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McKenney" , Steven Rostedt , Uladzislau Rezki , rcu References: <20241106153213.38896-1-frederic@kernel.org> <20241106153213.38896-3-frederic@kernel.org> <68c39e33-6281-4978-ba4e-131c6336aa7e@amd.com> Content-Language: en-US From: Neeraj Upadhyay In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-ClientProxiedBy: SG2PR04CA0184.apcprd04.prod.outlook.com (2603:1096:4:14::22) To DS0PR12MB6608.namprd12.prod.outlook.com (2603:10b6:8:d0::10) 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: DS0PR12MB6608:EE_|CY5PR12MB6156:EE_ X-MS-Office365-Filtering-Correlation-Id: e02239e2-a81a-4d40-329d-08dd03925f02 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|1800799024|376014|7416014|366016; X-Microsoft-Antispam-Message-Info: =?utf-8?B?QTZjdUYzUWU1QmFCVDlmakdra1dkS3k1V0IxS1F1UmhVV3dZM3NuWEFndXlr?= =?utf-8?B?aUltZ1hTZXlBRVdvMXhTRmJaOXhhM2FIQVN0QkJGejQxWFprbzZKd0dhbGNX?= =?utf-8?B?bDlQcWZFNmFyNWdGUVFFZFJrZzBtMnQ0TzZKaDlMbGJVV0d3UG1YRXk2amps?= =?utf-8?B?NzlURDlrL2lZTmUzRVkyb3V3Z01XQXZGTXJTMlhTUTZYaWVoYnVuZWR5SFdG?= =?utf-8?B?NS9GS2lKUVgvNjR4RWlLcWdsdEtBeXBRVjhIYSs0QkFWN25iWERKK0dxSno3?= =?utf-8?B?QVQ1bEthYjZVTlZDOWZsWHlDWWpkSVZhTzRjRGd4WXBSSDk0U0VFekRxaUdq?= =?utf-8?B?YWZnQWZndGNENkxvUDVGRURya0N1UW1STGJPYUV2ZXMrbG1TV3M0Z3hIOXNM?= =?utf-8?B?RittQTZRcUNRdlJnZnBGY3dDUG5pdVdKZVA3d00vRGt6Y1lLQWhDT29yZnJU?= =?utf-8?B?YzBwOXY5QUs1YmlTamthQzJPMXZCRDEvVFo2Zld5YWQyTU9RT3FaSmJSYURK?= =?utf-8?B?dGlhM0wyZlRRK0ZZOWRFcGZ5T3NITUthK2VmaXpFMnpRcHN1aVNYd3pDeVRS?= =?utf-8?B?ZENPUzhaVnZXdHpJdE5JV3o2ZlVaSE8yWDBSUUFGaGZwR2UyaFl2U3ZqNlNK?= =?utf-8?B?VHgvL3hKVGZDcktvYTB1N1BTQVN2WU9meWFuSUc5NEY3OXFwcERDMnVPcnRQ?= =?utf-8?B?MjYyUTVxT3g0b0hUMEpVci9TWEcvamJZbFhlbmdnZEdHMnJmME56UktVOXZu?= =?utf-8?B?N3IzZjl5ZnZEYWk1SWhzL3IvZW9FZTZmdi8wWmdDbm9zblh6VTY3ZHM2RFhV?= =?utf-8?B?SGV2WnZKRUtGWitBZjYvay9qNStRczVDT0JYV3NGM1FVbUpzQ0VJSEJ3OGk3?= =?utf-8?B?c2JHUHdFOEhKMEdjNmNRbVlXSk4zVGFhUjNacnBKM3ZZeFd2UnVnMHZpOFJi?= =?utf-8?B?MGpaZWhaM3k5UXRiYkgvK242M01BTDNwc3BrQk85NzdiQ0FwYlZ1ZFJxR3lu?= =?utf-8?B?bDhtcjF0Z253Um5SQ25sWXNmVjQ0Ly9CcXc1NHpIWGhlYm1IRlRnenl4MnZm?= =?utf-8?B?S2xtdjRNUUtUYlR5cERwMGJNYjZpMklacXRGcWgyUFNCOHRnWDU0Qzg3TXRY?= =?utf-8?B?dzhFV25XZ0xyMkw1THpIa1kyQkI4aGRMbmJCd0RObGVlWHoyK01USUljVHda?= =?utf-8?B?RmRBNHhtUVVVZ1pmWW5vOThab05zNnlwWjJpTlphSGluVld2STQyblprTVZG?= =?utf-8?B?Tm43aWJZMG1nZm1nSS9KLzg1TFJyZUlzc1V1MlpGejN0dThPVEhmeUJYY2Fp?= =?utf-8?B?bzkrNmxXUUp4MkEyTkZ2dFFJamNGeTFsZEc3QlkxWDdVMTB1a1p5bUVxeTBW?= =?utf-8?B?WmVPQ3FCNWVxWnhpeHJZcW9GdjgzSEx5RFk4Z01rQ3NIbUxNQU0wdWx3RFY4?= =?utf-8?B?SHl1QnhkakxjOGVkUHJ1ang0M2JIb1JuaWd0K3V0YnljMjY3NytldTNMbzJG?= =?utf-8?B?QUpNeW1rZEtLYUJORzU4Z2JiSzFHa3l4dG8zNTJscThvZUllMlhlUEJ1dVFQ?= =?utf-8?B?Ymk0UnVLNXVENENScUJIbWhBZDdLVW9Ocmh2a1JNanpaN0pZSEhYdG9kRjBH?= =?utf-8?B?dzg0SHFhZVZrcGtYaTJzVkZEMzRXWVhQOVF0Q0x0TE5xajNDRDE5MFFKdVVD?= =?utf-8?B?THBxREZya3RveU81Z1liK2VmTWtEWDUxWG9iV3Frdi9FVFRhT2l1SW9XN0FC?= =?utf-8?Q?DVCerIhHk9YERFhJ2aG+E2h9mL0Dm1eH8ZbXgl4?= X-Forefront-Antispam-Report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:DS0PR12MB6608.namprd12.prod.outlook.com;PTR:;CAT:NONE;SFS:(13230040)(1800799024)(376014)(7416014)(366016);DIR:OUT;SFP:1101; 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>>> if (kthread_should_park()) { >>> - kthread_parkme(); >>> + /* >>> + * kthread_park() must be preceded by an rcu_barrier(). >>> + * But yet another rcu_barrier() might have sneaked in between >>> + * the barrier callback execution and the callbacks counter >>> + * decrement. >>> + */ >>> + if (rdp->nocb_cb_sleep) { >> >> Is READ_ONCE() not required here? > > No because it can't be written concurrently at this point. The value observed > here if kthread_should_park() must have been written locally on the previous > call to nocb_cb_wait(). > Ok, got it. I was not aware of any other flow (other than the one described in this fix) which can race with it. So, asked. - Neeraj