Re: Threaded interrupt handlers broken?

Michael Buesch
2009-08-16T13:46:47Z

On Sunday 16 August 2009 15:22:29 Thomas Gleixner wrote:
> On Sun, 16 Aug 2009, Michael Buesch wrote:
> > On Sunday 16 August 2009 12:14:36 Michael Buesch wrote:
> > I need the following patch for threaded IRQs to work.
> > The first hunk obviously is incorrect. But without it the thread_fn is
> > never called.
> >
> > Index: wireless-testing/kernel/irq/manage.c
> > ===================================================================
> > --- wireless-testing.orig/kernel/irq/manage.c 2009-08-15 22:22:07.000000000 +0200
> > +++ wireless-testing/kernel/irq/manage.c 2009-08-16 14:05:23.000000000 +0200
> > @@ -504,7 +504,7 @@ static int irq_thread(void *data)
> > atomic_inc(&desc->threads_active);
> >
> > spin_lock_irq(&desc->lock);
> > - if (unlikely(desc->status & IRQ_DISABLED)) {
> > + if (0&&unlikely(desc->status & IRQ_DISABLED)) {
>
> So the interrupt is marked disabled. How do you setup the handler ?
> And what does the primary handler do ? Can you post your driver code please?

This patch converts the b43 driver to threaded interrupts:
http://bu3sch.de/patches/wireless-testing/20090816-1535/patches/002-b43-threaded-irq-handler.patch

It kind of works with this hack applied to kernel/irq/manage.c

> > /*
> > * CHECKME: We might need a dedicated
> > * IRQ_THREAD_PENDING flag here, which
> > @@ -520,7 +520,7 @@ static int irq_thread(void *data)
> > action->thread_fn(action->irq, action->dev_id);
> > }
> >
> > - wake = atomic_dec_and_test(&desc->threads_active);
> > + wake = !atomic_dec_and_test(&desc->threads_active);
>
> So you wake when the thread counter is != 0 after the decrement.
>
> #define atomic_dec_and_test(v) (atomic_sub_return(1, (v)) == 0)

Yeah, isn't that what we want to do? I read the test as "wake other threads,
if there are other threads" or something like that.