From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 815CA2FB0A6; Wed, 22 Oct 2025 20:27:57 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761164877; cv=none; b=Dloqag8x/2gdsD38hH+H0ZuIr42mxw/TrcHfuL9mUoctnlF975m3xOxg5psNIYsABC75/78UyjIQ+qDZfKJReyeovULrEAWbFF2ZZftQ2o76wxrQUH/hO/Rva7NPQITqgOu8t/lTDHD3Al25ruUMEkuNmt60M0GkbqNcbckG+7c= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761164877; c=relaxed/simple; bh=tVBEed3VAVgVl2VHnxu6EsWdt4x/Yjp9/jd2zsHBqFA=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=mPa+ICvJBdyjKs9H7fx0bOR6CHAcYrBMqid47uM6lMJ6VFhHdvDtD3iRTyeveQ8TJt5ckeaE96FqsF0rAZ2MJbxKp5x4DALKAnsHw7yfOENiAYSVsjM1XvBjnh0fygsWO1bafybe7wZ9QrHZ5kksi2hSOUU2DFAI37OOzX4BdKI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=pIthv+VO; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="pIthv+VO" Received: by smtp.kernel.org (Postfix) with ESMTPSA id D76E8C4CEE7; Wed, 22 Oct 2025 20:27:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1761164877; bh=tVBEed3VAVgVl2VHnxu6EsWdt4x/Yjp9/jd2zsHBqFA=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=pIthv+VObm6D7MYUOIQdB0uTf7cb2HFUVDiqbiOY1aKALjN1PRjvisVqQbvv5PAQJ kmASrUdXYDYNqk45JNOPlq4s9HkIWBMT+ZuBitEeirbWj1FKfkYlm1wL8MDWSn2vg8 oPLFPfMQmMFXDDQUS0z3KirqzzFZ6joXmYqu94Rf890iTJPijxPhtigwy7Dzdze68h /yCkCV6q4/NekJWZ5TWMf/PvHwM5UhOA2aVOZhY2mAYLhnOfQSt9rVgfg9qYAIQJAb NT2tY2UkZfP2DpSo4ymSkcTNLKK+jmEqYLxKwGg/cr/MaQVcmfozxbjR/qHIUl4s/5 eZm54dDpnOF+w== Date: Wed, 22 Oct 2025 10:27:55 -1000 From: Tejun Heo To: Andrea Righi Cc: David Vernet , Changwoo Min , Emil Tsalapatis , sched-ext@lists.linux.dev, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 sched_ext/for-6.19] sched_ext: Use ___v2 suffix for new kfuncs and fix scx build errors Message-ID: References: <20251022093826.113508-1-arighi@nvidia.com> <20251022153610.20111-1-arighi@nvidia.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Hello, On Wed, Oct 22, 2025 at 09:38:14PM +0200, Andrea Righi wrote: ... > Ahh ok, so user-space schedulers will always continue to pass all the > arguments "normally" and we just assemble the args struct via an inline > helper. > > So, IIUC, using an _argpack suffix or something similar (instead of ___v2) > should be a reasonable solution, right? Yeah, something with less than three underscores as that has a different meaning (ignore when matching). > > Here, there is no noticeable feature difference before and after for > > existing schedulers, so I don't think it's necessary to introduce __COMPAT > > prefix. > > The problem is that some schedulers (i.e., scx_bpfland, scx_cosmos) are > explicitly checking bpf_ksym_exists(scx_bpf_select_cpu_and). If > scx_bpf_select_cpu_and() becomes a static inline, we break the build and we > also break binary compatibility. Hence the __COMPAT for the inline > helpers... Hmm... binary compatibility shouldn't break as the original scx_bpf_select_cpu_and() is still there, right? Build breaks because now the symbol is an inline one, but the solution there, I think, is either providing a __COMPAT macro which helps testing the availability of scx_bpf_select_cpu_and() or just making them test the ___compat symbol, right? ie. kernel API changes aren't required to guarantee source level backward compatibility (like how we did the dsq_insert renames) as long as it provides a way to maintain both forward and backward binary compatibility. Thanks. -- tejun