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Commit fe971b95 authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
Browse files

net/mlx4_en: remove NETDEV_TX_BUSY 



Drivers should avoid NETDEV_TX_BUSY as much as possible.

They should stop the tx queue before qdisc even tries to push another
packet, to avoid requeues.

For a driver supporting skb->xmit_more, this is likely to be a prereq
anyway, otherwise we could have a tx deadlock : We need to force a
doorbell if TX ring is full.

Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Acked-by: default avatarAmir Vadai <amirv@mellanox.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 37742166

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

+24 −24
Original line number Diff line number Diff line
@@ -706,6 +706,7 @@ netdev_tx_t mlx4_en_xmit(struct sk_buff *skb, struct net_device *dev) 
	void *fragptr = NULL;

	bool bounce = false;

	bool send_doorbell;

	bool stop_queue;

	bool inline_ok;

	u32 ring_cons;
@@ -735,30 +736,6 @@ netdev_tx_t mlx4_en_xmit(struct sk_buff *skb, struct net_device *dev) 
	if (vlan_tx_tag_present(skb))

		vlan_tag = vlan_tx_tag_get(skb);



	/* Check available TXBBs And 2K spare for prefetch */

	if (unlikely(((int)(ring->prod - ring_cons)) >

		     ring->size - HEADROOM - MAX_DESC_TXBBS)) {

		/* every full Tx ring stops queue */

		netif_tx_stop_queue(ring->tx_queue);

		ring->queue_stopped++;



		/* 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();



		ring_cons = ACCESS_ONCE(ring->cons);

		if (unlikely(((int)(ring->prod - ring_cons)) <=

			     ring->size - HEADROOM - MAX_DESC_TXBBS)) {

			netif_tx_wake_queue(ring->tx_queue);

			ring->wake_queue++;

		} else {

			return NETDEV_TX_BUSY;

		}

	}



	prefetchw(&ring->tx_queue->dql);
@@ -929,6 +906,13 @@ netdev_tx_t mlx4_en_xmit(struct sk_buff *skb, struct net_device *dev) 


	skb_tx_timestamp(skb);



	/* Check available TXBBs And 2K spare for prefetch */

	stop_queue = (int)(ring->prod - ring_cons) >

		      ring->size - HEADROOM - MAX_DESC_TXBBS;

	if (unlikely(stop_queue)) {

		netif_tx_stop_queue(ring->tx_queue);

		ring->queue_stopped++;

	}

	send_doorbell = !skb->xmit_more || netif_xmit_stopped(ring->tx_queue);



	real_size = (real_size / 16) & 0x3f;
@@ -973,6 +957,22 @@ netdev_tx_t mlx4_en_xmit(struct sk_buff *skb, struct net_device *dev) 
		}

	}



	if (unlikely(stop_queue)) {

		/* If queue was emptied after the if (stop_queue) , and before

		 * the netif_tx_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.

		 */

		smp_rmb();



		ring_cons = ACCESS_ONCE(ring->cons);

		if (unlikely(((int)(ring->prod - ring_cons)) <=

			     ring->size - HEADROOM - MAX_DESC_TXBBS)) {

			netif_tx_wake_queue(ring->tx_queue);

			ring->wake_queue++;

		}

	}

	return NETDEV_TX_OK;



tx_drop_unmap: