Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753509AbcK1A6x (ORCPT ); Sun, 27 Nov 2016 19:58:53 -0500 Received: from mail-io0-f195.google.com ([209.85.223.195]:35081 "EHLO mail-io0-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753286AbcK1A6p (ORCPT ); Sun, 27 Nov 2016 19:58:45 -0500 MIME-Version: 1.0 In-Reply-To: <20161127224208.GA31101@dastard> References: <1479926662-21718-1-git-send-email-ross.zwisler@linux.intel.com> <1479926662-21718-4-git-send-email-ross.zwisler@linux.intel.com> <20161124173220.GR1555@ZenIV.linux.org.uk> <20161125024918.GX31101@dastard> <20161125041419.GT1555@ZenIV.linux.org.uk> <20161125070642.GZ31101@dastard> <20161125073747.GU1555@ZenIV.linux.org.uk> <20161127224208.GA31101@dastard> From: Linus Torvalds Date: Sun, 27 Nov 2016 16:58:43 -0800 X-Google-Sender-Auth: cKlgoePeKU1Wyj431p6RYSa8qk0 Message-ID: Subject: Re: [PATCH 3/6] dax: add tracepoint infrastructure, PMD tracing To: Dave Chinner Cc: Al Viro , Ross Zwisler , Linux Kernel Mailing List , Andrew Morton , Christoph Hellwig , Dan Williams , Ingo Molnar , Jan Kara , Matthew Wilcox , Steven Rostedt , "linux-ext4@vger.kernel.org" , linux-fsdevel , linux-mm , "linux-nvdimm@lists.01.org" Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1007 Lines: 23 On Sun, Nov 27, 2016 at 2:42 PM, Dave Chinner wrote: > > And that's exactly why we need a method of marking tracepoints as > stable. How else are we going to know whether a specific tracepoint > is stable if the kernel code doesn't document that it's stable? You are living in some unrealistic dream-world where you think you can get the right tracepoint on the first try. So there is no way in hell I would ever mark any tracepoint "stable" until it has had a fair amount of use, and there are useful tools that actually make use of it, and it has shown itself to be the right trace-point. And once that actually happens, what's the advantage of marking it stable? None. It's a catch-22. Before it has uses and has been tested and found to be good, it's not stable. And after, it's pointless. So at no point does such a "stable" tracepoint marking make sense. At most, you end up adding a comment saying "this tracepoint is used by tools such-and-such". Linus