Re: [Xen-devel] Re: [patch] xenfb: fix xenfb suspend/resume race

[Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>]

> > I am unclear from your description whether the patch fixes
> > the problem (I would presume so). Or does it take a long time
> > to hit this race?
> > 
> Yes, more than 100 migrations. we hit this issue around 3 times.

OK, so you are still trying to find the culprit.

Did you look at this patch from Ian:

https://patchwork.kernel.org/patch/403192/

?
> 
> I dumped vmcore when guest crashed, from vmcore everything
> looked good, fb_info, xenfb_info and so on.

And the event channels are correct?

.. snip..
> diff --git a/drivers/xen/events.c b/drivers/xen/events.c
> index ac7b42f..4cfb5e2 100644
> --- a/drivers/xen/events.c
> +++ b/drivers/xen/events.c
> @@ -175,6 +175,8 @@ static struct irq_info *info_for_irq(unsigned irq)
>  
>  static unsigned int evtchn_from_irq(unsigned irq)
>  {
> +	if (unlikely(irq < 0 || irq >= nr_irqs))
> +		return 0;

You could insert a WARN_ON here to see see if you get this during your
migration process.

Or use xen_raw_printk in case the guest is hung for good.

>  	return info_for_irq(irq)->evtchn;
>  }
>  
> 
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