From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753798Ab0HQNCk (ORCPT ); Tue, 17 Aug 2010 09:02:40 -0400 Received: from hrndva-omtalb.mail.rr.com ([71.74.56.124]:33164 "EHLO hrndva-omtalb.mail.rr.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752411Ab0HQNCk (ORCPT ); Tue, 17 Aug 2010 09:02:40 -0400 X-Authority-Analysis: v=1.1 cv=nbWoJD01ruQLYOYE44JZbYtzz81AmFDL3LnuPvZDHs8= c=1 sm=0 a=ToTR1L1PYWcA:10 a=Q9fys5e9bTEA:10 a=IXo+6rlC6z1XzBFn1RNpIA==:17 a=llhKIf-NW9iPoSPSSYkA:9 a=qI9Aod0nABEAgdZeD4BOvWhGycQA:4 a=PUjeQqilurYA:10 a=IXo+6rlC6z1XzBFn1RNpIA==:117 X-Cloudmark-Score: 0 X-Originating-IP: 74.67.87.39 Subject: Re: [tracing, hang] dumping events gets stuck in synchronise_sched From: Steven Rostedt To: Dave Chinner Cc: Lai Jiangshan , linux-kernel@vger.kernel.org In-Reply-To: <20100817115243.GE7362@dastard> References: <20100817073725.GO10429@dastard> <4C6A4A58.2030904@cn.fujitsu.com> <20100817115243.GE7362@dastard> Content-Type: text/plain; charset="ISO-8859-15" Date: Tue, 17 Aug 2010 09:02:38 -0400 Message-ID: <1282050158.3268.1303.camel@gandalf.stny.rr.com> Mime-Version: 1.0 X-Mailer: Evolution 2.30.2 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 2010-08-17 at 21:52 +1000, Dave Chinner wrote: > On Tue, Aug 17, 2010 at 04:37:44PM +0800, Lai Jiangshan wrote: > > On 08/17/2010 03:37 PM, Dave Chinner wrote: > > > Tracing folks, > > > > > > I've got a machine stuck with a cpu spinning in a tight loop (the > > > new writeback/sync livelock avoidance code is, well, livelocking), > > > and I was trying to find out what triggered by using the writeback > > > trace events. Unfortunately, I can't dump the trace events because > > > it gets stuck here: > > > > > > > > Given that the trace events are there mainly for debugging, this > > > seems like a bit of an oversight - hanging a CPU in a tight loop is > > > not an uncommon event during code development.... > > > > > > > You can try 'cat trace_pipe', if I did not miss you meaning. > > I'll try it, but I'm really after the static event list which is why > I'm using the trace file rather than trace_pipe. I want the history, > not new events as they happen. When the systems locks up, I assume you want to see why? The trace_pipe should show that without locking the system. You could also try downloading trace-cmd and running the tracer with that. That will save all traces to a file while running the trace. -- Steve