From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1761034AbZCTTqd (ORCPT ); Fri, 20 Mar 2009 15:46:33 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755786AbZCTTqZ (ORCPT ); Fri, 20 Mar 2009 15:46:25 -0400 Received: from mail-fx0-f158.google.com ([209.85.220.158]:42857 "EHLO mail-fx0-f158.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754069AbZCTTqY (ORCPT ); Fri, 20 Mar 2009 15:46:24 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=date:from:to:cc:subject:message-id:references:mime-version :content-type:content-disposition:in-reply-to:user-agent; b=HLgQb2r+UizgAy1WK7hS6LMoMr4qHBVq2+j25PSpBYj3Yyeh0VyU5Tj1L4m2++cOD3 jLfHjjbjwu9hfbjDtbMTDS2sqdQYp30ane2KXa+pIF1KiS080emrqkqLY/yBU/5HS8ih PAxPcrr/BVZDvRjHrOmJoARpPAUotaLR28Xrs= Date: Fri, 20 Mar 2009 20:46:18 +0100 From: Frederic Weisbecker To: Ingo Molnar Cc: "Paul E. McKenney" , Steven Rostedt , LKML , Thomas Gleixner , Peter Zijlstra Subject: Re: [PATCH 0/5] [GIT PULL] updates for tip/tracing/ftrace Message-ID: <20090320194617.GA5934@nowhere> References: <20090318031423.981603258@goodmis.org> <20090318055924.GA24627@elte.hu> <20090318073903.GA31341@elte.hu> <20090319073357.GA14615@elte.hu> <20090320174331.GH6698@linux.vnet.ibm.com> <20090320183642.GA2070@elte.hu> <20090320183849.GA3657@elte.hu> <20090320191926.GJ6698@linux.vnet.ibm.com> <20090320192721.GI6224@elte.hu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20090320192721.GI6224@elte.hu> 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, Mar 20, 2009 at 08:27:21PM +0100, Ingo Molnar wrote: > > * Paul E. McKenney wrote: > > > On Fri, Mar 20, 2009 at 07:38:49PM +0100, Ingo Molnar wrote: > > > > > > * Ingo Molnar wrote: > > > > > > > > > This looks like it is RCU/stop_machine related. The CPU is > > > > > > stuck in in stop_machine? I see that rcu_torture is running. > > > > > > Does this go away if you turn off rcu_torture? > > > > > > > > > > Grasping at straws... Does Lai's rcu_barrier() fix help? > > > > > > > > which one is that? > > > > > > ok, found it. Will know in about ~24 hours whether it helps. > > > > http://lkml.org/lkml/2009/3/20/71 was the one I was thinking of, > > just to double-check. > > Yeah - i just picked it up into tip:core/rcu. > > I didnt immediately connect the two things, as 'tracer self-test' > does not lend itself to 'CPU hotplug and RCU race fix' - but indeed > in the case of the function tracer there's a dependency due to > stop_machine_run(). Thanks for point it out! > > Ingo I've successfully triggered a crash, the problem is that I can't be sure this is the same because I don't have a serial line on my x86-64, and the trace goes too far. Moreover boot_delay=N make it disappear. I can trigger it each time I boot with ftrace=function_graph and the following patch applied: diff --git a/kernel/rcutorture.c b/kernel/rcutorture.c index 7c4142a..e9914a8 100644 --- a/kernel/rcutorture.c +++ b/kernel/rcutorture.c @@ -616,7 +616,7 @@ rcu_torture_writer(void *arg) static DEFINE_RCU_RANDOM(rand); VERBOSE_PRINTK_STRING("rcu_torture_writer task started"); - set_user_nice(current, 19); + set_user_nice(current, -1); do { schedule_timeout_uninterruptible(1); @@ -736,7 +736,7 @@ rcu_torture_reader(void *arg) struct timer_list t; VERBOSE_PRINTK_STRING("rcu_torture_reader task started"); - set_user_nice(current, 19); + set_user_nice(current, -1); if (irqreader && cur_ops->irqcapable) setup_timer_on_stack(&t, rcu_torture_timer, 0);