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8293864: fails with SIGSEGV in JfrCheckpointManager::lease #10467

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@mgronlun mgronlun commented Sep 28, 2022


With JDK-8289692, a need arose to introduce a mutex mechanism for the buffers on the global list to prevent the JFR Recorder Thread from resetting buffers currently in use.

The introduced mutex mechanism was adequate as far as preventing the race condition. However, its protective characteristic was overemphasized, leading to the mistake of introducing a release, or removal, operation onto a current epoch list, as part of periodic flushing. The problem is that although the callback operations are safe, the underlying list type used with the global mspace does not allow for concurrent excision of nodes. The crash occurs because a thread attempts to dereference the next pointer to traverse a node that is excised and deleted after the thread loaded it.

I have reviewed how to handle better the introduction of virtual threads and their checkpoint data. I have concluded that the best way is to preserve the old system (pre-Loom) as much as possible, keeping the global and thread-local mspaces as before. Instead, an additional mspace dedicated solely to virtual threads is introduced. This categorization preserves the matching of operations against the underlying list infrastructure. It also provides flexibility in handling virtual threads distinct from regular, or "carrier", threads. The separate mspace of virtual threads is more dynamic as it does not need to preallocate buffers, a memory win for systems not using virtual threads. Also, the sizes of the different buffer types can be better controlled. With this restructuring, there are no longer any list concurrency issues; hence the mutex mechanism introduced with JDK-8289692 becomes obsolete. Applying a release operation for the current epoch list, of the global mspace, as part of flushing is a broken invariant and is therefore removed.

Testing: jdk_jfr, stress testing



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  • JDK-8293864: fails with SIGSEGV in JfrCheckpointManager::lease



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bridgekeeper bot commented Sep 28, 2022

👋 Welcome back mgronlun! 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 openjdk bot added the rfr Pull request is ready for review label Sep 28, 2022
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openjdk bot commented Sep 28, 2022

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

  • hotspot-jfr

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 the hotspot-jfr label Sep 28, 2022
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openjdk bot commented Oct 6, 2022

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

ℹ️ This project also has non-automated pre-integration requirements. Please see the file for details.

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

8293864: fails with SIGSEGV in JfrCheckpointManager::lease

Reviewed-by: egahlin

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 218 new commits pushed to the master branch:

  • 85569e9: 8286037: Bump minimum boot jdk to JDK 19
  • fef345b: 8293672: Update freetype md file
  • 5c030cc: 8290973: In AffineTransform, equals(Object) is inconsistent with hashCode()
  • f888aa9: 8293061: Combine CDSOptions and AppCDSOptions test utility classes
  • 73f0646: 8294839: Disable StressLongCountedLoop in compiler/loopopts/
  • 2ceebf6: 8294456: Fix misleading-indentation warnings in core JDK libraries
  • ad7b7d4: 8294697: java/lang/Thread/virtual/ThreadAPI.testGetStackTrace2 failed with non-empty stack trace
  • e38ae8a: 8294759: Print actual lock/monitor ranking
  • 7012d4b: 8294837: unify Windows 2019 version check in os_windows and java_props_md
  • 8c15f77: 8270915: GIFImageReader disregards ignoreMetadata flag which causes memory exhaustion
  • ... and 208 more:

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 6, 2022
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openjdk bot commented Oct 10, 2022

Going to push as commit 35d17a0.
Since your change was applied there have been 245 commits pushed to the master branch:

  • c5f462e: 8294956: GHA: qemu-debootstrap is deprecated, use the regular one
  • 269252a: 8295007: javax/swing/JRadioButton/4314194/ fails in mach5 for WIndowLookAndFeel
  • 6ed74ef: 8295005: compiler/loopopts/ fails with release VMs after JDK-8294839
  • 8a148bc: 8294848: Unnecessary SSLCipher dispose implementations
  • 8713dfa: 8294541: java/io/BufferedInputStream/ fails with OOME
  • 542cc60: 8294366: RISC-V: Partially mark out incompressible regions
  • 495c043: 7124710: interleaved RedefineClasses() and RetransformClasses() calls may have a problem
  • d39d8c8: 8170389: java.text.DigitList.getDouble() : Controversy between javadoc and code
  • 3466e99: 8294691: dynamicArchive/ is running other test case
  • 823b53d: 8294987: Streamline DerOutputStream write
  • ... and 235 more:

Your commit was automatically rebased without conflicts.

@openjdk openjdk bot added the integrated Pull request has been integrated label Oct 10, 2022
@openjdk openjdk bot closed this Oct 10, 2022
@openjdk openjdk bot removed ready Pull request is ready to be integrated rfr Pull request is ready for review labels Oct 10, 2022
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openjdk bot commented Oct 10, 2022

@mgronlun Pushed as commit 35d17a0.

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

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