8312777: notifyJvmtiMount before notifyJvmtiUnmount

[AlanBateman]

JVMTI is notified after a virtual thread unmounts. Right not, this notification is done after the virtual thread has finished parking or yielding so it's possible for the virtual to continue, and be mounted on a different carrier, before the unmount notification has completed on the original carrier. If this happens it means the the JVMTI mount and unmount notifications will race and it's possible they could be unbalanced. The unmount notification needs to move to after the unmount and before the virtual thread state is changed.

While in the area, I've removed @ChangesCurrentThread from VirtualThread.run. This annotation was in place to workaround an issue with the notifyJvmtiXXX instrinsics, fixed recently by JDK-8316130.

Testing: tier1-6.

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Issue

• JDK-8312777: notifyJvmtiMount before notifyJvmtiUnmount (Bug - P3)

Reviewers

• Hamlin Li (@Hamlin-Li - Reviewer) ⚠️ Review applies to aa9587b7
• Serguei Spitsyn (@sspitsyn - Reviewer)

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👋 Welcome back alanb! 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]

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[AlanBateman]

/label remove core-libs
/label add serviceability

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@AlanBateman
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[mlbridge]

Webrevs

• 01: Full - Incremental (b6462986)
• 00: Full (aa9587b7)

[Hamlin-Li]

LGTM.

[openjdk]

@AlanBateman 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:

8312777: notifyJvmtiMount before notifyJvmtiUnmount

Reviewed-by: mli, sspitsyn

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At the time when this comment was updated there had been 8 new commits pushed to the master branch:

• 9cf334f: 8318383: Remove duplicated checks in os::get_native_stack() in posix implementation
• defc7e0: 8318454: TestLayoutPaths broken on Big Endian platforms after JDK-8317837
• 3c70f2c: 8318418: hsdis build fails with system binutils on Ubuntu
• 15acf4b: 8318324: Drop redundant default methods from FFM API
• 1a09835: 8317358: G1: Make TestMaxNewSize use createTestJvm
• 47bb1a1: 8318415: Adjust describing comment of os_getChildren after 8315026
• 80bd22d: 8316144: Remove unused field jdk.internal.util.xml.impl.XMLStreamWriterImpl.Element._Depth
• c0e154c: 8318089: Class space not marked as such with NMT when CDS is off

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.

[sspitsyn]

Looks good. It is more elegant now.
I was thinking if it'd make sense to move:

• notifyJvmtiMount(/*hide*/true); at start of mount()
• notifyJvmtiUnmount(/*hide*/false); at end of unmount()
  but I guess you wanted to have them at the runContinuation() level.

Thanks,
Serguei

[AlanBateman]

Looks good. It is more elegant now. I was thinking if it'd make sense to move:

• notifyJvmtiMount(/*hide*/true); at start of mount()
• notifyJvmtiUnmount(/*hide*/false); at end of unmount()
  but I guess you wanted to have them at the runContinuation() level.

I'd be happy to move them to mount/unmount. As I recall, this wasn't possible because it lead to unbalanced method enter/exit, e.g. enter mount, exit unmount. I can re-test with to see what issues we might have but I suspect you will remember the issues with balancing the enter/exit.

[AlanBateman]

I tested tier1-tier6 with the JVMTI notifications moved to mount/unmount and don't see any failures. So if you are okay with that then it would be a bit nicer. The main thing is that the notification is done before the virtual thread state changes.

[sspitsyn]

Thank you for the update. It looks good to me.
Thanks,
Serguei

[AlanBateman]

/integrate

[openjdk]

Going to push as commit c46a54e.
Since your change was applied there have been 13 commits pushed to the master branch:

• 8f5f440: 8317692: jcmd GC.heap_dump performance regression after JDK-8292818
• 684b91e: 8315064: j.text.ChoiceFormat provides no specification on quoting behavior
• 1740950: 8314901: AES-GCM interleaved implementation using AVX2 instructions
• cc8f8da: 8318322: Update IANA Language Subtag Registry to Version 2023-10-16
• 599560a: 8317635: Improve GetClassFields test to verify correctness of field order
• 9cf334f: 8318383: Remove duplicated checks in os::get_native_stack() in posix implementation
• defc7e0: 8318454: TestLayoutPaths broken on Big Endian platforms after JDK-8317837
• 3c70f2c: 8318418: hsdis build fails with system binutils on Ubuntu
• 15acf4b: 8318324: Drop redundant default methods from FFM API
• 1a09835: 8317358: G1: Make TestMaxNewSize use createTestJvm
• ... and 3 more: https://git.openjdk.org/jdk/compare/24bc5bd104b8b4b96a61cffd3ec35cc795744eb9...master

Your commit was automatically rebased without conflicts.

[openjdk]

@AlanBateman Pushed as commit c46a54e.

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