skge: transmit locking improvements

Don't need to lock when processing transmit complete unless queue fills.
Modeled after tg3.

Signed-off-by: Stephen Hemminger <shemminger@linux-foundation.org>
Signed-off-by: Jeff Garzik <jeff@garzik.org>

diff --git a/drivers/net/skge.c b/drivers/net/skge.c
index f1a0e6c..bc531fd 100644 (file)
--- a/drivers/net/skge.c
+++ b/drivers/net/skge.c
@@ -2621,6 +2621,7 @@ static int skge_down(struct net_device *dev)
 
 static inline int skge_avail(const struct skge_ring *ring)
 {
+       smp_mb();
        return ((ring->to_clean > ring->to_use) ? 0 : ring->count)
                + (ring->to_clean - ring->to_use) - 1;
 }
@@ -2709,6 +2710,8 @@ static int skge_xmit_frame(struct sk_buff *skb, struct net_device *dev)
                       dev->name, e - skge->tx_ring.start, skb->len);
 
        skge->tx_ring.to_use = e->next;
+       smp_wmb();
+
        if (skge_avail(&skge->tx_ring) <= TX_LOW_WATER) {
                pr_debug("%s: transmit queue full\n", dev->name);
                netif_stop_queue(dev);
@@ -2726,8 +2729,6 @@ static void skge_tx_free(struct skge_port *skge, struct skge_element *e,
 {
        struct pci_dev *pdev = skge->hw->pdev;
 
-       BUG_ON(!e->skb);
-
        /* skb header vs. fragment */
        if (control & BMU_STF)
                pci_unmap_single(pdev, pci_unmap_addr(e, mapaddr),
@@ -2745,7 +2746,6 @@ static void skge_tx_free(struct skge_port *skge, struct skge_element *e,
 
                dev_kfree_skb(e->skb);
        }
-       e->skb = NULL;
 }
 
 /* Free all buffers in transmit ring */
@@ -3017,21 +3017,29 @@ static void skge_tx_done(struct net_device *dev)
 
        skge_write8(skge->hw, Q_ADDR(txqaddr[skge->port], Q_CSR), CSR_IRQ_CL_F);
 
-       netif_tx_lock(dev);
        for (e = ring->to_clean; e != ring->to_use; e = e->next) {
-               struct skge_tx_desc *td = e->desc;
+               u32 control = ((const struct skge_tx_desc *) e->desc)->control;
 
-               if (td->control & BMU_OWN)
+               if (control & BMU_OWN)
                        break;
 
-               skge_tx_free(skge, e, td->control);
+               skge_tx_free(skge, e, control);
        }
        skge->tx_ring.to_clean = e;
 
-       if (skge_avail(&skge->tx_ring) > TX_LOW_WATER)
-               netif_wake_queue(dev);
+       /* Can run lockless until we need to synchronize to restart queue. */
+       smp_mb();
+
+       if (unlikely(netif_queue_stopped(dev) &&
+                    skge_avail(&skge->tx_ring) > TX_LOW_WATER)) {
+               netif_tx_lock(dev);
+               if (unlikely(netif_queue_stopped(dev) &&
+                            skge_avail(&skge->tx_ring) > TX_LOW_WATER)) {
+                       netif_wake_queue(dev);
 
-       netif_tx_unlock(dev);
+               }
+               netif_tx_unlock(dev);
+       }
 }
 
 static int skge_poll(struct net_device *dev, int *budget)