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Thu, 24 Oct 2024 14:29:28 +0000 Date: Thu, 24 Oct 2024 09:29:23 -0500 From: Ira Weiny To: Dan Williams , CC: , , , Subject: Re: [PATCH v2 2/6] cxl/port: Fix cxl_bus_rescan() vs bus_rescan_devices() Message-ID: <671a59c390a88_f5b202943f@iweiny-mobl.notmuch> References: <172964779333.81806.8852577918216421011.stgit@dwillia2-xfh.jf.intel.com> <172964781104.81806.4277549800082443769.stgit@dwillia2-xfh.jf.intel.com> Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <172964781104.81806.4277549800082443769.stgit@dwillia2-xfh.jf.intel.com> X-ClientProxiedBy: MW4PR03CA0338.namprd03.prod.outlook.com (2603:10b6:303:dc::13) To SA1PR11MB6733.namprd11.prod.outlook.com (2603:10b6:806:25c::17) Precedence: bulk X-Mailing-List: linux-cxl@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: SA1PR11MB6733:EE_|CH0PR11MB5316:EE_ X-MS-Office365-Filtering-Correlation-Id: 24dc127c-c05f-43d1-0ccd-08dcf438441a X-LD-Processed: 46c98d88-e344-4ed4-8496-4ed7712e255d,ExtAddr X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|376014|366016|1800799024; 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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?lIPm3aXf2pS+I7Yv7OGeuiHXm1BY8oVVtPouFkin8z7n3scJDF8tdSQyHZpJ?= =?us-ascii?Q?xMN3tJu+t9FyWohkjxveiXQAv9lkvOmIuXR6yJxQLHsKNvi78c1RU0XsTMiB?= =?us-ascii?Q?8M3K7Uo2XrKP1J2gCS9y5xVPADuet34OPzv7cUdplrbn4A9/A5uVLb6RzvXd?= =?us-ascii?Q?MbjoQb4vvkbW84riKdVNpp3FGO1aGRypDmtoKAJLdU73SSMsrEdc0u7A6EEE?= =?us-ascii?Q?HjV1e3qahH3jpiS/IUAaTuk9NZqSkmeYbj2FO6llnN1cCtKa9GuQLf/a0VRJ?= =?us-ascii?Q?dEjes/G0OK/7zIJVLzL4LdDymK8uv0GLsT8NP2fEuoNNw3VHkc5adypdzSW2?= =?us-ascii?Q?7pDjYqFJsvQ5jQmwYOJcuam0yQ8N+uPpHgplIYwvZCTzzka7G/rnN4bApRkQ?= =?us-ascii?Q?ZfNGpMM0AHrZvTsNzSlQXVwbe983rMyswTDuPcdAdzN54pOFpSHhoWehM7pg?= =?us-ascii?Q?mIUIp3qLXxCNDiHJjb+CpgGjbqDgjpfBRd3ev651pXmBLK93l+Vo1cjeto5e?= =?us-ascii?Q?3JVkloYCuykjvB5vgkkOREZPwVTjhCZ2ssOMyoRJU0JfNqqAKgI2n71p8NR7?= =?us-ascii?Q?jDwrTHhWAot3g44KSHnNrGA0X4Ksy/+HLgAqUJJsW2ZWrWKMc5wZc25qaL29?= =?us-ascii?Q?PC1TTBDCcszK0TEjpm5tt/hbsMnSksaiNmuCH1KJ5/ElEBo1z0sJ7AjV0Ton?= =?us-ascii?Q?uwyAEeY6EWBRdaaluJfrdgin/SVLPD3F5c+3vVCbIbAPFGt+G6EKMV0KMonc?= =?us-ascii?Q?4YmIkMrp9a//yah6++jehdeY66h1uB+NeXnc2lHuK90Oap8Rvlezf2zfBpCJ?= =?us-ascii?Q?w5B0AAa/uAgnAqsAkP96T90IQnvyszj16HARVjNJK3lxdXBz9NipiYKMLyAv?= =?us-ascii?Q?cWsvk5zTlEgl2oPKrDvI8LYuEiVahieRJUpeXTDLqjm2op87B5TzQjzxKDtE?= =?us-ascii?Q?ZdDgIyEdo3UPFSmX2UyNk7d++DzyEFXQWR1sZH5HzStslcIu8GNyMjOLiAJj?= =?us-ascii?Q?BQOnbXMRBtC1cUjTDGNv8JpsHXntgWkw5kj0wat+vMz7eGXK6Gfi0PusGbF7?= =?us-ascii?Q?urmt/PfOrsBOWwCnX2ToZUztq+EK6zGuIbqVfwr6Stj795rUIpturrTiVhya?= =?us-ascii?Q?JN7NLxPBNaeIMB++rAcW+szxye2wr32LFqDpzcUYXqVqx0mz7+rXrPEceuwD?= =?us-ascii?Q?TYYiGZV8oNLkGGDgzOSdxk1o47vzK0jMxsG7cl4TVSVYegpzwBO8pywX20Hp?= =?us-ascii?Q?EclqN7nkbWxPv8Y22janDCMk/LrsD2XUbt35buZLqMPx6h4e05EmXBP4pvZy?= =?us-ascii?Q?M+5Iguyza4uO07Qj7FuemnwD0euPQTP7jXZBmtBPgBYh+tZpbFzvBdTNayQE?= =?us-ascii?Q?ksjvQgzzPOdCZWGqTV8OuEJOjdE+GcfJuIsIeKsim9kUBUjlANREMeFX+7De?= =?us-ascii?Q?02kU/cq52t9gHjn3BMYZ2dfnR51xPPbyGyPaxaPjo3scdXQD6bTrUdepirhp?= =?us-ascii?Q?ND0Ofkp96oOsAM2CtOGmylLeuc6yBLP75mTXIQNvb7PHJV6/LCmEiKoeaH3C?= =?us-ascii?Q?Zn7aaYexttUWQPABENB/tOBdjQf6vI1GAMjdo0yB?= X-MS-Exchange-CrossTenant-Network-Message-Id: 24dc127c-c05f-43d1-0ccd-08dcf438441a X-MS-Exchange-CrossTenant-AuthSource: SA1PR11MB6733.namprd11.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 24 Oct 2024 14:29:27.9227 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 46c98d88-e344-4ed4-8496-4ed7712e255d X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: ATzliztnkxTg70+K6peV5baTZG2pz20XESqAjnnwq+C4GmbOx5vF8e1619fZtMXJ0bMu+9KE8p8S+A2eTKKN6g== X-MS-Exchange-Transport-CrossTenantHeadersStamped: CH0PR11MB5316 X-OriginatorOrg: intel.com Dan Williams wrote: > It turns out since its original introduction, pre-2.6.12, > bus_rescan_devices() has skipped devices that might be in the process of > attaching or detaching from their driver. For CXL this behavior is > unwanted and expects that cxl_bus_rescan() is a probe barrier. > > That behavior is simple enough to achieve with bus_for_each_dev() paired > with call to device_attach(), and it is unclear why bus_rescan_devices() > took the position of lockless consumption of dev->driver which is racy. > > The "Fixes:" but no "Cc: stable" on this patch reflects that the issue > is merely by inspection since the bug that triggered the discovery of > this potential problem [1] is fixed by other means. However, a stable > backport should do no harm. > > Fixes: 8dd2bc0f8e02 ("cxl/mem: Add the cxl_mem driver") > Link: http://lore.kernel.org/20241004212504.1246-1-gourry@gourry.net [1] > Signed-off-by: Dan Williams Reviewed-by: Ira Weiny [snip]