From patchwork Wed Aug 10 17:47:41 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "D. Wythe" X-Patchwork-Id: 12940853 X-Patchwork-Delegate: kuba@kernel.org Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3B962C19F2A for ; Wed, 10 Aug 2022 17:48:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232523AbiHJRsP (ORCPT ); Wed, 10 Aug 2022 13:48:15 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53014 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232695AbiHJRsC (ORCPT ); Wed, 10 Aug 2022 13:48:02 -0400 Received: from out30-131.freemail.mail.aliyun.com (out30-131.freemail.mail.aliyun.com [115.124.30.131]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 038168C02E; Wed, 10 Aug 2022 10:47:53 -0700 (PDT) X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R331e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=ay29a033018045170;MF=alibuda@linux.alibaba.com;NM=1;PH=DS;RN=7;SR=0;TI=SMTPD_---0VLvtrne_1660153670; Received: from localhost(mailfrom:alibuda@linux.alibaba.com fp:SMTPD_---0VLvtrne_1660153670) by smtp.aliyun-inc.com; Thu, 11 Aug 2022 01:47:51 +0800 From: "D. Wythe" To: kgraul@linux.ibm.com, wenjia@linux.ibm.com Cc: kuba@kernel.org, davem@davemloft.net, netdev@vger.kernel.org, linux-s390@vger.kernel.org, linux-rdma@vger.kernel.org Subject: [PATCH net-next 10/10] net/smc: fix application data exception Date: Thu, 11 Aug 2022 01:47:41 +0800 Message-Id: <2c6e99846828f7c409ec641ce047e810b89c7130.1660152975.git.alibuda@linux.alibaba.com> X-Mailer: git-send-email 1.8.3.1 In-Reply-To: References: Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org X-Patchwork-Delegate: kuba@kernel.org From: "D. Wythe" After we optimize the parallel capability of SMC-R connection establishment, There is a certain probability that following exceptions will occur in the wrk benchmark test: Running 10s test @ http://11.213.45.6:80 8 threads and 64 connections Thread Stats Avg Stdev Max +/- Stdev Latency 3.72ms 13.94ms 245.33ms 94.17% Req/Sec 1.96k 713.67 5.41k 75.16% 155262 requests in 10.10s, 23.10MB read Non-2xx or 3xx responses: 3 We will find that the error is HTTP 400 error, which is a serious exception in our test, which means the application data was corrupted. Consider the following scenarios: CPU0 CPU1 buf_desc->used = 0; cmpxchg(buf_desc->used, 0, 1) deal_with(buf_desc) memset(buf_desc->cpu_addr,0); This will cause the data received by a victim connection to be cleared, thus triggering an HTTP 400 error in the server. This patch exchange the order between clear used and memset, add barrier to ensure memory consistency. Signed-off-by: D. Wythe --- net/smc/smc_core.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/net/smc/smc_core.c b/net/smc/smc_core.c index b90970a..7d42125 100644 --- a/net/smc/smc_core.c +++ b/net/smc/smc_core.c @@ -1406,8 +1406,9 @@ static void smcr_buf_unuse(struct smc_buf_desc *buf_desc, bool is_rmb, smc_buf_free(lgr, is_rmb, buf_desc); } else { - buf_desc->used = 0; - memset(buf_desc->cpu_addr, 0, buf_desc->len); + /* memzero_explicit provides potential memory barrier semantics */ + memzero_explicit(buf_desc->cpu_addr, buf_desc->len); + WRITE_ONCE(buf_desc->used, 0); } }