Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752748AbYKRMSP (ORCPT ); Tue, 18 Nov 2008 07:18:15 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752066AbYKRMR5 (ORCPT ); Tue, 18 Nov 2008 07:17:57 -0500 Received: from nfitmail.nfit.au.dk ([130.225.31.129]:19636 "EHLO smtp.nfit.au.dk" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752029AbYKRMR4 (ORCPT ); Tue, 18 Nov 2008 07:17:56 -0500 To: Ingo Molnar Cc: "Rafael J. Wysocki" , Linux Kernel Mailing List , Kernel Testers List , Eric Anholt , Steven Rostedt , Peter Zijlstra , Thomas Gleixner Subject: Re: [Bug #11954] sysprof tracer ABI regression in 2.6.28rc1 References: <20081117162431.GG12081@elte.hu> From: Soeren Sandmann Date: 18 Nov 2008 13:17:53 +0100 In-Reply-To: <20081117162431.GG12081@elte.hu> Message-ID: User-Agent: Gnus/5.09 (Gnus v5.9.0) Emacs/21.4 MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1147 Lines: 22 Ingo Molnar writes: > * Soeren Sandmann wrote: > > > There are no ABI guarantees for the sysprof tracer at this point, > > given that it is in debugfs [...] > > to avoid situations like this, it would be nice to print out the > format string itself in the trace header, in printf format string > style. That way if there's a trivial expansion in trace format, it can > be detected (and even followed) by user-space - without some ugly > version based API. It's not clear to me that sysprof userspace could realistically do runtime detection. It would require (a) using sscanf() to parse the output and (b) that only the types changed, not the actual content or ordering. (a) is likely a non-starter performance-wise (the first version actually did this and it was too slow), and (b) means there are strict limits to what could be changed anyway. Soren -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/