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Mon, 19 Dec 2022 22:08:14 +0000 Received: from CO1PR11MB5089.namprd11.prod.outlook.com ([fe80::f5ad:b66f:d549:520d]) by CO1PR11MB5089.namprd11.prod.outlook.com ([fe80::f5ad:b66f:d549:520d%7]) with mapi id 15.20.5924.016; Mon, 19 Dec 2022 22:08:14 +0000 Message-ID: <234f11c3-b83b-3c7b-2ee6-8e90a761cae1@intel.com> Date: Mon, 19 Dec 2022 14:08:11 -0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:102.0) Gecko/20100101 Thunderbird/102.6.0 Subject: Re: [RFC net-next 04/10] devlink: always check if the devlink instance is registered Content-Language: en-US To: Jakub Kicinski CC: , , References: <20221217011953.152487-1-kuba@kernel.org> <20221217011953.152487-5-kuba@kernel.org> <84151471-4404-d944-417f-2982569f44da@intel.com> <20221219135541.6e0a7cfd@kernel.org> From: Jacob Keller In-Reply-To: <20221219135541.6e0a7cfd@kernel.org> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit X-ClientProxiedBy: BYAPR11CA0106.namprd11.prod.outlook.com (2603:10b6:a03:f4::47) To CO1PR11MB5089.namprd11.prod.outlook.com (2603:10b6:303:9b::16) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: CO1PR11MB5089:EE_|IA1PR11MB6394:EE_ X-MS-Office365-Filtering-Correlation-Id: bd3bf001-fa9f-4c10-23fe-08dae20d8620 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; 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So now the reference ensures less about whats valid. It guarantees a >> lock but doesn't ensure that the devlink remains registered unless you >> acquire the lock and check that the devlink is alive under lock now? > > Correct. > >>> This is a no-op for the most part, as the unregistration path currently >>> waits for all references. On the init path, however, we may temporarily >>> open up a race with netdev code, if netdevs are registered before the >>> devlink instance. This is temporary, the next change fixes it, and this >>> commit has been split out for the ease of review. >>> >> >> This means you're adding the problem here, but its fixed in next commit..? > > Yes, I can squash when posting for applying, but TBH I think the clarity > of the changes outweighs the tiny and transient race. I would agree. The only reason I could think it to be a problem is if a bisect lands precisely on this commit and you happen to hit this... what are the side effects of the race here? If the side effects don't include significant issues I think its fine.