8255847: Shenandoah: Shenandoah should not mark through weak roots

[zhengyu123]

After moving weak root processing into concurrent phase, Shenandoah should no longer marks through weak roots, even when class unloading is disabled, given weak root processing no longer contributes to latency.

There are a couple of bugs:

1. ShenandoahRootVerifier was not updated to reflect the change.
   The problem did not show up due to SH::parallel_cleaning() uses wrong flag to determine if it should cleanup weak roots, and it will be addressed in separate CR.

2. Concurrent roots scanner should not mark through string dedup roots.

Test:

• hotspot_gc_shenandoah
• hotspot_gc_shenandoah with -XX:+ShenandoahVerify -XX:-ClassUnloading
• hotspot_gc_shenandoah with -XX:+ShenandoahVerify -XX:+UseStringDeduplication

---

Progress

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

Testing

	Linux x64	Linux x86	Windows x64	macOS x64
Build	✔️ (5/5 passed)	❌ (2/2 failed)	✔️ (2/2 passed)	✔️ (2/2 passed)
Test (tier1)	✔️ (9/9 passed)		✔️ (9/9 passed)	✔️ (9/9 passed)

Failed test tasks

• Linux x86 (build debug)
• Linux x86 (build release)

Issue

• JDK-8255847: Shenandoah: Shenandoah should not mark through weak roots

Reviewers

• Roman Kennke (@rkennke - Reviewer) ⚠️ Review applies to 2dc9248

Download

$ git fetch https://git.openjdk.java.net/jdk pull/1050/head:pull/1050
$ git checkout pull/1050

[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]

@zhengyu123 The following labels will be automatically applied to this pull request:

• hotspot-gc
• shenandoah

When this pull request is ready to be reviewed, an "RFR" email will be sent to the corresponding mailing lists. If you would like to change these labels, use the /label pull request command.

[mlbridge]

Webrevs

• 01: Full - Incremental (fca6617)
• 00: Full (2dc9248)

[rkennke]

Looks good. Make sure to merge latest tip to get full pre-submit testing in GitHub actions.

[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:

8255847: Shenandoah: Shenandoah should not mark through weak roots

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 no new commits pushed to the master branch. If another commit should be pushed before you perform the /integrate command, your PR will be automatically rebased. If you prefer to avoid any potential 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.

[zhengyu123]

Looks good. Make sure to merge latest tip to get full pre-submit testing in GitHub actions.

Reran pre-submit tests, all clean.

[zhengyu123]

/integrate

[openjdk]

@zhengyu123 Since your change was applied there have been 12 commits pushed to the master branch:

• 867a484: 8255214: Unsupported 'valign' attribute for 'th' tag used in j.u.l.LogManager
• d3c43c2: 8255937: Better cleanup for test/jdk/javax/imageio/stream/StreamFlush.java
• b65ff60: 8255226: (tz) Upgrade time-zone data to tzdata2020d
• 2b78a43: 8255584: HttpPrincipal::getName returns incorrect name
• a6ce6a5: 8252103: Parallel heap inspection for ParallelScavengeHeap
• cdef186: 8232856: jshell crashes when pressing up arrow after /!
• 700447f: 8255909: Remove unused delayed_value methods
• 397972e: 8255848: -Xlog:gc+heap+exit shows "used 0K"
• eb85b8d: 8255665: C2 should aggressively remove temporary hook nodes
• 18bc95b: 8250625: Compiler implementation of Pattern Matching for instanceof (Final)
• ... and 2 more: https://git.openjdk.java.net/jdk/compare/97a81cee252ab35e8c8e0beb60cc3e6d1e2cebde...master

Your commit was automatically rebased without conflicts.

Pushed as commit 31918c5.

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