8364111: InstanceMirrorKlass iterators should handle CDS and hidden classes consistently

[shipilev]

Improves GC reliability with CDS and hidden classes, unblocks Shenandoah improvements that use these iterators.

Additional testing:

• Linux x86_64 server fastdebug, all
• Linux AArch64 server fastdebug, all
• Linux AArch64 server fastdebug, all + -XX:+UseShenandoahGC

---

Progress

• JDK-8364111 needs maintainer approval
• Change must not contain extraneous whitespace
• Commit message must refer to an issue

Issue

• JDK-8364111: InstanceMirrorKlass iterators should handle CDS and hidden classes consistently (Bug - P4 - Approved)

Reviewing

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[bridgekeeper]

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[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:

8364111: InstanceMirrorKlass iterators should handle CDS and hidden classes consistently

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 49 new commits pushed to the master branch:

• ec0d44c: 8367017: Remove legacy checks from WrappedToolkitTest and convert from bash
• 9776e4d: 8368071: Compilation throughput regressed 2X-8X after JDK-8355003
• 5861aa7: 8365726: Test crashed with assert in C1 thread: Possible safepoint reached by thread that does not allow it
• ... and 46 more: https://git.openjdk.org/jdk25u/compare/156fdbe911d215750d04cd8917e86ae72ab7bfd9...master

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.

[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

• 00: Full (0b590c24)

[shipilev]

/approval request Fixes the runtime/GC bug with classes loaded from CDS (and likely hidden classes too) by extending existing check to other iterators in InstanceMirrorKlass. Unblocks CDS support for Generational Shenandoah. Applies cleanly. All tests pass. There is no bugtail recorded after 7 weeks since integration to mainline. Risk is low-medium: affects a fairly common VM code path, but in the way sibling path already works, and no problems have been identified since integration.

[openjdk]

@shipilev
8364111: The approval request has been created successfully.

[shipilev]

Push approval granted.

/integrate

[openjdk]

Going to push as commit 789ead6.
Since your change was applied there have been 52 commits pushed to the master branch:

• ab772dd: 8333783: java/nio/channels/FileChannel/directio/DirectIOTest.java is unstable with AV software
• 6c751f2: 8367333: C2: Vector math operation intrinsification failure
• 668808f: 8362530: VM crash with -XX:+PrintTieredEvents when collecting AOT profiling
• ... and 49 more: https://git.openjdk.org/jdk25u/compare/156fdbe911d215750d04cd8917e86ae72ab7bfd9...master

Your commit was automatically rebased without conflicts.

[openjdk]

@shipilev Pushed as commit 789ead6.

💡 You may see a message that your pull request was closed with unmerged commits. This can be safely ignored.