[PATCH net 05/11] net: au1000: serialize TX completion with packet submission

[Florian Fainelli <f.fainelli@gmail.com>]

TX completion runs in hard IRQ context while ndo_start_xmit updates the
same descriptors and ring state without locking. In particular, an
interrupt between netif_stop_queue() and setting tx_full can miss the
wakeup and leave the queue stopped until the watchdog runs. Use the
existing IRQ-safe device lock in both paths to serialize descriptor
reclamation and queue state changes.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
---
 drivers/net/ethernet/amd/au1000_eth.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/net/ethernet/amd/au1000_eth.c b/drivers/net/ethernet/amd/au1000_eth.c
index a507a524370f..90887dac26bc 100644
--- a/drivers/net/ethernet/amd/au1000_eth.c
+++ b/drivers/net/ethernet/amd/au1000_eth.c
@@ -873,7 +873,9 @@ static void au1000_tx_ack(struct net_device *dev)
 {
 	struct au1000_private *aup = netdev_priv(dev);
 	struct tx_dma *ptxd;
+	unsigned long flags;
 
+	spin_lock_irqsave(&aup->lock, flags);
 	ptxd = aup->tx_dma_ring[aup->tx_tail];
 
 	while (ptxd->buff_stat & TX_T_DONE) {
@@ -890,6 +892,8 @@ static void au1000_tx_ack(struct net_device *dev)
 			netif_wake_queue(dev);
 		}
 	}
+
+	spin_unlock_irqrestore(&aup->lock, flags);
 }
 
 /*
@@ -973,17 +977,20 @@ static netdev_tx_t au1000_tx(struct sk_buff *skb, struct net_device *dev)
 	u32 buff_stat;
 	struct db_dest *pDB;
 	int i;
+	unsigned long flags;
 
 	netif_dbg(aup, tx_queued, dev, "tx: aup %x len=%d, data=%p, head %d\n",
 				(unsigned)aup, skb->len,
 				skb->data, aup->tx_head);
 
+	spin_lock_irqsave(&aup->lock, flags);
 	ptxd = aup->tx_dma_ring[aup->tx_head];
 	buff_stat = ptxd->buff_stat;
 	if (buff_stat & TX_DMA_ENABLE) {
 		/* We've wrapped around and the transmitter is still busy */
 		netif_stop_queue(dev);
 		aup->tx_full = 1;
+		spin_unlock_irqrestore(&aup->lock, flags);
 		return NETDEV_TX_BUSY;
 	} else if (buff_stat & TX_T_DONE) {
 		au1000_update_tx_stats(dev, ptxd->status);
@@ -1012,6 +1019,7 @@ static netdev_tx_t au1000_tx(struct sk_buff *skb, struct net_device *dev)
 	wmb(); /* drain writebuffer */
 	dev_kfree_skb(skb);
 	aup->tx_head = (aup->tx_head + 1) & (NUM_TX_DMA - 1);
+	spin_unlock_irqrestore(&aup->lock, flags);
 	return NETDEV_TX_OK;
 }
 
-- 
2.53.0