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: Eric Dumazet <edumazet@google.com>
Acked-by: Amir Vadai <amirv@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/ethernet/mellanox/mlx4/en_tx.c b/drivers/net/ethernet/mellanox/mlx4/en_tx.c
index 92a7cf4..8726a4a 100644
--- a/drivers/net/ethernet/mellanox/mlx4/en_tx.c
+++ b/drivers/net/ethernet/mellanox/mlx4/en_tx.c
@@ -706,6 +706,7 @@
void *fragptr = NULL;
bool bounce = false;
bool send_doorbell;
+ bool stop_queue;
bool inline_ok;
u32 ring_cons;
@@ -735,30 +736,6 @@
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 @@
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 @@
}
}
+ 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: