Re: [PATCH RFC: linux-next 1/2] irq: Add CPU mask affinity hint callback framework

Peter P Waskiewicz Jr
2010-04-30T17:39:30Z

On Thu, 2010-04-29 at 13:39 -0700, Thomas Gleixner wrote:
> On Thu, 29 Apr 2010, Peter P Waskiewicz Jr wrote:
> > On Thu, 2010-04-29 at 12:48 -0700, Thomas Gleixner wrote:
> > > Thinking more about it, I wonder whether you have a cpu_mask in your
> > > driver/device private data anyway. I bet you have :)
> >
> > Well, at this point we don't, but nothing says we can't.
>
> Somewhere you need to store that information in your driver, right ?

Yes. But right now, storing a cpu_mask for an interrupt wouldn't buy us
anything since we have no mechanism to make use of it today. :-)

I'll be putting the cpu_mask entry in our q_vector structure, which is
our abstraction of the MSI-X vector (it's where I have the hint struct
right now in patch 2/2 for the ixgbe driver). It's a simple place to
stick it.

> > > So it should be sufficient to set a pointer to that cpu_mask in
> > > irq_desc and get rid of the callback completely.
> >
> > So "register" would just assign the pointer, and "unregister" would make
> > sure to NULL the mask pointer out. I like it. It'll sure clean things
> > up too.
>
> Yep, that'd be like the set_irq_chip() function. Just assign the
> pointer under desc->lock.
>
> Thanks,
>
> tglx