On 2011-03-04 09:11, Richard Cochran wrote:
> On Fri, Mar 04, 2011 at 08:51:00AM +0100, Philippe Gerum wrote:
>>
>> I'm not saying this would be impossible to enable MSIs there, I'm just
>> saying that so far: nobody cared. Terrae incognitae.
> 
> I care!
> 
> When the first MSI interrupt from my PCIe card should arrive, running
> on a P2020RBD, the machine locks up. My BDI shows me that both cores
> are going round in circles.
> 
> * core 1
>   __ipipe_check_percpu_access ()  at kernel/ipipe/core.c:2067
>   ipipe_suspend_domain ()         at kernel/ipipe/core.c:826
>   __ipipe_check_percpu_access ()  at arch/powerpc/include/asm/ipipe_hwirq.h:57
>   ipipe_suspend_domain ()         at kernel/ipipe/core.c:860
>   cpu_idle ()                     at arch/powerpc/kernel/idle.c:64
>   ipipe_suspend_domain ()         at arch/powerpc/include/asm/ipipe_hwirq.h:57
> 
> * core 2
>   ipipe_suspend_domain ()         at kernel/ipipe/core.c:858
>   cpu_idle ()                     at arch/powerpc/kernel/idle.c:64
>   ipipe_suspend_domain ()         at arch/powerpc/include/asm/ipipe_hwirq.h:57
> 
> Any thoughts?

Well, if PPC masks MSIs on ack, you may run on a bug check or on an
already acquired Linux spin lock.

Independent of the need to add RT-safe mask/unmask support for MSIs
midterm, you likely first of all want to get rid of this masking in the
fast-path. I suspect it's not needed, also on PPC.

Jan