Re: [PATCH 3/3] IRQ: Maintain regs pointer globally rather than passing to IRQ handlers

Andrew Morton
2006-10-02T21:01:47Z

On Mon, 2 Oct 2006 13:54:33 -0700 (PDT)
Linus Torvalds <torvalds@osdl.org> wrote:

>
>
> On Mon, 2 Oct 2006, Ingo Molnar wrote:
> >
> > i agree that we should do this in one go and in Linus' tree. I suspect
> > David has a script for this, so we can do it anytime for any tree,
> > right?
> >
> > the amount of code that truly relies on regs being present is very low.
> > Mostly only sysrq type of stuff and the timer interrupt is such.
>
> Yeah, well, it's been discussed before, and the real problem is not the
> patch itself, it's the damn drivers maintained outside the tree, and
> people who want to maintain the same driver for multiple different
> versions of the kernel.
>
> Things like the kernel graphics direct-rendering code, for example -
> mostly maintained in X.org trees that then want to compile with other
> kernels too.
>
> I don't personally mind the patch, I just wanted to bring that issue up.

yup. Perhaps we could add

#define IRQ_HANDLERS_DONT_USE_PTREGS

so that out-of-tree drivers can reliably do their ifdefing.

> So far, when this has come up, the gains it gives have not been worth the
> pain. I don't quite see why FRV is so broken that it would matter 20%
> worth, and I suspect that number was somehow really not real, but more a
> matter of "this small code snippet that is part of the irq delivery and
> isn't really measurable improves by 20%", which is a different thing.
>
> That said, it's almost certainly worth it, and I don't think anybody
> really objects deep down.
>
> So if the patch works against my current tree, and nobody objects, I can
> certainly apply it.
>
> So speak up, people...
>

Whimper. Later in the week, please.