From 14c998f034bdc9a5bfa53bca18fbd0738cbc65e8 Mon Sep 17 00:00:00 2001 From: Mark McLoughlin Date: Sun, 8 Jun 2008 20:50:56 +1000 Subject: [PATCH] virtio: virtio_net free transmit skbs in a timer virtio_net currently only frees old transmit skbs just before queueing new ones. If the queue is full, it then enables interrupts and waits for notification that more work has been performed. However, a side-effect of this scheme is that there are always xmit skbs left dangling when no new packets are sent, against the Documentation/networking/driver.txt guideline: "... it is not allowed for your TX mitigation scheme to let TX packets "hang out" in the TX ring unreclaimed forever if no new TX packets are sent." Add a timer to ensure that any time we queue new TX skbs, we will shortly free them again. This fixes an easily reproduced hang at shutdown where iptables attempts to unload nf_conntrack and nf_conntrack waits for an skb it is tracking to be freed, but virtio_net never frees it. Signed-off-by: Mark McLoughlin Signed-off-by: Rusty Russell Signed-off-by: Jeff Garzik --- drivers/net/virtio_net.c | 28 ++++++++++++++++++++++++++-- 1 file changed, 26 insertions(+), 2 deletions(-) diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c index 9a3b85e..156d76f 100644 --- a/drivers/net/virtio_net.c +++ b/drivers/net/virtio_net.c @@ -44,6 +44,8 @@ struct virtnet_info /* The skb we couldn't send because buffers were full. */ struct sk_buff *last_xmit_skb; + struct timer_list xmit_free_timer; + /* Number of input buffers, and max we've ever had. */ unsigned int num, max; @@ -240,9 +242,23 @@ static void free_old_xmit_skbs(struct virtnet_info *vi) } } +static void xmit_free(unsigned long data) +{ + struct virtnet_info *vi = (void *)data; + + netif_tx_lock(vi->dev); + + free_old_xmit_skbs(vi); + + if (!skb_queue_empty(&vi->send)) + mod_timer(&vi->xmit_free_timer, jiffies + (HZ/10)); + + netif_tx_unlock(vi->dev); +} + static int xmit_skb(struct virtnet_info *vi, struct sk_buff *skb) { - int num; + int num, err; struct scatterlist sg[2+MAX_SKB_FRAGS]; struct virtio_net_hdr *hdr; const unsigned char *dest = ((struct ethhdr *)skb->data)->h_dest; @@ -285,7 +301,11 @@ static int xmit_skb(struct virtnet_info *vi, struct sk_buff *skb) vnet_hdr_to_sg(sg, skb); num = skb_to_sgvec(skb, sg+1, 0, skb->len) + 1; - return vi->svq->vq_ops->add_buf(vi->svq, sg, num, 0, skb); + err = vi->svq->vq_ops->add_buf(vi->svq, sg, num, 0, skb); + if (!err) + mod_timer(&vi->xmit_free_timer, jiffies + (HZ/10)); + + return err; } static void xmit_tasklet(unsigned long data) @@ -456,6 +476,8 @@ static int virtnet_probe(struct virtio_device *vdev) tasklet_init(&vi->tasklet, xmit_tasklet, (unsigned long)vi); + setup_timer(&vi->xmit_free_timer, xmit_free, (unsigned long)vi); + err = register_netdev(dev); if (err) { pr_debug("virtio_net: registering device failed\n"); @@ -493,6 +515,8 @@ static void virtnet_remove(struct virtio_device *vdev) /* Stop all the virtqueues. */ vdev->config->reset(vdev); + del_timer_sync(&vi->xmit_free_timer); + /* Free our skbs in send and recv queues, if any. */ while ((skb = __skb_dequeue(&vi->recv)) != NULL) { kfree_skb(skb); -- 2.7.4