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Thu, 5 Mar 2026 13:59:06 +0000 Message-ID: <718ad034-8fc2-4b43-9b04-729c5befc3ca@amd.com> Date: Thu, 5 Mar 2026 14:59:02 +0100 User-Agent: Mozilla Thunderbird Subject: Re: dma_fence: force users to take the lock manually To: phasta@kernel.org Cc: dakr@kernel.org, Tvrtko Ursulin , Boris Brezillon , dri-devel References: <080395923c92ef758ca6062f1e01392186413015.camel@mailbox.org> Content-Language: en-US From: =?UTF-8?Q?Christian_K=C3=B6nig?= In-Reply-To: <080395923c92ef758ca6062f1e01392186413015.camel@mailbox.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-ClientProxiedBy: FR2P281CA0069.DEUP281.PROD.OUTLOOK.COM (2603:10a6:d10:9a::10) To PH7PR12MB5685.namprd12.prod.outlook.com (2603:10b6:510:13c::22) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: PH7PR12MB5685:EE_|CY8PR12MB8411:EE_ X-MS-Office365-Filtering-Correlation-Id: 9f41971b-3ba1-40ee-afc8-08de7abf5d9c X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|1800799024|366016|376014; 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> dma_fence_signal(f); // racy! > > > I think you mentioned that you are considering to redesign the > dma_fence API so that users have to take the lock themselves to touch > the fence: > > dma_fence_lock(f); > dma_fence_set_error(f, -ECANCELED); > dma_fence_signal(f); > dme_fence_unlock(f); > > > Is that still up to date? Is there work in progress about that? It's on my "maybe if I ever have time for that" list, but yeah I think it would be really nice to have and a great cleanup. We have a bunch of different functions which provide both a _locked() and _unlocked() variant just because callers where to lazy to lock the fence. Especially the dma_fence_signal function is overloaded 4 (!) times with locked/unlocked and with and without timestamp functions. > I discovered that I might need / want that for the Rust abstractions. Well my educated guess is for Rust you only want the locked function and never allow callers to be lazy. Regards, Christian. > > > Regards, > P.