From mboxrd@z Thu Jan 1 00:00:00 1970 From: Rafal Wojtczuk Subject: Re: dom0 is stalled until a keypress Date: Wed, 7 Sep 2011 15:29:53 +0200 Message-ID: <20110907132953.GB1185@email> References: <20110905091937.GA1906@email> <36a5b662-4420-41aa-be01-445f83b15a7b@default4E664BEE.9000208@invisiblethingslab.com> <71fba00b-9a7a-4029-ac11-4d37732bb53f@default> <4E673351.6060206@invisiblethingslab.com> <4E6757110200007800055040@nat28.tlf.novell.com> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-2 Return-path: Content-Disposition: inline In-Reply-To: <4E6757110200007800055040@nat28.tlf.novell.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: Jan Beulich Cc: Dan Magenheimer , xen-devel@lists.xensource.com, Joanna Rutkowska List-Id: xen-devel@lists.xenproject.org On Wed, Sep 07, 2011 at 10:35:45AM +0100, Jan Beulich wrote: > >>> On 07.09.11 at 11:03, Joanna Rutkowska wrote: > > On 09/06/11 19:17, Dan Magenheimer wrote: > >>> From: Joanna Rutkowska [mailto:joanna@invisiblethingslab.com] > >>> Subject: Re: [Xen-devel] dom0 is stalled until a keypress > >>> > >>> On 09/06/11 17:49, Dan Magenheimer wrote: > >>>>> From: Rafal Wojtczuk [mailto:rafal@invisiblethingslab.com] > >>>>> Sent: Monday, September 05, 2011 3:20 AM > >>>>> To: xen-devel@lists.xensource.com > >>>>> Subject: [Xen-devel] dom0 is stalled until a keypress > >>>>> > >>>>> Hello, > >>>>> The following bizarre behaviour was observed on xen4.1+suse dom0 2.6.38, on > >>>>> an old Core Duo laptop; maybe someone can hint what is wrong. > >>>>> Dom0 boot stalls after an init.d script prints "Starting udev". Then nothing > >>>>> seems to happen. I need to press any key to observe progress - I need to do > >>>>> it tens of times for the boot to finish. After X starts fine, then there is > >>>>> no need for keypressing anymore. > >>>>> A particularly disturbing fact is that qrexec_daemon parent, that basically > >>>>> does > >>>>> for (;;) { sleep(1); fprintf(stderr, "."); } > >>>>> does not print dots, until a keypress arrives. So something is very wrong > >>>>> with timers. > >>>>> Somehow similarly, pm-suspend sometimes hangs at some stage - after detaching > >>>>> power cord, machine enters S3 immediately. > >>>>> This is vaguely similar to the issue described in > >>>>> https://lkml.org/lkml/2008/9/14/122 > >>>>> but this time, "nohz=off" does not help. > >>>>> > >>>>> "cpufreq=dom0-kernel" cures the symptoms; but it is not a sideeffectless > >>>>> solution. Any idea what is going on or how to debug it ? > >>>> > >>>> ISTR seeing this on a Core(2?)Duo laptop and I think the > >>>> workaround was setting max_cstate=0 (as Xen boot parameter). > >>>> > >>> But what was the actual problem? Setting max_cstate is probably even > >>> worse for power management than setting cpufreq=dom-kernel, isn't it? > >> > >> Sorry, dunno. I recall looking into it a bit and finding that > >> the Core processor (and possibly specifically Merom, the laptop > >> version) had some special C-state (C3, C1E maybe?) and giving > >> up at that point. Sorry I can't be more helpful. > > > > But the same system worked fine without any tweaks (cpufreq, max_cstate) > > on Xen 3.4 and only started exhibiting this behavior after we switched > > to Xen 4.1... > > 4.1.0 or 4.1.1? Originally tested on 4.1.0; same problem with 4.1.1. Jeremy> Try booting with "idle=halt". It does not help, either. Regards, RW