8357650: ThreadSnapshot to take snapshot of thread for thread dumps

[alexmenkov]

This is first (hotspot) part of the update for HotSpotDiagnosticMXBean.dumpThreads and jcmd Thread.dump_to_file to include lock information in thread dumps (JDK-8356870).
The update has been split into parts to simplify reviewing.
The fix contains an implementation of jdk.internal.vm.ThreadSnapshot class to gather required information about a thread.
Second (dependent) part includes changes in HotSpotDiagnosticMXBean.dumpThreads/jcmd Thread.dump_to_file, spec updates and tests for the functionality.

Testing: new HotSpotDiagnosticMXBean.dumpThreads/jcmd Thread.dump_to_file functionality was tested in loom repo;
sanity tier1 (this fix only)

---

Progress

• Change must be properly reviewed (1 review required, with at least 1 Reviewer)
• Change must not contain extraneous whitespace
• Commit message must refer to an issue

Issue

• JDK-8357650: ThreadSnapshot to take snapshot of thread for thread dumps (Sub-task - P4)

Reviewers

• Serguei Spitsyn (@sspitsyn - Reviewer)
• Kevin Walls (@kevinjwalls - Reviewer)

Contributors

• Alan Bateman <alanb@openjdk.org>
• Alex Menkov <amenkov@openjdk.org>

Reviewing

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[bridgekeeper]

👋 Welcome back amenkov! 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]

@alexmenkov 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:

8357650: ThreadSnapshot to take snapshot of thread for thread dumps

Co-authored-by: Alan Bateman <alanb@openjdk.org>
Co-authored-by: Alex Menkov <amenkov@openjdk.org>
Reviewed-by: sspitsyn, kevinw

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At the time when this comment was updated there had been 27 new commits pushed to the master branch:

• 26275a1: 8355753: @SuppressWarnings("this-escape") not respected for indirect leak via field
• ae3d96a: 8357683: (process) SIGQUIT still blocked after JDK-8234262 with jdk.lang.Process.launchMechanism=FORK or VFORK
• 12ee80c: 8357675: Amend headless message
• ... and 24 more: https://git.openjdk.org/jdk/compare/2ec6ab347a18f454e33a3a281daf1d50a1fd5e27...master

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➡️ To integrate this PR with the above commit message to the master branch, type /integrate in a new comment.

[openjdk]

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

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[alexmenkov]

/label remove core-libs

[mlbridge]

Webrevs

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• 04: Full - Incremental (025d9f27)
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[openjdk]

@alexmenkov
The core-libs label was successfully removed.

[alexmenkov]

/contributor add alexmenkov
/contributor add alanb

[openjdk]

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[openjdk]

@alexmenkov
Contributor Alan Bateman <alanb@openjdk.org> successfully added.

[alexmenkov]

/contributor add @alexmenkov

[openjdk]

@alexmenkov
Contributor Alex Menkov <amenkov@openjdk.org> successfully added.

[stefank]

Just a few drive-by questions:

1. Did you consider putting this implementation in another file, say threadServices.hpp or even its own file? I'm asking because javaClasses seems to have become a dumping ground for code that calls from Java code into the JVM. It would be nice if we could put features into files that are named after the feature.

2. Did you consider to put these OopHandle storages in something else than Universe::vm_globals()? We have, for example, ThreadService::_thread_service_storage.

[AlanBateman]

1. Did you consider putting this implementation in another file, say threadServices.hpp or even its own file? I'm asking because javaClasses seems to have become a dumping ground for code that calls from Java code into the JVM. It would be nice if we could put features into files that are named after the feature.

Alex can correct me but I think it started out here because of java_lang_Thread::async_get_stack_trace/GetStackTraceClosure. It has gone through a number of iterations and you are probably right that it would be better off in threadService or its own source file now.

2. Did you consider to put these OopHandle storages in something else than Universe::vm_globals()? We have, for example, ThreadService::_thread_service_storage.

That OopStorage is maintained in threadService.cpp so would be an option if the code moves.

[alexmenkov]

Just a few drive-by questions:

1. Did you consider putting this implementation in another file, say threadServices.hpp or even its own file? I'm asking because javaClasses seems to have become a dumping ground for code that calls from Java code into the JVM. It would be nice if we could put features into files that are named after the feature.

2. Did you consider to put these OopHandle storages in something else than Universe::vm_globals()? We have, for example, ThreadService::_thread_service_storage.

My concern about threadServices and _thread_service_storage was it's initialized conditionally. But now I see that they are always initialized. I'll try to move the stuff to threadServices.hpp/.cpp

[alexmenkov]

• moved implementation from javaClasses to threadServices;
• used ThreadService OopStorage instead of vm_global;
• fixed minimalVM build (Thread.dump_to_file command is not registered for builds without JVMTI);

[dholmes-ora]

Some initial drive-by comments ...

[sspitsyn]

Alex, thank you for the updates! It is getting better. :)

[sspitsyn]

Alex, thank you for the updates!
Looks good now.

[kevinjwalls]

Just to be clear, the ifdef JVMTI means Thread.dump_to_file not work in a build configuration using - --enable-jvm-feature-jvmti=no ?
Currently, Thread.dump_to_file works in such configs.
I don't think this is a problem.. just thought we could spell it out.
This all looks good to me.

[AlanBateman]

Just to be clear, the ifdef JVMTI means Thread.dump_to_file not work in a build configuration using - --enable-jvm-feature-jvmti=no ? Currently, Thread.dump_to_file works in such configs. I don't think this is a problem.. just thought we could spell it out. This all looks good to me.

The dependency on JvmtiVTMSTransitionDisabler is needed for now but maybe in the future this could be separated from JVMTI for other cases where transitions needs to be disabled.

Minimal VM disables management and jvmti, and is really only practical if you run jlink to create a run-time image with a small subset of the modules. So no jdk.management and no HotSpotDiagnosticMXBean. It's possible of course that someone configures with +management and -jvmti, in which case the HotSpotDiagnosticMXBean.dumpThreads will throw NPE. It should throw UOE (the method is specified to allow this), which means JVM_CreateThreadSnapshot or ThreadSnapshot.of(Thread) should throw.

[kevinjwalls]

Thanks Alan, and thanks Alex!

[alexmenkov]

/integrate

[openjdk]

Going to push as commit 406f1bc.
Since your change was applied there have been 117 commits pushed to the master branch:

• e984fa7: 8358539: ProblemList jdk/jfr/api/consumer/TestRecordingFileWrite.java
• 461cb84: 8345538: Robot.mouseMove doesn't clamp bounds on macOS when trying to move mouse off screen
• c382da5: 8358178: Some nsk/jdi tests should be run with includevirtualthreads=y even though they pass without
• ... and 114 more: https://git.openjdk.org/jdk/compare/2ec6ab347a18f454e33a3a281daf1d50a1fd5e27...master

Your commit was automatically rebased without conflicts.

[openjdk]

@alexmenkov Pushed as commit 406f1bc.

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