Re: [Xenomai-help] Interrupt latency greater than 250ms. Question.

[Makarand Pradhan <makarandpradhan@domain.hid>]

Hi Philippe,

On 28/03/12 12:17 PM, Philippe Gerum wrote:
> The log says your code wants to control when the IRQ is enabled again,
> by calling rt_intr_enable() from userland. I guess you are setting
> I_NOAUTOENA too. Correct?

That is correct. I_NOAUTOENA is used in rt_intr_create. Otherwise the 
level trigerred interrupt will not allow the userland processing of the 
int. The userland handler is very small and it unconditionally 
rt_intr_enables the intr.

Testing indicates that the interrupt is always enabled from user space 
within 250 usec after kernel gets the interrupt.

I have noted that unless I see "#end 0x0000002b" and a hit to the 
ipic_unmask_irq, the next interrupt is not processed.

And this is getting delayed once in a while which causes a delay in 
processing the next interrupt.

So the sequence of events leading to the problem is:

1. Get interrupt: #begin   0x0000002b noted in ipipe trace
2. Intr enabled from user space. Always happens roughly within 250usec.
3. #end 0x0000002b noted in ipipe trace where the int is unmasked by ipipe.

When I see the problem, step 3 is delayed. I am trying to capture a 
trace where the begin, int enable and end are captured.

Your thoughts on what might cause this delay would be appreciated.

Rgds,
Mak.





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