On 10/30/06, Colin Hirsch <mail@cohi.at> wrote:
> > The both use 'mfence' on AMD64. The AMD x86-64 manual:
> >
> > http://www.amd.com/us-en/assets/content_type/white_papers_and_tech_docs/24594.pdf
> >
> > 'mfence' is on page 182 of Vol 3:
>
> Aha, so we need a memory barrier on x86-64 too? The implementation currently
> seems to assume that the same rule as for x86-32 applies, namely that the
> architecture is NOT weakly ordered?

I don't profess to know.  But, AFAICT, both Intel and AMD CPUs support
the MFENCE op when in x86-64 mode.

> I haven't checked testatomic in depth, but it seems to test that the
> individual operations work correctly, but not whether all combinations
> of operations work correctly, otherwise it would have already found the
> issues that the patch tries to fix. The problem is of course that it is
> not so easy to test all operations, and all _combinations_, in a way
> that really breaks if there is a problem with the synchronisation...

Can we at least have it test the issues that this patch tries to fix?
Are they easily reproducable?

Thanks.  -- justin