Starting from jdk7b55, a number of VM tests from ParallelClassLoading suite start to fail intermittenlty with the following error:
java.lang.IllegalArgumentException exception is caught in "Loading Thread #10": custom
java.lang.IllegalArgumentException: custom
        at java.lang.ClassLoader.definePackage(ClassLoader.java:1591)
        at java.net.URLClassLoader.defineClass(URLClassLoader.java:343)
        at java.net.URLClassLoader.access$100(URLClassLoader.java:75)
        at java.net.URLClassLoader$1.run(URLClassLoader.java:294)
        at java.net.URLClassLoader$1.run(URLClassLoader.java:288)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.net.URLClassLoader.findClass(URLClassLoader.java:287)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:391)
        at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:307)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:331)
        at java.lang.Class.forName0(Native Method)
        at java.lang.Class.forName(Class.java:264)
        at runtime.ParallelClassLoading.shared.ProvokeType.provoke(ProvokeType.java:83)
        at runtime.ParallelClassLoading.shared.CustomProvokeType.provoke(CustomProvokeType.java:20)
        at runtime.ParallelClassLoading.shared.ClassLoadingThread.run(ClassLoadingThread.java:81)

Test scenario is:
1) create custom class loader
2) initiate loading of some class hierarchy from multiple threads
3) go to step #1 if the time & iteration limit isn't reached

The failure always occurs during first loading iteration. Seems like the problem relates to initialization stage.

According to ClassLoader.definePackage contract, it throws IllegalArgumentException if "package name duplicates an existing package either in this class loader or one of its ancestors". Test code doesn't explicitly call defineClass.

How to reproduce:
1) login to vm-t2000-01a.sfbay
2) cd /net/sqenfs-2.sfbay/export2/results/vm/gtee/HSX/PIT/VM/16/b01/jdk7b56/product/vm/solaris-sparc/client/mixed/solaris-sparc_client_mixed_vm.parallel_class_loading.testlist/ResultDir/anonymous-complex
3) bash rerun.sh

Test sources can be found at: /net/vmsqe.russia/export/testbase/sqe/vm/7/ws_int_spb/vm/src/runtime/ParallelClassLoading/shared