Re: Remove data race in libgcj interpreter

[Hans Boehm <Hans dot Boehm at hp dot com>]

On Fri, 5 Sep 2008, Andrew Haley wrote:

> You're right, I was assuming exactly that.  OK, but that is presumably
> simply a lack of volatility in the declaration of PC.
As a practical matter, that would probably help at the expense
of slowing things down a bit on some architectures.  Officially this
doesn't help much, since I believe Posix allows undefined behavior
for data races, even if they involve volatiles.  Even in terms of
current implementations, I don't believe it prevents hardware reordering
on architectures like PowerPC.

The C++ working paper provides atomic operations to address these issues. 
I think they're even somewhat implemented in the gcc trunk.  But I'm not 
sure you can avoid operations that generate fences on some architectures 
in what should be the fast path.

Hans