netdev - Re: [PATCH net-next v5 07/10] forcedeth: implement ndo_get

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Message-ID: <1321471967.2709.14.camel@bwh-desktop>
Date:	Wed, 16 Nov 2011 19:32:47 +0000
From:	Ben Hutchings <bhutchings@...arflare.com>
To:	David Decotigny <david.decotigny@...gle.com>
CC:	Stephen Hemminger <shemminger@...tta.com>,
	<netdev@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	"David S. Miller" <davem@...emloft.net>,
	Ian Campbell <ian.campbell@...rix.com>,
	Eric Dumazet <eric.dumazet@...il.com>,
	Jeff Kirsher <jeffrey.t.kirsher@...el.com>,
	Jiri Pirko <jpirko@...hat.com>, Joe Perches <joe@...ches.com>,
	Szymon Janc <szymon@...c.net.pl>,
	Richard Jones <rick.jones2@...com>,
	Ayaz Abdulla <AAbdulla@...dia.com>
Subject: Re: [PATCH net-next v5 07/10] forcedeth: implement
 ndo_get_stats64() API

On Wed, 2011-11-16 at 11:25 -0800, David Decotigny wrote:
> Thanks for your feedback on these concerns.
> 
> On Wed, Nov 16, 2011 at 9:14 AM, Ben Hutchings
> <bhutchings@...arflare.com> wrote:
> > On Wed, 2011-11-16 at 08:55 -0800, Stephen Hemminger wrote:
> >> Or realize that the Tx side is single threaded by dev->xmit_lock already
> >> and the Rx side is single threaded by NAPI.
> >
> > Right.
> 
> Yes, that's what I meant by "Each software stat field is updated by
> one single writer." in a previous email. However, I think that TX and
> RX paths are not always synchronized. So I'm afraid that if I'm using
> a single seqcount, I might run into trouble in the absence of a lock
> around each update.... and I'd really prefer to avoid such a lock. Are
> you suggesting I should use 2 independent seqcounts? One for RX path,
> the other for TX path, all this without a lock around writers?

Yes, there should be 1 for each path.

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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