From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mails.dpdk.org (mails.dpdk.org [217.70.189.124]) by inbox.dpdk.org (Postfix) with ESMTP id 2492443E39; Thu, 11 Apr 2024 05:20:07 +0200 (CEST) Received: from mails.dpdk.org (localhost [127.0.0.1]) by mails.dpdk.org (Postfix) with ESMTP id A26B2402A8; Thu, 11 Apr 2024 05:20:06 +0200 (CEST) Received: from szxga03-in.huawei.com (szxga03-in.huawei.com [45.249.212.189]) by mails.dpdk.org (Postfix) with ESMTP id DF0A8402A7 for ; Thu, 11 Apr 2024 05:20:04 +0200 (CEST) Received: from mail.maildlp.com (unknown [172.19.163.174]) by szxga03-in.huawei.com (SkyGuard) with ESMTP id 4VFPyd2d1XzNnbY; Thu, 11 Apr 2024 11:17:45 +0800 (CST) Received: from dggpeml500024.china.huawei.com (unknown [7.185.36.10]) by mail.maildlp.com (Postfix) with ESMTPS id 3DC381404D9; Thu, 11 Apr 2024 11:20:02 +0800 (CST) Received: from [10.67.121.161] (10.67.121.161) by dggpeml500024.china.huawei.com (7.185.36.10) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.1.2507.35; Thu, 11 Apr 2024 11:20:01 +0800 Subject: Re: Strict aliasing problem with rte_eth_linkstatus_set() To: Tyler Retzlaff , =?UTF-8?Q?Morten_Br=c3=b8rup?= CC: Stephen Hemminger , Ferruh Yigit , , Dengdui Huang References: <8175c905-e661-b910-7f20-59b6ab605c38@huawei.com> <20240410082704.4691d7df@hermes.local> <98CBD80474FA8B44BF855DF32C47DC35E9F391@smartserver.smartshare.dk> <20240410195834.GA25134@linuxonhyperv3.guj3yctzbm1etfxqx2vob5hsef.xx.internal.cloudapp.net> From: fengchengwen Message-ID: <84929ae8-54cc-43e7-b37e-f38a8963b259@huawei.com> Date: Thu, 11 Apr 2024 11:20:01 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.11.0 MIME-Version: 1.0 In-Reply-To: <20240410195834.GA25134@linuxonhyperv3.guj3yctzbm1etfxqx2vob5hsef.xx.internal.cloudapp.net> Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 8bit X-Originating-IP: [10.67.121.161] X-ClientProxiedBy: dggems701-chm.china.huawei.com (10.3.19.178) To dggpeml500024.china.huawei.com (7.185.36.10) X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org Hi All, On 2024/4/11 3:58, Tyler Retzlaff wrote: > On Wed, Apr 10, 2024 at 07:54:27PM +0200, Morten Brørup wrote: >>> From: Stephen Hemminger [mailto:stephen@networkplumber.org] >>> Sent: Wednesday, 10 April 2024 17.27 >>> >>> On Wed, 10 Apr 2024 17:33:53 +0800 >>> fengchengwen wrote: >>> >>>> Last： We think there are two ways to solve this problem. >>>> 1. Add the compilation option '-fno-strict-aliasing' for hold DPDK >>> project. >>>> 2. Use union to avoid such aliasing in rte_eth_linkstatus_set (please >>> see above). >>>> PS: We prefer first way. >>>> >>> >>> Please send a patch to replace alias with union. >> >> +1 >> >> Fixing this specific bug would be good. OK for this, and I already send a bugfix which use union. Thanks >> >> Instinctively, I think we should build with -fno-strict-aliasing, so the compiler doesn't make the same mistake with similar code elsewhere in DPDK. I fear there is more than this instance. >> I also wonder if -Wstrict-aliasing could help us instead, if we don't want -fno-strict-aliasing. > > agree, union is the correct way to get defined behavior. there are > valuable optimizatons that the compiler can make with strict aliasing > enabled so -Wstrict-aliasing is a good suggestion as opposed to > disabling it. > > also the union won't break the abi if introduced correctly. > . >