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=-2.1 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=no 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 C009DC33CAC for ; Thu, 6 Feb 2020 18:22:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 94DDA20659 for ; Thu, 6 Feb 2020 18:22:07 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="DJLL31cI" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727906AbgBFSWG (ORCPT ); Thu, 6 Feb 2020 13:22:06 -0500 Received: from mail-pj1-f66.google.com ([209.85.216.66]:53417 "EHLO mail-pj1-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726990AbgBFSWG (ORCPT ); Thu, 6 Feb 2020 13:22:06 -0500 Received: by mail-pj1-f66.google.com with SMTP id n96so324379pjc.3; Thu, 06 Feb 2020 10:22:06 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=subject:to:cc:references:from:message-id:date:user-agent :mime-version:in-reply-to:content-language:content-transfer-encoding; bh=54PTuSGsMZatUFJRggtY0ZPnRku13hgus2gUwpQbThU=; b=DJLL31cIptj/JwJcmnMQuxDCWzG2NMEB6d9KrNH6uxNCq67elwx9LgMDTuxpVwRbbk XwEOrvQvrCHraqAaw816Izx2l8FxTFAlH1kq1VvfyscsvOEZH7dqaZyoaZg5JzgQbHbk xcQqN98XAUYsu2rtjhS4TpFtiSDKxD1eyofrc5299fFy3rXmINeMHuogOsz5FsolJmJ8 F6HgLdZEh5GkHzD4RrsqSRerTI7s1+YUUu73wDW409NSCyyLbMY78MJ5NxPmfUVRDCGL sO+9U4iMiVhcmLBDvShR+6d/bDHtpI15r1jti12JrNM60KxMeiQ8jpyITR8LBZnZV5FJ 4zag== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=54PTuSGsMZatUFJRggtY0ZPnRku13hgus2gUwpQbThU=; b=sxnwUBvbWTsfsRu4pBOC6kHzGCFeMom9CYJb0rm4/hLpPYytUNyczuo+kbdTRcEhva Ko2BdUohrx8p6ocbPFUvgxaezTQmWk0401cYKMPFRozrgjQXV39UQyU4Qn2ouO0agDg6 iyWbUAbrnscCbOvaZ8f7WL4g5t+v1wcBzrojfW9wm1KgYmVNBPxjQurpbVC85GaSo6qB GnfwJ4biDhkEoIDw/XtvgytjrcOfZ2dTZWluzYY98aNysVPoB/Mspsx/LCiekfhi6HKL 77CxUaejjAVgPhYVqYnpUXjGkDye+LbymbiVlLMuEW3HxACkvD1xuSMjUq+UlLu48Fg3 5wBQ== X-Gm-Message-State: APjAAAWcdIfla3B7byywFHw4XVqJ4i+wy5d0F0sUXZ+KGWHpfU4Mbo5B hfrlLaerEOEDPUVf1UqMPH4= X-Google-Smtp-Source: APXvYqx9NC0lS1YLI/cu7N2wMO7HYmfx9BmQLUKvvEnN5VeJHLaRrQvN2FMNEpsoEBLSR6NhFv5h+w== X-Received: by 2002:a17:902:a984:: with SMTP id bh4mr5291321plb.281.1581013325916; Thu, 06 Feb 2020 10:22:05 -0800 (PST) Received: from ?IPv6:2620:15c:2c1:200:55c7:81e6:c7d8:94b? ([2620:15c:2c1:200:55c7:81e6:c7d8:94b]) by smtp.gmail.com with ESMTPSA id i6sm95146pgm.93.2020.02.06.10.22.04 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 06 Feb 2020 10:22:05 -0800 (PST) Subject: Re: [PATCH v3] skbuff: fix a data race in skb_queue_len() To: "Jason A. Donenfeld" , Eric Dumazet Cc: cai@lca.pw, Netdev , LKML , Marco Elver , Dmitry Vyukov References: <1580841629-7102-1-git-send-email-cai@lca.pw> <20200206163844.GA432041@zx2c4.com> <453212cf-8987-9f05-ceae-42a4fc3b0876@gmail.com> From: Eric Dumazet Message-ID: <495f79f5-ae27-478a-2a1d-6d3fba2d4334@gmail.com> Date: Thu, 6 Feb 2020 10:22:02 -0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.2.2 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2/6/20 10:12 AM, Jason A. Donenfeld wrote: > On Thu, Feb 6, 2020 at 6:10 PM Eric Dumazet wrote: >> Unfortunately we do not have ADD_ONCE() or something like that. > > I guess normally this is called "atomic_add", unless you're thinking > instead about something like this, which generates the same > inefficient code as WRITE_ONCE: > > #define ADD_ONCE(d, s) *(volatile typeof(d) *)&(d) += (s) > Dmitry Vyukov had a nice suggestion few months back how to implement this. https://lkml.org/lkml/2019/10/5/6