Index: rvm/src/org/jikesrvm/scheduler/RVMThread.java
===================================================================
--- rvm/src/org/jikesrvm/scheduler/RVMThread.java	(revision 15420)
+++ rvm/src/org/jikesrvm/scheduler/RVMThread.java	(working copy)
@@ -1480,7 +1480,14 @@
     this(MemoryManager.newStack((stacksize <= 0) ? STACK_SIZE_NORMAL : (int) stacksize), thread, name, daemon, false, priority);
   }
 
-  final void acknowledgeBlockRequests() {
+  /**
+   * Check if the thread has block requests (for example, for suspension and GC).  If
+   * it does, clear the requests and marked the thread as blocked for that request.
+   * If there were any block requests, do a broadcast() on the thread's monitor().
+   * This is an internal method and should only be called from code that implements
+   * thread blocking.  The monitor() lock must be held for this method to work properly.
+   */
+  private void acknowledgeBlockRequests() {
     boolean hadSome = false;
     if (VM.VerifyAssertions)
       VM._assert(blockAdapters != null);
@@ -1497,8 +1504,11 @@
   }
 
   /**
-   * Checks if the thread is supposed to be blocked. Only call this method when
-   * already holding the monitor(), for two reasons:
+   * Checks if the thread system has acknowledged that the thread is supposed
+   * to be blocked. This will return true if the thread is actually blocking, or
+   * if the thread is running native code but is guaranteed to block before
+   * returning to Java.  Only call this method when already holding the monitor(),
+   * for two reasons:
    * <ol>
    * <li>This method does not acquire the monitor() lock even though it needs
    * to have it acquired given the data structures that it is accessing.
@@ -1701,6 +1711,21 @@
     checkBlockNoSaveContext();
   }
 
+  /**
+   * Internal method for transitioning a thread from IN_JAVA or IN_JAVA_TO_BLOCK to
+   * either BLOCKED_IN_NATIVE or BLOCKED_IN_JNI, depending on the value of the jni
+   * parameter.  It is always safe to conservatively call this method when transitioning
+   * to native code, though it is faster to call either enterNative(),
+   * enterJNIFromCallIntoNative(), or enterJNIFromJNIFunctionCall().
+   * <p>
+   * This method takes care of all bookkeeping and notifications required when a
+   * a thread that has been requested to block instead decides to run native code.
+   * Threads enter native code never need to block, since they will not be executing
+   * any Java code.  However, such threads must ensure that any system services (like
+   * GC) that are waiting for this thread to stop are notified that the thread has
+   * instead chosen to exit Java.  As well, any requests to perform a sot handshake
+   * must be serviced and acknowledged.
+   */
   private void enterNativeBlockedImpl(boolean jni) {
     if (traceReallyBlock)
       VM.sysWriteln("Thread #", threadSlot, " entering native blocked.");
@@ -1716,6 +1741,7 @@
       nativeEnteredBlocked++;
       setExecStatus(BLOCKED_IN_NATIVE);
     }
+    handleHandshakeRequest();
     acknowledgeBlockRequests();
     commitSoftRendezvous = softRendezvousCheckAndClear();
     monitor().unlock();