Re: [PATCH] virtio-net: fix a race on 32bit arches
From: Eric Dumazet <hidden>
Date: 2012-06-06 13:10:20
Also in:
lkml, virtualization
Subsystem:
networking drivers, the rest, virtio net driver · Maintainers:
Andrew Lunn, "David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Linus Torvalds, "Michael S. Tsirkin", Jason Wang, Eugenio Pérez
On Wed, 2012-06-06 at 14:13 +0300, Michael S. Tsirkin wrote:
We currently do all stats either on napi callback or from start_xmit callback. This makes them safe, yes?
Hmm, then _bh() variant is needed in virtnet_stats(), as explained in include/linux/u64_stats_sync.h section 6) * 6) If counter might be written by an interrupt, readers should block interrupts. * (On UP, there is no seqcount_t protection, a reader allowing interrupts could * read partial values) Yes, its tricky...
diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 5214b1e..705aaa7 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c@@ -703,12 +703,12 @@ 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_bh(&stats->syncp); tpackets = stats->tx_packets; tbytes = stats->tx_bytes; rpackets = stats->rx_packets; rbytes = stats->rx_bytes; - } while (u64_stats_fetch_retry(&stats->syncp, start)); + } while (u64_stats_fetch_retry_bh(&stats->syncp, start)); tot->rx_packets += rpackets; tot->tx_packets += tpackets;