From mboxrd@z Thu Jan  1 00:00:00 1970
From: Olaf Hering <olaf@aepfle.de>
Subject: Re: [PATCH 5/6] xen/hvm kexec: unregister timer
	interrupt during reboot
Date: Wed, 27 Jul 2011 16:05:12 +0200
Message-ID: <20110727140512.GA17515@aepfle.de>
References: <20110726115209.655568638@aepfle.de>
	<20110726115211.204484318@aepfle.de>
	<20110726142223.GG5994@dumpdata.com>
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To: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
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On Tue, Jul 26, Konrad Rzeszutek Wilk wrote:

> On Tue, Jul 26, 2011 at 01:52:14PM +0200, Olaf Hering wrote:
> > The kexec kernel will crash because the timer interrupt is already
> > registerd with EVTCHNOP_bind_virq.  Unbind the event channel during
> > shutdown so that the kexec kernel can reregister the interrupt.
> > 
> > Signed-off-by: Olaf Hering <olaf@aepfle.de>
> > 
> > ---
> >  arch/x86/xen/time.c |   27 ++++++++++++++++++++++++---
> >  1 file changed, 24 insertions(+), 3 deletions(-)
> > 
> > Index: linux-3.0/arch/x86/xen/time.c
> > ===================================================================
> > --- linux-3.0.orig/arch/x86/xen/time.c
> > +++ linux-3.0/arch/x86/xen/time.c
> > @@ -14,6 +14,7 @@
> >  #include <linux/kernel_stat.h>
> >  #include <linux/math64.h>
> >  #include <linux/gfp.h>
> > +#include <linux/syscore_ops.h>
> >  
> >  #include <asm/pvclock.h>
> >  #include <asm/xen/hypervisor.h>
> > @@ -405,12 +406,20 @@ void xen_setup_timer(int cpu)
> >  	evt->irq = irq;
> >  }
> >  
> > -void xen_teardown_timer(int cpu)
> > +static void xen_unbind_timer(int cpu)
> >  {
> >  	struct clock_event_device *evt;
> > -	BUG_ON(cpu == 0);
> >  	evt = &per_cpu(xen_clock_events, cpu);
> > -	unbind_from_irqhandler(evt->irq, NULL);
> > +	if (evt->irq >= 0) {
> > +		unbind_from_irqhandler(evt->irq, NULL);
> > +		evt->irq = -1;
> > +	}
> > +}
> > +
> > +void xen_teardown_timer(int cpu)
> > +{
> > +	BUG_ON(cpu == 0);
> 
> Why the BUG? Ah you just copied it from xen_unbind_timer.
> Hm, I wonder if we actually need that BUG_ON.

A quick grep did not show up the place where
/sys/devices/system/cpu/cpu0/online would have been created. Since that
file is missing in my guest I think cpu0 can not be shutdown, So that
BUG_ON() can probably go.

Olaf