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SubjectRe: [PATCH 2/3] IRQ: allow check_wakeup_irqs to notice level-triggered interrupts.
On Wed, 25 Apr 2012 10:50:15 +0200 (CEST) Thomas Gleixner
<tglx@linutronix.de> wrote:

> On Wed, 25 Apr 2012, NeilBrown wrote:
>
> > Level triggered interrupts do not cause IRQS_PENDING to be set, so
> > check_wakeup_irqs ignores them.
> > They don't need to set IRQS_PENDING as the level stays high which
> > shows that they must be pending. However if such an interrupt fired
> > during late suspend, it will have been masked so the fact that it
> > is still asserted will not cause the suspend to abort.
> >
> > So if any wakeup interrupt is masked, unmask it when checking wakeup
> > irqs. If the interrupt is asserted, suspend will abort.
> >
> > Signed-off-by: NeilBrown <neilb@suse.de>
> > ---
> >
> > kernel/irq/pm.c | 6 ++++++
> > 1 file changed, 6 insertions(+)
> >
> > diff --git a/kernel/irq/pm.c b/kernel/irq/pm.c
> > index 15e53b1..0d26206 100644
> > --- a/kernel/irq/pm.c
> > +++ b/kernel/irq/pm.c
> > @@ -106,6 +106,12 @@ int check_wakeup_irqs(void)
> > if (irqd_is_wakeup_set(&desc->irq_data)) {
> > if (desc->istate & IRQS_PENDING)
> > return -EBUSY;
> > + if (irqd_irq_masked(&desc->irq_data))
> > + /* Probably a level interrupt
> > + * which fired recently and was
> > + * masked
> > + */
> > + unmask_irq(desc);
>
> Oh no. We don't unmask unconditionally. What about an interrupt which
> is disabled, has no handler ..... ? That needs more thought.

If there is no handler, then irqd_is_wakeup_set() should fail should it not?

For disabled: would it be OK to check desc->depth?
Something like:
if (desc->depth == 1 && (desc->state & IRQS_SUSPENDED) &&
irqd_irq_masked(&desc->irq_data))
unmask_irq(desc);
??

Thanks,
NeilBrown
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