netdev - Re: [PATCH] b44: add 64 bit stats

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Message-ID: <1342794821.2678.8.camel@bwh-desktop.uk.solarflarecom.com>
Date:	Fri, 20 Jul 2012 15:33:41 +0100
From:	Ben Hutchings <bhutchings@...arflare.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
CC:	Kevin Groeneveld <kgroeneveld@...il.com>, <netdev@...r.kernel.org>
Subject: Re: [PATCH] b44: add 64 bit stats

On Fri, 2012-07-20 at 07:24 +0200, Eric Dumazet wrote:
> On Fri, 2012-07-20 at 06:53 +0200, Eric Dumazet wrote:
> > On Thu, 2012-07-19 at 21:56 -0400, Kevin Groeneveld wrote:
> > 
> > > I am still trying to make sure I understand this fully.  I want to
> > > update some other drivers with 64 bit stats as well.  What you said
> > > seems to make sense, but...
> > > 
> > > I was looking at the virtio_net.c driver.  One spot in this driver
> > > which updates the stats is the receive_buf function.  recive_buf is
> > > called from virtnet_poll which is registered as a napi poll function.
> > > According to Documentation/networking/netdevices.txt the poll function
> > > is called in a softirq context.  However, the function which reads the
> > > stats uses u64_stats_fetch_begin/u64_stats_fetch_retry.  Shouldn't
> > > this be u64_stats_fetch_begin_bh/u64_stats_fetch_retry_bh for the
> > > exact reasons you described for my b44 patch?
> > 
> > Absolutely. You can argue that probably nobody use this driver on a
> > 32bit UP machine, but technically speaking the current implementation is
> > racy.
> > 
> 
> In fact all network drivers should use the _bh version.
> 
> Could you send a patch for all of them, based on net-next tree ?
> 
> Thanks !

Don't we need an _irq variant for drivers that support netpoll?

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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