On 04/10/2013 12:36 PM, Jan Kiszka wrote:
> On 2013-04-10 11:32, Philippe Gerum wrote:
>> On 04/08/2013 11:09 PM, Gilles Chanteperdrix wrote:
>>> On 04/06/2013 11:43 AM, Jan Kiszka wrote:
>>>
>>>> On 2013-04-02 23:44, Gilles Chanteperdrix wrote:
>>>>> On 03/27/2013 02:30 PM, Jan Kiszka wrote:
>>>>>
>>>>>> I'm wondering now why we need this differently for the I-pipe case.
>>>>>>
>>>>>> Let's revisit what happens with a fasteoi normally:
>>>>>>
>>>>>> - it's masked only if it's a oneshot IRQ before calling the flow
>>>>>> handler
>>>>>> - it's unmasked after the flow handling if the thread was not woken up
>>>>>>
>>>>>> With I-pipe we already enter handle_fasteoi_irq with the IRQ
>>>>>> masked. The
>>>>>> conditions and spots to unmask are:
>>>>>> - from handle_fasteoi_irq if the thread wasn't woken up or we have
>>>>>> non-threaded or non-oneshot handling
>>>>>> - otherwise on end_irq from the handler thread
>>>>>>
>>>>>> Do you think this is correct? If so, I do not think it matches this
>>>>>> patch yet.
>>>>>
>>>>>
>>>>> Hi,
>>>>>
>>>>> here is a much simpler patch:
>>>>> diff --git a/kernel/irq/chip.c b/kernel/irq/chip.c
>>>>> index 11e75d1..a1c9918 100644
>>>>> --- a/kernel/irq/chip.c
>>>>> +++ b/kernel/irq/chip.c
>>>>> @@ -421,6 +421,13 @@ static inline void preflow_handler(struct
>>>>> irq_desc *desc)
>>>>> static inline void preflow_handler(struct irq_desc *desc) { }
>>>>> #endif
>>>>>
>>>>> +static void cond_release_fasteoi_irq(struct irq_desc *desc)
>>>>> +{
>>>>> + if (desc->irq_data.chip->irq_release &&
>>>>> + !irqd_irq_disabled(&desc->irq_data) && !desc->threads_oneshot)
>>>>> + desc->irq_data.chip->irq_release(&desc->irq_data);
>>>>> +}
>>>>> +
>>>>> /**
>>>>> * handle_fasteoi_irq - irq handler for transparent controllers
>>>>> * @irq: the interrupt number
>>>>> @@ -463,8 +470,7 @@ handle_fasteoi_irq(unsigned int irq, struct
>>>>> irq_desc *desc)
>>>>>
>>>>> #ifdef CONFIG_IPIPE
>>>>> /* XXX: IRQCHIP_EOI_IF_HANDLED is ignored. */
>>>>
>>>> Makes me wonder what this comment wants to tell us. That there is an
>>>> unhandled corner case or that this is intentionally ignored? I support
>>>> the latter as I-pipe already does EOI when accepting the IRQ, no? Maybe
>>>> you can clarify that line at this chance.
>>>
>>>
>>> I have no idea where this comment come from. I do not think this flag
>>> can be handled with the I-pipe kernel, as the EOI is sent before trying
>>> to handle the IRQ. The only users are in arch/sparc and arch/powerpc,
>>> maybe Philippe knows more?
>>>
>>
>> Jan is right, we ignore EOI_IF_HANDLED and never send EOI from the
>> regular flow handler, as a consequence of doing eoi+mask when holding
>> the IRQ in the ipipe's flow handler.
>
> OK, then I'll write a clarification patch for that comment - to get rid
> of that triple X...
I understand the flag with a negative sense: do not eoi the interrupt if
the handler reports that it has not handled it. Obviously, if that is
what the flag means, we can not honour it when the I-pipe is on.
>
> Jan
>
--
Gilles.
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