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=-0.8 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS 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 015C3C33CAC for ; Thu, 6 Feb 2020 18:12:48 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B8B9621775 for ; Thu, 6 Feb 2020 18:12:47 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=zx2c4.com header.i=@zx2c4.com header.b="Tz+lsjK+" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727878AbgBFSMq (ORCPT ); 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-Google-Smtp-Source: APXvYqwi9AYzuxJrHUrhzrEkIf/41GV7WgHZqF0lxsB7tgmFTyvfWKzBVF/8St753FegXqcTG4UsEkYS2/KswPvedio= 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)