Re: [PATCH 2/2] genirq: Retain disable depth across irq shutdown/startup

[Brian Norris <briannorris@chromium.org>]

Hi Thomas,

On Wed, May 14, 2025 at 09:35:49AM +0200, Thomas Gleixner wrote:
> On Tue, May 13 2025 at 15:42, Brian Norris wrote:
> > @@ -272,7 +272,9 @@ int irq_startup(struct irq_desc *desc, bool resend, bool force)
> >  	const struct cpumask *aff = irq_data_get_affinity_mask(d);
> >  	int ret = 0;
> >  
> > -	desc->depth = 0;
> > +	desc->depth--;
> > +	if (desc->depth)
> > +		return 0;
> 
> This breaks a
> 
>      request_irq()
>      disable_irq()
>      free_irq()
>      request_irq()
> 
> sequence.

Ah, thanks for the callout. I factored that into another unit test in
v2.

> So the only case where the disable depth needs to be preserved is for
> managed interrupts in the hotunplug -> shutdown -> hotplug -> startup
> scenario. Making that explicit avoids chasing all other places and
> sprinkle desc->depth = 1 into them. Something like the uncompiled below
> should do the trick.

Seems reasonable, and it works for me. I've incorporated that in v2,
although I'm not sure how the attribution should work there.

Thanks,
Brian