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Wed, 21 Jan 2026 20:46:52 +0000 Received: from DS0PR12MB6486.namprd12.prod.outlook.com ([fe80::88a9:f314:c95f:8b33]) by DS0PR12MB6486.namprd12.prod.outlook.com ([fe80::88a9:f314:c95f:8b33%4]) with mapi id 15.20.9542.008; Wed, 21 Jan 2026 20:46:52 +0000 Message-ID: <9750dc9d-5aae-44a8-ba79-8277f78f7292@nvidia.com> Date: Wed, 21 Jan 2026 15:46:48 -0500 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH RFC v6 01/26] rust: clist: Add support to interface with C linked lists To: Gary Guo , linux-kernel@vger.kernel.org Cc: Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Simona Vetter , Jonathan Corbet , Alex Deucher , =?UTF-8?Q?Christian_K=C3=B6nig?= , Jani Nikula , Joonas Lahtinen , Rodrigo Vivi , Tvrtko Ursulin , Huang Rui , Matthew Auld , Matthew Brost , Lucas De Marchi , =?UTF-8?Q?Thomas_Hellstr=C3=B6m?= , Helge Deller , Danilo Krummrich , Alice Ryhl , Miguel Ojeda , Alex Gaynor , Boqun Feng , =?UTF-8?Q?Bj=C3=B6rn_Roy_Baron?= , Benno Lossin , Andreas Hindborg , Trevor Gross , John Hubbard , Alistair Popple , Timur Tabi , Edwin Peer , Alexandre Courbot , Andrea Righi , Andy Ritger , Zhi Wang , Alexey Ivanov , Balbir Singh , Philipp Stanner , Elle Rhumsaa , Daniel Almeida , joel@joelfernandes.org, nouveau@lists.freedesktop.org, dri-devel@lists.freedesktop.org, rust-for-linux@vger.kernel.org, linux-doc@vger.kernel.org, amd-gfx@lists.freedesktop.org, intel-gfx@lists.freedesktop.org, intel-xe@lists.freedesktop.org, linux-fbdev@vger.kernel.org References: <20260120204303.3229303-1-joelagnelf@nvidia.com> <20260120204303.3229303-2-joelagnelf@nvidia.com> <01a981f1-64c7-4504-b309-45a024258fe9@nvidia.com> Content-Language: en-US From: Joel Fernandes In-Reply-To: Content-Type: text/plain; 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>>>> + (*list).prev = list; >>> >>> This needs to be an atomic write or it'll depart from the C implementation. >> I am curious what you mean by atomic write, can you define it? Does rust >> compiler have load/store fusing, invented stores, etc, like C does? Sorry I am >> only familiar with these concepts on C. Could you provide example of a race >> condition in Rust that can happen? > > Oh yes, this would definitely happen. It's down to LLVM to compile anyway. If > you create a reference, there'll be even more freedom to do these. > Ok. >> Also I did this addition based on feedback from past review: >> https://lore.kernel.org/all/DEI89VUEYXAJ.1IQQPC3QRLITP@nvidia.com/ >> >> There was some concerns around pointless function call overhead when the rust >> implementation is already quite intertwined with internals of the C linked list >> implementation. I do agree with that point of view too. > > Overall our practice is to not duplicate code. Even `ERR_PTR` is calling into > helpers. > > For performance, it's a valid concern. However Alice and I have series out there > that enable you to inline the helpers. I'd say unless there's an absolute need, > we should do the helpers. Especially with caveats like WRITE_ONCE in this case. Sounds good, so I will then go back to adding a INIT_LIST_HEAD C helper for the next spin. I agree with the suggestion and now that we are inlining helpers, there seems little point in adding a separate rust function to do the same. -- Joel Fernandes