Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757994AbYLEMdi (ORCPT ); Fri, 5 Dec 2008 07:33:38 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750957AbYLEMd0 (ORCPT ); Fri, 5 Dec 2008 07:33:26 -0500 Received: from tomts25.bellnexxia.net ([209.226.175.188]:41536 "EHLO tomts25-srv.bellnexxia.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757803AbYLEMdZ (ORCPT ); Fri, 5 Dec 2008 07:33:25 -0500 X-IronPort-Anti-Spam-Filtered: true X-IronPort-Anti-Spam-Result: AvoEAKuoOElMROB9/2dsb2JhbACBbc0wgwU Date: Fri, 5 Dec 2008 07:28:22 -0500 From: Mathieu Desnoyers To: Peter Zijlstra Cc: prasad@linux.vnet.ibm.com, jan.kiszka@web.de, Gian Lorenzo Meocci , ltt-dev@lists.casi.polymtl.ca, linux-kernel@vger.kernel.org, mbligh@google.com Subject: Re: [ltt-dev] trace a futex Message-ID: <20081205122822.GA25816@Krystal> References: <8d94e9280812021142j2eb5ca72td730410e97ccd9a1@mail.gmail.com> <20081202195015.GA25792@Krystal> <8d94e9280812021215m6a63d6c2l4e64acd26274953d@mail.gmail.com> <20081202215519.GA734@Krystal> <4935B25F.7010701@web.de> <20081203052640.GA13701@Krystal> <20081203180131.GA2904@in.ibm.com> <1228380784.5092.18.camel@twins> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline In-Reply-To: <1228380784.5092.18.camel@twins> X-Editor: vi X-Info: http://krystal.dyndns.org:8080 X-Operating-System: Linux/2.6.21.3-grsec (i686) X-Uptime: 07:23:54 up 18 days, 13:04, 3 users, load average: 1.24, 1.07, 0.76 User-Agent: Mutt/1.5.16 (2007-06-11) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1067 Lines: 27 * Peter Zijlstra (peterz@infradead.org) wrote: > > FWIW, the ftrace infrastructure has on many an occasion (even before it > was called ftrace and specific to -rt) helped in debugging and fixing > futex races. > Hrm, I'm not sure futex races is the key aspect of interest here. Knowing which amount of pthread mutex lock calls ends up calling the scheduler looks a bit more like the topic brought by this particular use-case. Therefore, correlating the information from the nptl with the kernel information would be useful. Is lockdep called when a futex is taken ? Should we add instrumentation (tracepoints) to futex.c ? If yes, was there specific instrumentation you used with ftrace that should be added ? Mathieu -- Mathieu Desnoyers OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68 -- 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/