Re: [RFC PATCH 1/3] genirq: prevent system wakeup when dealing with IRQF_NO_SUSPEND IRQs

Rafael J. Wysocki
2015-02-25T21:38:08Z

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@free-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.