From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from relay.hostedemail.com (smtprelay0016.hostedemail.com [216.40.44.16]) (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 9E03028DF27 for ; Fri, 11 Jul 2025 18:21:39 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=216.40.44.16 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1752258102; cv=none; b=NDUNXAnzqJCPV+bX9nwP9JK5ZGASz/sKVSgypEpTl5SFBU7fGfrXgSclvf/T3h5S0LAcx892DkZC6kNX4ufEX5owZv3qLa63q9U6Jr2RLH9/1IAbe6jLl9c9H6npGAZpFCkYzQGCt+PiFNFpgLJIYb/9TXf4BRQ99eAyCdHT4E4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1752258102; c=relaxed/simple; bh=t9SoAgDI5u54iJABSuhm2MVmg5yAc0se6PKcN3/4Juw=; h=Date:From:To:Cc:Subject:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=eKkTTSezunoz829RQuUClK+WJh9cFgHmJix2cHbgRpodbsRHVCkHtJS5IWecsJ2QJvNKetfbFnE9FuMpfzU38GCVfNLGiKxk1ppOvJm8rVtmKCZN9mUoHXPsMk5rDNcKC0g999vqV8891imuTlXl71SpR7xMnUFzD2lN0LpB+WA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=goodmis.org; spf=pass smtp.mailfrom=goodmis.org; arc=none smtp.client-ip=216.40.44.16 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=goodmis.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=goodmis.org Received: from omf13.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay08.hostedemail.com (Postfix) with ESMTP id A4ED71402F2; Fri, 11 Jul 2025 18:21:36 +0000 (UTC) Received: from [HIDDEN] (Authenticated sender: rostedt@goodmis.org) by omf13.hostedemail.com (Postfix) with ESMTPA id 82D612000D; Fri, 11 Jul 2025 18:21:31 +0000 (UTC) Date: Fri, 11 Jul 2025 14:21:30 -0400 From: Steven Rostedt To: Cc: Greg KH , 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 , Subject: Re: [RFC PATCH 2/5] unwind: Export unwind_user symbol to GPL modules Message-ID: <20250711142130.041b951e@batman.local.home> In-Reply-To: <6871537ec0461_1d3d100c6@dwillia2-xfh.jf.intel.com.notmuch> 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> <6871537ec0461_1d3d100c6@dwillia2-xfh.jf.intel.com.notmuch> X-Mailer: Claws Mail 3.17.8 (GTK+ 2.24.33; x86_64-pc-linux-gnu) 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-Transfer-Encoding: 7bit X-Stat-Signature: 9qz86moh9af15n34yomyo9saa79fqzwj X-Rspamd-Server: rspamout05 X-Rspamd-Queue-Id: 82D612000D X-Session-Marker: 726F737465647440676F6F646D69732E6F7267 X-Session-ID: U2FsdGVkX18KPS5KLZyFfzxSHukJ/10MKcDEj7GxyhA= X-HE-Tag: 1752258091-787051 X-HE-Meta: U2FsdGVkX1/8kQ9FHe4BZcTQUtkHqVVcKUGaM45btgSZsD2QJi5i1ZyYD6Kui9eKXxK+F32fQ3OIi2RU34qiNlBtFRkAxabMdTAEZ1+wzJs0mB36tkUHe1wDDKW8RgNgfgChc9TGx5MpNl0CbjM84jXB3O5/pPSEqMzWvsm0/AKDXmmIjZC+dmVFILEstDaFbADD2P+YiSsISGruk7qx7AwntGd/EXqufbgtwyRjHJAu6J4aUVeDY2BBdZrxuCdsNiA3XeeBZWD4Pic5V4qtSYlr3ClX0ExMnDnz2cGRn/UIF0rx5rkU8F16k5KV0Mq9ri+j5mBjfZlpi/ldW7doquXATfsOlkSn On Fri, 11 Jul 2025 11:10:06 -0700 wrote: > > 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. Well I think the history matters a bit here. Mathieu tried to get LTTng upstream several times. There was never a "Can I keep it out of tree so I have this flexibility". Only after he gave up trying to get it upstream, did this advantage play a role. There's been a few times LTTng was able to take advantage of this "feature". Note, as Mathieu has stated, LTTng now has a "stable ABI" similar to what Linux has to make it easier for distributions to maintain LTTng. But he also said that he can deprecate older interfaces much easier than he would if it was upstream in Linux. My comment wasn't to advocate such a approach, it was to counter Greg's comment of "and living outside of the tree has it's penalities, both economic and technical. The main penalty that LTTng has being out of tree is the lack of access to these functions. But it's been doing very well outside of that. -- Steve