8255980: G1 Service thread register_task can be used after shutdown

[kstefanj]

Please review this change to improve the service thread task handling during shutdown.

This problem isn't currently visible, but with upcoming changes there is a race where tasks might be added to the service thread after it has been shut down. This becomes problematic because the task queue at that point consists of invalid objects. They are invalid because the tasks are currently stack-allocated on the service thread. This change both allocates the tasks handled by the service thread dynamically and add a check to avoid adding tasks when the service thread has been shut down. Just doing the dynamic allocation would be enough, but there is no reason to add tasks after the thread is shut down.

I've tested this fix together with my concurrent uncommit changes which highlight the problem, and also run tier1 and tier2 for sanity.

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Progress

• Change must not contain extraneous whitespace
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Testing

	Linux x64	Linux x86	Windows x64	macOS x64
Build	✔️ (5/5 passed)	✔️ (2/2 passed)	✔️ (2/2 passed)	✔️ (2/2 passed)
Test (tier1)	✔️ (9/9 passed)	✔️ (9/9 passed)	✔️ (9/9 passed)	✔️ (9/9 passed)

Issue

• JDK-8255980: G1 Service thread register_task can be used after shutdown

Reviewers

• Thomas Schatzl (@tschatzl - Reviewer)
• Albert Mingkun Yang (@albertnetymk - Author)

Download

$ git fetch https://git.openjdk.java.net/jdk pull/1093/head:pull/1093
$ git checkout pull/1093

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[openjdk]

@kstefanj The following label will be automatically applied to this pull request:

• hotspot-gc

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[mlbridge]

Webrevs

• 00: Full (647a7e7)

[tschatzl]

Since ServiceThread is never deleted (as owned by G1CollectedHeap) this sufficiently keeps alive the task queue so that the code can query it and the tasks in there.

Lgtm.

[openjdk]

@kstefanj 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:

8255980: G1 Service thread register_task can be used after shutdown

Reviewed-by: tschatzl, ayang

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 32 new commits pushed to the master branch:

• d99e1f6: 8255991: Shenandoah: Apply 'weak' LRB on cmpxchg and xchg
• c7551c3: 8256014: Eliminate the warning about serialization in non-public API of Swing
• 2d6c28d: 6847157: java.lang.NullPointerException: HDC for component at sun.java2d.loops.Blit.Blit
• 3ce09c0: 8255920: J2DBench should support CS_PYCC color profile
• 2c8f4e2: 8255799: AArch64: CPU_A53MAC feature may be set incorrectly
• 2cad836: 8255575: java.awt.color.ICC_ColorSpace is not thread-safe
• a53b12d: 8255722: Create a new test for rotated blit
• f39a2c8: 8256015: Shenandoah: Add missing Shenandoah implementation in WB_isObjectInOldGen
• ed7526a: 8247872: Upgrade HarfBuzz to the latest 2.7.2
• 6a183fb: 8255562: delete UseRDPCForConstantTableBase
• ... and 22 more: https://git.openjdk.java.net/jdk/compare/d3c43c28165d703570ba96e9c557927f23478947...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.

[albertnetymk]

I would prefer them being embedded directly, G1RemSetSamplingTask _remset_task;, since they share the same lifespan with the enclosing object. No strong opinion; up to you.

[kstefanj]

Me too, but then I would have to move the declaration of the tasks into the header. Now the above forward declaration is enough and I preferred that even more :)

[kstefanj]

/integrate

[openjdk]

@kstefanj Since your change was applied there have been 33 commits pushed to the master branch:

• dd8e4ff: 8255711: Fix and unify hotspot signal handlers
• d99e1f6: 8255991: Shenandoah: Apply 'weak' LRB on cmpxchg and xchg
• c7551c3: 8256014: Eliminate the warning about serialization in non-public API of Swing
• 2d6c28d: 6847157: java.lang.NullPointerException: HDC for component at sun.java2d.loops.Blit.Blit
• 3ce09c0: 8255920: J2DBench should support CS_PYCC color profile
• 2c8f4e2: 8255799: AArch64: CPU_A53MAC feature may be set incorrectly
• 2cad836: 8255575: java.awt.color.ICC_ColorSpace is not thread-safe
• a53b12d: 8255722: Create a new test for rotated blit
• f39a2c8: 8256015: Shenandoah: Add missing Shenandoah implementation in WB_isObjectInOldGen
• ed7526a: 8247872: Upgrade HarfBuzz to the latest 2.7.2
• ... and 23 more: https://git.openjdk.java.net/jdk/compare/d3c43c28165d703570ba96e9c557927f23478947...master

Your commit was automatically rebased without conflicts.

Pushed as commit 79b7909.

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