RFR 8078490: Missed submissions in ForkJoinPool

[Chris Hegarty]

Thanks for bringing this in Paul. The change looks ok to me, and suitable for backport.

Trivially, the test does not need the Classpath exception in its license header.

-Chris.

On 23 Apr 2015, at 14:00, Paul Sandoz <paul.sandoz at oracle.com> wrote:

> Hi.
> 
> Please review this patch from Doug that fixes an issue where a submitted task to a f/j pool never gets executed.
> 
>  http://cr.openjdk.java.net/~psandoz/jdk9/JDK-8078490-fj-missed-submissions/webrev/
> 
> I already counted myself and Alexey as reviewers.
> 
> The issue manifests itself under certain conditions where by a task is submitted to a ForkJoinPool of a certain size and that task is not joined. In ForkJoin.externalPush a release write is too weak and needs to be straightened to a volatile write, which stamps in a memory fence before signalling that there is work to be performed.
> 
> I anticipate Doug will provide a clearer fix at some point in the future. This fix is sufficient for now and for backporting to 8u60.
> 
> Paul.