linux-kernel - Re: [RFC][PATCH 1/4] PM: Rework handling of interrupts during suspend-resume (rev. 4)

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Date:	Mon, 2 Mar 2009 15:01:33 -0800
From:	Arve Hjønnevåg <arve@...roid.com>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Ingo Molnar <mingo@...e.hu>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Jeremy Fitzhardinge <jeremy@...p.org>,
	pm list <linux-pm@...ts.linux-foundation.org>,
	Len Brown <lenb@...nel.org>,
	Jesse Barnes <jbarnes@...tuousgeek.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Alan Stern <stern@...land.harvard.edu>,
	Johannes Berg <johannes@...solutions.net>
Subject: Re: [RFC][PATCH 1/4] PM: Rework handling of interrupts during 
	suspend-resume (rev. 4)

On Sun, Mar 1, 2009 at 2:24 PM, Rafael J. Wysocki <rjw@...k.pl> wrote:
> From: Rafael J. Wysocki <rjw@...k.pl>
>
> Introduce two helper functions allowing us to prevent device drivers
> from getting any interrupts (without disabling interrupts on the CPU)
> during suspend (or hibernation) and to make them start to receive
> interrupts again during the subsequent resume, respectively.  These
> functions make it possible to keep timer interrupts enabled while the
> "late" suspend and "early" resume callbacks provided by device
> drivers are being executed.
>
> Use these functions to rework the handling of interrupts during
> suspend (hibernation) and resume.  Namely, interrupts will only be
> disabled on the CPU right before suspending sysdevs, while device
> drivers will be prevented from receiving interrupts, with the help of
> the new helper function, before their "late" suspend callbacks run
> (and analogously during resume).
>
> In addition, since the device interrups are now disabled before the
> CPU has turned all interrupts off and the CPU will ACK the interrupts
> setting the IRQ_PENDING bit for them, check in sysdev_suspend() if
> any wake-up interrupts are pending and abort suspend if that's the
> case.
>


> +void resume_device_irqs(void)
> +{
> +       struct irq_desc *desc;
> +       int irq;
> +
> +       for_each_irq_desc(irq, desc)
> +               if (desc->status & IRQ_SUSPENDED)
> +                       enable_irq(irq);
> +}

I think you need to clear IRQ_SUSPENDED here, not in enable_irq.

> @@ -222,8 +222,9 @@ static void __enable_irq(struct irq_desc
>                WARN(1, KERN_WARNING "Unbalanced enable for IRQ %d\n", irq);
>                break;
>        case 1: {
> -               unsigned int status = desc->status & ~IRQ_DISABLED;
> +               unsigned int status;
>
> +               status = desc->status & ~(IRQ_DISABLED | IRQ_SUSPENDED);
>                /* Prevent probing on this irq: */
>                desc->status = status | IRQ_NOPROBE;
>                check_irq_resend(desc, irq);

This only clears IRQ_SUSPENDED if the interrupt was not disabled
elsewhere. If a driver calls interrupt_disable in suspend_late, but
calls interrupt_enable lazily, resume_device_irqs will reenable the
interrupt even though the driver has a disable reference.

The rest of the patch looks good.

-- 
Arve Hjønnevåg
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