From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757129Ab0JVOOe (ORCPT ); Fri, 22 Oct 2010 10:14:34 -0400 Received: from mx1.redhat.com ([209.132.183.28]:44618 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757092Ab0JVOOd (ORCPT ); Fri, 22 Oct 2010 10:14:33 -0400 Date: Fri, 22 Oct 2010 10:13:50 -0400 From: Jason Baron To: Peter Zijlstra Cc: Ingo Molnar , Steven Rostedt , LKML , Andrew Morton , Frederic Weisbecker , Thomas Gleixner , "H. Peter Anvin" , Arnaldo Carvalho de Melo , tj@kernel.org Subject: Re: [PATCH][GIT PULL] tracing: Fix compile issue for trace_sched_wakeup.c Message-ID: <20101022141349.GA6498@redhat.com> References: <1287508282.16971.386.camel@gandalf.stny.rr.com> <20101019184111.GA17266@elte.hu> <20101020154045.GA18353@elte.hu> <1287659656.16971.573.camel@gandalf.stny.rr.com> <20101021112614.GB26984@elte.hu> <20101022014441.GA1948@redhat.com> <1287735271.15336.18.camel@twins> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1287735271.15336.18.camel@twins> 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 On Fri, Oct 22, 2010 at 10:14:31AM +0200, Peter Zijlstra wrote: > On Thu, 2010-10-21 at 21:44 -0400, Jason Baron wrote: > > > I finally found that we actually continue to run after the above > > apparent 'hang'. That is, we continue to make progress updating the jump > > labels. And doing a dump of all the system tasks at the time of the hang > > showed the processes in various places besides the stop machine threads. > > Thus, I thought that perhaps, for some reason the stop machine threads > > weren't being scheduled. > > > > Thus, I tried commenting out the special scheduling that is set up for > > stop machine threads, and that fixed the hang. I haven't yet looked into > > what might be going wrong with that scheduling...but maybe somebody else > > knows... > > Hrmm, so are you saying rq->stop was runnable but not running? yes, that's what it seems like. > > That would imply broken wakeup-preemption, does something like the below > cure that? > > no still seeing the same hang with the below patch...also, as a data point I backed out the patch that adds the stop_sched_class and that resolved the hang as well - just as a data point. thanks, -Jason > --- > kernel/sched_stoptask.c | 1 + > 1 files changed, 1 insertions(+), 0 deletions(-) > > diff --git a/kernel/sched_stoptask.c b/kernel/sched_stoptask.c > index 45bddc0..50ad10f 100644 > --- a/kernel/sched_stoptask.c > +++ b/kernel/sched_stoptask.c > @@ -35,6 +35,7 @@ static struct task_struct *pick_next_task_stop(struct rq *rq) > static void > enqueue_task_stop(struct rq *rq, struct task_struct *p, int flags) > { > + resched_cpu(cpu_of(rq)); > } > > static void > >