On Thu, 10 May 2007 16:35:51 +1000 Benjamin Herrenschmidt <[email protected]> wrote:
> On Wed, 2007-05-09 at 22:41 -0700, Andrew Morton wrote:
> > On Thu, 10 May 2007 15:25:58 +1000 Benjamin Herrenschmidt <[email protected]> wrote:
> >
> > > --- linux-cell.orig/include/linux/interrupt.h 2007-05-10 14:51:22.000000000 +1000
> > > +++ linux-cell/include/linux/interrupt.h 2007-05-10 15:18:04.000000000 +1000
> > > @@ -241,6 +241,16 @@ static inline void __deprecated save_and
> > > #define save_and_cli(x) save_and_cli(&x)
> > > #endif /* CONFIG_SMP */
> > >
> > > +/* Some architectures might implement lazy enabling/disabling of
> > > + * interrupts. In some cases, such as stop_machine, we might want
> > > + * to ensure that after a local_irq_disable(), interrupts have
> > > + * really been disabled in hardware. Such architectures need to
> > > + * implement the following hook.
> > > + */
> > > +#ifndef hard_irq_disable
> > > +#define hard_irq_disable() do { } while(0)
> > > +#endif
> >
> > We absolutely require that the architecture's hard_irq_disable() be defined
> > when we do this. If it happens that the definition of hard_irq_disable()
> > is implemented three levels deep in nested includes then we risk getting
> > into a situation where different .c files see different implementations of
> > hard_irq_disable(), which could lead to confusing results, to say the least.
>
> Yes, I'm indeed a bit worried about that... I've been wondering what's
> the best include path here... I tried to follow who gets to hw_irq.h and
> didn't come to any conclusive results.
>
> powerpc gets it from asm/system.h but I haven't verified other arch
> (though it only matters on arch that have their own here).
>
> I've verified that a #error on ppc up there will not trigger thus it's
> fine on powerpc, but I agree it's a bit fragile.
I think saying "system.h must provide this" is reasonable. The fact that
powerpc does that via another inclusion is a powerpc detail - just don't
break it ;)
> > Your implementation comes via the inclusion of system.h which then includes
> > hw_irq.h. That's perhaps a little fragile and it would be better to
> >
> > a) include in the comment the name of the arch file which must implement
> > hard_irq_disable() and
> >
> > b) include that file directly from this one.
>
> Fair enough. I was just worried that including hw_irq.h here might cause
> trouble for some archs though (as I said, we get it indirectly on
> powerpc via some other asm thingy, not via some linux/*.h). I've looked
> around and seen all sort of horrors in arch include dependencies
> (including some circular stuff that must work by mere luck).
>
> > Oh, and your comment layout style is wrong ;)
>
> What about my comment layout style ? I've been using that forever ... Or
> do you mean I should use a function documentation style layout there ?
/* This
* is
* wrong
*/
/*
* This
* is
* right
*/
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