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_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, 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 4F750C33C9E for ; Fri, 17 Jan 2020 18:03:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 292972082F for ; Fri, 17 Jan 2020 18:03:33 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="Ltw0xlbb" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728853AbgAQSDa (ORCPT ); Fri, 17 Jan 2020 13:03:30 -0500 Received: from mail-qk1-f195.google.com ([209.85.222.195]:40338 "EHLO mail-qk1-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726603AbgAQSD3 (ORCPT ); Fri, 17 Jan 2020 13:03:29 -0500 Received: by mail-qk1-f195.google.com with SMTP id c17so23517156qkg.7; Fri, 17 Jan 2020 10:03:29 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=sender:from:date:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=xU4VBanglVPXt7ngdr39qz422X3JP6/qDcudzGbwI4E=; b=Ltw0xlbbDd3T6Yq0dSVi4aqLfuk0vFTBHazMFWMSYU8yiqLSSuA0lDb/1xen40XcH0 cqOv83k0WRiJqxXhwTJPNZJkmtgbduF1fYpW6H/8PtCLXjM+7SJ3caItDskt8EN0ZIN6 o5/tHmOftvWd7Cg+FIC69Yv6fjIhe8VcLA3qiRgRqODaq2oSW5Ef5wqb3iMP52WeZLqI iAzHGocaNXnRyhho0iERF5Clxmxr418Q/nESOJft0SqV4aShORm8SZj1/l5JkfOVHZZc mw1FYoYKH6FBNiq3vB/Nbizzo2k3wbWBjv0DGXIp1yICX6k9/A7nUW4UxvrzcNh0cR5p ilUg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:sender:from:date:to:cc:subject:message-id :references:mime-version:content-disposition:in-reply-to:user-agent; bh=xU4VBanglVPXt7ngdr39qz422X3JP6/qDcudzGbwI4E=; b=An6DJfFAcPoL/RlurF2u8FrMJ9u8xCSg6w8V4ggqRxLICijPI1KtZ0Y0eCQUV5Wbf0 hvAeBG2iJ2uor1+n9UpXuYV41VapI9zoe+3j+RB2wvEthDOa7KTT9xfQqrUx+3RJQ8T/ 58dStQDUB32OnooZhBrB83oYxNBYwNtYt2ydfjv1Y0PmyIcwpQK0REpAGKU12b1LEGga m/8uXQQgyiSt8DEAbh2J9UI6Asy1F6Tx9IsRqDuMNhDSFKqDgXCJ1G+/LyGc21BRT90F Os93JIjETf+dARxcmCzCce/VNwvETC1n9zHBXMVMXcV9Ha6ba/FP9DJqxCH0LceVe9M0 awqA== X-Gm-Message-State: APjAAAU4EVp4pYMygrIKfBd22a0hqk5czRuADFtFYc9unk6iPcvXMEM2 O9aoePs82Cyp30eKKBsDnBM= X-Google-Smtp-Source: APXvYqyCPiG09VXkOIjOy2jkrRHpRdY7DZQqsAECIdmiP32K/o24L2Khmyz3qUwMqv7EC7M+coGglw== X-Received: by 2002:a37:664d:: with SMTP id a74mr39032122qkc.4.1579284208522; Fri, 17 Jan 2020 10:03:28 -0800 (PST) Received: from rani.riverdale.lan ([2001:470:1f07:5f3::b55f]) by smtp.gmail.com with ESMTPSA id q35sm13523418qta.19.2020.01.17.10.03.27 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 17 Jan 2020 10:03:28 -0800 (PST) From: Arvind Sankar X-Google-Original-From: Arvind Sankar Date: Fri, 17 Jan 2020 13:03:26 -0500 To: Eric Dumazet Cc: Peter Zijlstra , Shaokun Zhang , David Miller , netdev@vger.kernel.org, linux-kernel@vger.kernel.org, jinyuqi@huawei.com, kuznet@ms2.inr.ac.ru, yoshfuji@linux-ipv6.org, edumazet@google.com, guoyang2@huawei.com, Will Deacon Subject: Re: [PATCH] net: optimize cmpxchg in ip_idents_reserve Message-ID: <20200117180324.GA2623847@rani.riverdale.lan> References: <1579058620-26684-1-git-send-email-zhangshaokun@hisilicon.com> <20200116.042722.153124126288244814.davem@davemloft.net> <930faaff-4d18-452d-2e44-ef05b65dc858@gmail.com> <1b3aaddf-22f5-1846-90f1-42e68583c1e4@gmail.com> <430496fc-9f26-8cb4-91d8-505fda9af230@hisilicon.com> <20200117123253.GC14879@hirez.programming.kicks-ass.net> <7e6c6202-24bb-a532-adde-d53dd6fb14c3@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <7e6c6202-24bb-a532-adde-d53dd6fb14c3@gmail.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Fri, Jan 17, 2020 at 08:35:07AM -0800, Eric Dumazet wrote: > > > On 1/17/20 4:32 AM, Peter Zijlstra wrote: > > > > > That's crazy, just accept that UBSAN is taking bonghits and ignore it. > > Use atomic_add_return() unconditionally. > > > > Yes, we might simply add a comment so that people do not bug us if > their compiler is too old. > > /* If UBSAN reports an error there, please make sure your compiler > * supports -fno-strict-overflow before reporting it. > */ > return atomic_add_return(segs + delta, p_id) - segs; > Do we need that comment any more? The flag was apparently introduced in gcc-4.2 and we only support 4.6+ anyway?