netdev - Re: [PATCH] virtio-net: fix a race on 32bit arches

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Date:	Wed, 6 Jun 2012 21:19:39 +0100
From:	Ben Hutchings <bhutchings@...arflare.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
CC:	"Michael S. Tsirkin" <mst@...hat.com>,
	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, 2012-06-06 at 22:08 +0200, Eric Dumazet wrote:
> On Wed, 2012-06-06 at 22:58 +0300, Michael S. Tsirkin wrote:
> 
> > 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.
> 
> Which lock do you own in the RX path ?
> 
> You'll have to add a lock in fast path. This sounds really a bad choice
> to me.

You have the NAPI 'lock', so when gathering stats you can synchronise
using napi_disable() ;-)

Ben.

-- 
Ben Hutchings, Staff Engineer, Solarflare
Not speaking for my employer; that's the marketing department's job.
They asked us to note that Solarflare product names are trademarked.

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