[ofa-general] [PATCH 2/9] mlx4_en: Removed TX locking when polling TX cq

[Yevgeny Petrilin]

There is no need to synchronize the polling with the transmit
function. The only place to synchronize is when we process
the cq from the transmit function. Also removed spin_lock_irq,
and using spin_trylock, if somebody else is already processing the cq,
no need to wait for it to finish.

Signed-off-by: Yevgeny Petrilin <yevgenyp at mellanox.co.il>
---
 drivers/net/mlx4/en_tx.c |   24 +++++++++++++-----------
 1 files changed, 13 insertions(+), 11 deletions(-)

diff --git a/drivers/net/mlx4/en_tx.c b/drivers/net/mlx4/en_tx.c
index 8592f8f..1f25821 100644
--- a/drivers/net/mlx4/en_tx.c
+++ b/drivers/net/mlx4/en_tx.c
@@ -404,14 +404,12 @@ void mlx4_en_tx_irq(struct mlx4_cq *mcq)
 	struct mlx4_en_priv *priv = netdev_priv(cq->dev);
 	struct mlx4_en_tx_ring *ring = &priv->tx_ring[cq->ring];

-	spin_lock_irq(&ring->comp_lock);
 	cq->armed = 0;
+	if (!spin_trylock(&ring->comp_lock))
+		return;
 	mlx4_en_process_tx_cq(cq->dev, cq);
-	if (ring->blocked)
-		mlx4_en_arm_cq(priv, cq);
-	else
-		mod_timer(&cq->timer, jiffies + 1);
-	spin_unlock_irq(&ring->comp_lock);
+	mod_timer(&cq->timer, jiffies + 1);
+	spin_unlock(&ring->comp_lock);
 }


@@ -424,8 +422,10 @@ void mlx4_en_poll_tx_cq(unsigned long data)

 	INC_PERF_COUNTER(priv->pstats.tx_poll);

-	netif_tx_lock(priv->dev);
-	spin_lock_irq(&ring->comp_lock);
+	if (!spin_trylock(&ring->comp_lock)) {
+		mod_timer(&cq->timer, jiffies + MLX4_EN_TX_POLL_TIMEOUT);
+		return;
+	}
 	mlx4_en_process_tx_cq(cq->dev, cq);
 	inflight = (u32) (ring->prod - ring->cons - ring->last_nr_txbb);

@@ -435,8 +435,7 @@ void mlx4_en_poll_tx_cq(unsigned long data)
 	if (inflight && priv->port_up)
 		mod_timer(&cq->timer, jiffies + MLX4_EN_TX_POLL_TIMEOUT);

-	spin_unlock_irq(&ring->comp_lock);
-	netif_tx_unlock(priv->dev);
+	spin_unlock(&ring->comp_lock);
 }

 static struct mlx4_en_tx_desc *mlx4_en_bounce_to_desc(struct mlx4_en_priv *priv,
@@ -479,7 +478,10 @@ static inline void mlx4_en_xmit_poll(struct mlx4_en_priv *priv, int tx_ind)

 	/* Poll the CQ every mlx4_en_TX_MODER_POLL packets */
 	if ((++ring->poll_cnt & (MLX4_EN_TX_POLL_MODER - 1)) == 0)
-		mlx4_en_process_tx_cq(priv->dev, cq);
+		if (spin_trylock(&ring->comp_lock)) {
+			mlx4_en_process_tx_cq(priv->dev, cq);
+			spin_unlock(&ring->comp_lock);
+		}
 }

 static void *get_frag_ptr(struct sk_buff *skb)
-- 
1.5.4