linux-kernel - Re: [RFC][PATCH 2/2] PM: Rework handling of interrupts during suspend-resume

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Date:	Mon, 23 Feb 2009 14:44:17 -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>
Subject: Re: [RFC][PATCH 2/2] PM: Rework handling of interrupts during 
	suspend-resume

On Mon, Feb 23, 2009 at 2:23 PM, Rafael J. Wysocki <rjw@...k.pl> wrote:
> On Monday 23 February 2009, Arve Hjønnevåg wrote:
>> On Sun, Feb 22, 2009 at 9:39 AM, Rafael J. Wysocki <rjw@...k.pl> wrote:
>> > From: Rafael J. Wysocki <rjw@...k.pl>
>> >
>> > Introduce two helper functions allowing us to disable device
>> > interrupts (at the IO-APIC level) during suspend or hibernation
>> > and enable them during the subsequent resume, respectively, so that
>> > the timer interrupts are enabled while "late" suspend callbacks 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
>> > interrupts will be disabled (at the IO-APIC level), with the help of
>> > the new helper function, before calling "late" suspend callbacks
>> > provided by device drivers and analogously during resume.
>> >
>>
>> What impact does this have on wakeup interrupts? Unless you add a
>> check, after masking all interrupt at the CPU, to abort suspend if any
>> wakeup interrupt has IRQ_PENDING set I think you will loose wakeup
>> interrupts (at least for irqs that use default_disable).
>
> I _think_ they would have to be reenabled after we've called
> local_irq_disable().

Are you talking about the irq_chip switching from enabled interrupts
to wake interrupts? It is not enough for the irq_chip to reenable the
hardware interrupt. If the interrupt is edge triggered and occurred
after you disabled it, but before local_irq_disable, the only record
of it is the IRQ_PENDING flag.

-- 
Arve Hjønnevåg
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