Philippe Gerum wrote:
> On Thu, 2007-03-08 at 11:08 +0100, Steven Scholz wrote:
>> Philippe,
>>>> using an oscilloscope I found that the AT91RM9200 spends up to 300┬Ás in the
>>>> interrupt handler for ethernet controller.
>>>> Now I wonder if this interrupt handler will be preempted by Xenomai if 
>>>> there
>>>> is a high priority, periodic real time task?
>>> Hw interrupts are forcibly enabled before entering any Linux IRQ
>>> handler, exactely to prevent the issue you described (e.g. fiddling with
>>> an IDE controller in PIO mode also gives funky latency results unless
>>> the latter is true), so the answer is yes.
>> Thanks.
>>>>  Thus will the duration of the
>>>> ethernet interrupt handler add the the worst case latency?
>>> Not from Linux IRQ handlers; you may want to check this using the
>>> tracer. If hw interrupts are masked there, then it's a blatant bug.
>> How could I check this using the tracer? Small hint please?

I know this. But I was asking how I could use it to check the above problem.

Is "Trace IRQs-off times CONFIG_IPIPE_TRACE_IRQSOFF ... Instrument each
disable and re-enable of hardware IRQs. This allows to identify the longest
path in a system with IRQs disabled." the important stuff?


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