linux-kernel - Re: [PATCH] genirq/PM: Fix IRQCHIP_ENABLE_WAKEUP_ON

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Message-ID: <aCPPgiamOQSSHH-m@google.com>
Date: Tue, 13 May 2025 16:02:26 -0700
From: Brian Norris <briannorris@...omium.org>
To: Douglas Anderson <dianders@...omium.org>
Cc: Thomas Gleixner <tglx@...utronix.de>, chintanpandya@...gle.com,
	Marc Zyngier <maz@...nel.org>,
	Maulik Shah <quic_mkshah@...cinc.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] genirq/PM: Fix IRQCHIP_ENABLE_WAKEUP_ON_SUSPEND if depth
 > 1

On Mon, May 12, 2025 at 05:32:52PM -0700, Doug Anderson wrote:
> --- a/kernel/irq/chip.c
> +++ b/kernel/irq/chip.c
> @@ -272,7 +272,7 @@ 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--;

I'm certainly no expert here, but I'm treading on the same code and ran
into a problem with this line too. It seems wise to make this a
decrement, and not an unconditional 0. But I'm not sure that we should
then proceed to unmask an interrupt that might have depth==1 in the
general case. I think we should defer the unmask until we actually reach
0.

In fact, that's one aspect of the very problem I'm dealing with here:

Subject: [PATCH 0/2] genirq: Retain disable-depth across irq_{shutdown,startup}()
https://lore.kernel.org/all/20250513224402.864767-1-briannorris@chromium.org/

It seems to me (again, not an expert) that maybe you need to solve your
problems by dodging the disable-depth entirely. But I'm not sure the
best way to do that.

>  
>  	if (irqd_is_started(d)) {
>  		irq_enable(desc);

Brian