On Wed, Jun 06, 2012 at 10:35:24AM +0200, Eric Dumazet wrote: > From: Eric Dumazet <[email protected]> > > commit 3fa2a1df909 (virtio-net: per cpu 64 bit stats (v2)) added a race > on 32bit arches. > > We must use separate syncp for rx and tx path as they can be run at the > same time on different cpus. Thus one sequence increment can be lost and > readers spin forever. > > Signed-off-by: Eric Dumazet <[email protected]> > Cc: Stephen Hemminger <[email protected]> > Cc: Michael S. Tsirkin <[email protected]> > Cc: Jason Wang <[email protected]>
I'm still thinking about moving tx to take a xmit lock long term, meanwhile this fix appears appropriate for 3.5. Acked-by: Michael S. Tsirkin <[email protected]> Dave, can you pick this up pls? > --- > drivers/net/virtio_net.c | 19 ++++++++++++------- > 1 file changed, 12 insertions(+), 7 deletions(-) > > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c > index 5214b1e..f18149a 100644 > --- a/drivers/net/virtio_net.c > +++ b/drivers/net/virtio_net.c > @@ -42,7 +42,8 @@ module_param(gso, bool, 0444); > #define VIRTNET_DRIVER_VERSION "1.0.0" > > struct virtnet_stats { > - struct u64_stats_sync syncp; > + struct u64_stats_sync tx_syncp; > + struct u64_stats_sync rx_syncp; > u64 tx_bytes; > u64 tx_packets; > > @@ -300,10 +301,10 @@ static void receive_buf(struct net_device *dev, void > *buf, unsigned int len) > > hdr = skb_vnet_hdr(skb); > > - u64_stats_update_begin(&stats->syncp); > + u64_stats_update_begin(&stats->rx_syncp); > stats->rx_bytes += skb->len; > stats->rx_packets++; > - u64_stats_update_end(&stats->syncp); > + u64_stats_update_end(&stats->rx_syncp); > > if (hdr->hdr.flags & VIRTIO_NET_HDR_F_NEEDS_CSUM) { > pr_debug("Needs csum!\n"); > @@ -565,10 +566,10 @@ static unsigned int free_old_xmit_skbs(struct > virtnet_info *vi) > while ((skb = virtqueue_get_buf(vi->svq, &len)) != NULL) { > pr_debug("Sent skb %p\n", skb); > > - u64_stats_update_begin(&stats->syncp); > + u64_stats_update_begin(&stats->tx_syncp); > stats->tx_bytes += skb->len; > stats->tx_packets++; > - u64_stats_update_end(&stats->syncp); > + u64_stats_update_end(&stats->tx_syncp); > > tot_sgs += skb_vnet_hdr(skb)->num_sg; > dev_kfree_skb_any(skb); > @@ -703,12 +704,16 @@ static struct rtnl_link_stats64 *virtnet_stats(struct > net_device *dev, > u64 tpackets, tbytes, rpackets, rbytes; > > do { > - start = u64_stats_fetch_begin(&stats->syncp); > + start = u64_stats_fetch_begin(&stats->tx_syncp); > tpackets = stats->tx_packets; > tbytes = stats->tx_bytes; > + } while (u64_stats_fetch_retry(&stats->tx_syncp, start)); > + > + do { > + start = u64_stats_fetch_begin(&stats->rx_syncp); > rpackets = stats->rx_packets; > rbytes = stats->rx_bytes; > - } while (u64_stats_fetch_retry(&stats->syncp, start)); > + } while (u64_stats_fetch_retry(&stats->rx_syncp, start)); > > tot->rx_packets += rpackets; > tot->tx_packets += tpackets; > _______________________________________________ Virtualization mailing list [email protected] https://lists.linuxfoundation.org/mailman/listinfo/virtualization
