netdev - Re: [PATCH net-next 1/4] via-rhine: commit receive buffer address before descriptor status update.

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Date:	Tue, 07 Apr 2015 15:12:28 -0700
From:	Alexander Duyck <alexander.h.duyck@...hat.com>
To:	Eric Dumazet <eric.dumazet@...il.com>,
	David Miller <davem@...emloft.net>
CC:	romieu@...zoreil.com, netdev@...r.kernel.org, nix@...eri.org.uk,
	rl@...lgate.ch, gurligebis@...too.org
Subject: Re: [PATCH net-next 1/4] via-rhine: commit receive buffer address
 before descriptor status update.

On 04/07/2015 02:54 PM, Eric Dumazet wrote:
> On Tue, 2015-04-07 at 17:27 -0400, David Miller wrote:
>
>> That's exactly dma_wmb().
>>
>> It barriers cpu writes so that the device sees things in a certain
>> order.
>>
>> It's what all the most common ethernet chip drivers use in their
>> descriptor handling routines now.
> To be fair, only 2 drivers currently use dma_wmb()

Hey, I got at least 4..  :-)  I only got around to patching 3 Intel 
drivers and one RealTek since that is what I had to test with.  I was 
honestly hoping there would be more interest from other developers to 
pick this up and update their drivers to avoid unnecessary barriers but 
it doesn't look like I have had much luck on that front.

Maybe what I can do is submit a set of patches over the next couple of 
weeks to try and update all the spots that either need to have a barrier 
added, such as what is being addressed here, or can have a barrier 
weakened as I have already done for a few other drivers.

- Alex
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