Re: [Xenomai-core] Handling PCI MSI interrupts

[Philippe Gerum <rpm@xenomai.org>]

Jeroen Van den Keybus wrote:
>     It's definitely an Adeos issue and msi.c needs fixing. What about
>     this patch, do
>     things improve with it (against 2.6.15-ipipe-1.2-00)?
> 
> I going to try the patch later on. I have currently a ´fully 
> instrumented´ kernel against which this patch would not ever work... I´m 
> keeping that kernel for now, because I´m also investigating why MSI also 
> doesn´t work under RTDM. It´s merely a coincidence that the above bug 
> (MSI interrupts from Linux devices getting blocked) emerged and produced 
> exactly the same behaviour (system hanging).
> 
> But, normally, that path is not used in RT mode, is it ? So something 
> else is getting in the way.
> 
> At the first look of it, I´m a bit wary of touching that msi.c . I was 
> rather thinking of kicking out __ack_APIC() altogether ? Or is that not 
> possible ? (I see only problems in p4.c and smp.c - but I haven´t looked 
> at these very closely.)
> 
> 

We do need __ack_APIC_irq() to run the actual APIC ack code all over the place in 
the APIC/IO-APIC support code, so that former regular uses of ack_APIC_irq() can 
be left untouched. Adeos already changes significant areas within Linux's innards 
in order to control its interrupt sub-system anyway, which in turn hides the gory 
details of interrupt prioritization to client software like Xenomai. 
drivers/pci/msi.c simply brings a new set of interrupt controllers we need to make 
Adeos-aware, just like it has been done for the i8259, the LAPIC and the IO-APIC 
supports.

-- 

Philippe.