[netdrvr e1000] tx_lock

* Fix race in Tx performance path with tx_lock.  Between checking
  if we're out of resources and stopping the queue, we can get
  a hard interrupt which will clean up all Tx work, and wake
  the queue.  Coming out of hard interrupt context, we stop the
  queue even though no work was queued, and all work completed
  has been cleaned up.  Scenario requires ring to be completely
  filled, which is more likely to happen with TSO, since each
  TSO send consumes multiple ring entries.

drivers/net/e1000/e1000.h

@@ -202,6 +202,7 @@ struct e1000_adapter {
 
 	/* TX */
 	struct e1000_desc_ring tx_ring;
+	spinlock_t tx_lock;
 	uint32_t txd_cmd;
 	uint32_t tx_int_delay;
 	uint32_t tx_abs_int_delay;

drivers/net/e1000/e1000_main.c

@@ -678,6 +678,7 @@ e1000_sw_init(struct e1000_adapter *adapter)
 
 	atomic_set(&adapter->irq_sem, 1);
 	spin_lock_init(&adapter->stats_lock);
+	spin_lock_init(&adapter->tx_lock);
 
 	return 0;
 }
@@ -1765,6 +1766,7 @@ e1000_xmit_frame(struct sk_buff *skb, struct net_device *netdev)
 	struct e1000_adapter *adapter = netdev->priv;
 	unsigned int first;
 	unsigned int tx_flags = 0;
+	unsigned long flags;
 	int count;
 
 	if(skb->len <= 0) {
@@ -1772,10 +1774,13 @@ e1000_xmit_frame(struct sk_buff *skb, struct net_device *netdev)
 		return 0;
 	}
 
+	spin_lock_irqsave(&adapter->tx_lock, flags);
+
 	if(adapter->hw.mac_type == e1000_82547) {
 		if(e1000_82547_fifo_workaround(adapter, skb)) {
 			netif_stop_queue(netdev);
 			mod_timer(&adapter->tx_fifo_stall_timer, jiffies);
+			spin_unlock_irqrestore(&adapter->tx_lock, flags);
 			return 1;
 		}
 	}
@@ -1796,11 +1801,14 @@ e1000_xmit_frame(struct sk_buff *skb, struct net_device *netdev)
 		e1000_tx_queue(adapter, count, tx_flags);
 	else {
 		netif_stop_queue(netdev);
+		spin_unlock_irqrestore(&adapter->tx_lock, flags);
 		return 1;
 	}
 
 	netdev->trans_start = jiffies;
 
+	spin_unlock_irqrestore(&adapter->tx_lock, flags);
+	
 	return 0;
 }
 
@@ -2154,6 +2162,8 @@ e1000_clean_tx_irq(struct e1000_adapter *adapter)
 	unsigned int i, eop;
 	boolean_t cleaned = FALSE;
 
+	spin_lock(&adapter->tx_lock);
+
 	i = tx_ring->next_to_clean;
 	eop = tx_ring->buffer_info[i].next_to_watch;
 	eop_desc = E1000_TX_DESC(*tx_ring, eop);
@@ -2198,6 +2208,8 @@ e1000_clean_tx_irq(struct e1000_adapter *adapter)
 	if(cleaned && netif_queue_stopped(netdev) && netif_carrier_ok(netdev))
 		netif_wake_queue(netdev);
 
+	spin_unlock(&adapter->tx_lock);
+
 	return cleaned;
 }