Fix potential race condition in DocumentsWriter & DocumentsWriterDeleteQueue (#13169)

* Fix potential race condition in DocumentsWriter & DocumentsWriterDeleteQueue

* add changes

lucene/CHANGES.txt

@@ -232,6 +232,8 @@ Bug Fixes
 
 * GITHUB#13162: Fix NPE when LeafReader return null VectorValues (Pan Guixin)
 
+* GITHUB#13169: Fix potential race condition in DocumentsWriter & DocumentsWriterDeleteQueue (Ben Trent)
+
 Other
 ---------------------
 

lucene/core/src/java/org/apache/lucene/index/DocumentsWriter.java

@@ -540,13 +540,16 @@ final class DocumentsWriter implements Closeable, Accountable {
     return deleteQueue.getNextSequenceNumber();
   }
 
-  synchronized void resetDeleteQueue(DocumentsWriterDeleteQueue newQueue) {
+  synchronized long resetDeleteQueue(int maxNumPendingOps) {
+    final DocumentsWriterDeleteQueue newQueue = deleteQueue.advanceQueue(maxNumPendingOps);
     assert deleteQueue.isAdvanced();
     assert newQueue.isAdvanced() == false;
     assert deleteQueue.getLastSequenceNumber() <= newQueue.getLastSequenceNumber();
     assert deleteQueue.getMaxSeqNo() <= newQueue.getLastSequenceNumber()
         : "maxSeqNo: " + deleteQueue.getMaxSeqNo() + " vs. " + newQueue.getLastSequenceNumber();
+    long oldMaxSeqNo = deleteQueue.getMaxSeqNo();
     deleteQueue = newQueue;
+    return oldMaxSeqNo;
   }
 
   interface FlushNotifications { // TODO maybe we find a better name for this?

lucene/core/src/java/org/apache/lucene/index/DocumentsWriterFlushControl.java

@@ -570,10 +570,7 @@ final class DocumentsWriterFlushControl implements Accountable, Closeable {
         // Insert a gap in seqNo of current active thread count, in the worst case each of those
         // threads now have one operation in flight.  It's fine
         // if we have some sequence numbers that were never assigned:
-        DocumentsWriterDeleteQueue newQueue =
-            documentsWriter.deleteQueue.advanceQueue(perThreadPool.size());
-        seqNo = documentsWriter.deleteQueue.getMaxSeqNo();
-        documentsWriter.resetDeleteQueue(newQueue);
+        seqNo = documentsWriter.resetDeleteQueue(perThreadPool.size());
       } finally {
         perThreadPool.unlockNewWriters();
       }