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Fri, 11 Jul 2025 18:10:09 +0000 From: Date: Fri, 11 Jul 2025 11:10:06 -0700 To: Steven Rostedt , Greg KH CC: Christoph Hellwig , Mathieu Desnoyers , , "Josh Poimboeuf" , Masami Hiramatsu , Peter Zijlstra , Ingo Molnar , "Jiri Olsa" , Namhyung Kim , Thomas Gleixner , Andrii Nakryiko , Indu Bhagat , "Jose E. Marchesi" , Beau Belgrave , Jens Remus , "Linus Torvalds" , Andrew Morton , Message-ID: <6871537ec0461_1d3d100c6@dwillia2-xfh.jf.intel.com.notmuch> In-Reply-To: <20250711100239.55434108@gandalf.local.home> References: <20250709212556.32777-1-mathieu.desnoyers@efficios.com> <20250709212556.32777-3-mathieu.desnoyers@efficios.com> <20250711065742.00d6668b@gandalf.local.home> <2025071124-cola-slouching-9dd2@gregkh> <20250711100239.55434108@gandalf.local.home> Subject: Re: [RFC PATCH 2/5] unwind: Export unwind_user symbol to GPL modules Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit X-ClientProxiedBy: BYAPR01CA0047.prod.exchangelabs.com (2603:10b6:a03:94::24) To PH8PR11MB8107.namprd11.prod.outlook.com (2603:10b6:510:256::6) 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: PH8PR11MB8107:EE_|SA3PR11MB7609:EE_ X-MS-Office365-Filtering-Correlation-Id: cf769d8c-d3e5-43da-7be3-08ddc0a62bc2 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|366016|1800799024|7416014|376014; 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This is > > one of those penalities, sorry. > > BTW, when it comes to tracers, being out of tree is actually a huge > advantage. Tracers, unlike drivers, are only monitoring the kernel. Which > means it doesn't really rely on the workings of the kernel, so it really > doesn't get much help from changes made by other kernel developers. Like > the BPF folks have said keeping BPF programs up to date, isn't that much of > a burden. > > The huge advantage that LTTng has over perf and ftrace for being out of > tree is that it controls the ABI between the LTTng kernel side and the user > space side. LTTng can experiment with new interfaces, and if something > breaks, it can simply change it and deliver a new tool that includes the > new module with the update. It is odd to read this claimed benefit when viewing it from the wider Linux kernel project. Upstream maintenance of ABI contracts is the fundamental struggle of subsystems. The request, "can we get the kernel out of the way and maintain our own ABI to our users?" is a consistent refrain, and it consistently receives a qualified "no" for regression, security, and other interface evolution concerns.