Re: [Xenomai] Interrupt latency close to 1ms on powerpc Xenomai 2.6.4

[Philippe Gerum <rpm@xenomai.org>]

On 10/08/2015 04:43 PM, Lennart Sorensen wrote:
> On Thu, Oct 08, 2015 at 08:50:26AM +0200, Philippe Gerum wrote:
>> This is a recent change (d818ed7d0a4682) after it became clear that
>> dealing with some interrupt types for enabling/disabling IRQ lines would
>> require this.
> 
> Well at least that is an excellent explanation for the change in
> behaviour.
> 
> Too bad that it has to be done for everything, just because some types
> require it, but there almost certainly isn't any nice way to do it
> otherwise.
>

I could not find one that would not look weird. That logic is deeply
buried in kernel space, and introducing a dynamic dependency on whether
e.g. the PCI layer has to be traversed for carrying out such ops would
be rather confusing for the end user, especially when porting the
application code over different SoCs.

> And as you said, xenomai 3 doesn't even allow doing interrupt handling
> from userspace the way we have been trying to do it.
> 
> I suppose we could revert that patch for now until we can fix the real
> problem.
> 

Likely, yes. The relevant handlers dealing with the interrupt controller
of the QUICC Engine do not tread on problematic code, so this should be
ok for this platform.

-- 
Philippe.