From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759292AbYEPRcZ (ORCPT ); Fri, 16 May 2008 13:32:25 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753286AbYEPRcQ (ORCPT ); Fri, 16 May 2008 13:32:16 -0400 Received: from bombadil.infradead.org ([18.85.46.34]:51592 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752569AbYEPRcQ (ORCPT ); Fri, 16 May 2008 13:32:16 -0400 Subject: Re: [regression bisected] HR-timers bug >=2.6.25 From: Peter Zijlstra To: Justin Madru Cc: Jesse Barnes , lkml , Thomas Gleixner In-Reply-To: <482DC3B2.3040907@gawab.com> References: <482C8FD6.10808@gawab.com> <1210922458.7886.14.camel@twins> <482DC3B2.3040907@gawab.com> Content-Type: text/plain Date: Fri, 16 May 2008 19:31:56 +0200 Message-Id: <1210959116.6524.26.camel@lappy.programming.kicks-ass.net> Mime-Version: 1.0 X-Mailer: Evolution 2.22.1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 2008-05-16 at 10:26 -0700, Justin Madru wrote: > Peter Zijlstra wrote: > > The kernel doesn't hang, right? My reading of the description tells me > > the splash just doesn't work. > > > > If it does hang the kernel, an NMI trace collected over serial or > > netconsole (regular console being out of the question since its > > graphical stuff :/) would be most helpful. > > I've seen it blank out in 2 different ways. > > 1) Usplash completely finishes. Then screen goes blank for the usual mode change/screen refreshing, > doing several refreshes of a blank screen. But, the screen then stays black. > I do still hear the gdm sound, and can switch to a console. > Pressing ctrl+alt+f1 makes the screen "refresh" again, but stay blank/black. I can still login but blindly. > > 2) More rarely. Usplash hasn't finished (but near the end). The usplash screen fades out to black. > It's like a screen burn in, or after image; the screen slowly fades out to black. > After this the computer is _seemingly_unresponsive_ - Only alt+sysrq+b seems to work. (I have to hard reset) > After I reboot the backlight is at the lowest level. > > Anyways, I think I can figure out how to set up a netconsole, but > is there something more to setup a NMI trace? I found Documentation/networking/netconsole.txt > But, it doesn't say anything about a NMI trace. those can be obtained by adding: nmi_watchdog=[12] to the kernel boot parameters - it depends a bit on the hardware which of the two choices works best, just start with 1 and if that doesn't work try 2. This enabled the NMI watchdog and that will print a backtrace when it times out after 30 or so seconds.