Received: by 2002:a25:1506:0:0:0:0:0 with SMTP id 6csp1813610ybv; Thu, 6 Feb 2020 10:14:51 -0800 (PST) X-Google-Smtp-Source: APXvYqwYA+AFK4qjDPJ/7UYWRxjP6AtnRj5Dun++rg63hgHnSyl4M7Na9pLcx5H+69ACoQzwNC7J X-Received: by 2002:a05:6830:1d91:: with SMTP id y17mr30122572oti.276.1581012891247; Thu, 06 Feb 2020 10:14:51 -0800 (PST) ARC-Seal: i=1; a=rsa-sha256; t=1581012891; cv=none; d=google.com; s=arc-20160816; b=sNa+RBGFfho+MnV+hMxlxqJaBNHM5DLOhtctpd0FOFL/DwSkoPWApXVQiql8U395Y1 4XYaUui2MMxQgdz6z+bpPg5siKX869AmuqVMVop6Jb0av/HaK4evD5u9iuBKbZw6UXw3 wGggPOTunDGXgfEXWxjbcx/wbpy/UJIaD20fwuczfCH53r0t1DSiyOQgPzud4XdhqhSL 7ORBZvJf6D+bVs3PyFaDWBBWFW/wL1pSoysMTNHtK5PXXlBCNKIimdPjO8L7e7koZ+Qc 89pnZYAOopKoPMV/Djd18FGrp/UlVBlVs/piyRUSGhNFMYBNmOggck51O/lzpygfT3cF nAbA== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-id:precedence:sender:cc:to:subject:message-id:date:from :in-reply-to:references:mime-version:dkim-signature; bh=YnbipmDuXBo7N879K82LItw3DosASr7kl0AI79/8svs=; b=nm1j1osUSxkfA7pG5UXGJSWDUXDEltbtqdRuG6q0w7BGvKiLuwdc1qHV1g7yJQaoPD 2vfKK5P/5woY528Cd2gFmijk3YH4AwaTJdWO+kdkOhm61b10rL7ugIug+p8WRlEisZRG wBbGSZxAMKAzh7Ixhe0s/Yzh/SUTch7Amps2uz+3gleTF/7pmG4YoXLhi1fHzHZnIXef edwaLdRtAPlcLx6z8Ayc2FSyaT3d35/JSht58Ke/pcPhadTpbgpmPbbGnjgNRJ/LwnYt /AEBmC5ikHFpW1SfIX7dRANysMrrKYT4bG2js3s4ptBjIziwOP4Zax3xZFKbgSrNsRmH nVlQ== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@zx2c4.com header.s=mail header.b=Tz+lsjK+; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=zx2c4.com Return-Path: Received: from vger.kernel.org (vger.kernel.org. [209.132.180.67]) by mx.google.com with ESMTP id q126si2653864oia.8.2020.02.06.10.14.38; Thu, 06 Feb 2020 10:14:51 -0800 (PST) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; dkim=pass header.i=@zx2c4.com header.s=mail header.b=Tz+lsjK+; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=zx2c4.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727866AbgBFSMq (ORCPT + 99 others); Thu, 6 Feb 2020 13:12:46 -0500 Received: from frisell.zx2c4.com ([192.95.5.64]:52711 "EHLO frisell.zx2c4.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727747AbgBFSMq (ORCPT ); Thu, 6 Feb 2020 13:12:46 -0500 Received: by frisell.zx2c4.com (ZX2C4 Mail Server) with ESMTP id d9a24a0a; Thu, 6 Feb 2020 18:11:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha1; c=relaxed; d=zx2c4.com; h=mime-version :references:in-reply-to:from:date:message-id:subject:to:cc :content-type; s=mail; bh=UoMsJlCUQufKURXYWGLwJRUQbeM=; b=Tz+lsj K+Hb+gbCTWtPUm1u0UdjAyLgoKoXYz4WxCVbO7vGf9fxwzEkFJ1jCHwBlR8h9jEv zpQ77BkmR9zzDRlO67hJIOdh6ySq6wLEc1xnjF3xSV5/zX3Ww0glJvIFYEAn1tRd qpTsnsIi+TgD/LkrxUUhopVyJiyUv+4LIHcOLkfXrbNWJJ/fp8DuixB0QNLTaHRn b0VYMJbAZ7N2cu+3f+zGfiYtFCToelyuIyqVgS5+K8NlBO1Qvazt4lelAM54uhaP Gx35KEzw76rxY3+E+LdVw2AEutIvHHPkoLt+uwJyPhY4lw+9ZCY5IsYhmSl/EXO7 IgeIRIFX963mY6DA== Received: by frisell.zx2c4.com (ZX2C4 Mail Server) with ESMTPSA id 551f680d (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256:NO); Thu, 6 Feb 2020 18:11:38 +0000 (UTC) Received: by mail-ot1-f41.google.com with SMTP id j20so6418788otq.3; Thu, 06 Feb 2020 10:12:43 -0800 (PST) X-Gm-Message-State: APjAAAVD1AJCmF5rTpCSUwvK9Tr5FyeCawPc317zPhE+fkwhqg2zwzhP UVT6h07S7vpjEsjKA5hMyB6dzLzSf839RYxo2sI= X-Received: by 2002:a9d:7a47:: with SMTP id z7mr32144890otm.179.1581012763147; Thu, 06 Feb 2020 10:12:43 -0800 (PST) MIME-Version: 1.0 References: <1580841629-7102-1-git-send-email-cai@lca.pw> <20200206163844.GA432041@zx2c4.com> <453212cf-8987-9f05-ceae-42a4fc3b0876@gmail.com> In-Reply-To: <453212cf-8987-9f05-ceae-42a4fc3b0876@gmail.com> From: "Jason A. Donenfeld" Date: Thu, 6 Feb 2020 19:12:32 +0100 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH v3] skbuff: fix a data race in skb_queue_len() To: Eric Dumazet Cc: cai@lca.pw, Netdev , LKML , Marco Elver Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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)