netdev - [PATCH net-next-2.6] ifb: RCU locking avoids touching dev refcount

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Date:	Mon, 02 Nov 2009 06:45:16 +0100
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	"David S. Miller" <davem@...emloft.net>,
	Linux Netdev List <netdev@...r.kernel.org>
Subject: [PATCH net-next-2.6] ifb: RCU locking avoids touching dev refcount

Avoids touching dev refcount in hotpath

Signed-off-by: Eric Dumazet <eric.dumazet@...il.com>
---
 drivers/net/ifb.c |    6 ++++--
 1 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ifb.c b/drivers/net/ifb.c
index 030913f..69c2566 100644
--- a/drivers/net/ifb.c
+++ b/drivers/net/ifb.c
@@ -98,13 +98,15 @@ static void ri_tasklet(unsigned long dev)
 		stats->tx_packets++;
 		stats->tx_bytes +=skb->len;
 
-		skb->dev = dev_get_by_index(&init_net, skb->iif);
+		rcu_read_lock();
+		skb->dev = dev_get_by_index_rcu(&init_net, skb->iif);
 		if (!skb->dev) {
+			rcu_read_unlock();
 			dev_kfree_skb(skb);
 			stats->tx_dropped++;
 			break;
 		}
-		dev_put(skb->dev);
+		rcu_read_unlock();
 		skb->iif = _dev->ifindex;
 
 		if (from & AT_EGRESS) {
--
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