Index: ThreadStateMapping.java
===================================================================
--- ThreadStateMapping.java	(revision 7066)
+++ ThreadStateMapping.java	(working copy)
@@ -1,26 +1,69 @@
 package org.python.core;
 
+import java.util.ArrayList;
+import java.lang.ref.WeakReference;
+
 class ThreadStateMapping {
-    private static final ThreadLocal<ThreadState> cachedThreadState = new ThreadLocal<ThreadState>();
+    private static final ThreadLocal<Object[]> cachedThreadState =
+            new ThreadLocal<Object[]>()
+            {
+                @Override
+                protected Object[] initialValue()
+                {
+                    return new Object[1];
+                }
+            };
 
+    private ArrayList<WeakReference<Object[]>> threadStateList = new ArrayList<WeakReference<Object[]>>();
+    private boolean isShutdown = false;
+
     public ThreadState getThreadState(PySystemState newSystemState) {
-        ThreadState ts = cachedThreadState.get();
+
+        //initial check for usual case outside syncronized block for efficiency
+        ThreadState ts = (ThreadState)cachedThreadState.get()[0];
+
         if (ts != null) {
             return ts;
         }
 
+        synchronized(this)
+        {
+            //check again within synchronized block to guard against race condition
+            Object[] threadLocal = cachedThreadState.get();
+            if(threadLocal[0] != null)
+                return (ThreadState)threadLocal[0];
 
-        Thread t = Thread.currentThread();
-        if (newSystemState == null) {
-            Py.writeDebug("threadstate", "no current system state");
-            if (Py.defaultSystemState == null) {
-                PySystemState.initialize();
+            Thread t = Thread.currentThread();
+            if (newSystemState == null) {
+                Py.writeDebug("threadstate", "no current system state");
+                if (Py.defaultSystemState == null) {
+                    PySystemState.initialize();
+                }
+                newSystemState = Py.defaultSystemState;
             }
-            newSystemState = Py.defaultSystemState;
+
+            ts = new ThreadState(t, newSystemState);
+
+            if(! isShutdown)
+            {
+                threadLocal[0] = ts;
+                threadStateList.add(new WeakReference<Object[]>(threadLocal));
+            }
+            return ts;
         }
+    }
 
-        ts = new ThreadState(t, newSystemState);
-        cachedThreadState.set(ts);
-        return ts;
+    public synchronized void shutdown()
+    {
+        isShutdown = true;
+        for(WeakReference<Object[]> ref : threadStateList)
+        {
+            Object[] o = ref.get();
+            if(o != null)
+            {
+                o[0] = null;
+            }
+        }
+        threadStateList.clear();
     }
 }