Index: lucene/core/src/test/org/apache/lucene/index/TestIndexWriterExceptions.java
===================================================================
--- lucene/core/src/test/org/apache/lucene/index/TestIndexWriterExceptions.java	(revision 1406157)
+++ lucene/core/src/test/org/apache/lucene/index/TestIndexWriterExceptions.java	(working copy)
@@ -424,7 +424,10 @@
   public void testExceptionOnMergeInit() throws IOException {
     Directory dir = newDirectory();
     IndexWriterConfig conf = newIndexWriterConfig( TEST_VERSION_CURRENT, new MockAnalyzer(random()))
-      .setMaxBufferedDocs(2).setMergeScheduler(new ConcurrentMergeScheduler()).setMergePolicy(newLogMergePolicy());
+      .setMaxBufferedDocs(2).setMergePolicy(newLogMergePolicy());
+    ConcurrentMergeScheduler cms = new ConcurrentMergeScheduler();
+    cms.setSuppressExceptions();
+    conf.setMergeScheduler(cms);
     ((LogMergePolicy) conf.getMergePolicy()).setMergeFactor(2);
     MockIndexWriter3 w = new MockIndexWriter3(dir, conf);
     w.doFail = true;
Index: lucene/core/src/java/org/apache/lucene/index/LiveIndexWriterConfig.java
===================================================================
--- lucene/core/src/java/org/apache/lucene/index/LiveIndexWriterConfig.java	(revision 1406157)
+++ lucene/core/src/java/org/apache/lucene/index/LiveIndexWriterConfig.java	(working copy)
@@ -555,7 +555,7 @@
     sb.append("commit=").append(commit == null ? "null" : commit).append("\n");
     sb.append("openMode=").append(getOpenMode()).append("\n");
     sb.append("similarity=").append(getSimilarity().getClass().getName()).append("\n");
-    sb.append("mergeScheduler=").append(getMergeScheduler().getClass().getName()).append("\n");
+    sb.append("mergeScheduler=").append(getMergeScheduler()).append("\n");
     sb.append("default WRITE_LOCK_TIMEOUT=").append(IndexWriterConfig.WRITE_LOCK_TIMEOUT).append("\n");
     sb.append("writeLockTimeout=").append(getWriteLockTimeout()).append("\n");
     sb.append("codec=").append(getCodec()).append("\n");
Index: lucene/core/src/java/org/apache/lucene/index/ConcurrentMergeScheduler.java
===================================================================
--- lucene/core/src/java/org/apache/lucene/index/ConcurrentMergeScheduler.java	(revision 1406157)
+++ lucene/core/src/java/org/apache/lucene/index/ConcurrentMergeScheduler.java	(working copy)
@@ -302,7 +302,7 @@
   }
 
   @Override
-  public void merge(IndexWriter writer) throws IOException {
+  public synchronized void merge(IndexWriter writer) throws IOException {
 
     assert !Thread.holdsLock(writer);
 
@@ -328,31 +328,34 @@
     // pending merges, until it's empty:
     while (true) {
 
-      synchronized(this) {
-        long startStallTime = 0;
-        while (mergeThreadCount() >= 1+maxMergeCount) {
-          startStallTime = System.currentTimeMillis();
-          if (verbose()) {
-            message("    too many merges; stalling...");
-          }
-          try {
-            wait();
-          } catch (InterruptedException ie) {
-            throw new ThreadInterruptedException(ie);
-          }
+      long startStallTime = 0;
+      while (writer.hasPendingMerges() && mergeThreadCount() >= maxMergeCount) {
+        // This means merging has fallen too far behind: we
+        // have already created maxMergeCount threads, and
+        // now there's at least one more merge pending.
+        // Note that only maxThreadCount of
+        // those created merge threads will actually be
+        // running; the rest will be paused (see
+        // updateMergeThreads).  We stall this producer
+        // thread to prevent creation of new segments,
+        // until merging has caught up:
+        startStallTime = System.currentTimeMillis();
+        if (verbose()) {
+          message("    too many merges; stalling...");
         }
+        try {
+          wait();
+        } catch (InterruptedException ie) {
+          throw new ThreadInterruptedException(ie);
+        }
+      }
 
-        if (verbose()) {
-          if (startStallTime != 0) {
-            message("  stalled for " + (System.currentTimeMillis()-startStallTime) + " msec");
-          }
+      if (verbose()) {
+        if (startStallTime != 0) {
+          message("  stalled for " + (System.currentTimeMillis()-startStallTime) + " msec");
         }
       }
 
-
-      // TODO: we could be careful about which merges to do in
-      // the BG (eg maybe the "biggest" ones) vs FG, which
-      // merges to do first (the easiest ones?), etc.
       MergePolicy.OneMerge merge = writer.getNextMerge();
       if (merge == null) {
         if (verbose()) {
@@ -361,34 +364,28 @@
         return;
       }
 
-      // We do this w/ the primary thread to keep
-      // deterministic assignment of segment names
-      writer.mergeInit(merge);
-
       boolean success = false;
       try {
-        synchronized(this) {
-          if (verbose()) {
-            message("  consider merge " + writer.segString(merge.segments));
-          }
+        if (verbose()) {
+          message("  consider merge " + writer.segString(merge.segments));
+        }
 
-          // OK to spawn a new merge thread to handle this
-          // merge:
-          final MergeThread merger = getMergeThread(writer, merge);
-          mergeThreads.add(merger);
-          if (verbose()) {
-            message("    launch new thread [" + merger.getName() + "]");
-          }
+        // OK to spawn a new merge thread to handle this
+        // merge:
+        final MergeThread merger = getMergeThread(writer, merge);
+        mergeThreads.add(merger);
+        if (verbose()) {
+          message("    launch new thread [" + merger.getName() + "]");
+        }
 
-          merger.start();
+        merger.start();
 
-          // Must call this after starting the thread else
-          // the new thread is removed from mergeThreads
-          // (since it's not alive yet):
-          updateMergeThreads();
+        // Must call this after starting the thread else
+        // the new thread is removed from mergeThreads
+        // (since it's not alive yet):
+        updateMergeThreads();
 
-          success = true;
-        }
+        success = true;
       } finally {
         if (!success) {
           writer.mergeFinish(merge);
@@ -482,7 +479,6 @@
           // merge that writer says is necessary:
           merge = tWriter.getNextMerge();
           if (merge != null) {
-            tWriter.mergeInit(merge);
             updateMergeThreads();
             if (verbose()) {
               message("  merge thread: do another merge " + tWriter.segString(merge.segments));
@@ -546,4 +542,13 @@
   void clearSuppressExceptions() {
     suppressExceptions = false;
   }
+  
+  @Override
+  public String toString() {
+    StringBuilder sb = new StringBuilder(getClass().getSimpleName() + ": ");
+    sb.append("maxThreadCount=").append(maxThreadCount).append(", ");    
+    sb.append("maxMergeCount=").append(maxMergeCount).append(", ");    
+    sb.append("mergeThreadPriority=").append(mergeThreadPriority);
+    return sb.toString();
+  }
 }
Index: lucene/core/src/java/org/apache/lucene/index/IndexWriter.java
===================================================================
--- lucene/core/src/java/org/apache/lucene/index/IndexWriter.java	(revision 1406157)
+++ lucene/core/src/java/org/apache/lucene/index/IndexWriter.java	(working copy)
@@ -1891,6 +1891,15 @@
   }
 
   /**
+   * Expert: returns true if there are merges waiting to be scheduled.
+   * 
+   * @lucene.experimental
+   */
+  public synchronized boolean hasPendingMerges() {
+    return pendingMerges.size() != 0;
+  }
+
+  /**
    * Close the <code>IndexWriter</code> without committing
    * any changes that have occurred since the last commit
    * (or since it was opened, if commit hasn't been called).