gianfar: Fix crashes on RX path (Was Re: [Bugme-new] [Bug 19692] New: linux-2.6.36-rc5 crash with gianfar ethernet at full line rate traffic)

The rx_recycle queue is global per device but can be accesed by many
napi handlers at the same time, so it needs full skb_queue primitives
(with locking). Otherwise, various crashes caused by broken skbs are
possible.

This patch resolves, at least partly, bugzilla bug 19692. (Because of
some doubts that there could be still something around which is hard
to reproduce my proposal is to leave this bug opened for a month.)

Fixes commit: 0fd56bb5be6455d0d42241e65aed057244665e5e ("gianfar: Add
support for skb recycling")

Reported-by: emin ak <eminak71@gmail.com>
Tested-by: emin ak <eminak71@gmail.com>
Signed-off-by: Jarek Poplawski <jarkao2@gmail.com>
CC: Andy Fleming <afleming@freescale.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/gianfar.c

@@ -2511,7 +2511,7 @@ static int gfar_clean_tx_ring(struct gfar_priv_tx_q *tx_queue)
 				skb_recycle_check(skb, priv->rx_buffer_size +
 					RXBUF_ALIGNMENT)) {
 			gfar_align_skb(skb);
-			__skb_queue_head(&priv->rx_recycle, skb);
+			skb_queue_head(&priv->rx_recycle, skb);
 		} else
 			dev_kfree_skb_any(skb);
 
@@ -2594,7 +2594,7 @@ struct sk_buff * gfar_new_skb(struct net_device *dev)
 	struct gfar_private *priv = netdev_priv(dev);
 	struct sk_buff *skb = NULL;
 
-	skb = __skb_dequeue(&priv->rx_recycle);
+	skb = skb_dequeue(&priv->rx_recycle);
 	if (!skb)
 		skb = gfar_alloc_skb(dev);
 
@@ -2750,7 +2750,7 @@ int gfar_clean_rx_ring(struct gfar_priv_rx_q *rx_queue, int rx_work_limit)
 			if (unlikely(!newskb))
 				newskb = skb;
 			else if (skb)
-				__skb_queue_head(&priv->rx_recycle, skb);
+				skb_queue_head(&priv->rx_recycle, skb);
 		} else {
 			/* Increment the number of packets */
 			rx_queue->stats.rx_packets++;