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virtio_net: return NETDEV_TX_BUSY instead of queueing an extra skb. 

This effectively reverts 99ffc696d1
"virtio: wean net driver off NETDEV_TX_BUSY".

The complexity of queuing an skb (setting a tasklet to re-xmit) is
questionable, especially once we get rid of the other reason for the
tasklet in the next patch.

If the skb won't fit in the tx queue, just return NETDEV_TX_BUSY.
This is frowned upon, so a followup patch uses a more complex solution.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
This commit is contained in:
Rusty Russell 2009-09-24 09:59:18 -06:00
parent 2b5bbe3b8b
commit 8958f574db
1 changed files with 10 additions and 36 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

46
drivers/net/virtio_net.c
View File

@ -48,9 +48,6 @@ struct virtnet_info
struct napi_struct napi;
unsigned int status;
/* The skb we couldn't send because buffers were full. */
struct sk_buff *last_xmit_skb;
/* If we need to free in a timer, this is it. */
struct timer_list xmit_free_timer;
@ -120,9 +117,8 @@ static void skb_xmit_done(struct virtqueue *svq)
/* We were probably waiting for more output buffers. */
netif_wake_queue(vi->dev);
/* Make sure we re-xmit last_xmit_skb: if there are no more packets
* queued, start_xmit won't be called. */
tasklet_schedule(&vi->tasklet);
if (vi->free_in_tasklet)
tasklet_schedule(&vi->tasklet);
}
static void receive_skb(struct net_device *dev, struct sk_buff *skb,
@ -543,12 +539,7 @@ static void xmit_tasklet(unsigned long data)
struct virtnet_info *vi = (void *)data;
netif_tx_lock_bh(vi->dev);
if (vi->last_xmit_skb && xmit_skb(vi, vi->last_xmit_skb) >= 0) {
vi->svq->vq_ops->kick(vi->svq);
vi->last_xmit_skb = NULL;
}
if (vi->free_in_tasklet)
free_old_xmit_skbs(vi);
free_old_xmit_skbs(vi);
netif_tx_unlock_bh(vi->dev);
}
@ -560,28 +551,16 @@ again:
/* Free up any pending old buffers before queueing new ones. */
free_old_xmit_skbs(vi);
/* If we has a buffer left over from last time, send it now. */
if (unlikely(vi->last_xmit_skb) &&
xmit_skb(vi, vi->last_xmit_skb) < 0)
goto stop_queue;
vi->last_xmit_skb = NULL;
/* Put new one in send queue and do transmit */
if (likely(skb)) {
__skb_queue_head(&vi->send, skb);
if (xmit_skb(vi, skb) < 0) {
vi->last_xmit_skb = skb;
skb = NULL;
goto stop_queue;
}
__skb_queue_head(&vi->send, skb);
if (likely(xmit_skb(vi, skb) >= 0)) {
vi->svq->vq_ops->kick(vi->svq);
return NETDEV_TX_OK;
}
done:
vi->svq->vq_ops->kick(vi->svq);
return NETDEV_TX_OK;
stop_queue:
/* Ring too full for this packet, remove it from queue again. */
pr_debug("%s: virtio not prepared to send\n", dev->name);
__skb_unlink(skb, &vi->send);
netif_stop_queue(dev);
/* Activate callback for using skbs: if this returns false it
@ -591,12 +570,7 @@ stop_queue:
netif_start_queue(dev);
goto again;
}
if (skb) {
/* Drop this skb: we only queue one. */
vi->dev->stats.tx_dropped++;
kfree_skb(skb);
}
goto done;
return NETDEV_TX_BUSY;
}
static int virtnet_set_mac_address(struct net_device *dev, void *p)