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Re: [Xen-devel] irq problem with 3.3-rc3 on guest

On Mon, Feb 13, 2012 at 02:12:08PM +0000, M A Young wrote:
> On Mon, 13 Feb 2012, Ian Campbell wrote:
> >On Sun, 2012-02-12 at 21:33 +0000, M A Young wrote:
> >>I get the backtrace below if I try to boot a PV guest running F17 Alpha
> >>TC2 in graphical mode. Is this a known problem?
> >
> >It came up last year https://lkml.org/lkml/2011/1/6/19 which resulted in
> >the WARN_ON you saw instead of a kernel crash. I'm not sure if anyone
> >got to the bottom of the root cause though.
> >
> >That occasion was a suspend/resume thing so perhaps not really related
> >but it seems fishily similar.
> >
> >I've not looked at the code recently but it seems that back then I was
> >of the opinion that info->update_wanted == 0 must remain true until the
> >irq etc was all fully setup, that might be relevant now?
> Yes, it does sound fishily similar. I didn't mention that it does work if 
> I do a text boot and then switch to a graphical runlevel, so it could be 

So how does F17 do it now? Is all in the graphical mode (KMS?) and it never
tries to hit text mode (so plymouth is on by default?)

> somthing happening in the wrong order, such as the framebuffer starting 
> before the irq is properly set up.

Hm, could you instrument xen-fbfront.c and see what the flow is during
bootup and compare that when running it under F16? That might shed some
light on this.
>       Michael Young
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