8276201: Shenandoah: Race results degenerated GC to enter wrong entry point

[zhengyu123]

A clean backport of Shenandoah specific bug. The patch fixes a subtle race condition that results degenerated GC to enter wrong degen entry.

Test:

• hotspot_gc_shenandoah

---

Progress

• Change must not contain extraneous whitespace
• Commit message must refer to an issue

Issue

• JDK-8276201: Shenandoah: Race results degenerated GC to enter wrong entry point

Reviewing

Using git

Checkout this PR locally:
$ git fetch https://git.openjdk.java.net/jdk17u pull/232/head:pull/232
$ git checkout pull/232

Update a local copy of the PR:
$ git checkout pull/232
$ git pull https://git.openjdk.java.net/jdk17u pull/232/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 232

View PR using the GUI difftool:
$ git pr show -t 232

Using diff file

Download this PR as a diff file:
https://git.openjdk.java.net/jdk17u/pull/232.diff

[bridgekeeper]

👋 Welcome back zgu! 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]

@zhengyu123 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:

8276201: Shenandoah: Race results degenerated GC to enter wrong entry point

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 2 new commits pushed to the master branch:

• e829c85: 8273021: C2: Improve Add and Xor ideal optimizations
• dc93934: 8270901: Typo PHASE_CPP in CompilerPhaseType

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.

[mlbridge]

Webrevs

• 00: Full (f9378c01)

[zhengyu123]

/integrate

[openjdk]

Going to push as commit 7176520.
Since your change was applied there have been 2 commits pushed to the master branch:

• e829c85: 8273021: C2: Improve Add and Xor ideal optimizations
• dc93934: 8270901: Typo PHASE_CPP in CompilerPhaseType

Your commit was automatically rebased without conflicts.

[openjdk]

@zhengyu123 Pushed as commit 7176520.

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