On Thu, 2005-02-17 at 19:33 +1100, Nick Piggin wrote:
> Benjamin Herrenschmidt wrote:
> > Hi !
> >
> > When using 4level-fixup.h, a PMD page may end up beeing freed before the
> > matching PGD entry is cleared due to the way the compatibility macros
> > work. This can cause nasty races on some architectures.
> >
> > This patch fixes it by defining pud_clear() to be pgd_clear(). That
> > means we'll actually write 0 twice, a small price to pay here,
> > especially seeing how easy it is to convert to the new headers anyway
> > (hint hint, ppc & ppc64 patches as soon as 2.6.11 is out).
> >
> > Signed-off-by: Benjamin Herrenschmidt <[EMAIL PROTECTED]>
> >
> > Index: linux-work/include/asm-generic/4level-fixup.h
> > ===================================================================
> > --- linux-work.orig/include/asm-generic/4level-fixup.h 2005-01-24
> > 17:09:49.000000000 +1100
> > +++ linux-work/include/asm-generic/4level-fixup.h 2005-02-17
> > 18:10:38.000000000 +1100
> > @@ -24,7 +24,7 @@
> > #define pud_bad(pud) 0
> > #define pud_present(pud) 1
> > #define pud_ERROR(pud) do { } while (0)
> > -#define pud_clear(pud) do { } while (0)
> > +#define pud_clear(pud) pgd_clear((pgd_t *)(pud))
> >
>
> Just a small nit - no cast needed here.
Well, do you know ? pud is a pud_t* and the arch is free to implement
pgd_clear as an inline with strong typing no ?
Ben.
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