From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756230AbYKEK4P (ORCPT ); Wed, 5 Nov 2008 05:56:15 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755115AbYKEKz7 (ORCPT ); Wed, 5 Nov 2008 05:55:59 -0500 Received: from mx3.mail.elte.hu ([157.181.1.138]:57277 "EHLO mx3.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754774AbYKEKz7 (ORCPT ); Wed, 5 Nov 2008 05:55:59 -0500 Date: Wed, 5 Nov 2008 11:55:41 +0100 From: Ingo Molnar To: =?iso-8859-1?Q?Fr=E9d=E9ric?= Weisbecker Cc: Steven Rostedt , Linux Kernel Subject: Re: [PATCH] tracing: use raw spinlocks instead of spinlocks Message-ID: <20081105105541.GB19361@elte.hu> References: <490E3F73.1000405@gmail.com> <20081103064647.GA4826@elte.hu> <20081104094341.GO23790@elte.hu> <20081104120355.GA19969@elte.hu> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: 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,DNS_FROM_SECURITYSAGE autolearn=no SpamAssassin version=3.2.3 -1.5 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] 0.0 DNS_FROM_SECURITYSAGE RBL: Envelope sender in blackholes.securitysage.com Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Frédéric Weisbecker wrote: > 2008/11/4 Ingo Molnar : > > just make sure normal printk is totally silent. (otherwise you get > > double lines on the console plus no reduction in recursion risk) > > > > i usually add a return; hack to kernel/printk.c:printk(), to make sure > > it never executes anything. (and add a notrace to it as well) Maybe we > > could even make this dependent on early_printk=...,keep. > > Thanks for your help! > > I tried the earlyprintk=vga,keep and I thought that the normal printk > output would > be replaced by early_printk output but that's not the case... > So I replaced the content of printk by this of early_printk and it worked. > But it seems that after the setting of the console, the early_printk > doesn't work anymore. > > Should I disable something else? I haven't any console=.... parameter > but I guess I missed > something there... perhaps try a "console=tty 3" bootup - to boot into non-graphics initlevel 3, and to have a vga tty set up. Then comment out the regular printk(), to make sure it never tries to output to the regular tty. does earlyprintk=vga,keep work in that case? > But, I set the parameter nmi_watchdog=2 (I didn't know I had to > start explicitly the nmi watchdog) and at last... I had my > backtraces :-) heh :-) > All these backtraces were related to time function. And one of the > special things of the time functions is that they often manipulate > 64 bits numbers. Actually I totally forgot that a function could > return a long long, so I had to save edx register in the return > handler to restore it in its end because 64 bits numbers are > returned as a couple into eax and edx in x86-32. > > So the main problem is now solved. But it remains a last (but more > rare) deadlock somewhere. I don't know why at this time and the nmi > watchdog doesn't tell anything. So I will have to use early_printk > to see the last functions traced. But the problem is that it doesn't > print on the console... hm. Let me know if you cannot get this to work. I regularly use earlyprintk=serial,...,keep myself, and it works there - but i dont use earlyprintk=vga,keep that often. Ingo