From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.6 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id BA143C04AB6 for ; Fri, 31 May 2019 16:29:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 121D126C1C for ; Fri, 31 May 2019 16:29:56 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=amarulasolutions.com header.i=@amarulasolutions.com header.b="OfhF4bDi" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726800AbfEaQ3z (ORCPT ); Fri, 31 May 2019 12:29:55 -0400 Received: from mail-wr1-f67.google.com ([209.85.221.67]:45371 "EHLO mail-wr1-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726037AbfEaQ3y (ORCPT ); Fri, 31 May 2019 12:29:54 -0400 Received: by mail-wr1-f67.google.com with SMTP id b18so6886178wrq.12 for ; Fri, 31 May 2019 09:29:54 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=amarulasolutions.com; s=google; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=snJ/aiipUWHYAukpTuHmyUR0949JmdgOyqNQh/Ho730=; b=OfhF4bDi5CETHDqmFyZssWa0nOfyA7fOFJZw2YnBOjZiP4g6WiTJqK4ufYlQzfe5vv xSpZDl+7wSjcGj9GQoydoyV9Qj0SDOQVCbgWuUe4r0D5/TjQ8jSMtGU6UpvaTBI4Txhj 6cAvjGxPrf7We+FwMvnojvjV/qqklqlsZqhFM= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=snJ/aiipUWHYAukpTuHmyUR0949JmdgOyqNQh/Ho730=; b=tQTMtNyDlqnHth7wo2T8+Nv94nDF/VNZnWnyHBaLc+8nVw4gKwc4GRIIE/htF2sDvw V/Rz2uZAZkMMyIF7ldjC/GZHrPDYLPEYfiQTfmhLPtGV1/yP8KzjhiJkGi01UGX6h6IL y45pBwt3pRvdCzQqzSVA9EEAGzH1Hfr8rA+vlWdAevDEEln2h2cs6XZgrIiiRL58ZYcn 4ylOef5CSSqHTtFo8JwQR2Vv6OqupuWiEWpVuXosJDMOYz5IX43Vf84jzTj3gv1HY+zL fl7Bb667dfrJnK1M3Q8NwDSQOlRb9wGpal5ICR02t8GrNp0r8xI41UxcfxHJ+tYucBf7 6Q6A== X-Gm-Message-State: APjAAAXaojwdJrmyGzTVYG9bjXx/iCIb3p2eUzgZdTbQ1Rodmm2JDwKO dDv525CnIXKHteE1cNpqDxETUw== X-Google-Smtp-Source: APXvYqx1Gh23iVqRLLkpqHW5D6ewYI5DlftxxfB2CqwbOKHWAFh76m2Z50O2hXeV4EmpkHzDuKvRsQ== X-Received: by 2002:adf:e909:: with SMTP id f9mr7470430wrm.231.1559320193309; Fri, 31 May 2019 09:29:53 -0700 (PDT) Received: from andrea (86.100.broadband17.iol.cz. [109.80.100.86]) by smtp.gmail.com with ESMTPSA id b8sm4294059wrr.88.2019.05.31.09.29.52 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 31 May 2019 09:29:52 -0700 (PDT) Date: Fri, 31 May 2019 18:29:45 +0200 From: Andrea Parri To: Eric Dumazet Cc: Herbert Xu , Dmitry Vyukov , "Paul E. McKenney" , Alan Stern , Eric Dumazet , David Miller , netdev , syzbot Subject: Re: [PATCH] inet: frags: Remove unnecessary smp_store_release/READ_ONCE Message-ID: <20190531162945.GA600@andrea> References: <20190524160340.169521-12-edumazet@google.com> <20190528063403.ukfh37igryq4u2u6@gondor.apana.org.au> <20190529054026.fwcyhzt33dshma4h@gondor.apana.org.au> <20190529054759.qrw7h73g62mnbica@gondor.apana.org.au> <20190531144549.uiyht5hcy7lfgoge@gondor.apana.org.au> <4e2f7f20-5b7f-131f-4d8b-09cfc6e087d4@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4e2f7f20-5b7f-131f-4d8b-09cfc6e087d4@gmail.com> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Fri, May 31, 2019 at 08:45:47AM -0700, Eric Dumazet wrote: > On 5/31/19 7:45 AM, Herbert Xu wrote: > > In this case the code doesn't need them because an implicit > > barrier() (which is *stronger* than READ_ONCE/WRITE_ONCE) already > > exists in both places. > I have already explained that the READ_ONCE() was a leftover of the first version > of the patch, that I refined later, adding correct (and slightly more complex) RCU > barriers and rules. AFAICT, neither barrier() nor RCU synchronization can be used as a replacement for {READ,WRITE}_ONCE() here (and in tons of other different situations). IOW, you might want to try harder. ;-) Thanks, Andrea