From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alexander Duyck Subject: Re: [PATCH net-next 1/4] via-rhine: commit receive buffer address before descriptor status update. Date: Tue, 07 Apr 2015 15:12:28 -0700 Message-ID: <5524564C.9090809@redhat.com> References: <87c90b27962c818239073d3a65341054922bd563.1428340371.git.romieu@fr.zoreil.com> <20150407.155209.47396464487922345.davem@davemloft.net> <20150407210248.GC24631@electric-eye.fr.zoreil.com> <20150407.172748.700634713750750146.davem@davemloft.net> <1428443685.25985.212.camel@edumazet-glaptop2.roam.corp.google.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Cc: romieu@fr.zoreil.com, netdev@vger.kernel.org, nix@esperi.org.uk, rl@hellgate.ch, gurligebis@gentoo.org To: Eric Dumazet , David Miller Return-path: Received: from mx1.redhat.com ([209.132.183.28]:39343 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752241AbbDGWMb (ORCPT ); Tue, 7 Apr 2015 18:12:31 -0400 In-Reply-To: <1428443685.25985.212.camel@edumazet-glaptop2.roam.corp.google.com> Sender: netdev-owner@vger.kernel.org List-ID: 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