From patchwork Thu Jan 24 11:54:18 2013 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Subject: [net-next,V2,5/6] net/mlx4_en: Fix a race when closing TX queue Date: Thu, 24 Jan 2013 01:54:18 -0000 From: Amir Vadai X-Patchwork-Id: 215333 Message-Id: <1359028459-30961-6-git-send-email-amirv@mellanox.com> To: "David S. Miller" Cc: netdev@vger.kernel.org, Or Gerlitz , Amir Vadai , Eric Dumazet , Yevgeny Petrilin , Eugenia Emantayev 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. CC: Eric Dumazet Signed-off-by: Yevgeny Petrilin Signed-off-by: Eugenia Emantayev Signed-off-by: Amir Vadai --- drivers/net/ethernet/mellanox/mlx4/en_tx.c | 16 +++++++++++++++- 1 files changed, 15 insertions(+), 1 deletions(-) diff --git a/drivers/net/ethernet/mellanox/mlx4/en_tx.c b/drivers/net/ethernet/mellanox/mlx4/en_tx.c index 16af338..1e793e3 100644 --- a/drivers/net/ethernet/mellanox/mlx4/en_tx.c +++ b/drivers/net/ethernet/mellanox/mlx4/en_tx.c @@ -588,7 +588,21 @@ 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; + /* If queue was emptied after the if, and before the + * stop_queue - need to wake the queue, or else it will remain + * stopped forever. + * Need a memory barrier to make sure ring->cons was not + * updated before queue was stopped. + */ + wmb(); + + 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 */