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Commit c18520bd authored by Yevgeny Petrilin's avatar Yevgeny Petrilin Committed by David S. Miller
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net/mlx4_en: Fixing TX queue stop/wake flow 



Removing the ring->blocked flag, it is redundant and leads to a race:

We close the TX queue and then set the "blocked" flag.
Between those 2 operations the completion function can check the "blocked"
flag, sees that it is 0, and wouldn't open the TX queue.

Using netif_tx_queue_stopped to check the state of the queue to avoid this race.

Signed-off-by: default avatarYevgeny Petrilin <yevgenyp@mellanox.co.il>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent c8c40b7f

drivers/net/ethernet/mellanox/mlx4/en_tx.c

+7 −10
Original line number Diff line number Diff line
@@ -164,7 +164,6 @@ int mlx4_en_activate_tx_ring(struct mlx4_en_priv *priv, 
	ring->cons = 0xffffffff;

	ring->last_nr_txbb = 1;

	ring->poll_cnt = 0;

	ring->blocked = 0;

	memset(ring->tx_info, 0, ring->size * sizeof(struct mlx4_en_tx_info));

	memset(ring->buf, 0, ring->buf_size);
@@ -365,16 +364,15 @@ static void mlx4_en_process_tx_cq(struct net_device *dev, struct mlx4_en_cq *cq) 
	ring->cons += txbbs_skipped;

	netdev_tx_completed_queue(ring->tx_queue, packets, bytes);



	/* Wakeup Tx queue if this ring stopped it */

	if (unlikely(ring->blocked)) {

		if ((u32) (ring->prod - ring->cons) <=

		     ring->size - HEADROOM - MAX_DESC_TXBBS) {

			ring->blocked = 0;

	/*

	 * Wakeup Tx queue if this stopped, and at least 1 packet

	 * was completed

	 */

	if (netif_tx_queue_stopped(ring->tx_queue) && txbbs_skipped > 0) {

		netif_tx_wake_queue(ring->tx_queue);

		priv->port_stats.wake_queue++;

	}

}

}



void mlx4_en_tx_irq(struct mlx4_cq *mcq)

{
@@ -592,7 +590,6 @@ netdev_tx_t mlx4_en_xmit(struct sk_buff *skb, struct net_device *dev) 
		     ring->size - HEADROOM - MAX_DESC_TXBBS)) {

		/* every full Tx ring stops queue */

		netif_tx_stop_queue(ring->tx_queue);

		ring->blocked = 1;

		priv->port_stats.queue_stopped++;



		return NETDEV_TX_BUSY;

drivers/net/ethernet/mellanox/mlx4/mlx4_en.h

+0 −1
Original line number Diff line number Diff line
@@ -248,7 +248,6 @@ struct mlx4_en_tx_ring { 
	u32 doorbell_qpn;

	void *buf;

	u16 poll_cnt;

	int blocked;

	struct mlx4_en_tx_info *tx_info;

	u8 *bounce_buf;

	u32 last_nr_txbb;