From 83a27052c3376793bc879e00e6e6805d6fb7aab9 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Tue, 5 Jun 2012 22:35:24 +0000 Subject: [PATCH] virtio-net: fix a race on 32bit arches 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 Cc: Stephen Hemminger Cc: Michael S. Tsirkin Cc: Jason Wang Acked-by: Rusty Russell Acked-by: Michael S. Tsirkin Signed-off-by: David S. Miller --- 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 5214b1eceb95..f18149ae2588 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; -- 2.20.1