lock */
 static int br_handle_local_finish(struct sk_buff *skb)
 {
 	struct net_bridge_port *p = rcu_dereference(skb->dev->br_port);
@@ -133,7 +133,7 @@
 /*
  * Called via br_handle_frame_hook.
  * Return NULL if skb is handled
- * note: already called with rcu_read_lock (preempt_disabled)
+ * note: already called with rcu_read_lock
  */
 struct sk_buff *br_handle_frame(struct net_bridge_port *p, struct sk_buff *skb)
 {