RFR: 8305186: Reference.waitForReferenceProcessing should be more accessible to tests

[Kim Barrett]

On Tue, 15 Apr 2025 00:00:35 GMT, Hans Boehm <hboehm at google.com> wrote:

> > Racy initialization is fine, the field can be static and the last one (any
> > racy init would all the same) wins:
> 
> How did you conclude that? From what I can see, Method has non-final fields. If another thread reads waitForReferenceProcessingMethod shortly after it is set, wfrp may be non-null, but its fields may not appear to be set correctly.
> 
> Furthermore, it seems to me there is nothing to stop the compiler from moving up the assignment to waitForReferenceProcessingMethod.
> 
> AFAICT, waitForReferenceProcessingMethod needs to be volatile here. Which shouldn't matter that much anymore on most modern hardware.

Agreed.  I'm pretty sure that all of the places I know of where I want to use
this are single-threaded, but being cautious is better.

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PR Comment: https://git.openjdk.org/jdk/pull/24527#issuecomment-2803873414