Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932407Ab2EYSqS (ORCPT ); Fri, 25 May 2012 14:46:18 -0400 Received: from hrndva-omtalb.mail.rr.com ([71.74.56.122]:21472 "EHLO hrndva-omtalb.mail.rr.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752896Ab2EYSqR (ORCPT ); Fri, 25 May 2012 14:46:17 -0400 X-Authority-Analysis: v=2.0 cv=ae7jbGUt c=1 sm=0 a=ZycB6UtQUfgMyuk2+PxD7w==:17 a=XQbtiDEiEegA:10 a=Aua4qMZyJ18A:10 a=5SG0PmZfjMsA:10 a=Q9fys5e9bTEA:10 a=meVymXHHAAAA:8 a=ayC55rCoAAAA:8 a=ofITSWqhkfWE5f55TTIA:9 a=PUjeQqilurYA:10 a=ZycB6UtQUfgMyuk2+PxD7w==:117 X-Cloudmark-Score: 0 X-Originating-IP: 74.67.80.29 Message-ID: <1337971575.13348.268.camel@gandalf.stny.rr.com> Subject: Re: BUG - function tracing with breakpoints From: Steven Rostedt To: "H. Peter Anvin" Cc: Dave Jones , Linux Kernel , Frederic Weisbecker , Ingo Molnar , Andi Kleen Date: Fri, 25 May 2012 14:46:15 -0400 In-Reply-To: <4FBFC421.3020901@linux.intel.com> References: <20120524160146.GA6226@redhat.com> <1337876398.13348.178.camel@gandalf.stny.rr.com> <20120524172223.GA10689@redhat.com> <1337902816.13348.224.camel@gandalf.stny.rr.com> <4FBEC9E6.8040301@linux.intel.com> <1337909963.13348.232.camel@gandalf.stny.rr.com> <1337910106.13348.234.camel@gandalf.stny.rr.com> <1337956262.13348.257.camel@gandalf.stny.rr.com> <1337959746.13348.264.camel@gandalf.stny.rr.com> <4FBFC421.3020901@linux.intel.com> Content-Type: text/plain; charset="ISO-8859-15" X-Mailer: Evolution 3.2.2-1 Content-Transfer-Encoding: 7bit Mime-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1166 Lines: 30 On Fri, 2012-05-25 at 10:40 -0700, H. Peter Anvin wrote: > On 05/25/2012 08:29 AM, Steven Rostedt wrote: > > > > This would make sense for this bug, as if modifying_ftrace_code was not > > seen by other CPUs, it wouldn't go into the ftrace_int3_handler() path. > > That would cause this issue. But the bug remains after the smp_mb()'s > > were put in place. Although it behaves a little differently not. Maybe > > there's something else I missed? > > > > Perhaps you should make the modifying_ftrace_code modification atomic... > it seems odd to have it not be atomic when it is clearly accessed across > CPUs that way. I guess I can make it atomic. Not really a big deal as this (and soon one other place) is the only place that changes its value. I've found another place that may be causing harm, and I'm currently working on fixing it. Hopefully after that's done, this problem will go away. Thanks, -- Steve -- 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/