Re: Threaded interrupts for synaptic touchscreen in HTC dream

Thomas Gleixner
2009-07-21T21:48:44Z

On Tue, 21 Jul 2009, Dmitry Torokhov wrote:

> On Tue, Jul 21, 2009 at 10:30:26PM +0200, Thomas Gleixner wrote:
> > On Tue, 21 Jul 2009, Dmitry Torokhov wrote:
> >
> > > On Tue, Jul 21, 2009 at 01:49:33PM +0100, Mark Brown wrote:
> > > > On Tue, Jul 21, 2009 at 06:00:07PM +0530, Trilok Soni wrote:
> > > >
> > > > > Hopefully, this thread can give all details about threaded irq discussion.
> > > >
> > > > > http://lkml.org/lkml/2009/2/27/255
> > > >
> > > > Yes, I'm aware of that - I read it at the time. It seemed to peter out
> > > > without any satisfactory solution, unfortunately. There's two separate
> > > > issues here:
> > > >
> > > > - Ordinary devices on interrupt driven or slow buses like I2C. These
> > > > need something along the lines of request_threaded_irq() that's allows
> > > > them to schedule the main IRQ handler outside hardirq context so
> > > > that they can interact with the device. They need to do something in
> > > > hardirq context to disable the interrupt if it's level triggered but
> > > > most of the time the only option they've got is to disable the IRQ
> > > > and reenable it when the worker thread is done. This is the issue
> > > > here.
> >
> > There is already a sane solution to the problem:
> >
> > See http://lkml.org/lkml/2009/7/17/174
> >
> > > > My immediate thought when I noticed this was that we should probably
> > > > fix request_threaded_irq() so that it's useful for them; I'd been
> > > > intending to do some digging and try to understand why it is
> > > > currently implemented as it is.
> >
> > What's to fix there ?
> >
>
> duisable_irq_nosync() in the hard interrupt handler stops the thread
> handler from running. Unfortunately there are devices where it is the
> only thing we can do in the hard interrupt.

Again:

There is already a sane solution to the problem:

See http://lkml.org/lkml/2009/7/17/174

Thanks,

tglx