Re: [Xen-devel] [PATCH] x86/xen: resume timer irqs early

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

On Fri, Aug 08, 2014 at 03:35:27PM +0100, David Vrabel wrote:
> On 08/08/14 15:04, Boris Ostrovsky wrote:
> > On 08/08/2014 06:41 AM, David Vrabel wrote:
> >> On 07/08/14 18:29, Boris Ostrovsky wrote:
> >>> On 08/07/2014 01:16 PM, David Vrabel wrote:
> >>>> If the timer irqs are resumed during device resume it is possible in
> >>>> certain circumstances for the resume to hang early on, before device
> >>>> interrupts are resumed.
> >>>>
> >>>> It is not entirely clear what is occuring the point of the hang but I
> >>>> think a task necessary for the resume calls schedule_timeout(),
> >>>> waiting for a timer interrupt (which never arrives).  This failure may
> >>>> require specific tasks to be running on the other VCPUs to trigger
> >>>> (processes are not frozen during a suspend/resume if PREEMPT is
> >>>> disabled).
> >>>>
> >>>> Add IRQF_EARLY_RESUME to the timer interrupts so they are resumed in
> >>>> syscore_resume().
> >>>>
> >>>> Also add IRQF_NO_SUSPEND as it is not necessary to suspend the timer
> >>>> interrupts and IRQF_FORCE_RESUME was already set.
> >>>
> >>> IRQF_NO_SUSPEND is a component of IRQF_TIMER.
> >> So it is.  How about this instead?
> > 
> > The change makes sense so
> > 
> >     Reviewed-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
> > 
> > but I am curious whether you actually were able to prove that it in fact
> > fixes the hang (the description doesn't make it clear).
> 
> Without the patch repeatedly migrating a VM would hang during resume
> after < 500 iterations.  With the patch the VM was migrated > 8000 times
> without a problem.

Ah, should said patch have a Reported-by too then?

It would also be neat to have that in the description of the patch I think.
> 
> David
> 

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