1 files changed, 32 insertions, 11 deletions

diff --git a/drivers/net/ethernet/arc/emac_main.c b/drivers/net/ethernet/arc/emac_main.c
index f7ab90d9cd7e..5919394d9f58 100644
--- a/drivers/net/ethernet/arc/emac_main.c
+++ b/drivers/net/ethernet/arc/emac_main.c
@@ -30,6 +30,17 @@
 #define DRV_VERSION     "1.0"
 
 /**
+ * arc_emac_tx_avail - Return the number of available slots in the tx ring.
+ * @priv: Pointer to ARC EMAC private data structure.
+ *
+ * returns: the number of slots available for transmission in tx the ring.
+ */
+static inline int arc_emac_tx_avail(struct arc_emac_priv *priv)
+{
+        return (priv->txbd_dirty + TX_BD_NUM - priv->txbd_curr - 1) % TX_BD_NUM;
+}
+
+/**
  * arc_emac_adjust_link - Adjust the PHY link duplex.
  * @ndev:       Pointer to the net_device structure.
  *
@@ -180,10 +191,15 @@ static void arc_emac_tx_clean(struct net_device *ndev)
                 txbd->info = 0;
 
                 *txbd_dirty = (*txbd_dirty + 1) % TX_BD_NUM;
-
-                if (netif_queue_stopped(ndev))
-                        netif_wake_queue(ndev);
         }
+
+        /* Ensure that txbd_dirty is visible to tx() before checking
+         * for queue stopped.
+         */
+        smp_mb();
+
+        if (netif_queue_stopped(ndev) && arc_emac_tx_avail(priv))
+                netif_wake_queue(ndev);
 }
 
 /**
@@ -574,11 +590,9 @@ static int arc_emac_tx(struct sk_buff *skb, struct net_device *ndev)
 
         len = max_t(unsigned int, ETH_ZLEN, skb->len);
 
-        /* EMAC still holds this buffer in its possession.
-         * CPU must not modify this buffer descriptor
-         */
-        if (unlikely((le32_to_cpu(*info) & OWN_MASK) == FOR_EMAC)) {
+        if (unlikely(!arc_emac_tx_avail(priv))) {
                 netif_stop_queue(ndev);
+                netdev_err(ndev, "BUG! Tx Ring full when queue awake!\n");
                 return NETDEV_TX_BUSY;
         }
 
@@ -607,12 +621,19 @@ static int arc_emac_tx(struct sk_buff *skb, struct net_device *ndev)
         /* Increment index to point to the next BD */
         *txbd_curr = (*txbd_curr + 1) % TX_BD_NUM;
 
-        /* Get "info" of the next BD */
-        info = &priv->txbd[*txbd_curr].info;
+        /* Ensure that tx_clean() sees the new txbd_curr before
+         * checking the queue status. This prevents an unneeded wake
+         * of the queue in tx_clean().
+         */
+        smp_mb();
 
-        /* Check if if Tx BD ring is full - next BD is still owned by EMAC */
-        if (unlikely((le32_to_cpu(*info) & OWN_MASK) == FOR_EMAC))
+        if (!arc_emac_tx_avail(priv)) {
                 netif_stop_queue(ndev);
+                /* Refresh tx_dirty */
+                smp_mb();
+                if (arc_emac_tx_avail(priv))
+                        netif_start_queue(ndev);
+        }
 
         arc_reg_set(priv, R_STATUS, TXPL_MASK);