Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755189Ab2FFIff (ORCPT ); Wed, 6 Jun 2012 04:35:35 -0400 Received: from mail-ee0-f46.google.com ([74.125.83.46]:49891 "EHLO mail-ee0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752190Ab2FFIfc (ORCPT ); Wed, 6 Jun 2012 04:35:32 -0400 Subject: [PATCH] virtio-net: fix a race on 32bit arches From: Eric Dumazet To: Jason Wang Cc: netdev@vger.kernel.org, rusty@rustcorp.com.au, linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, mst@redhat.com, Stephen Hemminger Content-Type: text/plain; charset="UTF-8" Date: Wed, 06 Jun 2012 10:35:24 +0200 Message-ID: <1338971724.2760.3913.camel@edumazet-glaptop> Mime-Version: 1.0 X-Mailer: Evolution 2.28.3 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2841 Lines: 83 From: Eric Dumazet 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 --- 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; -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/