RE: dom0 is stalled until a keypress

[Dan Magenheimer <dan.magenheimer@oracle.com>]

> 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).