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

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Message-Id: <200902270010.38291.rjw@sisk.pl>
Date:	Fri, 27 Feb 2009 00:10:35 +0100
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Arve Hjønnevåg <arve@...roid.com>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Ingo Molnar <mingo@...e.hu>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	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 Thursday 26 February 2009, Arve Hjønnevåg wrote:
> On Thu, Feb 26, 2009 at 2:10 PM, Linus Torvalds
> <torvalds@...ux-foundation.org> wrote:
> >
> >
> > On Thu, 26 Feb 2009, Rafael J. Wysocki wrote:
> >>
> >> Well, how exactly the $subject patch does cause this problem to happen?
> >
> > Rafael, the problem is that if an interrupt happens while it's disabled -
> > but before the CPU has actually turned all interrupts off - the CPU will
> > ACK the interrupt (but just set a flag for it being PENDING), so now the
> > chipset logic around it will not see it as pending any more, so now the
> > chipset won't auto-wake the CPU immediately (or more likely, it won't
> > even suspend it).
> >
> > It's trivial to fix multiple ways, so I wouldn't worry. The most trivial
> > way is to just have some sysdev drievr code simply do something like
> >
> >  static int sysdev_suspend()
> >  {
> >        for_each_irq(irq,desc) {
> >                if (!(desc->flags & IRQF_WAKE))
> >                        continue;
> >                if (desc->flags & IRQ_PENDING)
> >                        return -EBUSY;
> >        }
> >        return 0;
> >  }
> >
> > and that should automatically mean that if any irq is pending, the suspend
> > will fail and we'll immediately wake up again.
> >
> > It looks trivial, and I don't understand why Arve can't just do the sysdev
> > thing.
> 
> I can. My point is that the patch breaks our existing code.

Is that a mainline kernel code?

> If anyone else uses edge triggered wakeup interrupt it may break from them as
> well. The main question if this should be fixed separately for every
> platform that needs it, or if pending wakeup interrupts should always
> abort sleep.

Well, I'm not really sure if this is the problem.  In fact the problem is that
you have a regular device the interrupt of which can be a wake-up one.  I think
the problem wouldn't have existed at all if it had been a sysdev.  Is that
correct?

Rafael
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