linux-kernel - Re: [PATCH v2] genirq: avoid long loops in handle_edge

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Message-ID: <ZRPfjC9JEeUx8zKY@MacBook-Pro-3.local>
Date:   Wed, 27 Sep 2023 15:53:48 +0800
From:   Wei Gong <gongwei833x@...il.com>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     linux-kernel@...r.kernel.org, gongwei833x@...il.com
Subject: Re: [PATCH v2] genirq: avoid long loops in handle_edge_irq

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.
Therefore, I understand that the scenario you mentioned will not occur?

> 
> Thanks,
> 
>         tglx


Thanks,

Wei Gong