8327501: Common ForkJoinPool prevents class unloading in some cases

[shipilev]

The change is stabilizing in mainline, but it looks simple, so we start testing it for JDK 21 pickup here.

Additional testing:

• Linux x86_64 server fastdebug, all

---

Progress

• JDK-8327501 needs maintainer approval
• JDK-8328366 needs maintainer approval
• Change must not contain extraneous whitespace
• Commit message must refer to an issue

Issues

• JDK-8327501: Common ForkJoinPool prevents class unloading in some cases (Bug - P4 - Approved)
• JDK-8328366: Thread.setContextClassloader from thread in FJP commonPool task no longer works after JDK-8327501 (Bug - P3 - Approved)

Reviewing

Using git

Checkout this PR locally:
$ git fetch https://git.openjdk.org/jdk21u-dev.git pull/338/head:pull/338
$ git checkout pull/338

Update a local copy of the PR:
$ git checkout pull/338
$ git pull https://git.openjdk.org/jdk21u-dev.git pull/338/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 338

View PR using the GUI difftool:
$ git pr show -t 338

Using diff file

Download this PR as a diff file:
https://git.openjdk.org/jdk21u-dev/pull/338.diff

Webrev

Link to Webrev Comment

[bridgekeeper]

👋 Welcome back shade! A progress list of the required criteria for merging this PR into master will be added to the body of your pull request. There are additional pull request commands available for use with this pull request.

[openjdk]

This backport pull request has now been updated with issue from the original commit.

[openjdk]

⚠️ @shipilev This change is now ready for you to apply for maintainer approval. This can be done directly in each associated issue or by using the /approval command.

[mlbridge]

Webrevs

• 02: Full (febeb48b)
• 01: Full - Incremental (f17aeca1)
• 00: Full (bce8bcfc)

[jerboaa]

Lets wait on getting this one backported until the compatibility impact wrt. setting the context class loader of a thread in the common pool is addressed.

[shipilev]

Lets wait on getting this one backported until the compatibility impact wrt. setting the context class loader of a thread in the common pool is addressed.

Yup. With this PR, I just confirmed all tests that I throw at this change pass in jdk21u-dev.

[openjdk]

@shipilev This change now passes all automated pre-integration checks.

ℹ️ This project also has non-automated pre-integration requirements. Please see the file CONTRIBUTING.md for details.

After integration, the commit message for the final commit will be:

8327501: Common ForkJoinPool prevents class unloading in some cases
8328366: Thread.setContextClassloader from thread in FJP commonPool task no longer works after JDK-8327501

You can use pull request commands such as /summary, /contributor and /issue to adjust it as needed.

At the time when this comment was updated there had been 10 new commits pushed to the master branch:

• 0e9b9f2: 8310072: JComboBox/DisabledComboBoxFontTestAuto: Enabled and disabled ComboBox does not match in these LAFs: GTK+
• 0d9833e: 8323552: AbstractMemorySegmentImpl#mismatch returns -1 when comparing distinct areas of the same instance of MemorySegment
• 0dcbc1d: 8324668: JDWP process management needs more efficient file descriptor handling
• 42e6a97: 8323670: A few client tests intermittently throw ConcurrentModificationException
• 55e97ce: 8319773: Avoid inflating monitors when installing hash codes for LM_LIGHTWEIGHT
• b56f0c0: 8326106: Write and clear stack trace table outside of safepoint
• 8d4f686: 8312229: Crash involving yield, switch and anonymous classes
• 2a21044: 8331573: Rename CollectedHeap::is_gc_active to be explicitly about STW GCs
• 362ecac: 8331164: createJMHBundle.sh download jars fail when url needed to be redirected
• dc8b95f: 8328075: Shenandoah: Avoid forwarding when objects don't move in full-GC

Please see this link for an up-to-date comparison between the source branch of this pull request and the master branch.
As there are no conflicts, your changes will automatically be rebased on top of these commits when integrating. If you prefer to avoid this automatic rebasing, please check the documentation for the /integrate command for further details.

➡️ To integrate this PR with the above commit message to the master branch, type /integrate in a new comment.

[shipilev]

/issue add JDK-8328366

[openjdk]

@shipilev
Adding additional issue to issue list: 8328366: Thread.setContextClassloader from thread in FJP commonPool task no longer works after JDK-8327501.

[shipilev]

Both backports are clean.

/clean

[openjdk]

@shipilev This backport pull request is now marked as clean

[shipilev]

/approval 8327501 request Fixes the class unloading regression since JDK 19. Applies cleanly. Tests pass, but there is a regression, which is fixed by JDK-8328366. Risk is medium: affects common paths, has bugtail with easily detectable failures.

/approval 8328366 request Fixes the regression introduced by JDK-8327501. Applies cleanly. Tests pass.

[openjdk]

@shipilev
8327501: The approval request has been created successfully.

[openjdk]

@shipilev
8328366: The approval request has been created successfully.