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

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Date:	Tue, 24 Feb 2009 14:51:45 -0800 (PST)
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
cc:	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Ingo Molnar <mingo@...e.hu>,
	LKML <linux-kernel@...r.kernel.org>,
	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 Tue, 24 Feb 2009, Rafael J. Wysocki wrote:
>
> > The only safe way on x86 to shutdown a level triggered ioapic irq
> > outside of irq context is for the driver to program the hardware to
> > not generate an irq.
> 
> Well, that changes things quite a bit, because it means we can't change the
> suspend-resume sequence in a way we thought we could without fixing all
> drivers first, but this is exactly what we'd like to avoid by changing the
> core.

Calling "disable_irq()" is perfectly fine.

What is not possible on that broken IO-APIC (among other things) is to 
actually turn the interrupts off at the apic (ie the whole ->shutdown() 
thing). But that's not what we even want to do. What we care about is 
just disabling the interrupt from a drievr perspective.

IOW, the patches I have seen are fine, and all the comments from Eric are 
just confusion about what we want done.

WE DO NOT WANT TO TURN OFF THE IO-APIC. That may or may happen later, but 
that's totally unrelated to this whole "suspend_device_irq()" thing.

		Linus
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