Use ReentrackLock instead of Semaphore

Also decrease the size of the critical section the lock protects.

Related to OF-857.

src/java/org/jivesoftware/openfire/nio/NIOConnection.java

@@ -31,7 +31,7 @@ import java.nio.charset.CharsetEncoder;
 import java.nio.charset.CodingErrorAction;
 import java.security.KeyStore;
 import java.security.cert.Certificate;
-import java.util.concurrent.Semaphore;
+import java.util.concurrent.locks.ReentrantLock;
 
 import javax.net.ssl.KeyManager;
 import javax.net.ssl.SSLContext;
@@ -116,16 +116,20 @@ public class NIOConnection implements Connection {
     private boolean closed;
     
     /**
-     * Lock used to ensure the integrity of the underlying IoSession 
-     * (refer to https://issues.apache.org/jira/browse/DIRMINA-653 for details)
+     * Lock used to ensure the integrity of the underlying IoSession (refer to
+     * https://issues.apache.org/jira/browse/DIRMINA-653 for details)
+     * <p>
+     * This lock can be removed once Openfire guarantees a stable delivery
+     * order, in which case {@link #deliver(Packet)} won't be called
+     * concurrently any more, which made this lock necessary in the first place.
+     * </p>
      */
-    private Semaphore ioSessionLock;
+    private final ReentrantLock ioSessionLock = new ReentrantLock(true);
 
     public NIOConnection(IoSession session, PacketDeliverer packetDeliverer) {
         this.ioSession = session;
         this.backupDeliverer = packetDeliverer;
         closed = false;
-        ioSessionLock = new Semaphore(1, true);
     }
 
     public boolean validate() {
@@ -261,12 +265,9 @@ public class NIOConnection implements Connection {
         }
         else {
             boolean errorDelivering = false;
-            try {
-            	ioSessionLock.acquire();
-
             IoBuffer buffer = IoBuffer.allocate(4096);
             buffer.setAutoExpand(true);
-
+            try {
             	// OF-464: if the connection has been dropped, fail over to backupDeliverer (offline)
             	if (!ioSession.isConnected()) {
             		throw new IOException("Connection reset/closed by peer");
@@ -279,15 +280,18 @@ public class NIOConnection implements Connection {
                     buffer.put((byte) '\0');
                 }
                 buffer.flip();
+                
+                ioSessionLock.lock();
+                try {
                     ioSession.write(buffer);
+                } finally {
+                    ioSessionLock.unlock();
+                }
             }
             catch (Exception e) {
                 Log.debug("Error delivering packet:\n" + packet, e);
                 errorDelivering = true;
             }
-            finally {
-            	ioSessionLock.release();
-            }
             if (errorDelivering) {
                 close();
                 // Retry sending the packet again. Most probably if the packet is a
@@ -307,14 +311,10 @@ public class NIOConnection implements Connection {
 
     private void deliverRawText(String text, boolean asynchronous) {
         if (!isClosed()) {
-
             boolean errorDelivering = false;
-            try {
-            	ioSessionLock.acquire();
-
             IoBuffer buffer = IoBuffer.allocate(text.length());
             buffer.setAutoExpand(true);
-
+            try {
                 //Charset charset = Charset.forName(CHARSET);
                 //buffer.putString(text, charset.newEncoder());
                 buffer.put(text.getBytes(CHARSET));
@@ -322,6 +322,8 @@ public class NIOConnection implements Connection {
                     buffer.put((byte) '\0');
                 }
                 buffer.flip();
+                ioSessionLock.lock();
+                try {
                     if (asynchronous) {
                         // OF-464: handle dropped connections (no backupDeliverer in this case?)
                         if (!ioSession.isConnected()) {
@@ -338,13 +340,15 @@ public class NIOConnection implements Connection {
                         }
                     }
                 } 
+                finally {
+                    ioSessionLock.unlock();
+                }
+            }
             catch (Exception e) {
                 Log.debug("Error delivering raw text:\n" + text, e);
                 errorDelivering = true;
             }
-            finally {
-            	ioSessionLock.release();
-            }
+
             // Close the connection if delivering text fails and we are already not closing the connection
             if (errorDelivering && asynchronous) {
                 close();