Deadlock in DelegateUnitTestCase

[starksm64]

While doing an install of the mc I saw the install fail in the following unit test due to the deadlock shown in the thread dump:

11824 DEBUG [DelegateUnitTestCase] Got class: class org.jboss.test.classloader.delegate.support.a.TestAbstractFactory{cl=BaseClassLoader@670fe2b9 codeSource=(file:/home/svn/JBossMC/jbossmc/classloader/target/tests-classes/ <no signer certificates>)} for org.jboss.test.classloader.delegate.support.a.TestAbstractFactory from BaseClassLoader@670fe2b9

Full thread dump Java HotSpot(TM) 64-Bit Server VM (1.5.0_11-b03 mixed mode):

"B" prio=1 tid=0x0000002ae35e1fa0 nid=0x536c waiting for monitor entry [0x0000000041563000..0x0000000041565c30]
 at org.jboss.classloader.spi.base.BaseClassLoader.unlock(BaseClassLoader.java:701)
 - waiting to lock <0x0000002acaf81e50> (a org.jboss.classloader.spi.base.BaseClassLoader)
 at org.jboss.classloader.spi.base.BaseClassLoader.unlock(BaseClassLoader.java:583)
 at org.jboss.classloader.spi.base.ClassLoaderManager.nextTask(ClassLoaderManager.java:286)
 at org.jboss.classloader.spi.base.ClassLoaderManager.process(ClassLoaderManager.java:145)
 at org.jboss.classloader.spi.base.BaseClassLoaderDomain.loadClass(BaseClassLoaderDomain.java:193)
 at org.jboss.classloader.spi.base.BaseClassLoaderDomain.loadClass(BaseClassLoaderDomain.java:752)
 at org.jboss.classloader.spi.base.BaseClassLoader.loadClassFromDomain(BaseClassLoader.java:483)
 at org.jboss.classloader.spi.base.BaseClassLoader.loadClass(BaseClassLoader.java:158)
 - locked <0x0000002acaf88c70> (a org.jboss.classloader.spi.base.BaseClassLoader)
 at java.lang.ClassLoader.loadClass(ClassLoader.java:251)
 at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:319)
 - locked <0x0000002acaf88c70> (a org.jboss.classloader.spi.base.BaseClassLoader)
 at java.lang.ClassLoader.defineClass1(Native Method)
 at java.lang.ClassLoader.defineClass(ClassLoader.java:620)
 at org.jboss.classloader.spi.base.BaseClassLoader.access$200(BaseClassLoader.java:58)
 at org.jboss.classloader.spi.base.BaseClassLoader$1.run(BaseClassLoader.java:279)
 at org.jboss.classloader.spi.base.BaseClassLoader$1.run(BaseClassLoader.java:246)
 at java.security.AccessController.doPrivileged(Native Method)
 at org.jboss.classloader.spi.base.BaseClassLoader.loadClassLocally(BaseClassLoader.java:244)
 - locked <0x0000002acaf88c70> (a org.jboss.classloader.spi.base.BaseClassLoader)
 at org.jboss.classloader.spi.base.BaseClassLoader.loadClassLocally(BaseClassLoader.java:217)
 at org.jboss.classloader.spi.base.BaseDelegateLoader.loadClass(BaseDelegateLoader.java:75)
 at org.jboss.classloader.spi.filter.FilteredDelegateLoader.loadClass(FilteredDelegateLoader.java:90)
 at org.jboss.classloader.spi.base.ClassLoadingTask$ThreadTask.run(ClassLoadingTask.java:449)
 at org.jboss.classloader.spi.base.ClassLoaderManager.nextTask(ClassLoaderManager.java:251)
 at org.jboss.classloader.spi.base.ClassLoaderManager.process(ClassLoaderManager.java:145)
 at org.jboss.classloader.spi.base.BaseClassLoaderDomain.loadClass(BaseClassLoaderDomain.java:193)
 at org.jboss.classloader.spi.base.BaseClassLoaderDomain.loadClass(BaseClassLoaderDomain.java:752)
 at org.jboss.classloader.spi.base.BaseClassLoader.loadClassFromDomain(BaseClassLoader.java:483)
 at org.jboss.classloader.spi.base.BaseClassLoader.loadClass(BaseClassLoader.java:158)
 - locked <0x0000002acaf88c70> (a org.jboss.classloader.spi.base.BaseClassLoader)
 at java.lang.ClassLoader.loadClass(ClassLoader.java:251)
 at org.jboss.test.classloader.AbstractClassLoaderTest.assertLoadClass(AbstractClassLoaderTest.java:176)
 at org.jboss.test.classloader.AbstractClassLoaderTest.assertLoadClass(AbstractClassLoaderTest.java:158)
 at org.jboss.test.classloader.AbstractClassLoaderTest.assertLoadClass(AbstractClassLoaderTest.java:143)
 at org.jboss.test.classloader.delegate.test.DelegateUnitTestCase.access$100(DelegateUnitTestCase.java:54)
 at org.jboss.test.classloader.delegate.test.DelegateUnitTestCase$2.run(DelegateUnitTestCase.java:299)

"A" prio=1 tid=0x0000002ae31e7220 nid=0x536b in Object.wait() [0x0000000040f5e000..0x0000000040f5fdb0]
 at java.lang.Object.wait(Native Method)
 - waiting on <0x0000002acb05a558> (a java.util.Collections$SynchronizedList)
 at java.lang.Object.wait(Object.java:474)
 at org.jboss.classloader.spi.base.ClassLoaderManager.nextTask(ClassLoaderManager.java:204)
 - locked <0x0000002acb05a558> (a java.util.Collections$SynchronizedList)
 at org.jboss.classloader.spi.base.ClassLoaderManager.process(ClassLoaderManager.java:145)
 at org.jboss.classloader.spi.base.BaseClassLoaderDomain.loadClass(BaseClassLoaderDomain.java:193)
 at org.jboss.classloader.spi.base.BaseClassLoaderDomain.loadClass(BaseClassLoaderDomain.java:752)
 at org.jboss.classloader.spi.base.BaseClassLoader.loadClassFromDomain(BaseClassLoader.java:483)
 at org.jboss.classloader.spi.base.BaseClassLoader.loadClass(BaseClassLoader.java:158)
 - locked <0x0000002acaf81e50> (a org.jboss.classloader.spi.base.BaseClassLoader)
 at java.lang.ClassLoader.loadClass(ClassLoader.java:251)
 at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:319)
 - locked <0x0000002acaf81e50> (a org.jboss.classloader.spi.base.BaseClassLoader)
 at java.lang.Class.getDeclaredMethods0(Native Method)
 at java.lang.Class.privateGetDeclaredMethods(Class.java:2395)
 at java.lang.Class.getMethod0(Class.java:2642)
 at java.lang.Class.getMethod(Class.java:1579)
 at org.jboss.test.classloader.delegate.test.DelegateUnitTestCase$1.run(DelegateUnitTestCase.java:277)

[alesj]

While doing an install of the mc I saw the install fail in the following unit test due to the deadlock shown in the thread dump:

I randomly got the same deadlock, though tests mostly passed.
Should probably report it sooner ... :-(

[adrian.brock]

If you can reproduce it can you try to debug it or
add enableTrace("org.jboss.classloader") to the test.

There's obviously a bug somewhere since thread "B" is trying to unlock
the classloader:

"B" prio=1 tid=0x0000002ae35e1fa0 nid=0x536c waiting for monitor entry [0x0000000041563000..0x000000004
1565c30]
 at org.jboss.classloader.spi.base.BaseClassLoader.unlock(BaseClassLoader.java:701)
 - waiting to lock <0x0000002acaf81e50> (a org.jboss.classloader.spi.base.BaseClassLoader)
 at org.jboss.classloader.spi.base.BaseClassLoader.unlock(BaseClassLoader.java:583)
 at org.jboss.classloader.spi.base.ClassLoaderManager.nextTask(ClassLoaderManager.java:286)

But at this point in the code "A" has obtained the lock:

 at org.jboss.classloader.spi.base.BaseClassLoader.loadClassFromDomain(BaseClassLoader.java:4
83)
 at org.jboss.classloader.spi.base.BaseClassLoader.loadClass(BaseClassLoader.java:158)
 - locked <0x0000002acaf81e50> (a org.jboss.classloader.spi.base.BaseClassLoader)

So the two questions are:
1) Is this is spurious unlock and "B" didn't have the lock?
2) Did "A" obtain the lock when it shouldn't have done?

I'd guess it is (1) since I didn't *fully* understand the
"release in next task" in the old LoadMgr3, I just copied the logic. :-)