netdev - [PATCH net-next V1 5/6] net/mlx4_en: Fix a race when closing TX queue

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Date:	Thu, 17 Jan 2013 13:47:20 +0200
From:	Amir Vadai <amirv@...lanox.com>
To:	"David S. Miller" <davem@...emloft.net>
Cc:	netdev@...r.kernel.org, Or Gerlitz <ogerlitz@...lanox.com>,
	Amir Vadai <amirv@...lanox.com>,
	Yevgeny Petrilin <yevgenyp@...lanox.com>,
	Eugenia Emantayev <eugenia@...lanox.com>
Subject: [PATCH net-next V1 5/6] net/mlx4_en: Fix a race when closing TX queue

There is a possible race where the TX completion handler can clean the
entire TX queue between the decision that the queue is full and actually
closing it. To avoid this situation, check again if the queue is really
full, if not, reopen the transmit and continue with sending the packet.

Signed-off-by: Yevgeny Petrilin <yevgenyp@...lanox.com>
Signed-off-by: Eugenia Emantayev <eugenia@...lanox.com>
Signed-off-by: Amir Vadai <amirv@...lanox.com>
---
 drivers/net/ethernet/mellanox/mlx4/en_tx.c |    9 ++++++++-
 1 files changed, 8 insertions(+), 1 deletions(-)

diff --git a/drivers/net/ethernet/mellanox/mlx4/en_tx.c b/drivers/net/ethernet/mellanox/mlx4/en_tx.c
index 2b799f4..1d17f5f 100644
--- a/drivers/net/ethernet/mellanox/mlx4/en_tx.c
+++ b/drivers/net/ethernet/mellanox/mlx4/en_tx.c
@@ -592,7 +592,14 @@ netdev_tx_t mlx4_en_xmit(struct sk_buff *skb, struct net_device *dev)
 		netif_tx_stop_queue(ring->tx_queue);
 		priv->port_stats.queue_stopped++;
 
-		return NETDEV_TX_BUSY;
+		/* Check again whether the queue was cleaned */
+		if (unlikely(((int)(ring->prod - ring->cons)) <=
+				ring->size - HEADROOM - MAX_DESC_TXBBS)) {
+			netif_tx_wake_queue(ring->tx_queue);
+			priv->port_stats.wake_queue++;
+		} else {
+			return NETDEV_TX_BUSY;
+		}
 	}
 
 	/* Track current inflight packets for performance analysis */
-- 
1.7.8.2

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