RFR: 8314480: Memory ordering spec updates in java.lang.ref [v32]

[Joe Darcy]

On Fri, 24 May 2024 21:39:33 GMT, Brent Christian <bchristi at openjdk.org> wrote:

>> Classes in the `java.lang.ref` package would benefit from an update to bring the spec in line with how the VM already behaves. The changes would focus on _happens-before_ edges at some key points during reference processing.
>> 
>> A couple key things we want to be able to say are:
>> - `Reference.reachabilityFence(x)` _happens-before_ reference processing occurs for 'x'.
>> - `Cleaner.register()` _happens-before_ the Cleaner thread runs the registered cleaning action.
>> 
>> This will bring Cleaner in line (or close) with the memory visibility guarantees made for finalizers in [JLS 17.4.5](https://docs.oracle.com/javase/specs/jls/se18/html/jls-17.html#jls-17.4.5):
>> _"There is a happens-before edge from the end of a constructor of an object to the start of a finalizer (§12.6) for that object."_
>
> Brent Christian has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains 69 commits:
> 
>  - Merge branch 'master' into refDocs2
>  - add link to Thread.isAlive()
>  - small review tweaks; shorten MemoryConsistency links
>  - small grammar fixes
>  - new section for finalizer memviz
>  - add memviz bullet for finalization
>  - remove quotes from dequeue
>  - package spec updates, mostly about reference queues and dequeueing
>  - move reachability section before notification; update section header
>  - add details on use of reference queues; swap reachability/memviz sections
>  - ... and 59 more: https://git.openjdk.org/jdk/compare/7bf1989f...d7cbf0d3

src/java.base/share/classes/java/lang/ref/Reference.java line 556:

> 554:      *   int myIndex;
> 555:      *   Resource(...) {
> 556:      *     myIndex = ...

Convert this code sample to a snippet?

-------------

PR Review Comment: https://git.openjdk.org/jdk/pull/16644#discussion_r1619935008