JEP 171: Fence Intrinsics

[David Chase]

I'll defer to your judgement on the JMM issues, but from a user (programmer) POV, does this distinction make a difference?  I think their (in)ability to write "portable" code (across style checkers, across class loaders) would be a big deal.

How about "sun.misc.VM" instead?  Unsafe seems to be booby-trapped against use by non-system classloaders; I don't see how that is necessary here.

David

On 2012-12-03, at 12:54 PM, Doug Lea <dl at cs.oswego.edu> wrote:

> On 12/03/12 12:45, David Chase wrote:
>> Is this the right place to comment on this? I think these should not go in
>> Unsafe; fence intrinsics belong with compareAndSet in j.u.concurrent.atomic.
> 
> They cannot. The methods cannot be spec'ed using only the concepts
> in the JLS/JMM. So they are not "Java methods", but "JVM methods".
> (This is the same rationale for placing @Contended in sun.misc.)
> Someday, a serious effort is needed to enable rigorous specs
> of core intrinsics along these lines (possible even with a
> Java-level JMM memory model overhaul). But I don't think anyone
> wants to hold these methods hostage for years until this happens.
> 
> -Doug
> 
> 
>