linux-kernel - Re: [linux-pm] [RFC][PATCH][1/8] PM: Rework handling of interrupts during suspend-resume (rev. 5)

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Date:	Sun, 8 Mar 2009 10:20:22 -0700 (PDT)
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Alan Stern <stern@...land.harvard.edu>
cc:	"Rafael J. Wysocki" <rjw@...k.pl>,
	Jeremy Fitzhardinge <jeremy@...p.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Jesse Barnes <jbarnes@...tuousgeek.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Ingo Molnar <mingo@...e.hu>,
	pm list <linux-pm@...ts.linux-foundation.org>,
	Arve  Hjønnevåg <arve@...roid.com>
Subject: Re: [linux-pm] [RFC][PATCH][1/8] PM: Rework handling of interrupts
 during suspend-resume (rev. 5)

On Sat, 7 Mar 2009, Alan Stern wrote:
> 
> You didn't answer my question.  Why bother to distinguish between 
> "wake-up" interrupts and non-"wake-up" interrupts?
> 
> In other words, why not simply abort the suspend if IRQ_PENDING is set
> for _any_ interrupt during sysdev_suspend()?

.. because some drivers might not actually shut down the hardware until 
they get to "suspend_late"? If even then, for that matter - a driver may 
simply not care, knowing that the hardware will be powered off, and will 
be re-initialized at resume.

The thinking that you have to shut your hardware down at "->suspend()" 
time is a _disease_. There are literally classes of hardware out there 
where that would be an outright _bug_, like for a PCI bridge device. For 
many devices, "suspend()" has to be the phase where you shut down the 
_external_ stuff (eg for a disk controller, it's when you'd flush and stop 
your disks), but the controller itself may well be alive until later.

			Linus
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