Am Freitag, 8. September 2006 23:26 schrieb Alan Stern:
> On Fri, 8 Sep 2006, Oliver Neukum wrote:
>
> > It seems you are correct.
> > Therefore the correct code on CPU 1 would be:
> >
> > y = -1;
> > b = 1;
> > //mb();
> > //x = a;
> > while (y < 0) relax();
> >
> > mb();
> > x = a;
> >
> > assert(x==1 || y==1); //???
> >
> > And yes, it is confusing. I've been forced to change my mind twice.
>
> Again you have misunderstood. The original code was _not_ incorrect. I
> was asking: Given the code as stated, would the assertion ever fail?
I claim the right to call code that fails its own assertions incorrect. :-)
> The code _was_ correct for my purposes, namely, to illustrate a technical
> point about the behavior of memory barriers.
I would say that the code may fail the assertion purely based
on the formal definition of a memory barrier. And do so in a subtle
and inobvious way.
Regards
Oliver
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