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

Rafael J. Wysocki
2009-02-26T23:10:35Z

On Thursday 26 February 2009, Arve Hjønnevåg wrote:
> On Thu, Feb 26, 2009 at 2:10 PM, Linus Torvalds
> <torvalds@linux-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