Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752808AbaKVAFJ (ORCPT ); Fri, 21 Nov 2014 19:05:09 -0500 Received: from mail-ig0-f175.google.com ([209.85.213.175]:47943 "EHLO mail-ig0-f175.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752467AbaKVAFG (ORCPT ); Fri, 21 Nov 2014 19:05:06 -0500 Message-ID: <1416614703.20938.0.camel@edumazet-glaptop2.roam.corp.google.com> Subject: Re: [PATCH v2 9/9] netfilter: Replace smp_read_barrier_depends() with lockless_dereference() From: Eric Dumazet To: Pranith Kumar Cc: Pablo Neira Ayuso , Patrick McHardy , Jozsef Kadlecsik , "David S. Miller" , Alexey Kuznetsov , James Morris , Hideaki YOSHIFUJI , netfilter-devel@vger.kernel.org, coreteam@netfilter.org, "open list:NETWORKING [IPv4/..." , open list Date: Fri, 21 Nov 2014 16:05:03 -0800 In-Reply-To: References: <1416582363-20661-1-git-send-email-bobby.prani@gmail.com> <1416582363-20661-10-git-send-email-bobby.prani@gmail.com> <1416586364.8629.104.camel@edumazet-glaptop2.roam.corp.google.com> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.10.4-0ubuntu2 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 2014-11-21 at 16:57 -0500, Pranith Kumar wrote: > Hi Eric, > > Thanks for looking at this patch. > > I've been scratching my head since morning trying to find out what was > so obviously wrong with this patch. Alas, I don't see what you do. > > Could you point it out and show me how incompetent I am, please? > > Thanks! Well, even it the code is _not_ broken, I don't see any value with this patch. If I use git blame on current code, line containing smp_read_barrier_depends() exactly points to the relevant commit [1] After your change, it will point to some cleanup, which makes little sense to me, considering you did not change the smp_wmb() in xt_replace_table(). I, as a netfilter contributor would like to keep current code as is, because it is how I feel safe with it. We have a proliferation of interfaces, but this does not help to understand the issues and code maintenance. smp_read_barrier_depends() better documents the read barrier than lockless_dereference(). The point of having a lock or not is irrelevant here. [1] http://git.kernel.org/cgit/linux/kernel/git/davem/net.git/commit/?id=b416c144f46af1a30ddfa4e4319a8f077381ad63 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/