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, 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 731F1C33CB3 for ; Fri, 17 Jan 2020 16:35:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4A0C22087E for ; Fri, 17 Jan 2020 16:35:17 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="c+aoFo0Y" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727231AbgAQQfO (ORCPT ); Fri, 17 Jan 2020 11:35:14 -0500 Received: from mail-pj1-f65.google.com ([209.85.216.65]:39533 "EHLO mail-pj1-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726506AbgAQQfL (ORCPT ); Fri, 17 Jan 2020 11:35:11 -0500 Received: by mail-pj1-f65.google.com with SMTP id e11so3549058pjt.4; Fri, 17 Jan 2020 08:35:11 -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=mNwIwagSDRdEcritBAJ+cZ+CoMsUw6XeDByiOPsSvGU=; b=c+aoFo0Y+lvtMfvc642gD4QUGha+92uABLZ5MCoEb6aSbIukexfZ+qBQf0fOPRMetG QCvruneRdqQGzLemJ1VBcipcA0GE6Mr2HIIE0kND8DVoHsvfyg2LPR292i+zJsuHO5tR QKH/BgQklyDCGmEO2aaMB0s4Pyn6NBSNawGc3qyju9uuI8aeF4z0oqNsO7jdw8QpItol agtuchvFck9k+uOdKj2mQIC63HNvpSAGNX/RYsK5vF1Un4sKgEQ96G9DjdQzrb/mEXJk acXrq9ecc6qfa7o217OrXNzsHJN5pjIn7JEWiXNi3ePuuH4FBP2bs46N3CAY7bRbkl2b vfaw== 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=mNwIwagSDRdEcritBAJ+cZ+CoMsUw6XeDByiOPsSvGU=; b=AG4k43d9UXOcrFCwwTSRZ6FtkoFyLvkfzzFgHZQaHmpw3xHtwwaICuIcxzjmemwcJK 7KbGDghW18gLSDuF466barsaTOh4kmJwKfjWvfI4YpvzmIjCTBHmTte45hGWV7LOXdsN EGFNFGqQ2OfK9dvF0iCENzu2chBgAS/nkOd1Lm0wwNbKRGPTFjPUeBP5YtlR3YuxstVU VohC4jredhLFGfGXlD0UtybJij8xsTdVep0CnUUwWsU0N/E9KBxKJIfejQvofak9/1Kj bvhZgMXsEuWTL7GmGjRGpLrxdUUn38u88lbLBJ5udtgxkuvb2crxQGyumVvpbcg4B3qD dK2A== X-Gm-Message-State: APjAAAVD/mtns8d4pWzdmgq7tv6+m5bomzzloz7kHkINHVDQCvjneaYV Z2brGhnDHl67ODAMMd/j3R0= X-Google-Smtp-Source: APXvYqxr2K5JnU80mtYaxoPvReZWPg1BWc2oFawzf55arIJWDZxMg6cD+XMPWE04o2pEsnPrBWWJFQ== X-Received: by 2002:a17:902:a617:: with SMTP id u23mr11034698plq.20.1579278910619; Fri, 17 Jan 2020 08:35:10 -0800 (PST) Received: from [192.168.86.235] (c-73-241-150-58.hsd1.ca.comcast.net. [73.241.150.58]) by smtp.gmail.com with ESMTPSA id v143sm30494035pfc.71.2020.01.17.08.35.08 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 17 Jan 2020 08:35:09 -0800 (PST) Subject: Re: [PATCH] net: optimize cmpxchg in ip_idents_reserve To: Peter Zijlstra , Shaokun Zhang Cc: Eric Dumazet , 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 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> From: Eric Dumazet Message-ID: <7e6c6202-24bb-a532-adde-d53dd6fb14c3@gmail.com> Date: Fri, 17 Jan 2020 08:35:07 -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: <20200117123253.GC14879@hirez.programming.kicks-ass.net> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org 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;