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

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Date:	Wed, 25 Feb 2009 00:07:11 +0100
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
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 Tuesday 24 February 2009, Linus Torvalds wrote:
> 
> 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.

Ah, OK.  Thanks for the explanation, I got confused too.

> 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.

Yeah.

Rafael
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