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  1. JDK
  2. JDK-8316469

Java 21 class initialization deadlock with Jetty

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    • Bug
    • Resolution: Not an Issue
    • P4
    • None
    • 21
    • hotspot
    • None

    Description

      On 8/09/2023 12:38 am, Simone Bordet wrote:> Hello,
      >
      > We switched the Jetty builds to Java 21 a while ago, and they randomly
      > fail with a hard deadlock during class initialization.
      >
      > We tried to understand if we were doing something wrong, but the code
      > compiles fine, and at first glance there seems to be nothing wrong
      > with it, but it may well be a popular Java puzzler that I am not aware
      > of :)
      >
      > We did not see these failures with Java 20, and we do not see them with Java 17.
      >
      > I was wondering if something changed in Java 21 to cause this deadlock?

      Taking a thread dump we see one thread in this state:

      java.lang.Thread.State: RUNNABLE
      at org.eclipse.jetty.http.HttpFields.build(org.eclipse.jetty.http@12.0.2-SNAPSHOT/HttpFields.java:76)
      - waiting on the Class initialization monitor for
      org.eclipse.jetty.http.MutableHttpFields
      at org.eclipse.jetty.http.HttpFields.<clinit>(org.eclipse.jetty.http@12.0.2-SNAPSHOT/HttpFields.java:67)
      "ForkJoinPool-1-worker-1" #23 [1457161] daemon prio=5 os_prio=0
      cpu=320.77ms elapsed=8870.98s allocated=18414K defined_classes=928
      tid=0x00007f6ec0c6a6f0 nid=1457161 waiting on condition
      [0x00007f6e91ffb000]

      And other threads are in this state (or similar -- the bottom frame is
      different but still triggering the clinit of HttpFields):

      java.lang.Thread.State: RUNNABLE
      at org.eclipse.jetty.http.HttpTester.parseResponse(org.eclipse.jetty.http@12.0.2-SNAPSHOT/HttpTester.java:274)
      - waiting on the Class initialization monitor for
      org.eclipse.jetty.http.HttpFields
      at org.eclipse.jetty.http.HttpTester.parseResponse(org.eclipse.jetty.http@12.0.2-SNAPSHOT/HttpTester.java:261)
      "ForkJoinPool-1-worker-2" #24 [1457162] daemon prio=5 os_prio=0
      cpu=136.15ms elapsed=8870.96s allocated=3303K defined_classes=340
      tid=0x00007f6e4c01ddb0 nid=1457162 waiting on condition
      [0x00007f6e91efc000]

      Class hierarchy:

      MutableHttpFields implements HttpFields.Mutable
      HttpFields.Mutable extends HttpFields

      Full thread dump:
      https://gist.github.com/olamy/7e883adcf51b2410337abfa775a79a0b

      Code:
      https://github.com/eclipse/jetty.project/blob/jetty-12.0.1/jetty-core/jetty-http/src/main/java/org/eclipse/jetty/http/HttpFields.java

      --
      Simone Bordet
      ---
      Finally, no matter how good the architecture and design are,
      to deliver bug-free software with optimal performance and reliability,
      the implementation technique must be flawless. Victoria Livschitz

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              dholmes David Holmes
              dholmes David Holmes
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                Updated:
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