From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759091AbZDSSq2 (ORCPT ); Sun, 19 Apr 2009 14:46:28 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755837AbZDSSqT (ORCPT ); Sun, 19 Apr 2009 14:46:19 -0400 Received: from mx2.mail.elte.hu ([157.181.151.9]:54875 "EHLO mx2.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751954AbZDSSqT (ORCPT ); Sun, 19 Apr 2009 14:46:19 -0400 Date: Sun, 19 Apr 2009 20:45:51 +0200 From: Ingo Molnar To: Frederic Weisbecker Cc: Li Zefan , Steven Rostedt , Zhaolei , Tom Zanussi , KOSAKI Motohiro , LKML , Peter Zijlstra Subject: Re: [PATCH] tracing/core: Add current context on tracing recursion warning Message-ID: <20090419184551.GA6120@elte.hu> References: <1240117295-6873-1-git-send-email-fweisbec@gmail.com> <49EAC15E.7080702@cn.fujitsu.com> <20090419123430.GA5967@nowhere> <20090419134927.GA6262@nowhere> <20090419140154.GB28919@elte.hu> <20090419142201.GB6262@nowhere> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20090419142201.GB6262@nowhere> User-Agent: Mutt/1.5.18 (2008-05-17) X-ELTE-VirusStatus: clean X-ELTE-SpamScore: -1.5 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-1.5 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.2.3 -1.5 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Frederic Weisbecker wrote: > On Sun, Apr 19, 2009 at 04:01:54PM +0200, Ingo Molnar wrote: > > It would be nice to have this ... but there's no need to do that > > atomic thing - just use printk_once() please. (if we race with > > another instance and get two messages that's not a problem) > > > > Ingo > > > Ah, indeed I forgot about printk_once() > I've updated the repo with the following v2 on: > git://git.kernel.org/pub/scm/linux/kernel/git/frederic/random-tracing tracing/recursion > > --- > >From e894732989e345ea012de146c37d71dd7ed3575d Mon Sep 17 00:00:00 2001 > From: Frederic Weisbecker > Date: Sun, 19 Apr 2009 16:18:16 +0200 > Subject: [PATCH v2] tracing/core: Add current context on tracing recursion warning > > In case of tracing recursion detection, we only get the stacktrace. > But the current context may be very useful to debug the issue. > > This patch adds the softirq/hardirq/nmi context with the warning > using lockdep context display to have a familiar output. > > v2: Use printk_once() > > [ Impact: more information in tracing recursion ] > > Signed-off-by: Frederic Weisbecker > --- > kernel/trace/ring_buffer.c | 10 ++++++++++ > 1 files changed, 10 insertions(+), 0 deletions(-) > > diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c > index b421b0e..e315178 100644 > --- a/kernel/trace/ring_buffer.c > +++ b/kernel/trace/ring_buffer.c > @@ -1495,6 +1495,16 @@ static int trace_recursive_lock(void) > if (unlikely(current->trace_recursion & (1 << level))) { > /* Disable all tracing before we do anything else */ > tracing_off_permanent(); > + > + printk_once(KERN_WARNING "Tracing recursion: " > + "[HC%u[%lu]:SC%u[%lu]:NMI[%lu]:HE%u:SE%u]\n", > + current->hardirq_context, > + hardirq_count() >> HARDIRQ_SHIFT, > + current->softirq_context, > + softirq_count() >> SOFTIRQ_SHIFT, > + in_nmi(), current->hardirqs_enabled, > + current->softirqs_enabled); > + > WARN_ON_ONCE(1); Pulled, thanks Frederic! btw., we might have done it via: if (WARN_ON_ONCE(1)) { printk(...); } as well ... but i have not checked how WARN_ON_ONCE() return value behaves after the first warning - does it return true or false? Ingo