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8282900: runtime/stringtable/StringTableCleaningTest.java verify unavailable at this moment #10527

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@robehn robehn commented Oct 3, 2022

Hi, please consider:

verify() is called by GC in safepoint so it should use the corresponding scanning method.
verify_and_compare_entries() can wait for until there is no resize.

This makes these methods always succeed, passes t1-t6.


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  • JDK-8282900: runtime/stringtable/StringTableCleaningTest.java verify unavailable at this moment

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Checkout this PR locally:
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Update a local copy of the PR:
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$ git pull https://git.openjdk.org/jdk pull/10527/head

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Checkout this PR locally:
$ git pr checkout 10527

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Download this PR as a diff file:
https://git.openjdk.org/jdk/pull/10527.diff

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bridgekeeper bot commented Oct 3, 2022

👋 Welcome back rehn! 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.

@robehn robehn marked this pull request as ready for review October 3, 2022 06:38
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openjdk bot commented Oct 3, 2022

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

  • hotspot-runtime

When this pull request is ready to be reviewed, an "RFR" email will be sent to the corresponding mailing list. If you would like to change these labels, use the /label pull request command.

@openjdk openjdk bot added hotspot-runtime hotspot-runtime-dev@openjdk.org rfr Pull request is ready for review labels Oct 3, 2022
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mlbridge bot commented Oct 3, 2022

Webrevs

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Looks good! Thanks for fixing this.

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openjdk bot commented Oct 3, 2022

@robehn 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:

8282900: runtime/stringtable/StringTableCleaningTest.java verify unavailable at this moment

Reviewed-by: coleenp, dholmes

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 37 new commits pushed to the master branch:

  • 43dbf58: 8186765: Speed up test sun/net/www/protocol/https/HttpsClient/ProxyAuthTest.java
  • 755958e: 8294376: Minimize disabled warnings in java.base
  • 1dafbe3: 8294539: Augment discussion of equivalence relations on floating-point values
  • b2e86a6: 8294255: Add link to DEFAULT_WAIT_TIME in javadoc for SunToolKit.realsSync
  • b22a38d: 8292309: Fix java/awt/PrintJob/ConstrainedPrintingTest/ConstrainedPrintingTest.java test
  • 121d4a5: 8293579: tools/jpackage/share/jdk/jpackage/tests/UnicodeArgsTest.java fails on Japanese Windows platform
  • 1166a8a: 8292214: Memory leak in getAllConfigs of awt_GraphicsEnv.c:386
  • 3644e26: 8294673: JFR: Add SecurityProviderService#threshold to TestActiveSettingEvent.java
  • 085949a: 8294712: G1: Use index-base iteration for G1FlushHumongousCandidateRemSets
  • b850f05: 8294758: JFR: Docs build fails after changes to RecordedObject and Timespan
  • ... and 27 more: https://git.openjdk.org/jdk/compare/a69ee85308ae2fd5d9fd5aed69b16ca70119976a...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.

@openjdk openjdk bot added the ready Pull request is ready to be integrated label Oct 3, 2022
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coleenp commented Oct 3, 2022

Is there an equivalent problem in SymbolTable?

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robehn commented Oct 3, 2022

I'll check.

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Using do_scan in verify seems appropriate as it is at a safepoint as you note. But the code says that the resize_lock may be dropped to allow a safepoint, but I can't see where exactly this dropping occurs? If we were to drop in the middle of a resize then it need not follow that the CHT can be scanned safely at a safepoint. ??

Why is it okay to have verify_and_compare_entries wait? What thread, doing what action, will it be waiting for? The fact it is only used during VM shutdown somewhat mitigates concerns as we only have to establish that one case is correct.

Thanks.

src/hotspot/share/classfile/stringTable.cpp Outdated Show resolved Hide resolved
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robehn commented Oct 4, 2022

Using do_scan in verify seems appropriate as it is at a safepoint as you note. But the code says that the resize_lock may be dropped to allow a safepoint, but I can't see where exactly this dropping occurs? If we were to drop in the middle of a resize then it need not follow that the CHT can be scanned safely at a safepoint. ??

Why is it okay to have verify_and_compare_entries wait? What thread, doing what action, will it be waiting for? The fact it is only used during VM shutdown somewhat mitigates concerns as we only have to establish that one case is correct.

When we are resizing some data (nodes) can be reached from both old table and new table.
(a concurrent scan could visits data (nodes) multiple time.
During a safepoint data/nodes are exclusively accessible from old or new table.
Safepoint scanning thus scans first old table and then new table.

The ServiceThread does the resizing, and only doing 4096 buckets at the time before safepoint checking.
The exact code would in "StringTable::grow(...)" when calling "gt.pause(jt)".

The ServiceThread is stopped by the final VM_Exit which happens after "before_exit".

Thanks.

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robehn commented Oct 4, 2022

Is there an equivalent problem in SymbolTable?

Kind of yes, but it looks the verify() is used both inside and out side of safepoints.
Create a new issue for SymbolTable if you like.

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But the code says that the resize_lock may be dropped to allow a safepoint, but I can't see where exactly this dropping occurs?

Can you answer this query? Thanks

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robehn commented Oct 5, 2022

Can you answer this query? Thanks

I thought did with:

The exact code would in "StringTable::grow(...)" when calling "gt.pause(jt)".

  // Pauses for safepoint
  void pause(Thread* thread) {
    // This leaves internal state locked.
    this->thread_owns_resize_lock(thread);
    BucketsOperation::_cht->_resize_lock->unlock();     
    this->thread_owns_only_state_lock(thread);        
  }

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I thought did with

Sorry I seem to have developed a selective reading disorder :(

Thanks for explaining.

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robehn commented Oct 5, 2022

Thanks David and Coleen!

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robehn commented Oct 5, 2022

/integrate

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openjdk bot commented Oct 5, 2022

Going to push as commit bd90c4c.
Since your change was applied there have been 45 commits pushed to the master branch:

  • 979efd4: 8289004: investigate if SharedRuntime::get_java_tid parameter should be a JavaThread*
  • b9eeec2: 8294310: compare.sh fails on macos after JDK-8293550
  • 13a5000: 8294151: JFR: Unclear exception message when dumping stopped in memory recording
  • 8ebebbc: 8294368: Java incremental builds broken on Windows after JDK-8293116
  • 4bdd1c9: 8290964: C2 compilation fails with assert "non-reduction loop contains reduction nodes"
  • b4e74ae: 8294514: Wrong initialization of nmethod::_consts_offset for native nmethods
  • 953ce8d: 8293701: jdeps InverseDepsAnalyzer runs into NoSuchElementException: No value present
  • be82cff: 8294748: Cleanup unneeded references to hg
  • 43dbf58: 8186765: Speed up test sun/net/www/protocol/https/HttpsClient/ProxyAuthTest.java
  • 755958e: 8294376: Minimize disabled warnings in java.base
  • ... and 35 more: https://git.openjdk.org/jdk/compare/a69ee85308ae2fd5d9fd5aed69b16ca70119976a...master

Your commit was automatically rebased without conflicts.

@openjdk openjdk bot added the integrated Pull request has been integrated label Oct 5, 2022
@openjdk openjdk bot closed this Oct 5, 2022
@openjdk openjdk bot removed ready Pull request is ready to be integrated rfr Pull request is ready for review labels Oct 5, 2022
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openjdk bot commented Oct 5, 2022

@robehn Pushed as commit bd90c4c.

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

@robehn robehn deleted the 8282900 branch December 6, 2022 14:09
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