Re: [PATCH v2] genirq: avoid long loops in handle_edge_irq

[Thomas Gleixner]

On Thu, Sep 28 2023 at 10:22, Wei Gong wrote:
> On Wed, Sep 27, 2023 at 05:25:24PM +0200, Thomas Gleixner wrote:
>> On Wed, Sep 27 2023 at 15:53, Wei Gong wrote:
>> > O Tue, Sep 26, 2023 at 02:28:21PM +0200, Thomas Gleixner wrote:
>> >> On Mon, Sep 25 2023 at 10:51, Wei Gong wrote:
>> >> > diff --git a/kernel/irq/chip.c b/kernel/irq/chip.c
>> >> > index dc94e0bf2c94..6da455e1a692 100644
>> >> > --- a/kernel/irq/chip.c
>> >> > +++ b/kernel/irq/chip.c
>> >> > @@ -831,7 +831,8 @@ void handle_edge_irq(struct irq_desc *desc)
>> >> >  		handle_irq_event(desc);
>> >> >  
>> >> >  	} while ((desc->istate & IRQS_PENDING) &&
>> >> > -		 !irqd_irq_disabled(&desc->irq_data));
>> >> > +		 !irqd_irq_disabled(&desc->irq_data) &&
>> >> > +		 cpumask_test_cpu(smp_processor_id(), irq_data_get_affinity_mask(&desc->irq_data)));
>> >> 
>> >> Assume affinty mask has CPU0 and CPU1 set and the loop is on CPU0, but
>> >> the effective affinity is on CPU1 then how is this going to move the
>> >> interrupt?
>> >
>> > Loop is on the CPU0 means that the previous effective affinity was on CPU0.
>> > When the previous effective affinity is a subset of the new affinity mask,
>> > the effective affinity will not be updated.
>> 
>> That's an implementation detail of a particular interrupt chip driver,
>> but not a general guaranteed behaviour.
>> 
>
> Can replacing irq_data_get_affinity_mask with irq_data_get_effective_affinity_mask
> solve this issue?

Yes.