Index: lucene/core/src/java/org/apache/lucene/index/ConcurrentMergeScheduler.java
===================================================================
--- lucene/core/src/java/org/apache/lucene/index/ConcurrentMergeScheduler.java	(revision 1364613)
+++ lucene/core/src/java/org/apache/lucene/index/ConcurrentMergeScheduler.java	(working copy)
@@ -243,7 +243,7 @@
     sync();
   }
 
-  /** Wait for any running merge threads to finish */
+  /** Wait for any running merge threads to finish. This call is not interruptible as used by {@link #close()}. */
   public void sync() {
     while (true) {
       MergeThread toSync = null;
@@ -259,7 +259,7 @@
         try {
           toSync.join();
         } catch (InterruptedException ie) {
-          throw new ThreadInterruptedException(ie);
+          // ignore this Exception, we will retry until all threads are dead
         }
       } else {
         break;
Index: lucene/core/src/java/org/apache/lucene/index/IndexWriter.java
===================================================================
--- lucene/core/src/java/org/apache/lucene/index/IndexWriter.java	(revision 1364613)
+++ lucene/core/src/java/org/apache/lucene/index/IndexWriter.java	(working copy)
@@ -842,7 +842,7 @@
         if (hitOOM) {
           rollbackInternal();
         } else {
-          closeInternal(waitForMerges, !hitOOM);
+          closeInternal(waitForMerges, true);
         }
       }
     }
@@ -891,19 +891,41 @@
         docWriter.abort(); // already closed
       }
 
-      if (waitForMerges)
-        // Give merge scheduler last chance to run, in case
-        // any pending merges are waiting:
-        mergeScheduler.merge(this);
-
+      ThreadInterruptedException priorE = null;
+      if (waitForMerges) {
+        try {
+          // Give merge scheduler last chance to run, in case
+          // any pending merges are waiting:
+          mergeScheduler.merge(this);
+        } catch (ThreadInterruptedException tie) {
+          priorE = tie;
+        }
+      }
+      
       mergePolicy.close();
 
+      boolean success = false;
       synchronized(this) {
-        finishMerges(waitForMerges);
+        while (!success) {
+          try {
+            finishMerges(waitForMerges);
+            success = true;
+          } catch (ThreadInterruptedException tie) {
+            // change to waitForMerges = false, so we just try
+            // to let the scheduler stop:
+            waitForMerges = false;
+            if (priorE == null) priorE = tie;
+          }
+        }
         stopMerges = true;
       }
+      
+      // shutdown scheduler and all threads (this call is not interruptible):
       mergeScheduler.close();
-
+      
+      // if any interrupt occurred we now throw the prior Exception:
+      if (priorE != null) throw priorE;
+      
       if (infoStream.isEnabled("IW")) {
         infoStream.message("IW", "now call final commit()");
       }
Index: lucene/core/src/java/org/apache/lucene/index/MergeScheduler.java
===================================================================
--- lucene/core/src/java/org/apache/lucene/index/MergeScheduler.java	(revision 1364613)
+++ lucene/core/src/java/org/apache/lucene/index/MergeScheduler.java	(working copy)
@@ -17,6 +17,7 @@
  * limitations under the License.
  */
 
+import java.io.Closeable;
 import java.io.IOException;
 
 /** <p>Expert: {@link IndexWriter} uses an instance
@@ -26,7 +27,7 @@
  *
  * @lucene.experimental
 */
-public abstract class MergeScheduler {
+public abstract class MergeScheduler implements Closeable {
 
   /** Run the merges provided by {@link IndexWriter#getNextMerge()}. */
   public abstract void merge(IndexWriter writer) throws IOException;