Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752532AbZIIClt (ORCPT ); Tue, 8 Sep 2009 22:41:49 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751662AbZIIClt (ORCPT ); Tue, 8 Sep 2009 22:41:49 -0400 Received: from cn.fujitsu.com ([222.73.24.84]:50376 "EHLO song.cn.fujitsu.com" rhost-flags-OK-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1751184AbZIICls (ORCPT ); Tue, 8 Sep 2009 22:41:48 -0400 Message-ID: <4AA715A3.8040108@cn.fujitsu.com> Date: Wed, 09 Sep 2009 10:40:35 +0800 From: Li Zefan User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.1b3pre) Gecko/20090513 Fedora/3.0-2.3.beta2.fc11 Thunderbird/3.0b2 MIME-Version: 1.0 To: KOSAKI Motohiro CC: rostedt@goodmis.org, Ingo Molnar , Frederic Weisbecker , LKML Subject: Re: [PATCH 1/2] tracing: Add sysctl to enable/disable tracing on oops References: <4AA7092C.4070706@cn.fujitsu.com> <1252461867.11070.6.camel@gandalf.stny.rr.com> <20090909113231.0CE6.A69D9226@jp.fujitsu.com> In-Reply-To: <20090909113231.0CE6.A69D9226@jp.fujitsu.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1736 Lines: 49 >>>>>>> Currently we always disable tracing on oops, and this patch >>>>>>> adds a sysctl so one can choose to enable it. >>>>>> Hmm, we already have a way to enable it. >>>>>> >>>>>> # echo 1 > /debug/tracing/tracing_on >>>>>> >>>>> What I want is a way to not disable it when an oops happened. :) >>>>> >>>> Ah, I misunderstood. May I ask a silly question? >>>> >>>> Why? >>>> >>> Otherwise we won't get trace output from trae_crash_kexec if >>> crash_kexec() is not called by panic(). For example: >>> >>> oops_begin() >>> ->trace_off() >>> ->panic_on_oops >>> ->kexec_should_crash() >>> ->crash_kexec() >> OK, but I'm not exactly sure what you final goal is here. To have a >> something to search for in the ring buffer after the crash? Maybe >> instead we can add a "trace_oops" event? Just put it before the >> tracing_off call. > > I have another silly question. > Why should we call tracing_off() in oops_enter()? > I guess it's because trace outputs generated during oops can overwrite/mess up those generated before oops? It was added by this commit, but I can't find trace_printk_on_oops. commit bdff78707f3ce47e891f3201c9666122a70556ce Author: Thomas Gleixner Date: Fri Jul 24 15:30:45 2009 -0400 trace: stop tracer in oops_enter() If trace_printk_on_oops is set we lose interesting trace information when the tracer is enabled across oops handling and printing. We want the trace which might give us information _WHY_ we oopsed. -- 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/