8264788: Make SequentialSubTasksDone use-once

[tschatzl]

Hi all,

can I have reviews for this change that simplifies code ahead?

SequentialSubTasksDone has some machinery to reset itself automatically after all tasks were claimed.

This is not used at all and can/should be removed.

Test: tier1-3

---

Progress

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Issue

• JDK-8264788: Make SequentialSubTasksDone use-once

Reviewers

• Albert Mingkun Yang (@albertnetymk - Committer) ⚠️ Review applies to 5393097
• Stefan Johansson (@kstefanj - Reviewer)

Reviewing

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[bridgekeeper]

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[openjdk]

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[mlbridge]

Webrevs

• 01: Full - Incremental (919ff6e7)
• 00: Full (53930970)

[tschatzl]

Note that it is possible to remove the CAS loop in SequentialSubTasksDone with an atomic add. I wasn't sure to do this, but if somebody thinks it is a good idea (and probably faster in many implementations) similar to the following:

bool SequentialSubTasksDone::try_claim_task(uint& t) {
  if (t < _num_tasks) {
    t = Atomic::add(&_num_claimed, 1) - 1;
  }
  return t < _num_tasks;
}

(And slightly fixing that assert in the destructor)

[albertnetymk]

Looking at how SequentialSubTasksDone is used, I don't really see the benefit of having assert(_num_claimed == _num_tasks) in the destructor. If we drop that assertion, Atomic::add is more readable.

I prefer Atomic::add with the assertion removed, but this version is fine as well.

[tschatzl]

I changed to the Atomic::add but kept the assert (modified).

[kstefanj]

Looks good.

[openjdk]

@tschatzl 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:

8264788: Make SequentialSubTasksDone use-once

Reviewed-by: ayang, sjohanss

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 105 new commits pushed to the master branch:

• e2106d5: 8265104: CpuLoad and SystemCpuLoad in OperatingSystem MXBean returns -1.0
• ebbce91: 8264681: Use the blessed modifier order in java.security
• ea5c55a: 8265103: Remove unnecessary inclusion of oopMap.hpp
• 26186ec: 8039261: [TEST_BUG]: There is not a minimal security level in Java Preferences and the TestApplet.html is blocked.
• 283d64f: 8262896: [macos_aarch64] Crash in jni_fast_GetLongField
• 55d5649: 8263157: [macos]: java.library.path is being set incorrectly
• e80012e: 8264768: JFR: Allow events to be printed to the log
• 3b576ed: 8265100: (fs) WindowsFileStore.hashCode() should read cached hash code once
• 8df8512: 8265125: IGV: cannot edit forms with NetBeans GUI builder
• 9cd5400: 8265138: Simplify DerUtils::checkAlg
• ... and 95 more: https://git.openjdk.java.net/jdk/compare/a611c462f938176d8fad303ec7a53191ce85c5d1...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.

[tschatzl]

/integrate

[tschatzl]

Thanks @albertnetymk @kstefanj for your reviews.

[openjdk]

@tschatzl Since your change was applied there have been 126 commits pushed to the master branch:

• 0793fcb: 8260255: C1: LoopInvariantCodeMotion constructor can leave some fields uninitialized
• b224b56: 8265225: jdk/jfr/tool/TestConfigure.java fails to cleanup the output files after the testing
• 7c6e379: 8265120: hs_err improvement: align the output of Virtual space metadata
• e7cbeba: 8259070: Add jcmd option to dump CDS
• 5931948: 8265246: Fix macos-Aarch64 build after JDK-8263709
• 79bff21: 8263709: Cleanup THREAD/TRAPS/CHECK usage in JRT_ENTRY routines
• f4c3efd: 8265192: [macos_aarch64] configure script fails if GNU uname in PATH
• e167577: 8265078: jpackage tests on Windows leave large temp files
• 05f851e: 8265236: ProblemList java/foreign/TestUpcall.java on macosx-aarch64
• d1b28e7: 8265231: (fc) ReadDirect and WriteDirect tests fail after fix for JDK-8264821
• ... and 116 more: https://git.openjdk.java.net/jdk/compare/a611c462f938176d8fad303ec7a53191ce85c5d1...master

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