RFR: 8344332: (bf) Migrate DirectByteBuffer to use java.lang.ref.Cleaner [v10]

[Aleksey Shipilev]

On Wed, 29 Jan 2025 19:28:31 GMT, Kim Barrett <kbarrett at openjdk.org> wrote:

>> Aleksey Shipilev has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains 14 additional commits since the last revision:
>> 
>>  - Merge branch 'master' into JDK-8344332-dbb-cleaner
>>  - No instantiation for BufferCleaner, javadocs
>>  - Remove hasReferencePendingList
>>  - Revert test exclusion, moved to JDK-8348301
>>  - Alan's review
>>  - Remove vestigial reference to waitForReferenceProcessing in tests
>>  - Track Cleaner progress with canaries
>>  - Amend benchmarks
>>  - Fix tests
>>  - Review feedback and benchmarks
>>  - ... and 4 more: https://git.openjdk.org/jdk/compare/f2507063...bcfab1ba
>
> src/java.base/share/classes/java/lang/ref/Reference.java line 282:
> 
>> 280:     // references, or (2) the reference processing thread is
>> 281:     // processing references. Otherwise, returns false immediately.
>> 282:     private static boolean waitForReferenceProcessing()
> 
> Removing waitForReferenceProcessing is contrary to 
> https://bugs.openjdk.org/browse/JDK-8305186
> Reference.waitForReferenceProcessing should be more accessible
> I've pointed to JDK-8305186 in a number of discussions about problems encountered with various tests.
> So I'm doubtful about removing it.

No problem, I will revert those removals. I did the removals proactively, thinking none of this infrastructure is needed after we migrate DBB, but since there are apparently plausible use cases for it, I'll leave it in.

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PR Review Comment: https://git.openjdk.org/jdk/pull/22165#discussion_r1934481142