From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752036Ab0CSSqO (ORCPT ); Fri, 19 Mar 2010 14:46:14 -0400 Received: from mail.openrapids.net ([64.15.138.104]:38203 "EHLO blackscsi.openrapids.net" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751346Ab0CSSqM (ORCPT ); Fri, 19 Mar 2010 14:46:12 -0400 Date: Fri, 19 Mar 2010 14:46:10 -0400 From: Mathieu Desnoyers To: Randy Dunlap , Li Zefan Cc: Steven Rostedt , Linux Kernel Mailing List , Frederic Weisbecker Subject: Re: 2.6.33 GP fault only when built with tracing Message-ID: <20100319184610.GA29161@Krystal> References: <4BA2B69D.3000309@oracle.com> <1268956555.758.18.camel@gandalf.stny.rr.com> <20100319005901.GB23020@Krystal> <4BA3C0CF.6070005@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4BA3C0CF.6070005@oracle.com> X-Editor: vi X-Info: http://www.efficios.com X-Operating-System: Linux/2.6.26-2-686 (i686) X-Uptime: 14:38:49 up 55 days, 21:15, 9 users, load average: 1.00, 1.02, 1.00 User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Randy Dunlap (randy.dunlap@oracle.com) wrote: > On 03/18/10 17:59, Mathieu Desnoyers wrote: > > * Steven Rostedt (rostedt@goodmis.org) wrote: > >> On Thu, 2010-03-18 at 16:26 -0700, Randy Dunlap wrote: > >>> I can build/boot 2.6.33 with CONFIG_TRACE/TRACING disabled successfully, > >>> but when I enable lots of tracing config options and then boot with > >>> ftrace=nop on the kernel command line, I see a GP fault when the parport & > >>> parport_pc modules are loading/initializing. > >> > >> Do you see it without adding the "ftrace=nop"? The only thing that > >> should do is expand the ring buffer on boot up. > >> > >>> > >>> It happens in drivers/parport/share.c::parport_register_device(), when that > >>> function calls try_module_get(). > >>> > >>> If I comment out the trace_module_get() calls in include/linux/module.h, > >>> the kernel boots with no problems. > >> > >> > >> Interesting. Well, trace_module_get() is a TRACE_EVENT tracepoint. But > >> should be disabled here. It may be something to do with DEFINE_TRACE. > >> > >> (added Mathieu to Cc since he wrote that code) > > > > can you try replacing the "local_read(__module_ref_addr(module, cpu))" argument > > with "0" ? > > Yes, that boots with no problems. clickety-clicketa... git blame include/linux/module.h : commit 7ead8b8313d92b3a69a1a61b0dcbc4cd66c960dc Author: Li Zefan Date: Mon Aug 17 16:56:28 2009 +0800 tracing/events: Add module tracepoints (Adding Li Zefan in CC) Two things: 1) In this commit, most of the tracepoints contain argument with side-effects. These do not belong there; they should be moved into TRACE_EVENT macros. 2) There seem to be a null-pointer bug with local_read(__module_ref_addr(module, cpu)) in try_module_get(). This should be investigated even if we move the argument to TRACE_EVENT. Thanks, Mathieu > > > Arguments with side-effects are not skipped by the jump over disabled > > instrumentation. This is why we should do that part within the probe declaration > > in the TRACE_EVENT macros. > > > > But if we find out that the problem really is this argument, then it should be > > fixed, because something would be wrong with it (just moving it to TRACE_EVENT > > is not a proper solution). > > > > Thanks, > > > > Mathieu > > > -- > ~Randy -- Mathieu Desnoyers Operating System Efficiency R&D Consultant EfficiOS Inc. http://www.efficios.com