Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752113Ab3FJWKg (ORCPT ); Mon, 10 Jun 2013 18:10:36 -0400 Received: from e36.co.us.ibm.com ([32.97.110.154]:39795 "EHLO e36.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750790Ab3FJWKf (ORCPT ); Mon, 10 Jun 2013 18:10:35 -0400 Date: Mon, 10 Jun 2013 15:10:31 -0700 From: "Paul E. McKenney" To: Dave Jones , Steven Rostedt , Linux Kernel , fweisbec@gmail.com Subject: Re: Another RCU trace. (3.10-rc5) Message-ID: <20130610221031.GV5146@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <20130610195145.GA26068@redhat.com> <20130610203355.GO5146@linux.vnet.ibm.com> <20130610210123.GA27154@redhat.com> <20130610211803.GR5146@linux.vnet.ibm.com> <1370900256.9844.128.camel@gandalf.local.home> <20130610215421.GA31251@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20130610215421.GA31251@redhat.com> User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-MML: No X-Content-Scanned: Fidelis XPS MAILER x-cbid: 13061022-7606-0000-0000-00000C598402 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3512 Lines: 84 On Mon, Jun 10, 2013 at 05:54:21PM -0400, Dave Jones wrote: > On Mon, Jun 10, 2013 at 05:37:36PM -0400, Steven Rostedt wrote: > > On Mon, 2013-06-10 at 14:18 -0700, Paul E. McKenney wrote: > > > On Mon, Jun 10, 2013 at 05:01:23PM -0400, Dave Jones wrote: > > > > On Mon, Jun 10, 2013 at 01:33:55PM -0700, Paul E. McKenney wrote: > > > > > > > > > > I saw some of Steven's patches get merged on Friday, is there anything else > > > > > > outstanding that didn't make it in yet that I could test ? > > > > > > Or is this another new bug ? > > > > > > > > > > I have three fixes queued up at: > > > > > > > > > > git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git rcu/urgent > > > > > > > > > > Kind of hard to tell whether they are relevant given the interleaved > > > > > stack traces, but can't hurt to try them out. > > > > > > > > Here's another. Looks different. > > > > > > I bet that commit d6284099 (trace: Allow idle-safe tracepoints to be > > > called from irq) from the above git archive fixes this one. Just don't > > > ask how much I am willing to bet. ;-) > > > > Don't bet much ;-) This has nothing to do with tracepoints. It's due to > > the function tracer. > > dammit, 20 minutes after I finally cloned the repo. > Can we go back to posting diffs instead of hashes please ? > > So while updating my list of bugs I've found this cycle, I noticed > I'd already posted this one a month ago on -rc2. > https://lkml.org/lkml/2013/5/21/327 > which led us to this patch https://lkml.org/lkml/2013/5/24/379 > After which I hit a bunch of what seem to be other RCU related bugs. > > So maybe that patch was a winner after all and got dropped ? Please see below for the patch that I was thinking of. It has not been dropped, I was on travel and a bit slow about pushing things. Thanx, Paul ------------------------------------------------------------------------ trace: Allow idle-safe tracepoints to be called from irq __DECLARE_TRACE_RCU() currently creates an _rcuidle() tracepoint which may safely be invoked from what RCU considers to be an idle CPU. However, these _rcuidle() tracepoints may -not- be invoked from the handler of an irq taken from idle, because rcu_idle_enter() zeroes RCU's nesting-level counter, so that the rcu_irq_exit() returning to idle will trigger a WARN_ON_ONCE(). This commit therefore substitutes rcu_irq_enter() for rcu_idle_exit() and rcu_irq_exit() for rcu_idle_enter() in order to make the _rcuidle() tracepoints usable from irq handlers as well as from process context. Reported-by: Dave Jones Signed-off-by: Paul E. McKenney Cc: Steven Rostedt diff --git a/include/linux/tracepoint.h b/include/linux/tracepoint.h index 2f322c3..f8e084d 100644 --- a/include/linux/tracepoint.h +++ b/include/linux/tracepoint.h @@ -145,8 +145,8 @@ static inline void tracepoint_synchronize_unregister(void) TP_PROTO(data_proto), \ TP_ARGS(data_args), \ TP_CONDITION(cond), \ - rcu_idle_exit(), \ - rcu_idle_enter()); \ + rcu_irq_enter(), \ + rcu_irq_exit()); \ } #else #define __DECLARE_TRACE_RCU(name, proto, args, cond, data_proto, data_args) -- 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/