8348268: Test gc/shenandoah/TestResizeTLAB.java#compact: fatal error: Before Updating References: Thread C2 CompilerThread1: expected gc-state 9, actual 21

[earthling-amzn]

Non-java threads were not having their gc-state configured when they attach. Additionally, we need to hold the Threads_lock when concurrently changing the gc state to make sure that any stale gc state observed when the thread attaches is fixed by the handshake when the thread list is iterated.

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Issue

• JDK-8348268: Test gc/shenandoah/TestResizeTLAB.java#compact: fatal error: Before Updating References: Thread C2 CompilerThread1: expected gc-state 9, actual 21 (Bug - P3)

Reviewers

• Aleksey Shipilev (@shipilev - Reviewer)

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[openjdk]

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

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After integration, the commit message for the final commit will be:

8348268: Test gc/shenandoah/TestResizeTLAB.java#compact: fatal error: Before Updating References: Thread C2 CompilerThread1: expected gc-state 9, actual 21

Reviewed-by: shade

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At the time when this comment was updated there had been 91 new commits pushed to the master branch:

• e7157d1: 8150442: Enforce Supported Platforms in Packager for MSI bundles
• 6428165: 8349254: Disable "best-fit" mapping on Windows environment variables
• 32dc41c: 8349624: Validation for slot missing in CodeBuilder local variable instructions
• a1bcda2: 8349579: jsvml.dll incorrect RDATA SEGMENT specification
• ee079fd: 8349820: Temporarily increase MemLimit for tests until JDK-8349772 and JDK-8337821 are fixed
• 545d19f: 8349771: Replace usages of -mx and -ms in some monitor tests
• 5ee44c1: 8349662: SSLTube SSLSubscriptionWrapper has potential races when switching subscriptions
• 964dd18: 8349515: [REDO] Framework for tracing makefile inclusion and parsing
• 8e85829: 8349213: G1: Clearing bitmaps during collection set merging not claimed by region
• 1a8212e: 8348678: [PPC64] C2: unaligned vector load/store is ok
• ... and 81 more: https://git.openjdk.org/jdk/compare/618c5eb27b4c719afd577b690e6bcb21a45fcb0d...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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Webrevs

• 02: Full - Incremental (c57bf8a0)
• 01: Full - Incremental (1a4e3bb1)
• 00: Full (f402628e)

[shipilev]

It looks generally okay, but I am confused how this fixes a bad state in C2 CompilerThread1, since compiler threads are Java threads?

jdk/src/hotspot/share/compiler/compilerThread.hpp

Line 42 in beb43e2

class CompilerThread : public JavaThread {

[earthling-amzn]

@shipilev , that is a good point. Will take a closer look.

[shipilev]

Great find.

So that means we cannot safely do ShenandoahHeap::set_gc_state_concurrent, unless we hold Threads_lock and do a handshake afterwards? I think a part of comment that you have near MutexLocker can go to ShenandoahHeap::set_gc_state_concurrent with the assert(Threads_lock->is_locked(), ....

[earthling-amzn]

That's right. The on_thread_attach callback and the thread being added to the list of threads does happen under the Thread_lock, by the handshake mechanism (and the java thread iterator) do not take the thread lock. In this particular assertion violation, the thread received a stale gc_state when it attached (before the control thread even entered concurrent_prepare_for_update_refs), however, the control thread executed the handshake before the recently attached thread was actually added to the java thread list.

I will update the comment and add an assert in set_gc_state_concurrent.

[earthling-amzn]

/integrate

[openjdk]

Going to push as commit 8c09d40.
Since your change was applied there have been 91 commits pushed to the master branch:

• e7157d1: 8150442: Enforce Supported Platforms in Packager for MSI bundles
• 6428165: 8349254: Disable "best-fit" mapping on Windows environment variables
• 32dc41c: 8349624: Validation for slot missing in CodeBuilder local variable instructions
• a1bcda2: 8349579: jsvml.dll incorrect RDATA SEGMENT specification
• ee079fd: 8349820: Temporarily increase MemLimit for tests until JDK-8349772 and JDK-8337821 are fixed
• 545d19f: 8349771: Replace usages of -mx and -ms in some monitor tests
• 5ee44c1: 8349662: SSLTube SSLSubscriptionWrapper has potential races when switching subscriptions
• 964dd18: 8349515: [REDO] Framework for tracing makefile inclusion and parsing
• 8e85829: 8349213: G1: Clearing bitmaps during collection set merging not claimed by region
• 1a8212e: 8348678: [PPC64] C2: unaligned vector load/store is ok
• ... and 81 more: https://git.openjdk.org/jdk/compare/618c5eb27b4c719afd577b690e6bcb21a45fcb0d...master

Your commit was automatically rebased without conflicts.

[openjdk]

@earthling-amzn Pushed as commit 8c09d40.

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