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=-6.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,MSGID_FROM_MTA_HEADER,SPF_HELO_NONE,SPF_PASS 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 2C3CAC49EA7 for ; Fri, 25 Jun 2021 12:48:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0B67B6147F for ; Fri, 25 Jun 2021 12:48:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231357AbhFYMug (ORCPT ); Fri, 25 Jun 2021 08:50:36 -0400 Received: from mail-bn1nam07on2072.outbound.protection.outlook.com ([40.107.212.72]:12142 "EHLO NAM02-BN1-obe.outbound.protection.outlook.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S229653AbhFYMuf (ORCPT ); Fri, 25 Jun 2021 08:50:35 -0400 ARC-Seal: i=1; a=rsa-sha256; s=arcselector9901; d=microsoft.com; cv=none; b=kEfB3wkFwD7J7LDqnEZDeMgsegV5rqSFdO2uV3z3gKZS0XC214c8ipAqKO2iF9/f/lyqsq7cAvHv1Qn4ZiBIFL1ltOyir6h4DWttjsiBwXxmFx8KSS+JGl7cxOUw01vK+gTypOVuVK80KJGd41z+RLtxIDiO/vVC4Z/E+cy7yAYgsHMI/ZbNStIZHL1bLkQNQ5cZrTt4RdDP+oHWv5/cQ4Du8Eh3lpssp5AO9R/4hVwhUhQpf2BwbIJyP3DSiWDGFCJDS+Bn30KWXNQk3GyxNI6DzY1osFveluRzSO2J5zK3gitTRnziklrOA7tGYVd7Xtv1F0F1O82el0eIn1J39A== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=microsoft.com; s=arcselector9901; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=Gb9CSXjdXUMWQphwR3Ej5TsPbsDmtDchfxcd4dIo16M=; b=maGw9paiQdU3XP11EEKCoZVu4O8q7MsGv4RBERmUsBkHUifMv5PRI0Re8//1hlFmbMYrpZnYdQy8lh9BtdkldHAgy8TL6utveWVoL9oniiom+9zG0H6LKM8BpMcCMRIbIFbMrrtvMO5HkqXiyrKt9OBFrsGneeK4KEsX9NGFd7GQ6XI+Jv3xrt/slHQaRYQ1MjyZbCbWoDH0ey+kghDfXWhTRjBx0fO7ZTC/nprG9mNGjHuDzbw0hRvjcQP+jV7NxDhxPwi3VSqMYWaaRsRh50Ab4f8NqjAXvbppcjQk5RTjRylvhYsE3vNoWmoWZ/EbPLgIqFgL2quOt2Kkbc27qQ== ARC-Authentication-Results: i=1; mx.microsoft.com 1; spf=pass smtp.mailfrom=nvidia.com; dmarc=pass action=none header.from=nvidia.com; dkim=pass header.d=nvidia.com; arc=none DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=Nvidia.com; s=selector2; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=Gb9CSXjdXUMWQphwR3Ej5TsPbsDmtDchfxcd4dIo16M=; b=m04l6xmRB0ObFk72aJj1f5NnnxoNPhv+bf9QvMS1FbKbDhJKiby587l53D8N4shpv5hsudRHFWvUpOHTFirWD0tpw6L2BF1pOSg2o7ggcyfU0q93U69sy3ZX3BUhhQxCiPZT97jVVSfBvhpFMFh96PhOpPP2L5s1yzPotcipuiY8+B2kCnibPXfSWq6SYVWOl3MwDBVpwVd9q2ATwWRNMQ0BOJez5OS3sy4+CmY+CHWgQ3LEMZKpa3CNPvPZwdmIIAJZAdhb1UhsfQ5OJigX0KRIMl7D5JgmH7U3bjFu718VzzalA2iIZs/yCYkPC7+/K8Buk0TZpvc4BosS3anjwA== Authentication-Results: oracle.com; dkim=none (message not signed) header.d=none;oracle.com; dmarc=none action=none header.from=nvidia.com; Received: from BL0PR12MB5506.namprd12.prod.outlook.com (2603:10b6:208:1cb::22) by BL1PR12MB5032.namprd12.prod.outlook.com (2603:10b6:208:30a::12) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.4264.20; Fri, 25 Jun 2021 12:48:13 +0000 Received: from BL0PR12MB5506.namprd12.prod.outlook.com ([fe80::3d51:a3b9:8611:684e]) by BL0PR12MB5506.namprd12.prod.outlook.com ([fe80::3d51:a3b9:8611:684e%8]) with mapi id 15.20.4264.023; Fri, 25 Jun 2021 12:48:13 +0000 Date: Fri, 25 Jun 2021 09:48:12 -0300 From: Jason Gunthorpe To: Anand Khoje Cc: linux-rdma@vger.kernel.org, linux-kernel@vger.kernel.org, dledford@redhat.com, haakon.bugge@oracle.com, leon@kernel.org Subject: Re: [PATCH v5 for-next 3/3] IB/core: Obtain subnet_prefix from cache in IB devices Message-ID: <20210625124812.GS2371267@nvidia.com> References: <20210616154509.1047-1-anand.a.khoje@oracle.com> <20210616154509.1047-4-anand.a.khoje@oracle.com> <20210621234913.GA2364052@nvidia.com> <012d6cd2-5167-ed81-80db-444fd2741ea8@oracle.com> <20210624175458.GR2371267@nvidia.com> <5fd99709-8a90-e875-1ed2-74f5bcce6eec@oracle.com> Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5fd99709-8a90-e875-1ed2-74f5bcce6eec@oracle.com> X-Originating-IP: [47.55.113.94] X-ClientProxiedBy: BL0PR02CA0061.namprd02.prod.outlook.com (2603:10b6:207:3d::38) To BL0PR12MB5506.namprd12.prod.outlook.com (2603:10b6:208:1cb::22) MIME-Version: 1.0 X-MS-Exchange-MessageSentRepresentingType: 1 Received: from mlx.ziepe.ca (47.55.113.94) by BL0PR02CA0061.namprd02.prod.outlook.com (2603:10b6:207:3d::38) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.4264.18 via Frontend Transport; Fri, 25 Jun 2021 12:48:13 +0000 Received: from jgg by mlx with local (Exim 4.94) (envelope-from ) id 1lwlFk-00CWe0-C4; Fri, 25 Jun 2021 09:48:12 -0300 X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: 02fd808f-087f-4d58-f3bc-08d937d77e98 X-MS-TrafficTypeDiagnostic: BL1PR12MB5032: X-Microsoft-Antispam-PRVS: X-MS-Oob-TLC-OOBClassifiers: OLM:7691; X-MS-Exchange-SenderADCheck: 1 X-Microsoft-Antispam: BCL:0; X-Microsoft-Antispam-Message-Info: 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 X-Forefront-Antispam-Report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:BL0PR12MB5506.namprd12.prod.outlook.com;PTR:;CAT:NONE;SFS:(4636009)(39860400002)(346002)(136003)(376002)(366004)(396003)(38100700002)(186003)(426003)(4744005)(2616005)(1076003)(9786002)(2906002)(9746002)(33656002)(6916009)(316002)(26005)(5660300002)(83380400001)(478600001)(36756003)(86362001)(8936002)(66476007)(66946007)(66556008)(8676002)(4326008);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?rOQ5AFb19a9nxD+40KwpM/QQjiHsohYuHiXX5/CHlXaDXOyowrswuQRzWg5X?= =?us-ascii?Q?2mFqZGE9/TeBUN1cEi2lRWitIb3jAmm/BhzhWzZRsB5PRx7XeJ9WjVizjmPf?= =?us-ascii?Q?lUeZ+lti8HNT0pS/hE/jR4GlHYbr0I20GbiD7M0ux2eagqxF/xC0KNpGk+Z7?= =?us-ascii?Q?aqYNAKe1waTLaCi/JDH3TCzSpWzk/vGoZ1+IrsriMO7TFbfTsDAmi3bWIw80?= =?us-ascii?Q?tia7XXefsxXOjUAEuARochKGUdwQuYoc+Da8IVqxZobWxZ6megwhddoTmH4M?= =?us-ascii?Q?TAA8IaTPd42f7JoHF3Y3u155dmWaJ7quzI7l6CFRLorEQT9Oh9/KHVpz3wNk?= =?us-ascii?Q?t9tIicDMkng9bmoy+CA5vIulGzuUfbxu+ukVsm8/yMjnkNIGHaM5ZAmiT62q?= =?us-ascii?Q?FTZv1KqTKuLYyYR01vPz8iUZMO4yBi1W26JWSTHTLZLo8NZtowzsA+1iW/8F?= =?us-ascii?Q?PhXYPES/bf+09q1TnpSxJh5E2wejhaWtS4Fk+1YARCbEndqY3XG9/QqFG8Kv?= =?us-ascii?Q?vYGM3rng/0dUXYPXnsjEZ6o0Dj7ZHk99mslEqkIOh2hq0LEKILMAwsaSqP+L?= =?us-ascii?Q?FYSgft82SP1UMTNGlnHB8gd0LXguN8DIGStiSkeR6b4zuKZcgpMV/hZSsvqF?= =?us-ascii?Q?uxR9NS776yETba6Q36EtzWkh5mCtKhbRY+1U2+8b3NgzWi8vAlvwoD8PJp2j?= =?us-ascii?Q?HyQK60SDT/munXrqxyhPRJI/BISs+uNHPkX8y4EAjzRSluGP34YZDTdwF4C2?= =?us-ascii?Q?je5EhoIOC7Xnl6/+3IRelI8POq0p2V2QBUdV9Ll77KSSkh9JtKRdMnD1POFf?= =?us-ascii?Q?IH0P3KbX3v46uRzLHjGf4iaKrButEYDcFSZ2okjj2QemgPOfiYikfWbT+XTY?= =?us-ascii?Q?bauTjUaqtIxSg6o5U8Gx27NIRpi2AmmhwWin3uppSnBekTGuiA0qQkvvnhAJ?= =?us-ascii?Q?ZuI/SLHkbrBqhPbqEMcE2IKoeB4HZ8tRyloVb72ka0ynZn6+JQfPOODzmg1F?= =?us-ascii?Q?ohyrWuwBU6QfwdDS6kfjZy2945oYOE7oxVtk00unb236iC01FH2dtzXPqElg?= =?us-ascii?Q?AVEccBZ9HnkC23jt40jMNIqO5L6Wdb/8oRXJTyLwTCzuz5iLskPD2FRj4lsg?= =?us-ascii?Q?0SXb4bTVaryLF796/u0FlIqDPJZ5Fk0MHiAy7d/ZADuKH5aJB1IJtUPA+G3c?= =?us-ascii?Q?eTR5atjsUSbBslWmOLUy+hapXlxXieMkLZtdw6hQGdt0gMp+ldj2a4fh4hYW?= =?us-ascii?Q?DU5h1MBQFC8iG/or68g2+duV+nPnFsI2V3r8wyE72/a/7NJRGgdliG0wyhsv?= =?us-ascii?Q?a3X627fQYafYBFzdWqyIAzQm?= X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: 02fd808f-087f-4d58-f3bc-08d937d77e98 X-MS-Exchange-CrossTenant-AuthSource: BL0PR12MB5506.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 25 Jun 2021 12:48:13.2449 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: yXGYXXgoCDGwUSsFXRVCRdvwujquoG3QLfl4MRhr14Ak3uoZK1+hEDYbpzZeWwls X-MS-Exchange-Transport-CrossTenantHeadersStamped: BL1PR12MB5032 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jun 25, 2021 at 11:33:58AM +0530, Anand Khoje wrote: > > If the above change is to be made, there could arise a scenario in which: > In case of a cache_update event, another application/module could try to > call ib_query_port() and read subnet_prefix while the cache is still getting > updated and the application/module could end up reading a stale value of > subnet_prefix. Applications relying on this data must hook the event and update their state when the event fires. So long as ib_query_port returns the correct value in the event handler it is all OK. This whole thing is racy - the HW can change the subnet_prefix at anytime, this is just shuffling the race around. > - Is it possible that different GIDs in the gid_table will have different > values of subnet_prefix? Valid GIDs should have the same prefix Jason