From: "Michael S. Tsirkin" <mst@redhat.com>
To: Eric Dumazet <eric.dumazet@gmail.com>
Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
virtualization@lists.linux-foundation.org,
Stephen Hemminger <shemminger@vyatta.com>
Subject: Re: [PATCH] virtio-net: fix a race on 32bit arches
Date: Wed, 6 Jun 2012 22:58:15 +0300 [thread overview]
Message-ID: <20120606195814.GA20677@redhat.com> (raw)
In-Reply-To: <1339012441.26966.48.camel@edumazet-glaptop>
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
WARNING: multiple messages have this Message-ID (diff)
From: "Michael S. Tsirkin" <mst@redhat.com>
To: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Stephen Hemminger <shemminger@vyatta.com>,
Jason Wang <jasowang@redhat.com>,
netdev@vger.kernel.org, rusty@rustcorp.com.au,
linux-kernel@vger.kernel.org,
virtualization@lists.linux-foundation.org
Subject: Re: [PATCH] virtio-net: fix a race on 32bit arches
Date: Wed, 6 Jun 2012 22:58:15 +0300 [thread overview]
Message-ID: <20120606195814.GA20677@redhat.com> (raw)
In-Reply-To: <1339012441.26966.48.camel@edumazet-glaptop>
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
next prev parent reply other threads:[~2012-06-06 19:58 UTC|newest]
Thread overview: 64+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-06-06 8:35 [PATCH] virtio-net: fix a race on 32bit arches Eric Dumazet
2012-06-06 8:35 ` Eric Dumazet
2012-06-06 8:45 ` Eric Dumazet
2012-06-06 8:45 ` Eric Dumazet
2012-06-06 9:37 ` Jason Wang
2012-06-06 9:37 ` Jason Wang
2012-06-06 11:13 ` Michael S. Tsirkin
2012-06-06 11:13 ` Michael S. Tsirkin
2012-06-06 13:10 ` Eric Dumazet
2012-06-06 13:10 ` Eric Dumazet
2012-06-06 14:49 ` Michael S. Tsirkin
2012-06-06 14:49 ` Michael S. Tsirkin
2012-06-06 15:14 ` Stephen Hemminger
2012-06-06 18:51 ` Michael S. Tsirkin
2012-06-06 18:51 ` Michael S. Tsirkin
2012-06-06 19:54 ` Eric Dumazet
2012-06-06 19:58 ` Michael S. Tsirkin [this message]
2012-06-06 19:58 ` Michael S. Tsirkin
2012-06-06 20:08 ` Eric Dumazet
2012-06-06 20:08 ` Eric Dumazet
2012-06-06 20:16 ` Michael S. Tsirkin
2012-06-06 20:16 ` Michael S. Tsirkin
2012-06-06 20:24 ` Eric Dumazet
2012-06-06 20:24 ` Eric Dumazet
2012-06-06 20:38 ` Eric Dumazet
2012-06-06 20:38 ` Eric Dumazet
2012-06-06 20:35 ` Ben Hutchings
2012-06-06 20:35 ` Ben Hutchings
2012-06-06 20:43 ` Michael S. Tsirkin
2012-06-06 20:43 ` Michael S. Tsirkin
2012-06-06 20:19 ` Ben Hutchings
2012-06-06 20:19 ` Ben Hutchings
2012-06-06 20:25 ` Eric Dumazet
2012-06-06 20:25 ` Eric Dumazet
2012-06-06 19:54 ` Eric Dumazet
2012-06-06 15:14 ` Stephen Hemminger
2012-06-06 15:19 ` Eric Dumazet
2012-06-06 15:19 ` Eric Dumazet
2012-06-06 16:17 ` Michael S. Tsirkin
2012-06-06 16:17 ` Michael S. Tsirkin
2012-06-06 17:13 ` Eric Dumazet
2012-06-06 18:43 ` Michael S. Tsirkin
2012-06-06 18:43 ` Michael S. Tsirkin
2012-06-06 20:06 ` Eric Dumazet
2012-06-06 20:06 ` Eric Dumazet
2012-06-06 20:19 ` Michael S. Tsirkin
2012-06-06 20:19 ` Michael S. Tsirkin
2012-06-06 17:13 ` Eric Dumazet
2012-06-06 16:57 ` Michael S. Tsirkin
2012-06-06 16:57 ` Michael S. Tsirkin
2012-06-06 20:00 ` Eric Dumazet
2012-06-06 20:00 ` Eric Dumazet
2012-06-10 6:36 ` Rusty Russell
2012-06-10 6:36 ` Rusty Russell
2012-06-10 7:03 ` Michael S. Tsirkin
2012-06-10 7:03 ` Michael S. Tsirkin
2012-06-10 10:21 ` Eric Dumazet
2012-06-10 10:21 ` Eric Dumazet
2012-06-10 10:22 ` Michael S. Tsirkin
2012-06-10 10:22 ` Michael S. Tsirkin
2012-06-10 10:25 ` Michael S. Tsirkin
2012-06-10 10:25 ` Michael S. Tsirkin
2012-06-11 3:23 ` David Miller
2012-06-11 3:23 ` David Miller
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