Deadlock between ResourceChangeNotifierImpl.subscribeResourceChangeListener and ResourceChangeScannerImpl.subscribeNotifier

This deadlock was found by our continouos integration system which is building drools using mvn.

Found one Java-level deadlock:
=============================
"Thread-42":
waiting to lock monitor 0x00002aaaf8f2e8d0 (object 0x00002aaab4645830, a java.util.HashMap),
which is held by "main"
"main":
waiting to lock monitor 0x00002aaaf4f3a028 (object 0x00002aaab46459b0, a java.util.HashMap),
which is held by "Thread-42"

Java stack information for the threads listed above:
===================================================
"Thread-42":
at org.drools.io.impl.ResourceChangeNotifierImpl.subscribeResourceChangeListener(ResourceChangeNotifierImpl.java:64)

• waiting to lock <0x00002aaab4645830> (a java.util.HashMap)
  at org.drools.io.impl.ResourceChangeNotifierImpl.subscribeChildResource(ResourceChangeNotifierImpl.java:103)
  at org.drools.io.impl.ResourceChangeScannerImpl.scan(ResourceChangeScannerImpl.java:128)
• locked <0x00002aaab46459b0> (a java.util.HashMap)
  at org.drools.io.impl.ResourceChangeScannerImpl$ProcessChangeSet.run(ResourceChangeScannerImpl.java:276)
• locked <0x00002aaab46459b0> (a java.util.HashMap)
• locked <0x00002aaade2c97d8> (a org.drools.io.impl.ResourceChangeScannerImpl$ProcessChangeSet)
  at java.lang.Thread.run(Thread.java:619)
  "main":
  at org.drools.io.impl.ResourceChangeScannerImpl.subscribeNotifier(ResourceChangeScannerImpl.java:64)
• waiting to lock <0x00002aaab46459b0> (a java.util.HashMap)
  at org.drools.io.impl.ResourceChangeNotifierImpl.subscribeResourceChangeListener(ResourceChangeNotifierImpl.java:70)
• locked <0x00002aaab4645830> (a java.util.HashMap)
  at org.drools.agent.impl.KnowledgeAgentImpl.processChangeSet(KnowledgeAgentImpl.java:150)
• locked <0x00002aaade2c9c18> (a java.util.HashMap)
  at org.drools.agent.impl.KnowledgeAgentImpl.applyChangeSet(KnowledgeAgentImpl.java:117)
• locked <0x00002aaade2c9c18> (a java.util.HashMap)
  at org.drools.agent.impl.KnowledgeAgentImpl.applyChangeSet(KnowledgeAgentImpl.java:109)
  at org.drools.agent.KnowledgeAgentTest.testModifyDirectory(KnowledgeAgentTest.java:776)
  at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
  at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
  at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
  at java.lang.reflect.Method.invoke(Method.java:597)
  at junit.framework.TestCase.runTest(TestCase.java:154)
  at junit.framework.TestCase.runBare(TestCase.java:127)
  at junit.framework.TestResult$1.protect(TestResult.java:106)
  at junit.framework.TestResult.runProtected(TestResult.java:124)
  at junit.framework.TestResult.run(TestResult.java:109)
  at junit.framework.TestCase.run(TestCase.java:118)
  at junit.framework.TestSuite.runTest(TestSuite.java:208)
  at junit.framework.TestSuite.run(TestSuite.java:203)
  at sun.reflect.GeneratedMethodAccessor44.invoke(Unknown Source)
  at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
  at java.lang.reflect.Method.invoke(Method.java:597)
  at org.apache.maven.surefire.junit.JUnitTestSet.execute(JUnitTestSet.java:213)
  at org.apache.maven.surefire.suite.AbstractDirectoryTestSuite.executeTestSet(AbstractDirectoryTestSuite.java:140)
  at org.apache.maven.surefire.suite.AbstractDirectoryTestSuite.execute(AbstractDirectoryTestSuite.java:127)
  at org.apache.maven.surefire.Surefire.run(Surefire.java:177)
  at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
  at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
  at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
  at java.lang.reflect.Method.invoke(Method.java:597)
  at org.apache.maven.surefire.booter.SurefireBooter.runSuitesInProcess(SurefireBooter.java:345)
  at org.apache.maven.surefire.booter.SurefireBooter.main(SurefireBooter.java:1009)

Found 1 deadlock.