Commit 20a41fba by Lendacky, Thomas Committed by David S. Miller

amd-xgbe: Use wmb before updating current descriptor count

The code currently uses the lightweight dma_wmb barrier before updating the current descriptor count. Under heavy load, the Tx cleanup routine was seeing the updated current descriptor count before the updated descriptor information. As a result, the Tx descriptor was being cleaned up before it was used because it was not "owned" by the hardware yet, resulting in a Tx queue hang. Using the wmb barrier insures that the descriptor is updated before the descriptor counter preventing the Tx queue hang. For extra insurance, the Tx cleanup routine is changed to grab the current decriptor count on entry and uses that initial value in the processing loop rather than trying to chase the current value. Signed-off-by: 's avatarTom Lendacky <> Tested-by: 's avatarChristoffer Dall <> Signed-off-by: 's avatarDavid S. Miller <>
parent d2fd719b
......@@ -1595,7 +1595,7 @@ static void xgbe_dev_xmit(struct xgbe_channel *channel)
packet->rdesc_count, 1);
/* Make sure ownership is written to the descriptor */
ring->cur = cur_index + 1;
if (!packet->skb->xmit_more ||
......@@ -1807,6 +1807,7 @@ static int xgbe_tx_poll(struct xgbe_channel *channel)
struct netdev_queue *txq;
int processed = 0;
unsigned int tx_packets = 0, tx_bytes = 0;
unsigned int cur;
......@@ -1814,10 +1815,11 @@ static int xgbe_tx_poll(struct xgbe_channel *channel)
if (!ring)
return 0;
cur = ring->cur;
txq = netdev_get_tx_queue(netdev, channel->queue_index);
while ((processed < XGBE_TX_DESC_MAX_PROC) &&
(ring->dirty != ring->cur)) {
(ring->dirty != cur)) {
rdata = XGBE_GET_DESC_DATA(ring, ring->dirty);
rdesc = rdata->rdesc;
Markdown is supported
0% or
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment