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=-5.9 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 E2259C48BE0 for ; Fri, 11 Jun 2021 17:41:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C9B4961287 for ; Fri, 11 Jun 2021 17:41:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230298AbhFKRnw (ORCPT ); Fri, 11 Jun 2021 13:43:52 -0400 Received: from mail-dm3nam07on2042.outbound.protection.outlook.com ([40.107.95.42]:19040 "EHLO NAM02-DM3-obe.outbound.protection.outlook.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S229480AbhFKRnu (ORCPT ); Fri, 11 Jun 2021 13:43:50 -0400 ARC-Seal: i=1; a=rsa-sha256; s=arcselector9901; d=microsoft.com; cv=none; b=Z9Vk1OYvDRfEie6uNocfeTNA9U0moZOdRxIA+hgHUPj9+szoV8QpFbtpbpOZHIgTt3JZQqHyNVINS5/MeCnAeGA3ZgvyPzGLr9qWMFcvpSq/gfMonpGj1gjR+nKbMAyKWA2o6lJOq2HzLhkOjmKzGSYke0Bx5k41h+HBfD9jaD1B3Pm024iWaEFaQ+uG0Ss25x/NOzDtlVnO0nTfsNWdfpPdDur9cLRt6cLz+KGUyQukrgwz8UOyORrUq01BZowesTH4nu0AZEFj9/qTTp4elhkxkPkCu+1zXr1dTPPgCFMEGOCUKhTFxFuDgvDFEFnr9KSyP8CF49dA83IsW+83IA== 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=hsEPWM3dnplZ2FTYTGniMDIr0FIIXLaB5QVLu6DLia8=; b=MOhfWR/kwbosKZF2M+togM/l8EFvDokbfkYnYoERqHTCNEyue6tQFQjdmKgGnGfhOdxfyNImqy9EjvegPFEn0y+7cOifti0NiCpUMvsCOswtwitAk4hrjZEmRtzkd5NWPqfgLOs5RtNFlH0AwUVK4Es0+lsLQrc76XK1mwlarwCwpnoal0A6FR+sFzOdavIYbi+OC3vuF7+uGAW682elvaX2FGvuEBHdN0mCyHAgNgyst3Pf13AFPb7wMxeT8Ck56sH2M0cz0MucaXT/BY3xvDesF+Esb7Sktbl9+jpGl6l+1niVZslQf48eLQCHXATr4gAvphcLOpSaONWnuxlj0Q== 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=hsEPWM3dnplZ2FTYTGniMDIr0FIIXLaB5QVLu6DLia8=; b=GMyqHLZD2njfTrQjrNodepsoRZJvZQNXXcaXaKICepfHNRoJYFGGn+l3QmFKW8QjqR48ZfgnR+uZnBsiId/SvhBIJCLv0BHPQ9rW+wryidqYMi/ZRbTNVv7kgK0bVLmw2ee265r7xn08glYg52fOOQPVel6+Kh+QRV4qPw9tc9hUMevXc6e40PaaBe7xnXjAkJmFQriELOauVsywTPx8tEhYWkraOes0wKfFti9jXAujLwuU+vPVzcIVPldr7tflLvUqg9FIqApALq88O11V9fuyd/QM8APKbz+xA6xNysEDmZj+kMvDIISwi0OQA5WakV77XQqdUqRmPH8AC65Wnw== Authentication-Results: redhat.com; dkim=none (message not signed) header.d=none;redhat.com; dmarc=none action=none header.from=nvidia.com; Received: from BL0PR12MB5506.namprd12.prod.outlook.com (2603:10b6:208:1cb::22) by BL1PR12MB5045.namprd12.prod.outlook.com (2603:10b6:208:310::15) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.4219.21; Fri, 11 Jun 2021 17:41:51 +0000 Received: from BL0PR12MB5506.namprd12.prod.outlook.com ([fe80::3d51:a3b9:8611:684e]) by BL0PR12MB5506.namprd12.prod.outlook.com ([fe80::3d51:a3b9:8611:684e%7]) with mapi id 15.20.4219.021; Fri, 11 Jun 2021 17:41:51 +0000 Date: Fri, 11 Jun 2021 14:41:50 -0300 From: Jason Gunthorpe To: David Hildenbrand Cc: Tony Krowiak , linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org, borntraeger@de.ibm.com, cohuck@redhat.com, pasic@linux.vnet.ibm.com, jjherne@linux.ibm.com, alex.williamson@redhat.com, kwankhede@nvidia.com, frankja@linux.ibm.com, imbrenda@linux.ibm.com, hca@linux.ibm.com Subject: Re: [PATCH 2/3] s390/vfio-ap: introduce two new r/w locks to replace wait_queue_head_t Message-ID: <20210611174150.GX1002214@nvidia.com> References: <20210609224634.575156-1-akrowiak@linux.ibm.com> <20210609224634.575156-3-akrowiak@linux.ibm.com> <20210611170526.GU1002214@nvidia.com> <7ed059b0-5d58-eeec-167c-280917b47c00@redhat.com> Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <7ed059b0-5d58-eeec-167c-280917b47c00@redhat.com> X-Originating-IP: [47.55.113.94] X-ClientProxiedBy: BL1PR13CA0148.namprd13.prod.outlook.com (2603:10b6:208:2bb::33) 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 BL1PR13CA0148.namprd13.prod.outlook.com (2603:10b6:208:2bb::33) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.4242.9 via Frontend Transport; Fri, 11 Jun 2021 17:41:50 +0000 Received: from jgg by mlx with local (Exim 4.94) (envelope-from ) id 1lrlAE-005hcg-36; Fri, 11 Jun 2021 14:41:50 -0300 X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: 05ae0b69-739b-4b5c-1c4b-08d92d0031df X-MS-TrafficTypeDiagnostic: BL1PR12MB5045: X-MS-Exchange-Transport-Forked: True X-Microsoft-Antispam-PRVS: X-MS-Oob-TLC-OOBClassifiers: OLM:7219; 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)(366004)(346002)(396003)(39860400002)(376002)(136003)(8676002)(26005)(478600001)(4744005)(83380400001)(1076003)(2906002)(38100700002)(186003)(426003)(8936002)(9786002)(7416002)(33656002)(9746002)(316002)(36756003)(6916009)(86362001)(66946007)(2616005)(4326008)(5660300002)(66476007)(66556008);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?mH7xkTTLBA5eXGXWifa8YNPC5aVoM3a+JLGkY+SoQzBNH4ZrizafERKq2VMT?= =?us-ascii?Q?GNYNchf75wg/+3x3lgr1Dw3Zwa0qXPiwEZHujBBBS+0jl8PtUNOQK9ZiPYTz?= =?us-ascii?Q?h2IdvEtDsBaDTBTUCN3Vndh6n6dUXI3gLrPiP7S4KxtrGvG9mNhkRcQZOFJj?= =?us-ascii?Q?S4zZMr783DkBZb19CxdsK8jAEAIiTF6s87fbOFEuV/L6G/HjDCt9/rAtSWDJ?= =?us-ascii?Q?b5UH5ba+x9ZXn82cs1brn1lHxbu2n49Q1oAH2UD42ReXDCtlkQH1XTD/nXP0?= =?us-ascii?Q?5yYbXxIacpmYFXxGCBkQ53xjMNtmEZr6V98FsdSivgGTQcd3oU6lTm2wdhnN?= =?us-ascii?Q?af8tFiFU0OnW10XmqUKd4TiLoR3IH0y14qczL3Dgtidi0aH+0yu1YX7edFKB?= =?us-ascii?Q?Cvwa/qOXZ/+nmbKt8QkfyY7BC53vcAWYR0TaUNNPUS8kilqANqz45zzEZks0?= =?us-ascii?Q?V9AFSnI94gClbdrx7tLR5yYvmt2xSXAwzAC0xIPT0IkHBIOgnBdruV6bl2rj?= =?us-ascii?Q?qIvyi/b1QfOfEa5cArEMEWe4Vw3S/FVoslo1iT4GwTjAde0IqDhX3XbRwO5d?= =?us-ascii?Q?3ay7Q3bvjXcVownd5iBPHL8cnUVnS60Diuca0t5D2wodlZb68tW0ZN2EsjIc?= =?us-ascii?Q?S3je6M2OMca+yPLpyEnErC2V41DybPcCIpWqpi3RVSrJo6+sp48h7lkQ6avT?= =?us-ascii?Q?vU7j24iQ3wLYm/jhgGdHGKnjoSsDT5jYeoRnju3RVgBrERMEXuBKt7QekLTN?= =?us-ascii?Q?258PnBnlEEYgv179iFenAeMlUroh3o6h4se+/ZQ57vDRo3xxcztkg5+ajorH?= =?us-ascii?Q?AorBILI2U/LLbSP4knmGyvdMrVKY00M+T4P/wT1g27vRqbvPKWkh3HyRhxVq?= =?us-ascii?Q?8DZiL4sQN7aDKfJ/A7AnxonreVms0yllKIaIwGCC53yb/x755e8MOlua1b6L?= =?us-ascii?Q?vPqeHaTfIzPpV0lbBuSqzFdu3FOwrR3YRXuiWmc8dXWfr0q+Yar/fcGbTPYa?= =?us-ascii?Q?mYERcWh3vGyoclucbHCF4Xn/m7CmNn54K/aAU6jb66vw2/k5y9+GDFViRWKW?= =?us-ascii?Q?y5Ltlm1OM69r1Z5Po2bFJVPj6ChAovDJqghG6OS9fbRuIJpQDm3g+PfkQdlT?= =?us-ascii?Q?t4/pduMYz/Nln2JnS9j0YLDsinjB/U9FYAU6sA3XwvkPh8mdGSa7LmXstxm0?= =?us-ascii?Q?cPQicSGQOoZ9lkoVHBtAMr+PWwFyll3bkGgzUAijfT0tFUNamf64n/WpS+hU?= =?us-ascii?Q?Mc8vPAqqJXsQ7HQP+Q1y5vAfwaQWR6uFzzp9SJjLu36jqoueZIvEnUmmOSmS?= =?us-ascii?Q?orRlTwBQsXStuqNHcVLvOqGX?= X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: 05ae0b69-739b-4b5c-1c4b-08d92d0031df X-MS-Exchange-CrossTenant-AuthSource: BL0PR12MB5506.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 11 Jun 2021 17:41:51.0975 (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: LofcJAUmi1djM5YaJunc/1C1hF+FQhHwaCnwnwb7zJqXkERSlqpUQqvvY0WLj/G5 X-MS-Exchange-Transport-CrossTenantHeadersStamped: BL1PR12MB5045 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jun 11, 2021 at 07:11:50PM +0200, David Hildenbrand wrote: > > Also, not convinced down_write_trylock() is appropriate from a sysfs > > callback, it should block and wait, surely? Otherwise userspace gets > > random racy failures depending on what the kernel is doing?? > > It might we worth exploring lock_device_hotplug_sysfs() which does a > > "return restart_syscall()" with some delay. The ideal design from a sysfs should be a single down_write_killable(). restart_syscall will just create a weird spinlock that is hopefully unlikely to spin :\ Jason