From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751471AbaHHSmg (ORCPT ); Fri, 8 Aug 2014 14:42:36 -0400 Received: from e38.co.us.ibm.com ([32.97.110.159]:34032 "EHLO e38.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751041AbaHHSmf (ORCPT ); Fri, 8 Aug 2014 14:42:35 -0400 Date: Fri, 8 Aug 2014 11:42:30 -0700 From: "Paul E. McKenney" To: Steven Rostedt Cc: Dave Hansen , linux-kernel@vger.kernel.org, dave.hansen@linux.intel.com, davej@redhat.com, mingo@redhat.com Subject: Re: [PATCH] tracing: generate RCU warnings even when tracepoints are disabled Message-ID: <20140808184230.GE5821@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <20140807175204.C257CAC5@viggo.jf.intel.com> <20140807181356.GG5821@linux.vnet.ibm.com> <20140808143022.5262f6cb@gandalf.local.home> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140808143022.5262f6cb@gandalf.local.home> User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 14080818-1344-0000-0000-000003570DC6 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Aug 08, 2014 at 02:30:22PM -0400, Steven Rostedt wrote: > On Thu, 7 Aug 2014 11:13:56 -0700 > "Paul E. McKenney" wrote: > > > On Thu, Aug 07, 2014 at 10:52:04AM -0700, Dave Hansen wrote: > > > > > > From: Dave Hansen > > > > > > Dave Jones reported seeing a bug from one of my TLB tracepoints: > > > > > > http://lkml.kernel.org/r/20140806181801.GA4605@redhat.com > > > > > > I've been running these patches for months and never saw this. > > > But, a big chunk of my testing, especially with all the debugging > > > enabled, was in a vm where intel_idle doesn't work. On the > > > systems where I was using intel_idle, I never had lockdep enabled > > > and this tracepoint on at the same time. > > > > > > This patch ensures that whenever we have lockdep available, we do > > > _some_ RCU activity at the site of the tracepoint, despite > > > whether the tracepoint's condition matches or even if the > > > tracepoint itself is completely disabled. This is a bit of a > > > hack, but it is pretty self-contained. > > > > > > I confirmed that with this patch plus lockdep I get the same > > > splat as Dave Jones did, but without enabling the tracepoint > > > explicitly. > > > > > > Signed-off-by: Dave Hansen > > > Cc: Dave Jones , > > > Cc: paulmck@linux.vnet.ibm.com > > > Cc: Steven Rostedt > > > Cc: Ingo Molnar > > > > Looks good to me, but I must defer to Steven on this one. > > Looks fine. I can add it to my 3.18 queue. > > Paul, want to send me an "Acked-by"? Here you go: Acked-by: Paul E. McKenney Thanx, Paul