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Wysocki" , Danilo Krummrich , Jonathan Corbet , Shuah Khan , Laurent Pinchart , Wolfram Sang , Johan Hovold , "Paul E . McKenney" , Dan Williams Subject: Re: [PATCH 3/8] char: misc: Introduce misc_sync_register() Message-ID: <20260428160956.GC718365@nvidia.com> References: <20260427134659.95181-1-tzungbi@kernel.org> <20260427134659.95181-4-tzungbi@kernel.org> Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260427134659.95181-4-tzungbi@kernel.org> X-ClientProxiedBy: BN9PR03CA0324.namprd03.prod.outlook.com (2603:10b6:408:112::29) To LV8PR12MB9620.namprd12.prod.outlook.com (2603:10b6:408:2a1::19) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: LV8PR12MB9620:EE_|CY8PR12MB9033:EE_ X-MS-Office365-Filtering-Correlation-Id: 47e698e7-65bf-47b1-6826-08dea5409776 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|7416014|376014|366016|1800799024|56012099003|22082099003|18002099003; X-Microsoft-Antispam-Message-Info: 54AYvgJRndRFx1ZI8r3SQtJ0OTtqhBXmd+vXrOfcE6aG+8LH2ljlSuCMgvr1M8gaG0LhSyf0BCtp1jwVtrEE5MOswQpm+fmNPFlrzeg9CufnSKv7F2A0VEgCZkCYM+4wHry+bSG+Kl5cd0o6RzJanqYQ+YNVjggNRaMf3BvYjvo4iIoIeRBkAZmr9tYwPmPXKLie0UP8jvLzhIJmzxLvE+MtzgdlBcfoVcj9noNU/yGjABsVto3P52/AJGNbhWy63GudVHqlqhODGgcfrGUW5CPcRS76Rt7BGlqeNgUPuXt0wG1Ku2CO5Zr3x1Q+D+ZOxRDxM5GhH4yFIEh71Mf2rvYLo+yKV671/eXqjZI/mOueQjIbizgAfW4mJclqgenEeno1D168xEEfWqZufb8lHRc2bMQDwKJTLaX94w8I8QsoX1z4yQvjDbG0oNmlDqDX+lzizZO4oHgav7G7MYNNqFpfpOLgFHrJyb+Dzy1dvBHvzSHfIB4dXMZfd/14FsfUISj/C7KS3DfoiwSo813zU7TIY4Q+ae08P30n/swn8sUEkGEVlDBkcpxzXtsWYMFwF/s8ImCL0L7j5kxd8U0yLGVQ6zWKyg0lBBEt/dx+TBKNzXk3F58DS45U91y7WD4xad8CqlS6+4IRGDz3q7e4wi9ctKG/jh0iJBOr5Rgjykl4MN9Rl+hkXidyWgNePDCEJ12/fdmSCpbp1TicIR54VAiVaCZ7H6TOYYkvkcsEY+k= X-Forefront-Antispam-Report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:LV8PR12MB9620.namprd12.prod.outlook.com;PTR:;CAT:NONE;SFS:(13230040)(7416014)(376014)(366016)(1800799024)(56012099003)(22082099003)(18002099003);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?f9LP9oUhsbbQrxI1Y8mc1GidFbYQXIvHYKVz2d8PrUmIj5yxZcG0loZO+Rzn?= =?us-ascii?Q?mWR/QuVaTYjorELSaJRSMvvUQ/2LtQTLpsn9hF5eSJqsEiI65z9IPrkpgN3q?= =?us-ascii?Q?MFdqhxZrV3z9tk39cdf2aP7mXYr6Gqvv/U3iMwB3QWMgm5RLSskR/dUU35nm?= =?us-ascii?Q?4+uyfxmOuQ13mtqAbsXQpcx8mNJlXo6O8/mmBr4L9QaW/mogY36Ajfzx6Cwf?= =?us-ascii?Q?HjXI03OUOMO04lYjVYyZINilSSbmIsy2VDtxXz1H32pTfIuxBSHGSIeJ2oen?= =?us-ascii?Q?7q2nnMM9I4Tyt9J4SAsk/w07Xgm8IvGFcOYj2GMre0WOX5sidCZEGJ58llXB?= =?us-ascii?Q?u1y2h+R10n1y6kBfrgz3vVBT3KZwI0Q7VCWEmEFS8hsOGvw9vIY+Kdiy2OGw?= =?us-ascii?Q?i4x3JR/h/i3bSSnlc3Q8Cy7fOri7b7Y5hu6ZrlYLg7bIc148oXM50YHKbkdE?= =?us-ascii?Q?r7JALr0iE6BghADdQ9HzRZh7uWNi/wD2GTAZQAxEszJvaR8M2Ensylna2gJ3?= =?us-ascii?Q?a1TJmoTnlMEG9mEFCk2QlAxTdjzfpJ8fbJPnUeCwvhJwb+5jp642Cy0CDpoB?= =?us-ascii?Q?7GRGcAsIhHpVV0cWkF0pcT90rbZE5DhJaMTpdq1UwaoDrw0j8ZC06io021/P?= =?us-ascii?Q?Y3fbvB3FWlswuKNJq/eqexVMrYqsEzbEB/wi2Wa98b5gy49YQupRg5Q++nAR?= =?us-ascii?Q?zuJWv3qFLkUqvO1pwkdnIgqNHjkzk9jbvFahgYZBo9fCvE9AHs+197aqNzsk?= =?us-ascii?Q?ng9PV5Wia2GeQGbjSJ5v/y0d9V3HtKmpJPXKfP/pctY9FdenS6ob/WcH5H1I?= =?us-ascii?Q?5QsIPMHwe6SxnWuLyNF3tq5DxkjW+su6tUoORipvNqy+crqdpFLCcYHXbbq+?= =?us-ascii?Q?hBWy7fJY8+Q5o0Rb+DbkiKCwqwY3hwDpsH6jYOVYdlrnHCi0Y5Q+QeH5RkHX?= =?us-ascii?Q?5WybXPFCNYMwzpQaes8iTK/IUS5gBSdx/XVl3saI2RHd7BjckO08Fae+q1Ff?= =?us-ascii?Q?WXyy1M1hFRRxMKj94wAdBOJCm6YPYfQ/j8E42nyCQDqcfCmgd/VbVZH1SOON?= =?us-ascii?Q?ilyzTs4ai4EwFYlMYIoPDvKwk6fhsTVfDYzucfwSRJGBhfL49NfCL4BN4u3W?= =?us-ascii?Q?U0tqZZ+JD3GiVM8gb/dxM8vEoEz3AeFQq31CyTnHgRa43NrfiJ9vxHN1s8gs?= =?us-ascii?Q?aOQWUAtrHVdWt3LVuFhfail5PXU+ake4is4sgLOr8q2nJs9/xwEnqGIpRAZ+?= =?us-ascii?Q?6tuHiL8nVoAAmxy5r4/Pjxw7W3W6XpXoDACeQGLN1BcB2MtJX6DR6ryIi0+4?= =?us-ascii?Q?0kLNBXBBOYfociIVJ2BD1pP0boFjY9uGcQKsK2bIiZritSa9sHPmmOXBRZ+f?= =?us-ascii?Q?Xcrar0xdJ2VvdcBzZaeJ5PsO1xzGlD7zeHLe1NrYOV+EaC7/L0nY4gEzlHLX?= =?us-ascii?Q?xtqmzdPP/lz08BV24nNOIP85Qy4uMwJQaKjNKmn/+01T4v102BU50J4X79WG?= =?us-ascii?Q?tBN7N/72ASTej4ODmy3S2jRjbNi+pNudFT+JlNWjoZXv8dMT2xNH4e5xaWmB?= =?us-ascii?Q?usr3SFOttgj1i6wssplKkknVT4qqWC3A7YdQDVmo7L/MwponwJgqqKPPIo0d?= =?us-ascii?Q?jDyGfyahxhWImzwVqcCjTtUMJR1w62SM/l1xAZGqI4bcnv2a2mWBxf60EBjB?= =?us-ascii?Q?MT6szBH2/7Bi2kq1eRj/DRXQr+4pQh5HI1rsJIbBqGBtLYib?= X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: 47e698e7-65bf-47b1-6826-08dea5409776 X-MS-Exchange-CrossTenant-AuthSource: LV8PR12MB9620.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 28 Apr 2026 16:09:57.3823 (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: vadQq9f+jlUtvXI26tBILuJvVblCWcoSEQWEdzYfQNnRmRY3q1OrgOz2bVlZ7oQI X-MS-Exchange-Transport-CrossTenantHeadersStamped: CY8PR12MB9033 On Mon, Apr 27, 2026 at 09:46:54PM +0800, Tzung-Bi Shih wrote: > Introduce misc_sync_register() to support synchronous file operations > for misc devices. This aims to prevent Use-After-Free errors when a > device is deregistered while file operations are still in progress or > files are open. > > It creates a synchronization context that wraps supported file > operations and ensures the device is still registered before invoking > the file operations. > > The minor number is deferred from being freed immediately on > deregistration and is used as a primary key to search for the > synchronization context in `misc_sync_ctx_list` after the device is > unregistered. > > Performance impact: > - All file operations are serialized by a global lock. > - All file operations perform a linear search to find the corresponding > miscdevice. This doesn't seem like a serious proposal, this is too much performance cost. Jason