linux-kernel - Re: [RFC PATCH 1/3] genirq: prevent system wakeup when dealing with IRQF_NO

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Date:	Wed, 25 Feb 2015 23:01:31 +0100
From:	"Rafael J. Wysocki" <rjw@...ysocki.net>
To:	Boris Brezillon <boris.brezillon@...e-electrons.com>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Jason Cooper <jason@...edaemon.net>,
	Peter Zijlstra <peterz@...radead.org>,
	Mark Rutland <mark.rutland@....com>,
	linux-kernel@...r.kernel.org,
	Nicolas Ferre <nicolas.ferre@...el.com>,
	Jean-Christophe Plagniol-Villard <plagnioj@...osoft.com>,
	Alexandre Belloni <alexandre.belloni@...e-electrons.com>,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [RFC PATCH 1/3] genirq: prevent system wakeup when dealing with IRQF_NO_SUSPEND IRQs

On Tuesday, February 24, 2015 10:56:00 AM Boris Brezillon wrote:
> Mixing IRQF_NO_SUSPEND and !IRQF_NO_SUSPEND on the same IRQ line is highly
> discouraged, but in some cases (IRQ shared by a timer and other devices)
> you don't have any other choice.
> Since some devices sharing the IRQ line might tag it as a wakeup source,
> you might end up with your handler that requested IRQF_NO_SUSPEND not
> being called in suspended state, or invalid system wakeup (the system is
> woken up without any wakeup source actually requesting it).
> 
> To deal with such unlikely situations, you'll have to:
> 1/ prevent any automatic wakeup when at least one of the IRQ users
>    registered with IRQF_NO_SUSPEND
> 2/ let IRQ users decide if/when they should wake the system up
> 
> This patch is taking care of 1.
> 
> Signed-off-by: Boris Brezillon <boris.brezillon@...e-electrons.com>
> ---
>  kernel/irq/pm.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/kernel/irq/pm.c b/kernel/irq/pm.c
> index 3ca5325..1743162 100644
> --- a/kernel/irq/pm.c
> +++ b/kernel/irq/pm.c
> @@ -16,7 +16,8 @@
>  
>  bool irq_pm_check_wakeup(struct irq_desc *desc)
>  {
> -	if (irqd_is_wakeup_armed(&desc->irq_data)) {
> +	if (irqd_is_wakeup_armed(&desc->irq_data) &&
> +	    !desc->no_suspend_depth) {
>  		irqd_clear(&desc->irq_data, IRQD_WAKEUP_ARMED);
>  		desc->istate |= IRQS_SUSPENDED | IRQS_PENDING;
>  		desc->depth++;
> 

I'm not sure how this helps, because irqd_is_wakeup_armed() is false for
IRQs having no_suspend_depth different from zero (please see the first
check in suspend_device_irq()).


-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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