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  1. JDK
  2. JDK-7031759

Deadlock due to java.lang.Class.initAnnotationsIfNecessary

    Details

    • Type: Bug
    • Status: Closed
    • Priority: P4
    • Resolution: Duplicate
    • Affects Version/s: 6u24
    • Fix Version/s: None
    • Component/s: core-libs
    • Labels:

      Description

      FULL PRODUCT VERSION :
      java -version git:master
      java version "1.6.0_24"
      Java(TM) SE Runtime Environment (build 1.6.0_24-b07)
      Java HotSpot(TM) 64-Bit Server VM (build 19.1-b02, mixed mode)


      ADDITIONAL OS VERSION INFORMATION :
      Linux HOSTNAME 2.6.32-28-generic #55-Ubuntu SMP Mon Jan 10 23:42:43 UTC 2011 x86_64 GNU/Linux


      EXTRA RELEVANT SYSTEM CONFIGURATION :
      not relevant

      A DESCRIPTION OF THE PROBLEM :
      The private method initAnnotationsIfNecessary, called every time annotations are being retrieved from the Class object, is synchronized on the class instance.

      Any static synchronized method in a class also synchronizes on the class instance.

      This means that any static synchronized method on a class might cause deadlocks.

      STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
      Try to retrieve annotations on a class while another thread is holding the class lock, perhaps via a static synchronized method. See the submitted sample code.

      EXPECTED VERSUS ACTUAL BEHAVIOR :
      EXPECTED -
      [Ljava.lang.annotation.Annotation;@<hashcode>
      ACTUAL -
      deadlock

      REPRODUCIBILITY :
      This bug can be reproduced always.

      ---------- BEGIN SOURCE ----------
      import java.util.concurrent.*;


      public class Deadlock {
          public static synchronized void main(String[] args) throws Exception {
              Callable<Object> c = new Callable<Object>() {
                  @Override
                  public Object call() throws Exception {
                      return SyncBug.class.getAnnotations();
                  }
              };
              Future<Object> future = Executors.newSingleThreadExecutor().submit(c);
              System.out.println(future.get());
          }
      }

      ---------- END SOURCE ----------

      CUSTOMER SUBMITTED WORKAROUND :
      Don't ever use static synchronized methods or syncronize on the class.

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              • Assignee:
                Unassigned
                Reporter:
                webbuggrp Webbug Group
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                • Created:
                  Updated:
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