https://github.com/marschall/jfr-crasher

A reproducer for crashing JFR
https://github.com/marschall/jfr-crasher

bug crash java java-flight-recorder

Last synced: about 1 year ago
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A reproducer for crashing JFR

• Host: GitHub
• URL: https://github.com/marschall/jfr-crasher
• Owner: marschall
• Created: 2019-11-14T17:12:49.000Z (over 6 years ago)
• Default Branch: master
• Last Pushed: 2019-12-20T10:49:40.000Z (over 6 years ago)
• Last Synced: 2025-01-16T02:45:06.704Z (over 1 year ago)
• Topics: bug, crash, java, java-flight-recorder
• Language: Java
• Size: 11.7 KB
• Stars: 0
• Watchers: 3
• Forks: 0
• Open Issues: 0
• Metadata Files:
  • Readme: README.md

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README

          
JFR Crasher

===========

A reproducer for a crashing JFR bug.

JFR has a crashing bug when multiple threads call `#defineClass` at the same time for the same class on the same classloader. This can happen with a [parallel capable](https://docs.oracle.com/javase/7/docs/technotes/guides/lang/cl-mt.html) such as [JBoss Modules](http://jboss-modules.github.io/jboss-modules/manual/).

If you are using a class loader similar to this one an using multiple threads you may be affected.

This bug is [JDK-8232997](https://bugs.openjdk.java.net/browse/JDK-8232997) and has been fixed in Java 14. Running with `-XX:-FlightRecorder` does not help.

```java

public class CustomClassLoader extends ClassLoader {

  static {

    registerAsParallelCapable();

  }

  @Override

  protected Class> loadClass(String className, boolean resolve) throws ClassNotFoundException {

    Class> loadedClass = findLoadedClass(className);

    if (loadedClass != null) {

      if (resolve) {

        resolveClass(loadedClass);

      }

      return loadedClass;

    }

    Class> clazz;

    try {

      clazz = defineClass(className, byteCode, 0, byteCode.length);

    } catch (LinkageError e) {

      // we lost the race, somebody else loaded the class

      clazz = findLoadedClass(className);

    }

    if (resolve) {

      resolveClass(clazz);

    }

    return clazz;

  }

}

```