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=-7.4 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable 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 5F27DC18E5C for ; Tue, 10 Mar 2020 17:53:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 38A9D21927 for ; Tue, 10 Mar 2020 17:53:44 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=oracle.com header.i=@oracle.com header.b="DMlL9bXK" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726752AbgCJRxn (ORCPT ); Tue, 10 Mar 2020 13:53:43 -0400 Received: from aserp2120.oracle.com ([141.146.126.78]:42538 "EHLO aserp2120.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726283AbgCJRxm (ORCPT ); Tue, 10 Mar 2020 13:53:42 -0400 Received: from pps.filterd (aserp2120.oracle.com [127.0.0.1]) by aserp2120.oracle.com (8.16.0.42/8.16.0.42) with SMTP id 02AHqRnG095113; Tue, 10 Mar 2020 17:53:40 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oracle.com; h=subject : to : cc : references : from : message-id : date : mime-version : in-reply-to : content-type : content-transfer-encoding; s=corp-2020-01-29; bh=qT1ECbPEhETHAAouiX0phMVMFqQ41hr92DHNcuh9QlY=; b=DMlL9bXK5QNvJuQyurGwVCxQwS1F3WfINTNq3lcuPQ6AQCp2twEWTmRn8p8s1l4hTjfF 8NN5jbCcpbZwPsVqeROKZ6PfywfcN/Ybj90wHebZ0a4vKGnxxc6RJdcguNHt82QYkQW6 tae9pM6tUA7M18vs5W4wXw2SHzN9au8Jmiwqa3fgsD2KTMHkACCtD9VajhmFx+caSbv5 2+dONbL7xUr01gsiOeVvlJtmVgViRgVYUL9OC3LUjyvAnQp5Ds2Ks9+l5XzlLbLDbDWW gpsa30khpykbQeqMZwC6nZ+7PmIQ9TAwq2XP4hHFSwp1JXyApbOZwNF9FGp/4mi7ip+G rg== Received: from aserp3030.oracle.com (aserp3030.oracle.com [141.146.126.71]) by aserp2120.oracle.com with ESMTP id 2yp9v6273v-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 10 Mar 2020 17:53:40 +0000 Received: from pps.filterd (aserp3030.oracle.com [127.0.0.1]) by aserp3030.oracle.com (8.16.0.42/8.16.0.42) with SMTP id 02AHqH7o139423; Tue, 10 Mar 2020 17:53:40 GMT Received: from aserv0122.oracle.com (aserv0122.oracle.com [141.146.126.236]) by aserp3030.oracle.com with ESMTP id 2yp8psvvgh-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 10 Mar 2020 17:53:39 +0000 Received: from abhmp0014.oracle.com (abhmp0014.oracle.com [141.146.116.20]) by aserv0122.oracle.com (8.14.4/8.14.4) with ESMTP id 02AHrdAh013898; Tue, 10 Mar 2020 17:53:39 GMT Received: from [10.209.227.41] (/10.209.227.41) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Tue, 10 Mar 2020 10:53:39 -0700 Subject: Re: Maybe a race condition in net/rds/rdma.c? To: zerons Cc: netdev , OFED mailing list , haakon.bugge@oracle.com References: <94b20d30-1d7d-7a66-b943-d75a05bcb46e@oracle.com> From: santosh.shilimkar@oracle.com Organization: Oracle Corporation Message-ID: <54d1140d-3347-a2b1-1b20-9a3959d3b451@oracle.com> Date: Tue, 10 Mar 2020 10:53:38 -0700 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.14; rv:60.0) Gecko/20100101 Thunderbird/60.7.2 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=windows-1252; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9556 signatures=668685 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 phishscore=0 malwarescore=0 mlxlogscore=999 bulkscore=0 suspectscore=0 mlxscore=0 spamscore=0 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2001150001 definitions=main-2003100108 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9556 signatures=668685 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=0 spamscore=0 mlxscore=0 priorityscore=1501 lowpriorityscore=0 bulkscore=0 mlxlogscore=999 phishscore=0 adultscore=0 clxscore=1015 impostorscore=0 malwarescore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2001150001 definitions=main-2003100108 Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On 3/6/20 4:11 AM, zerons wrote: > > > On 2/28/20 02:10, santosh.shilimkar@oracle.com wrote: >> >>>> On 18 Feb 2020, at 14:13, zerons wrote: >>>> >>>> Hi, all >>>> >>>> In net/rds/rdma.c >>>> (https://urldefense.com/v3/__https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/tree/net/rds/rdma.c?h=v5.5.3*n419__;Iw!!GqivPVa7Brio!OwwQCLtjDsKmhaIz0sfaOVSuC4ai5t5_FgB7yqNExGOCBtACtIGLF61NNJyqSDtIAcGoPg$ ), >>>> there may be a race condition between rds_rdma_unuse() and rds_free_mr(). >>>> >> Hmmm.. I didn't see email before in my inbox. Please post questions/patches on netdev in future which is the correct mailing list. >> >>>> It seems that this one need some specific devices to run test, >>>> unfortunately, I don't have any of these. >>>> I've already sent two emails to the maintainer for help, no response yet, >>>> (the email address may not be in use). >>>> >>>> 0) in rds_recv_incoming_exthdrs(), it calls rds_rdma_unuse() when receive an >>>> extension header with force=0, if the victim mr does not have RDS_RDMA_USE_ONCE >>>> flag set, then the mr would stay in the rbtree. Without any lock, it tries to >>>> call mr->r_trans->sync_mr(). >>>> MR won't stay in the rbtree with force flag. If the MR is used or use_once is set in both cases its removed from the tree. See "if (mr->r_use_once || force)" >>>> 1) in rds_free_mr(), the same mr is found, and then freed. The mr->r_refcount >>>> doesn't change while rds_mr_tree_walk(). >>>> >>>> 0) back in rds_rdma_unuse(), the victim mr get used again, call >>>> mr->r_trans->sync_mr(). >>>> >>>> Could this race condition actually happen? So from what I see, this race doesn't exist but let me know if am missing something. regards, Santosh