Index: src/java/org/apache/lucene/index/MergePolicy.java
===================================================================
--- src/java/org/apache/lucene/index/MergePolicy.java	(revision 1029061)
+++ src/java/org/apache/lucene/index/MergePolicy.java	(working copy)
@@ -87,6 +87,8 @@
     boolean aborted;
     Throwable error;
 
+    volatile boolean mergeDone;     // used by IndexWriter
+
     public OneMerge(SegmentInfos segments, boolean useCompoundFile) {
       if (0 == segments.size())
         throw new RuntimeException("segments must include at least one segment");
Index: src/java/org/apache/lucene/index/ConcurrentMergeScheduler.java
===================================================================
--- src/java/org/apache/lucene/index/ConcurrentMergeScheduler.java	(revision 1029061)
+++ src/java/org/apache/lucene/index/ConcurrentMergeScheduler.java	(working copy)
@@ -138,11 +138,21 @@
   }
 
   private synchronized int mergeThreadCount() {
+    return mergeThreadCount(false);
+  }
+
+  private synchronized int mergeThreadCount(boolean excludeDone) {
     int count = 0;
     final int numThreads = mergeThreads.size();
-    for(int i=0;i<numThreads;i++)
-      if (((MergeThread) mergeThreads.get(i)).isAlive())
-        count++;
+    for(int i=0;i<numThreads;i++) {
+      MergeThread t = (MergeThread) mergeThreads.get(i);
+      if (t.isAlive()) {
+        MergePolicy.OneMerge runningMerge = t.getRunningMerge();
+        if (!excludeDone || (runningMerge != null && !runningMerge.mergeDone)) {
+          count++;
+        }
+      }
+    }
     return count;
   }
 
@@ -193,7 +203,7 @@
       try {
         synchronized(this) {
           final MergeThread merger;
-          while (mergeThreadCount() >= maxThreadCount) {
+          while (mergeThreadCount(true) >= maxThreadCount) {
             if (verbose())
               message("    too many merge threads running; stalling...");
             try {
@@ -209,8 +219,6 @@
           if (verbose())
             message("  consider merge " + merge.segString(dir));
       
-          assert mergeThreadCount() < maxThreadCount;
-
           // OK to spawn a new merge thread to handle this
           // merge:
           merger = getMergeThread(writer, merge);
Index: src/java/org/apache/lucene/index/TermsHash.java
===================================================================
--- src/java/org/apache/lucene/index/TermsHash.java	(revision 1029061)
+++ src/java/org/apache/lucene/index/TermsHash.java	(working copy)
@@ -44,8 +44,6 @@
   final int postingsFreeChunk;
   final DocumentsWriter docWriter;
   
-  private TermsHash primaryTermsHash;
-
   private RawPostingList[] postingsFreeList = new RawPostingList[1];
   private int postingsFreeCount;
   private int postingsAllocCount;
@@ -79,7 +77,10 @@
     consumer.setFieldInfos(fieldInfos);
   }
 
-  synchronized public void abort() {
+  // NOTE: do not make this sync'd; it's not necessary (DW
+  // ensures all other threads are idle), and it leads to
+  // deadlock
+  public void abort() {
     consumer.abort();
     if (nextTermsHash != null)
       nextTermsHash.abort();
Index: src/java/org/apache/lucene/index/IndexWriter.java
===================================================================
--- src/java/org/apache/lucene/index/IndexWriter.java	(revision 1029065)
+++ src/java/org/apache/lucene/index/IndexWriter.java	(working copy)
@@ -5257,6 +5257,12 @@
       }
     }
 
+    merge.mergeDone = true;
+
+    synchronized(mergeScheduler) {
+      mergeScheduler.notifyAll();
+    }
+
     // Force a sync after commiting the merge.  Once this
     // sync completes then all index files referenced by the
     // current segmentInfos are on stable storage so if the