Re: PCI, ACPI, IRQ, IOAPIC: reroute PCI interrupt to legacy boot interrupt equivalent

[Ingo Molnar <mingo@elte.hu>]

* Jon Masters <jcm@redhat.com> wrote:

> On Mon, 2009-01-12 at 19:47 -0800, Eric W. Biederman wrote:
> > Ingo Molnar <mingo@elte.hu> writes:
> 
> > > a number of mainline drivers also mask/unmask irqs from within the IRQ 
> > > handler. It's not particularly smart in a native driver, but can happen - 
> > > and if we get an active line after that point (and this can happen because 
> > > the driver is active), we are in trouble.
> > 
> > Yep.  Right now it might be simpler to fix the mainline drivers.
> 
> Taking the easy option now doesn't make the pain go away later :) Just 
> because ACPI doesn't provide a handy description doesn't mean we 
> shouldn't handle "boot interrupts" - the kernel is riddled with quirks 
> already to deal with broken, buggy, or just quirky hardware scenarios.
> 
> > We are outside the descriptions provided by ACPI so it requires 
> > chipset specific knowledge, and a general understanding of how 
> > chipsets work to actually even comprehend the problem.
> 
> But how does that differ from most other chipset code? I'm not being 
> belligerent but I'm not seeing how your argument is uniquely special to 
> this particular situation. Personally, I'm a little biased because I'd 
> eventually like to see RT merged upstream and I /know/ that's going to 
> re-open this whole can of worms once again, even if it's "fixed" now.

it's not just -rt, but it is also needed for the concept of threaded IRQ 
handlers - which was discussed at the Kernel Summit to be desired for 
mainline.

	Ingo