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Date: Tue, 29 Jul 2008 16:20:57 +0200
From: Gilles Chanteperdrix <gilles.chanteperdrix@xenomai.org>
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Subject: Re: [Xenomai-core] Error propagating ISR to Linux domain
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To: Ulrich Schwab <uli.schwab@domain.hid>
Cc: xenomai-core <xenomai@xenomai.org>

Gilles Chanteperdrix wrote:
> Ulrich Schwab wrote:
>> why not checking for irq origin like this:
>> int my_isr_handler (xnintr_t *irq)
>> {
>>  if ( ! test_my_card_for_irq_origin )
>>     return XN_ISR_NONE | XN_ISR_PROPAGATE;
>>   ... /* handling */
>>  return XN_ISR_HANDLED;
>> }
>>
>> this way XN_ISR_PROPAGATE is never returned in the not-shared case.
> 
> I think this idea needs an answer; the answer is no: it will not work.
> Because the IRQ will remain masked until Linux handles it, which
> basically means that the RT irq will wait for non-RT activity, you loose
> real-time response.

It will not work, but not for the reason I mention: Adeos WILL re-enable
the IRQ at interrupt controller level after the end of this handler,
however, since the interrupt was not cleared on the peripheral side, the
peripheral will reassert the interrupt when the interrupt is unmasked at
interrupt controller level, so the CPU will enter an infinite loop
invoking the ISR.

-- 
                                                 Gilles.