8352918: Shenandoah: Verifier does not deactivate barriers as intended

[earthling-amzn]

When verifying reachable objects, Shenandoah's verifier clears the _gc_state with the intention of deactivating barriers. However, the mechanism for this is a friend of the heap and does not toggle the flag to cause threads to use the value set on the verifier's safepoint. The net effect here is that the barriers are not deactivated during verification. Leaving the barriers on while the verifier traverses the heap may have unintended consequences (cards marked, objects evacuated, etc.)

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Issue

• JDK-8352918: Shenandoah: Verifier does not deactivate barriers as intended (Bug - P4)

Reviewers

• Kelvin Nilsen (@kdnilsen - Committer)
• Aleksey Shipilev (@shipilev - Reviewer)
• Y. Srinivas Ramakrishna (@ysramakrishna - Reviewer)

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[openjdk]

@earthling-amzn This change now passes all automated pre-integration checks.

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8352918: Shenandoah: Verifier does not deactivate barriers as intended

Reviewed-by: kdnilsen, shade, ysr

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At the time when this comment was updated there had been 25 new commits pushed to the master branch:

• 2483340: 8352579: Refactor CDS legacy optimization for lambda proxy classes
• 1397ee5: 8334322: Misleading values of keys in jpackage resource bundle
• 441bd12: 8352812: remove useless class and function parameter in SuspendThread impl
• e83cccf: 8352948: Remove leftover runtime_x86_32.cpp after 32-bit x86 removal
• 5672a93: 8348400: GenShen: assert(ShenandoahHeap::heap()->is_full_gc_in_progress() || (used_regions_size() <= _max_capacity)) failed: Cannot use more than capacity #
• c2a4fed: 8348907: Stress times out when is executed with ZGC
• 5392674: 8352766: Problemlist hotspot tier1 tests requiring tools that are not included in static JDK
• 1d205f5: 8352716: (tz) Update Timezone Data to 2025b
• a2a64da: 8352588: GenShen: Enabling JFR asserts when getting GCId
• 79bffe2: 8349361: C2: RShiftL should support all applicable transformations that RShiftI does
• ... and 15 more: https://git.openjdk.org/jdk/compare/dbc620fb1f754ca84f2a07abfdfbd4c5fcb55087...master

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[openjdk]

@earthling-amzn The following labels will be automatically applied to this pull request:

• hotspot-gc
• shenandoah

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[mlbridge]

Webrevs

• 01: Full - Incremental (2c86db47)
• 00: Full (64403639)

[shipilev]

Ouch. Took me a while to understand which field is updated, since fields are named the same in ShenandoahHeap and here. I suggest renaming fields in ShenandoahGCStateResetter to _saved_gc_state and _saved_gc_state_changed.

[ysramakrishna]

🚢

[earthling-amzn]

/integrate

[openjdk]

Going to push as commit 1bd0ce1.
Since your change was applied there have been 43 commits pushed to the master branch:

• dc5c414: 8352762: Use EXACTFMT instead of expanded version where applicable
• 2eeda64: 8325132: CDS: Make sure the ArchiveRelocationMode is always printed in the log
• 50ac24e: 8351593: [JMH] test PhoneCode.Bulk reports NPE exception
• 79824c3: 8352184: Jtreg tests using CommandLineOptionTest.getVMTypeOption() and optionsvalidation.JVMOptionsUtils fail on static JDK
• c50a0a1: 8352508: [Redo] G1: Pinned regions with pinned objects only reachable by native code crash VM
• 89e5c42: 8294954: Remove superfluous ResourceMarks when using LogStream
• 41f3eea: 8352624: Add missing {@code} to PassFailJFrame.Builder.splitUI
• e2cd70a: 8351151: Clean up x86 template interpreter after 32-bit x86 removal
• b990780: 8352393: AIX: Problem list serviceability/attach/AttachAPIv2/StreamingOutputTest.java
• 927aeb2: 8352617: IR framework test TestCompileCommandFileWriter.java runs TestCompilePhaseCollector instead of itself
• ... and 33 more: https://git.openjdk.org/jdk/compare/dbc620fb1f754ca84f2a07abfdfbd4c5fcb55087...master

Your commit was automatically rebased without conflicts.

[openjdk]

@earthling-amzn Pushed as commit 1bd0ce1.

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