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Date: Wed, 6 Jun 2012 22:58:15 +0300 From: "Michael S. Tsirkin" <mst@...hat.com> To: Eric Dumazet <eric.dumazet@...il.com> Cc: Stephen Hemminger <shemminger@...tta.com>, Jason Wang <jasowang@...hat.com>, netdev@...r.kernel.org, rusty@...tcorp.com.au, linux-kernel@...r.kernel.org, virtualization@...ts.linux-foundation.org Subject: Re: [PATCH] virtio-net: fix a race on 32bit arches On Wed, Jun 06, 2012 at 09:54:01PM +0200, Eric Dumazet wrote: > On Wed, 2012-06-06 at 21:51 +0300, Michael S. Tsirkin wrote: > > > BTW for cards that do implement the counters in software, > > under xmit lock, is anything wrong with simply taking the xmit lock > > when we get the stats instead of the per-cpu trick + seqlock? > > > > I still dont understand why you would do that. > > Most modern machines are 64bits, so there is no seqlock overhead, > nothing at all. > > If you focus on 32bit hardware, just stick on 32bit counters ? These wrap around. > Note that most u64_stats_sync users are virtual drivers, without xmit > lock (LLTX drivers) > > Absolutely, I am talking about virtio here. I'm not kicking u64_stats_sync idea I am just saying that simple locking would work for virtio and might be better as it gives us a way to get counters atomically. -- MST -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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