From patchwork Thu Oct 20 06:43:52 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "D. Wythe" X-Patchwork-Id: 13012690 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 531C8C41535 for ; Thu, 20 Oct 2022 06:44:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230211AbiJTGoN (ORCPT ); Thu, 20 Oct 2022 02:44:13 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34656 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230190AbiJTGoH (ORCPT ); Thu, 20 Oct 2022 02:44:07 -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 BBD4B1C25CC; Wed, 19 Oct 2022 23:44:05 -0700 (PDT) X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R861e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=ay29a033018046050;MF=alibuda@linux.alibaba.com;NM=1;PH=DS;RN=8;SR=0;TI=SMTPD_---0VSdzyKD_1666248242; Received: from j66a10360.sqa.eu95.tbsite.net(mailfrom:alibuda@linux.alibaba.com fp:SMTPD_---0VSdzyKD_1666248242) by smtp.aliyun-inc.com; Thu, 20 Oct 2022 14:44:03 +0800 From: "D.Wythe" To: kgraul@linux.ibm.com, wenjia@linux.ibm.com, jaka@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 v3 10/10] net/smc: fix application data exception Date: Thu, 20 Oct 2022 14:43:52 +0800 Message-Id: <1666248232-63751-11-git-send-email-alibuda@linux.alibaba.com> X-Mailer: git-send-email 1.8.3.1 In-Reply-To: <1666248232-63751-1-git-send-email-alibuda@linux.alibaba.com> References: <1666248232-63751-1-git-send-email-alibuda@linux.alibaba.com> Precedence: bulk List-ID: X-Mailing-List: linux-rdma@vger.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. Fixes: 1c5526968e27 ("net/smc: Clear memory when release and reuse buffer") Signed-off-by: D. Wythe --- net/smc/smc_core.c | 17 ++++++++--------- 1 file changed, 8 insertions(+), 9 deletions(-) diff --git a/net/smc/smc_core.c b/net/smc/smc_core.c index 42f3aae..d20a6dd 100644 --- a/net/smc/smc_core.c +++ b/net/smc/smc_core.c @@ -1401,8 +1401,9 @@ 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); } } @@ -1413,19 +1414,17 @@ static void smc_buf_unuse(struct smc_connection *conn, if (!lgr->is_smcd && conn->sndbuf_desc->is_vm) { smcr_buf_unuse(conn->sndbuf_desc, false, lgr); } else { - conn->sndbuf_desc->used = 0; - memset(conn->sndbuf_desc->cpu_addr, 0, - conn->sndbuf_desc->len); + memzero_explicit(conn->sndbuf_desc->cpu_addr, conn->sndbuf_desc->len); + WRITE_ONCE(conn->sndbuf_desc->used, 0); } } if (conn->rmb_desc) { if (!lgr->is_smcd) { smcr_buf_unuse(conn->rmb_desc, true, lgr); } else { - conn->rmb_desc->used = 0; - memset(conn->rmb_desc->cpu_addr, 0, - conn->rmb_desc->len + - sizeof(struct smcd_cdc_msg)); + memzero_explicit(conn->rmb_desc->cpu_addr, + conn->rmb_desc->len + sizeof(struct smcd_cdc_msg)); + WRITE_ONCE(conn->rmb_desc->used, 0); } } }