Francois, Shuyu,
this is the patch with the discussed changes.
Shuyu it would be great if you could test this one. If it passes
and there are no further objections I will resend it as a regular patch
(including commit message, etc.) to the mailing list.
diff --git a/drivers/net/ethernet/arc/emac_main.c b/drivers/net/ethernet/arc/emac_main.c
index a3a9392..ec656b3 100644
--- a/drivers/net/ethernet/arc/emac_main.c
+++ b/drivers/net/ethernet/arc/emac_main.c
@@ -153,18 +153,29 @@ static void arc_emac_tx_clean(struct net_device *ndev)
{
struct arc_emac_priv *priv = netdev_priv(ndev);
struct net_device_stats *stats = &ndev->stats;
+ unsigned int curr = priv->txbd_curr;
unsigned int i;
+ /* Make sure buffers and txbd_curr are consistent */
+ smp_rmb();
+
for (i = 0; i < TX_BD_NUM; i++) {
unsigned int *txbd_dirty = &priv->txbd_dirty;
struct arc_emac_bd *txbd = &priv->txbd[*txbd_dirty];
struct buffer_state *tx_buff = &priv->tx_buff[*txbd_dirty];
- struct sk_buff *skb = tx_buff->skb;
- unsigned int info = le32_to_cpu(txbd->info);
+ unsigned int info;
+ struct sk_buff *skb;
- if ((info & FOR_EMAC) || !txbd->data || !skb)
+ if (*txbd_dirty == curr)
break;
+ info = le32_to_cpu(txbd->info);
+
+ if (info & FOR_EMAC)
+ break;
+
+ skb = tx_buff->skb;
+
if (unlikely(info & (DROP | DEFR | LTCL | UFLO))) {
stats->tx_errors++;
stats->tx_dropped++;
@@ -195,8 +206,8 @@ static void arc_emac_tx_clean(struct net_device *ndev)
*txbd_dirty = (*txbd_dirty + 1) % TX_BD_NUM;
}
- /* Ensure that txbd_dirty is visible to tx() before checking
- * for queue stopped.
+ /* Ensure that txbd_dirty is visible to tx() and we see the most recent
+ * value for txbd_curr.
*/
smp_mb();
@@ -680,27 +691,24 @@ static int arc_emac_tx(struct sk_buff *skb, struct net_device *ndev)
dma_unmap_len_set(&priv->tx_buff[*txbd_curr], len, len);
priv->txbd[*txbd_curr].data = cpu_to_le32(addr);
-
- /* Make sure pointer to data buffer is set */
- wmb();
+ priv->tx_buff[*txbd_curr].skb = skb;
skb_tx_timestamp(skb);
*info = cpu_to_le32(FOR_EMAC | FIRST_OR_LAST_MASK | len);
- /* Make sure info word is set */
+ /* 1. Make sure that with respect to tx_clean everything is set up
+ * properly before we advance txbd_curr.
+ * 2. Make sure writes to DMA descriptors are completed before we inform
+ * the hardware.
+ */
wmb();
- priv->tx_buff[*txbd_curr].skb = skb;
-
/* Increment index to point to the next BD */
*txbd_curr = (*txbd_curr + 1) % TX_BD_NUM;
- /* 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();
+ /* Ensure tx_clean() sees the updated value of txbd_curr */
+ smp_wmb();
if (!arc_emac_tx_avail(priv)) {
netif_stop_queue(ndev);
--
1.9.1
