8302615: make JVMTI thread cpu time functions optional for virtual threads

[sspitsyn]

This is a minor JVM TI spec update for two timer functions GetCurrentThreadCpuTime and GetThreadCpuTime to allow implementations to support virtual threads.

The CSR is:
JDK-8302616: make JVMTI thread cpu time functions optional for virtual threads

No testing is needed.

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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
• Change requires CSR request JDK-8302616 to be approved

Issues

• JDK-8302615: make JVMTI thread cpu time functions optional for virtual threads
• JDK-8302616: make JVMTI thread cpu time functions optional for virtual threads (CSR)

Reviewers

• Alan Bateman (@AlanBateman - Reviewer)

Reviewing

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[mlbridge]

Webrevs

• 00: Full (c7c532b2)

[AlanBateman]

I assume we'll rev the JVMTI version at some point in 21.

The change looks fine. It might be that we'll need to add a new capacity or add a field to jvmtiTimerInfo to say whether the implementation supports CPU time for virtual threads, but what we have now is okay.

[sspitsyn]

Thank you for review, Alan.

[openjdk]

@sspitsyn 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:

8302615: make JVMTI thread cpu time functions optional for virtual threads

Reviewed-by: alanb

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 71 new commits pushed to the master branch:

• a917fb3: 7033677: potential cast error in MemberEnter
• 6120319: 8302226: failure_handler native.core should wait for coredump to finish
• fef3eab: 8302734: Parallel: Remove unused LGRPSpace::_invalid_region
• ea5bfea: 8302661: Parallel: Remove PSVirtualSpace::is_aligned
• edf238b: 8302635: Race condition in HttpBodySubscriberWrapper when cancelling request
• cd77fcf: 8290822: C2: assert in PhaseIdealLoop::do_unroll() is subject to undefined behavior
• 57c9bc3: 8302335: IGV: Bytecode not showing
• 57fde75: 8302113: Improve CRC32 intrinsic with crypto pmull on AArch64
• b8c9d6c: 8302158: PPC: test/jdk/jdk/internal/vm/Continuation/Fuzz.java: AssertionError: res: false shouldPin: false
• dc55a7f: 8302202: Incorrect desugaring of null-allowed nested patterns
• ... and 61 more: https://git.openjdk.org/jdk/compare/13b1ebba276940ff83e53b8ec3659280b3574204...master

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]

I will integrate this as a trivial fix.

[sspitsyn]

/integrate

[openjdk]

Going to push as commit 6b082fb.
Since your change was applied there have been 75 commits pushed to the master branch:

• 7c60b9c: 8302358: Behavior of adler32 changes after JDK-8300208
• 86b9fce: 8301992: Embed SymbolTable CHT node
• 03d613b: 8294402: Add diagnostic logging to VMProps.checkDockerSupport
• a263f28: 8302777: CDS should not relocate heap if mapping fails
• a917fb3: 7033677: potential cast error in MemberEnter
• 6120319: 8302226: failure_handler native.core should wait for coredump to finish
• fef3eab: 8302734: Parallel: Remove unused LGRPSpace::_invalid_region
• ea5bfea: 8302661: Parallel: Remove PSVirtualSpace::is_aligned
• edf238b: 8302635: Race condition in HttpBodySubscriberWrapper when cancelling request
• cd77fcf: 8290822: C2: assert in PhaseIdealLoop::do_unroll() is subject to undefined behavior
• ... and 65 more: https://git.openjdk.org/jdk/compare/13b1ebba276940ff83e53b8ec3659280b3574204...master

Your commit was automatically rebased without conflicts.

[openjdk]

@sspitsyn Pushed as commit 6b082fb.

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

[AlanBateman]

I've just spotted that we missed some text:

GetCurrentThreadCpuTime has "The current thread may not be a virtual thread".

GetThreadCpuTime has "The thread may not be a virtual thread".

The changes that have been integrated allow these functions to support CPU time measurement so I think we will need to adjust both of these sentences in a follow up issue.