On Mon, 5 May 2008, Linus Torvalds wrote:
> On Mon, 5 May 2008, Nick Piggin wrote:
> >
> > Index: linux-2.6/include/asm-x86/pgtable_32.h
> > ===================================================================
> > --- linux-2.6.orig/include/asm-x86/pgtable_32.h
> > +++ linux-2.6/include/asm-x86/pgtable_32.h
> > @@ -133,7 +133,12 @@ extern int pmd_bad(pmd_t pmd);
> > * pgd_offset() returns a (pgd_t *)
> > * pgd_index() is used get the offset into the pgd page's array of pgd_t's;
> > */
> > -#define pgd_offset(mm, address) ((mm)->pgd + pgd_index((address)))
> > +#define pgd_offset(mm, address) \
> > +({ \
> > + pgd_t *ret = ((mm)->pgd + pgd_index((address))); \
> > + smp_read_barrier_depends(); /* see mm/memory.c:__pte_alloc */ \
> > + ret; \
> > +})
>
> Is there some fundamental reason this needs to be a macro?
>
> It is really ugly, and it would be much nicer to make this an inline
> function if at all possible.
>
> Yeah, maybe it requires some more #include's, but ..
My recollection is that it gets difficult once you reach
pte_offset_map(), which involved kmap_atomic() (now kmap_atomic_pte()),
which gets twisty. Or perhaps my problems arose from doing
pte_offset_map_lock() in the generic linux/mm.h: harder to
herd that safely through the different arch builds.
Hugh
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