Re: [PATCH] ppc64: Fix possible race with set_pte on a present PTE

David S. Miller
2004-05-25T17:25:47Z

On Tue, 25 May 2004 09:19:52 -0700 (PDT)
Linus Torvalds <torvalds@osdl.org> wrote:

> On Tue, 25 May 2004, Keith M Wesolowski wrote:
> >
> > Some sparc32 CPUs are also vulnerable to this race; in fact the
> > supersparc manual describes it specifically and even outlines the
> > compare-exchange loop using our rotten swap instruction. In our case,
> > the race is with a hardware walker.
>
> Yes, but the sparc32 page tables are not the same as the linux kernel page
> tables, so in your case it's a different path and a different page table.
> Only the shared case really matters (ie things that do hw/microcode walk
> of a page table _tree_ not a hash).

Not true on 32-bit Sparc sun4m systems, it's exactly like i386 except
the hardware is stupid and we only have an atomic swap instruction.
:-)