Release queueMutex using finally blocks

Ensure queueMutex is always correctly released by using finally blocks. This is the closest approximation of AutoMutex style automatic release you can get in Java.

diff --git a/java/com/tigervnc/rfb/DecodeManager.java b/java/com/tigervnc/rfb/DecodeManager.java
index 9c7cacbbb2b92dd41bcc2e6507628d67f1f4cec7..d849444615a6138901d086815c342ae617946c3e 100644 (file)
--- a/java/com/tigervnc/rfb/DecodeManager.java
+++ b/java/com/tigervnc/rfb/DecodeManager.java
@@ -116,16 +116,18 @@ public class DecodeManager {
     // Wait for an available memory buffer
     queueMutex.lock();
 
-    while (freeBuffers.isEmpty())
-      try {
-      producerCond.await();
-      } catch (InterruptedException e) { }
-
-    // Don't pop the buffer in case we throw an exception
-    // whilst reading
-    bufferStream = freeBuffers.getFirst();
+    try {
+      while (freeBuffers.isEmpty())
+        try {
+        producerCond.await();
+        } catch (InterruptedException e) { }
 
-    queueMutex.unlock();
+      // Don't pop the buffer in case we throw an exception
+      // whilst reading
+      bufferStream = freeBuffers.getFirst();
+    } finally {
+      queueMutex.unlock();
+    }
 
     // First check if any thread has encountered a problem
     throwThreadException();
@@ -151,29 +153,33 @@ public class DecodeManager {
 
     queueMutex.lock();
 
-    // The workers add buffers to the end so it's safe to assume
-    // the front is still the same buffer
-    freeBuffers.removeFirst();
-
-    workQueue.addLast(entry);
+    try {
+      // The workers add buffers to the end so it's safe to assume
+      // the front is still the same buffer
+      freeBuffers.removeFirst();
 
-    // We only put a single entry on the queue so waking a single
-    // thread is sufficient
-    consumerCond.signal();
+      workQueue.addLast(entry);
 
-    queueMutex.unlock();
+      // We only put a single entry on the queue so waking a single
+      // thread is sufficient
+      consumerCond.signal();
+    } finally {
+      queueMutex.unlock();
+    }
   }
 
   public void flush()
   {
     queueMutex.lock();
 
-    while (!workQueue.isEmpty())
-      try {
-      producerCond.await();
-      } catch (InterruptedException e) { }
-
-    queueMutex.unlock();
+    try {
+      while (!workQueue.isEmpty())
+        try {
+        producerCond.await();
+        } catch (InterruptedException e) { }
+    } finally {
+      queueMutex.unlock();
+    }
 
     throwThreadException();
   }
@@ -183,11 +189,15 @@ public class DecodeManager {
     //os::AutoMutex a(queueMutex);
     queueMutex.lock();
 
-    if (threadException != null)
-      return;
+    try {
+      if (threadException != null)
+        return;
 
-    threadException =
-      new Exception("Exception on worker thread: "+e.getMessage());
+      threadException =
+        new Exception("Exception on worker thread: "+e.getMessage());
+    } finally {
+      queueMutex.unlock();
+    }
   }
 
   private void throwThreadException()
@@ -195,14 +205,18 @@ public class DecodeManager {
     //os::AutoMutex a(queueMutex);
     queueMutex.lock();
 
-    if (threadException == null)
-      return;
+    try {
+      if (threadException == null)
+        return;
 
-    Exception e = new Exception(threadException.getMessage());
+      Exception e = new Exception(threadException.getMessage());
 
-    threadException = null;
+      threadException = null;
 
-    throw e;
+      throw e;
+    } finally {
+      queueMutex.unlock();
+    }
   }
 
   private class QueueEntry {
@@ -236,13 +250,17 @@ public class DecodeManager {
       //os::AutoMutex a(manager.queueMutex);
       manager.queueMutex.lock();
 
-      if (!thread.isAlive())
-        return;
+      try {
+        if (!thread.isAlive())
+          return;
 
-      stopRequested = true;
+        stopRequested = true;
 
-      // We can't wake just this thread, so wake everyone
-      manager.consumerCond.signalAll();
+        // We can't wake just this thread, so wake everyone
+        manager.consumerCond.signalAll();
+      } finally {
+        manager.queueMutex.unlock();
+      }
     }
 
     public void run()