[logback-dev] svn commit: r2071 - logback/trunk/logback-core/src/main/java/ch/qos/logback/core

[noreply.ceki at qos.ch]

Author: ceki
Date: Fri Dec  5 17:53:29 2008
New Revision: 2071

Modified:
   logback/trunk/logback-core/src/main/java/ch/qos/logback/core/BasicStatusManager.java

Log:
- using explicit locks instead of relying on the internal details of
  the collection returned by Collections.synchronizedList()


Modified: logback/trunk/logback-core/src/main/java/ch/qos/logback/core/BasicStatusManager.java
==============================================================================
--- logback/trunk/logback-core/src/main/java/ch/qos/logback/core/BasicStatusManager.java	(original)
+++ logback/trunk/logback-core/src/main/java/ch/qos/logback/core/BasicStatusManager.java	Fri Dec  5 17:53:29 2008
@@ -1,16 +1,15 @@
 /**
- * LOGBack: the reliable, fast and flexible logging library for Java.
- *
- * Copyright (C) 1999-2006, QOS.ch
- *
- * This library is free software, you can redistribute it and/or
- * modify it under the terms of the GNU Lesser General Public License as
- * published by the Free Software Foundation.
+ * Logback: the generic, reliable, fast and flexible logging framework.
+ * 
+ * Copyright (C) 2000-2008, QOS.ch
+ * 
+ * This library is free software, you can redistribute it and/or modify it under
+ * the terms of the GNU Lesser General Public License as published by the Free
+ * Software Foundation.
  */
 package ch.qos.logback.core;
 
 import java.util.ArrayList;
-import java.util.Collections;
 import java.util.List;
 
 import ch.qos.logback.core.status.Status;
@@ -21,23 +20,24 @@
 
   public static final int MAX_COUNT = 200;
 
-  // This method is synchronized on the instance.
-  // Code
   int count = 0;
 
-  // reading SynchronizedCollection source code, we learn that the mutex is the
-  // returned synchronized list, we make use of this fact in getCopyOfStatusList
   // protected access was requested in http://jira.qos.ch/browse/LBCORE-36
-  final protected List<Status> statusList = Collections
-      .synchronizedList(new ArrayList<Status>());
+  final protected List<Status> statusList = new ArrayList<Status>();
+  final protected Object statusListLock = new Object();
+
   int level = Status.INFO;
 
-  // reading SynchronizedCollection source code, we learn that the mutex is the
-  // returned synchronized list, we make use of this fact in
-  // getCopyOfStatusListnerList
   // protected access was requested in http://jira.qos.ch/browse/LBCORE-36
-  final protected List<StatusListener> statusListenerList = Collections
-      .synchronizedList(new ArrayList<StatusListener>());
+  final protected List<StatusListener> statusListenerList = new ArrayList<StatusListener>();
+  final protected Object statusListenerListLock = new Object();
+
+  // Note on synchronization
+  // This class contains two separate locks statusListLock and
+  // statusListenerListLock guarding respectively the statusList and
+  // statusListenerList fields. The locks are used internally
+  // without cycles. They are exposed to derived classes which should be careful
+  // not to create deadlock cycles.
 
   /**
    * Add a new status object.
@@ -46,9 +46,9 @@
    *                the status message to add
    */
   public void add(Status newStatus) {
-    // LBCORE-72: fire event before the count check 
+    // LBCORE-72: fire event before the count check
     fireStatusAddEvent(newStatus);
-    
+
     if (count > MAX_COUNT) {
       return;
     }
@@ -57,12 +57,15 @@
     if (newStatus.getLevel() > level) {
       level = newStatus.getLevel();
     }
-    statusList.add(newStatus);
+
+    synchronized (statusListLock) {
+      statusList.add(newStatus);
+    }
 
   }
 
   private void fireStatusAddEvent(Status status) {
-    synchronized (statusListenerList) {
+    synchronized (statusListenerListLock) {
       for (StatusListener sl : statusListenerList) {
         sl.addStatusEvent(status);
       }
@@ -70,7 +73,7 @@
   }
 
   public List<Status> getCopyOfStatusList() {
-    synchronized (statusList) {
+    synchronized (statusListLock) {
       return new ArrayList<Status>(statusList);
     }
   }
@@ -84,15 +87,19 @@
   }
 
   public void add(StatusListener listener) {
-    statusListenerList.add(listener);
+    synchronized (statusListenerListLock) {
+      statusListenerList.add(listener);
+    }
   }
 
   public void remove(StatusListener listener) {
-    statusListenerList.remove(listener);
+    synchronized (statusListenerListLock) {
+      statusListenerList.remove(listener);
+    }
   }
 
   public List<StatusListener> getCopyOfStatusListenerList() {
-    synchronized (statusListenerList) {
+    synchronized (statusListenerListLock) {
       return new ArrayList<StatusListener>(statusListenerList);
     }
   }