On 09/20/2012 05:00 PM, Jan Kiszka wrote:
> On 2012-09-20 16:12, Gilles Chanteperdrix wrote:
>> On 09/20/2012 03:15 PM, Jan Kiszka wrote:
>>> On 2012-09-20 15:01, Gilles Chanteperdrix wrote:
>>>> On 09/20/2012 01:15 PM, Jan Kiszka wrote:
>>>>
>>>>> On 2012-09-20 12:57, Jan Kiszka wrote:
>>>>>> On 2012-09-20 12:56, Jan Kiszka wrote:
>>>>>>> On 2012-09-20 12:49, Philippe Gerum wrote:
>>>>>>>> On 09/20/2012 12:37 PM, Jan Kiszka wrote:
>>>>>>>>> This reverts commit 073ff1e8045d0311b8cf390687c0ba3619681672.
>>>>>>>>>
>>>>>>>>> Both service are NOT just root-only services. E.g., rtdm_irq_request
>>>>>>>>> requires by specification support also over non-Linux contexts.
>>>>>>>>
>>>>>>>> Nack. We can't run the enable code for MSIs over non-root, and
>>>>>>>> that code typically follows the irq request. Besides, we want to mask
>>>>>>>> the source upon irq free to handle the SMP case properly, which we
>>>>>>>> could
>>>>>>>> not do from non-root with MSIs.
>>>>>>>>
>>>>>>>> So either we have both request+enable and free usable over non-root, or
>>>>>>>> there is no point.
>>>>>>>
>>>>>>> OK, I get the point with legacy MSI. Then we have two other bugs to
>>>>>>> solve:
>>>>>>> - in I-pipe as it holds a hardened spin lock across enable/disable (of
>>>>>>> MSIs)
>>>>>
>>>>> I think this bug may only manifest over ARM as that arch does
>>>>> enable/disable_irq() inside __ipipe_enable/disable_irqdesc - unless
>>>>> something prevents that enabling will ever happen for interrupts that
>>>>> need Linux locks to work. Is that assured?
>>>>
>>>>
>>>> ARM does that because otherwise interrupts are not enabled after a call
>>>> to eg. rtdm_irq_request, and calling rtdm_irq_enable does not work,
>>>> calling request_irq is required to get them working.
>>>
>>> The generic pattern Xenomai currently uses is xnintr_attach +
>>> xnintr_enable. The latter happens to be rtdm_irq_enable as well. So,
>>> doesn't xnintr_enable work at all?
>>
>> No. It has in fact, never worked before the I-pipe core. People had to
>> call request_irq before xnintr_attach.
>>
>>> Or is it only not suited as interrupt
>>> startup? Then, is that a new issue or something core-3.x specific?
>>> Finally, can't we address it in xnarch_enable_irq?
>>
>> This is a very old issue, that I had forgotten, and that bit me when I
>> tried to use a separate timer for Xenomai and Linux on omap3: because
>> the timer interrupt of a different timer has no corresponding linux
>> interrupt.
>>
>> The problem is that irqs which are also used by Linux have to be treated
>> differently from irqs which are registered only for the linux domain.
>
> OK. Then we can safely assume that this initial enabling/disabling will
> not cause excessive latencies or even acquire Linux locks on ARM, right?
mmmm. enable_irq may take the descriptor spinlock, I have to check that.
--
Gilles.
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