Re: dom0 is stalled until a keypress

[Joanna Rutkowska <joanna@invisiblethingslab.com>]

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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?

Thanks,
joanna.


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