This fixes a potential dangling xmit problem.
We also suppress refill interrupts until we need them.
(Anthony and I have been working on performance recently, so this
is a WIP).
Signed-off-by: Rusty Russell <rusty@xxxxxxxxxxxxxxx>
diff -r 586fb6ff29dd drivers/net/virtio_net.c
--- a/drivers/net/virtio_net.c Thu Nov 15 23:19:12 2007 +1100
+++ b/drivers/net/virtio_net.c Thu Nov 15 23:21:18 2007 +1100
@@ -35,6 +35,8 @@ struct virtnet_info
struct net_device *dev;
struct napi_struct napi;
+ struct tasklet_struct xmit_free;
+
/* TX coalescing. */
struct hrtimer tx_timer;
@@ -59,13 +61,40 @@ static inline void vnet_hdr_to_sg(struct
sg_init_one(sg, skb_vnet_hdr(skb), sizeof(struct virtio_net_hdr));
}
+static unsigned free_old_xmit_skbs(struct virtnet_info *vi)
+{
+ struct sk_buff *skb;
+ unsigned int len, i = 0;
+
+ while ((skb = vi->svq->vq_ops->get_buf(vi->svq, &len)) != NULL) {
+ pr_debug("Sent skb %p\n", skb);
+ __skb_unlink(skb, &vi->send);
+ vi->dev->stats.tx_bytes += len;
+ vi->dev->stats.tx_packets++;
+ kfree_skb(skb);
+ i++;
+ }
+ return i;
+}
+
+static void xmit_free(unsigned long data)
+{
+ struct virtnet_info *vi = (void *)data;
+
+ netif_tx_lock(vi->dev);
+ free_old_xmit_skbs(vi);
+ netif_tx_unlock(vi->dev);
+
+ /* In case we were waiting for output buffers. */
+ netif_wake_queue(vi->dev);
+}
+
static bool skb_xmit_done(struct virtqueue *rvq)
{
struct virtnet_info *vi = rvq->vdev->priv;
- /* In case we were waiting for output buffers. */
- netif_wake_queue(vi->dev);
- return true;
+ tasklet_schedule(&vi->xmit_free);
+ return false;
}
static void receive_skb(struct net_device *dev, struct sk_buff *skb,
@@ -216,20 +245,6 @@ again:
return received;
}
-static void free_old_xmit_skbs(struct virtnet_info *vi)
-{
- struct sk_buff *skb;
- unsigned int len;
-
- while ((skb = vi->svq->vq_ops->get_buf(vi->svq, &len)) != NULL) {
- pr_debug("Sent skb %p\n", skb);
- __skb_unlink(skb, &vi->send);
- vi->dev->stats.tx_bytes += len;
- vi->dev->stats.tx_packets++;
- kfree_skb(skb);
- }
-}
-
static enum hrtimer_restart kick_xmit(struct hrtimer *t)
{
struct virtnet_info *vi = container_of(t,struct virtnet_info,tx_timer);
@@ -256,8 +271,6 @@ static int start_xmit(struct sk_buff *sk
sg_init_table(sg, 1+MAX_SKB_FRAGS);
pr_debug("%s: xmit %p %s\n", dev->name, skb, print_mac(mac, dest));
-
- free_old_xmit_skbs(vi);
/* Encode metadata header at front. */
hdr = skb_vnet_hdr(skb);
@@ -290,11 +303,25 @@ static int start_xmit(struct sk_buff *sk
vnet_hdr_to_sg(sg, skb);
num = skb_to_sgvec(skb, sg+1, 0, skb->len) + 1;
__skb_queue_head(&vi->send, skb);
+
+again:
err = vi->svq->vq_ops->add_buf(vi->svq, sg, num, 0, skb);
if (err) {
+ /* Can we free any used skbs? */
+ if (free_old_xmit_skbs(vi))
+ goto again;
+
+ /* Activate callback for using skbs: if this fails it
+ * means some were used in the meantime. */
+ if (unlikely(!vi->svq->vq_ops->restart(vi->svq))) {
+ printk("Unlikely: restart svq failed\n");
+ goto again;
+ }
+
+ __skb_unlink(skb, &vi->send);
+
pr_debug("%s: virtio not prepared to send\n", dev->name);
- skb_unlink(skb, &vi->send);
if (vi->out_max != vi->out_num)
printk("%s: out_max changed from %u to %u\n",
dev->name, vi->out_max, vi->out_num);
vi->out_max = vi->out_num;
@@ -400,5 +428,7 @@ static int virtnet_probe(struct virtio_d
vi->out_max = -1U;
+ tasklet_init(&vi->xmit_free, xmit_free, (unsigned long)vi);
+
/* We expect two virtqueues, receive then send. */
vi->rvq = vdev->config->find_vq(vdev, 0, skb_recv_done);
if (IS_ERR(vi->rvq)) {
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