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Thu, 23 Apr 2026 20:09:01 -0700 Received: from Asurada-Nvidia (10.127.8.12) by mail.nvidia.com (10.126.190.182) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.2562.20 via Frontend Transport; Thu, 23 Apr 2026 20:09:01 -0700 Date: Thu, 23 Apr 2026 20:08:59 -0700 From: Nicolin Chen To: Baolu Lu CC: Will Deacon , Robin Murphy , "Joerg Roedel" , Bjorn Helgaas , "Jason Gunthorpe" , "Rafael J . Wysocki" , "Len Brown" , Pranjal Shrivastava , "Mostafa Saleh" , Kevin Tian , , , , , , , Shuai Xue Subject: Re: [PATCH v3 05/11] iommu: Change group->devices to RCU-protected list Message-ID: References: <12a224061de4fff9e0725909fd0ba4e14996ff08.1776381841.git.nicolinc@nvidia.com> <779dad61-d7e7-4ae0-83a9-8c5920222219@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <779dad61-d7e7-4ae0-83a9-8c5920222219@linux.intel.com> X-NV-OnPremToCloud: ExternallySecured X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: MN1PEPF0000ECD7:EE_|PH0PR12MB999087:EE_ X-MS-Office365-Filtering-Correlation-Id: a21a36fc-d7aa-419f-1739-08dea1aedf33 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|1800799024|7416014|376014|36860700016|82310400026|22082099003|56012099003|18002099003; X-Microsoft-Antispam-Message-Info: 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 X-Forefront-Antispam-Report: CIP:216.228.118.232;CTRY:US;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:mail.nvidia.com;PTR:dc7edge1.nvidia.com;CAT:NONE;SFS:(13230040)(1800799024)(7416014)(376014)(36860700016)(82310400026)(22082099003)(56012099003)(18002099003);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: dZbDUIv1wFMx3HEb8mtHmyf9+CocfL9Zpg8hciEQ2as5xmL6Kks0W3DWV8Eol1EpY9o1aWIU5evnkckqaUAB4mjF6CVWhnqfPeqL7tX2gywfB02RP8vXDT87Bw7hf4Gojjg7r5QX4wUofDmu/UjnLdGLa8MSHRof0IUSIIHEXOokJYfXrJFBJeyRti6MfxboZK9DlDm6PHO26Aqw2pgL/Kh8HOEA8u7Q3+V7WjHa7tcFAoVLQIdpGPao+jm6nTQHTk1szPtkZEftgnHWMz42pIBIaThcxnTNJaw0Et2zV0DTp2UpBKQVZMvUYzlTxxZaKFT47veDKRrUgunXLL9Cv7092jsZWrcP/d7aYS4Xtz2Oh+WscspXK6uJT+SzzEe/r8xhyq5TK4RAAKoS4fZr5MSl3WHGKHv76fA4/hfkGC3hkRnGb1Cj/gtgKn7KFkEf X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 24 Apr 2026 03:09:17.2248 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: a21a36fc-d7aa-419f-1739-08dea1aedf33 X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=43083d15-7273-40c1-b7db-39efd9ccc17a;Ip=[216.228.118.232];Helo=[mail.nvidia.com] X-MS-Exchange-CrossTenant-AuthSource: MN1PEPF0000ECD7.namprd02.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: PH0PR12MB999087 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260423_200930_342149_BFC2D94B X-CRM114-Status: GOOD ( 10.41 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Fri, Apr 24, 2026 at 10:53:49AM +0800, Baolu Lu wrote: > On 4/17/26 07:28, Nicolin Chen wrote: > mutex_unlock(&group->mutex); > /* > * FIXME: Mis-locked because the ops->probe_finalize() call-back > * of some IOMMU drivers calls arm_iommu_attach_device() which > * in-turn might call back into IOMMU core code, where it tries > * to take group->mutex, resulting in a deadlock. > */ > for_each_group_device(group, gdev) > iommu_group_do_probe_finalize(gdev->dev); > } > > return 0; > } > > Will the change above trigger a lockdep splat due to this "mis-locked" > case?" Oh, I missed this one. That's a good finding! Perhaps we can just change it to list_for_each_entry_rcu holding rcu_read_lock() and drop the FIXME. Thanks! Nicolin