Clear young generation reference to old mark queues when starting global collect

[earthling-amzn]

If concurrent marking in old is preempted by a global collection, the old mark is abandoned. The young generation should no longer hold a reference to the old mark queues. Without this fix, collections in young generation may erroneously behave as though concurrent mark in old is still running.

---

Progress

• Change must not contain extraneous whitespace
• Change must be properly reviewed

Reviewers

• Roman Kennke (@rkennke - Reviewer)

Reviewing

Using git

Checkout this PR locally:
$ git fetch https://git.openjdk.java.net/shenandoah pull/99/head:pull/99
$ git checkout pull/99

Update a local copy of the PR:
$ git checkout pull/99
$ git pull https://git.openjdk.java.net/shenandoah pull/99/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 99

View PR using the GUI difftool:
$ git pr show -t 99

Using diff file

Download this PR as a diff file:
https://git.openjdk.java.net/shenandoah/pull/99.diff

[bridgekeeper]

👋 Welcome back wkemper! 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.

[mlbridge]

Webrevs

• 00: Full (5c8fc865)

[openjdk]

@earthling-amzn 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:

Clear young generation reference to old mark queues when starting global collect

Reviewed-by: rkennke

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 1 new commit pushed to the master branch:

• 641e665: Remove assert that plab allocation must succeed

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.

[earthling-amzn]

/integrate

[openjdk]

Going to push as commit 191dd79.
Since your change was applied there has been 1 commit pushed to the master branch:

• 641e665: Remove assert that plab allocation must succeed

Your commit was automatically rebased without conflicts.

[openjdk]

@earthling-amzn Pushed as commit 191dd79.

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