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 <edumazet@google.com>
Cc: Stephen Hemminger <shemminger@vyatta.com>
Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: Jason Wang <jasowang@redhat.com>
Acked-by: Rusty Russell <rusty@rustcorp.com.au>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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 @@
#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 @@
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 @@
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 @@
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;