8374145: Remove legacy locking remnants from markWord #28927

stefank · 2025-12-19T14:05:13Z

There's a bunch of unused code in markWord that used to be used by the removed legacy locking. I propose that we remove it.

There's a Shenandoah change that should be checked closer. My thinking is:
is_being_inflated: always returns false
has_displaced_mark_helper: Only returns true if both these are true:

!UseCompactObjectTable - there's an early return for this earlier in the function.
lockbits == monitor_value - checked in the if-statement above

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Issue

JDK-8374145: Remove legacy locking remnants from markWord (Enhancement - P4)

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Axel Boldt-Christmas (@xmas92 - Reviewer)
Kim Barrett (@kimbarrett - Reviewer)
Coleen Phillimore (@coleenp - Reviewer)

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$ git fetch https://git.openjdk.org/jdk.git pull/28927/head:pull/28927
$ git checkout pull/28927

Update a local copy of the PR:
$ git checkout pull/28927
$ git pull https://git.openjdk.org/jdk.git pull/28927/head

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$ git pr checkout 28927

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xmas92

Looks good. Just one thought.

xmas92 · 2025-12-19T14:10:24Z

src/hotspot/share/gc/shenandoah/shenandoahHeap.inline.hpp

-  } else if (w.is_being_inflated() || w.has_displaced_mark_helper()) {
-    // Informs caller that we aren't able to determine the age
-    return markWord::max_age + 1; // sentinel


Not sure if we want an !w.has_displaced_mark_helper() assert. Even if we already check for (and handled) the exact conditions (in the current implementation) for has_displaced_mark_helper().

That would work for me. I'll wait for input from the Shenandoah devs.

In the interest to get this integrated I've created an Enh for this:
https://bugs.openjdk.org/browse/JDK-8374191

bridgekeeper · 2025-12-19T14:21:42Z

👋 Welcome back stefank! 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 · 2025-12-19T14:24:10Z

@stefank 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:

8374145: Remove legacy locking remnants from markWord

Reviewed-by: aboldtch, kbarrett, coleenp

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 31 new commits pushed to the master branch:

400d8cf: 8373793: TestDynamicStore.java '/manual' disables use of '/timeout'
c1ad393: 8374048: Genshen: Backout fix for missed cancellation notice
23fc21a: 8374052: Use java/util/Calendar in ReplaceCriticalClasses.java test
... and 28 more: https://git.openjdk.org/jdk/compare/a31e6e0d3b806b3b1935d3b71dd0b111bc5fddf1...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.

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openjdk · 2025-12-19T14:25:47Z

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

hotspot
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 · 2025-12-19T14:30:05Z

Webrevs

00: Full (7973a71b)

kimbarrett

Looks good. No opinion about @xmas92 suggestion in the shenandoah change.

coleenp

Thanks for finding these.

stefank

Thanks for the reviews!

stefank · 2025-12-22T09:31:01Z

src/hotspot/share/gc/shenandoah/shenandoahHeap.inline.hpp

-  } else if (w.is_being_inflated() || w.has_displaced_mark_helper()) {
-    // Informs caller that we aren't able to determine the age
-    return markWord::max_age + 1; // sentinel


In the interest to get this integrated I've created an Enh for this:
https://bugs.openjdk.org/browse/JDK-8374191

stefank · 2025-12-22T09:31:47Z

/integrate

openjdk · 2025-12-22T09:32:25Z

Going to push as commit e6c3ebe.
Since your change was applied there have been 38 commits pushed to the master branch:

3579c75: 8373876: StackWalkNativeToJava print more output in case of failures
9435d5b: 8346154: [XWayland] Some tests fail intermittently in the CI, but not locally
25e8714: 8369515: Deadlock between JVMTI and JNI ReleasePrimitiveArrayCritical
... and 35 more: https://git.openjdk.org/jdk/compare/a31e6e0d3b806b3b1935d3b71dd0b111bc5fddf1...master

Your commit was automatically rebased without conflicts.

openjdk · 2025-12-22T09:32:39Z

@stefank Pushed as commit e6c3ebe.

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

8374145: Remove legacy locking remnants from markWord

7973a71

xmas92 approved these changes Dec 19, 2025

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openjdk bot mentioned this pull request Dec 19, 2025

8374151: Cleanup minor markWord function disorder #28928

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stefank commented Dec 22, 2025

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openjdk bot closed this Dec 22, 2025

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8374145: Remove legacy locking remnants from markWord #28927

8374145: Remove legacy locking remnants from markWord #28927

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