8358735: GenShen: block_start() may be incorrect after class unloading

[rgithubli]

Backport of JDK-8358735 and its two follow up fixes: JDK-8372110 and JDK-8371854.

The backport of the original issue (JDK-8358735) is almost clean except that atomic.hpp was renamed to atomicAccess.hpp in the later versions, and I had to resolve the conflict by retaining atomic.hpp import.

The two follow up backports are clean.

Our internal application crashed and we identified JDK-8358735 was the root cause. Backporting it for the fix.

Testing: all GHA tests passed.

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Progress

• Change must be properly reviewed (1 review required, with at least 1 Reviewer)
• Change must not contain extraneous whitespace
• JDK-8372110 needs maintainer approval
• Commit message must refer to an issue
• JDK-8358735 needs maintainer approval
• JDK-8371854 needs maintainer approval

Issues

• JDK-8358735: GenShen: block_start() may be incorrect after class unloading (Bug - P3)
• JDK-8372110: GenShen: Fix erroneous assert (Enhancement - P4)
• JDK-8371854: Shenandoah: Simplify WALK_FORWARD_IN_BLOCK_START use (Enhancement - P4)

Reviewers

• Kelvin Nilsen (@kdnilsen - no project role)
• Y. Srinivas Ramakrishna (@ysramakrishna - Reviewer)

Reviewing

Using git

Checkout this PR locally:
$ git fetch https://git.openjdk.org/jdk25u-dev.git pull/19/head:pull/19
$ git checkout pull/19

Update a local copy of the PR:
$ git checkout pull/19
$ git pull https://git.openjdk.org/jdk25u-dev.git pull/19/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 19

View PR using the GUI difftool:
$ git pr show -t 19

Using diff file

Download this PR as a diff file:
https://git.openjdk.org/jdk25u-dev/pull/19.diff

Using Webrev

Link to Webrev Comment

[bridgekeeper]

👋 Welcome back rgithubli! 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 change is not yet ready to be integrated.
See the Progress checklist in the description for automated requirements.

[openjdk]

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

[openjdk]

⚠️ @rgithubli 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

• 01: Full - Incremental (0fbe598e)
• 00: Full (ca08e4d2)

[rgithubli]

/issue add JDK-8372110
/issue add JDK-8371854

[openjdk]

@rgithubli
Adding additional issue to issue list: 8372110: GenShen: Fix erroneous assert.

[openjdk]

@rgithubli
Adding additional issue to issue list: 8371854: Shenandoah: Simplify WALK_FORWARD_IN_BLOCK_START use.

[ysramakrishna]

Thanks for a good description of the backport & conflicts.

LGTM! 🚢