evie/android_kernel_oneplus_msm8998
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net/mlx4_en: remove NETDEV_TX_BUSY

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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: Eric Dumazet <edumazet@google.com>
Acked-by: Amir Vadai <amirv@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2014-10-06 09:30:35 -07:00 • committed by David S. Miller
parent 377421662a
commit fe971b95c2
1 changed files with 24 additions and 24 deletions
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48
drivers/net/ethernet/mellanox/mlx4/en_tx.c
View file

@ -706,6 +706,7 @@ netdev_tx_t mlx4_en_xmit(struct sk_buff *skb, struct net_device *dev)
void *fragptr = NULL; void *fragptr = NULL;
bool bounce = false; bool bounce = false;
bool send_doorbell; bool send_doorbell;
bool stop_queue;
bool inline_ok; bool inline_ok;
u32 ring_cons; 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)) if (vlan_tx_tag_present(skb))
vlan_tag = vlan_tx_tag_get(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); 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); 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); send_doorbell = !skb->xmit_more || netif_xmit_stopped(ring->tx_queue);
real_size = (real_size / 16) & 0x3f; 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; return NETDEV_TX_OK;
tx_drop_unmap: tx_drop_unmap: