Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751607AbWIOOr2 (ORCPT ); Fri, 15 Sep 2006 10:47:28 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751608AbWIOOr1 (ORCPT ); Fri, 15 Sep 2006 10:47:27 -0400 Received: from opersys.com ([64.40.108.71]:39175 "EHLO www.opersys.com") by vger.kernel.org with ESMTP id S1751600AbWIOOr0 (ORCPT ); Fri, 15 Sep 2006 10:47:26 -0400 Message-ID: <450ABF59.4010301@opersys.com> Date: Fri, 15 Sep 2006 10:57:29 -0400 From: Karim Yaghmour Reply-To: karim@opersys.com Organization: Opersys inc. User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.8.0.6) Gecko/20060804 Fedora/1.0.4-0.5.1.fc5 SeaMonkey/1.0.4 MIME-Version: 1.0 To: Alan Cox CC: Roman Zippel , Tim Bird , Ingo Molnar , Mathieu Desnoyers , linux-kernel@vger.kernel.org, Christoph Hellwig , Andrew Morton , Ingo Molnar , Greg Kroah-Hartman , Thomas Gleixner , Tom Zanussi , ltt-dev@shafik.org, Michel Dagenais Subject: Re: [PATCH 0/11] LTTng-core (basic tracing infrastructure) 0.5.108 References: <20060914033826.GA2194@Krystal> <20060914112718.GA7065@elte.hu> <20060914135548.GA24393@elte.hu> <20060914171320.GB1105@elte.hu> <20060914181557.GA22469@elte.hu> <4509B03A.3070504@am.sony.com> <1158320406.29932.16.camel@localhost.localdomain> <1158323938.29932.23.camel@localhost.localdomain> <1158327696.29932.29.camel@localhost.localdomain> <1158331277.29932.66.camel@localhost.localdomain> <450ABA2A.9060406@opersys.com> <1158332324.29932.82.camel@localhost.localdomain> In-Reply-To: <1158332324.29932.82.camel@localhost.localdomain> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1603 Lines: 35 Alan Cox wrote: > The gdb debug data lets you find each line and also the variable > assignments (except when highly optimised in some cases). Try > breakpointing there with kgdb and using "where"... A kgdb script is the > wrong way to do instrumentation but it does demonstrate the information > is already out there, automatically generated and self maintaining. > > You do need the gdb -g debug data, but equally if it was static you'd > need to recompile with the tracepoint because it would be off by > default, and there is a very small risk in both cases you'll disturb or > change the code behaviour/flow. ... > Thats why we have things like systemtap. > > All we appear to lack is systemtap ability to parse debug data so it can > be told "trace on line 9 of sched.c and record rq and next" Thanks for the explanation. But I submit to you that both explanations actually highlight the argument I was making earlier with regards to dynamic tracing (and gdb info in this case) actually require a non- expert to chase kernel versions and create appropriate appropriate scripts/config-info for the post-insertion of instrumentation, with the risks to kernel developers this may have (ex.: bug report to lkml from user claiming to have discovered problem in subsystem when, in fact, trace point by external maintainer was ill-chosen.) Cheers, Karim - 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/