Index: lucene/CHANGES.txt
===================================================================
--- lucene/CHANGES.txt	(revision 1150663)
+++ lucene/CHANGES.txt	(working copy)
@@ -26,6 +26,10 @@
   suppressed exceptions in the original exception, so stack trace
   will contain them.  (Uwe Schindler)
 
+* LUCENE-3339: Fixed deadlock case when multiple threads use the new
+  block-add (IndexWriter.add/updateDocuments) methods.  (Robert Muir,
+  Mike McCandless)
+
 New Features
 
 * LUCENE-3290: Added FieldInvertState.numUniqueTerms 
Index: lucene/src/java/org/apache/lucene/index/DocumentsWriter.java
===================================================================
--- lucene/src/java/org/apache/lucene/index/DocumentsWriter.java	(revision 1150663)
+++ lucene/src/java/org/apache/lucene/index/DocumentsWriter.java	(working copy)
@@ -843,6 +843,12 @@
     final int startDocID = docState.docID;
     int docID = startDocID;
 
+    // We must delay pausing until the full doc block is
+    // added, else we can hit deadlock if more than one
+    // thread is adding a block and we need to pause when
+    // both are only part way done:
+    boolean doPauseWaitQueue = false;
+
     //System.out.println(Thread.currentThread().getName() + ": A " + docCount);
     for(Document doc : docs) {
       docState.doc = doc;
@@ -873,14 +879,11 @@
           assert perDoc == null || perDoc.docID == docState.docID;
           final boolean doPause;
           if (perDoc != null) {
-            doPause = waitQueue.add(perDoc);
+            doPauseWaitQueue |= waitQueue.add(perDoc);
           } else {
             skipDocWriter.docID = docState.docID;
-            doPause = waitQueue.add(skipDocWriter);
+            doPauseWaitQueue |= waitQueue.add(skipDocWriter);
           }
-          if (doPause) {
-            waitForWaitQueue();
-          }
         }
 
         success = true;
@@ -937,6 +940,10 @@
           }
         }
       }
+
+      if (doPauseWaitQueue) {
+        waitForWaitQueue();
+      }
     }
     //System.out.println(Thread.currentThread().getName() + ":   A " + docCount);