1 files changed, 36 insertions, 6 deletions
diff --git a/src/com/mbien/opencl/util/MultiQueueBarrier.java b/src/com/mbien/opencl/util/MultiQueueBarrier.java
index a23ca9ad..7ac45f6a 100644
--- a/src/com/mbien/opencl/util/MultiQueueBarrier.java
+++ b/src/com/mbien/opencl/util/MultiQueueBarrier.java
@@ -10,12 +10,14 @@ import java.util.concurrent.TimeUnit;
 
 /**
  * An utility for synchronizing multiple concurrent {@link CLCommandQueue}s.
+ * This Barrier can be reused after it has been broken.
  * @author Michael Bien
  */
 public class MultiQueueBarrier {
 
     private CountDownLatch latch;
     private final Set<CLCommandQueue> queues;
+    private final int count;
 
     /**
      * Creates a new MultiQueueBarrier with the given queueCount.
@@ -23,15 +25,23 @@ public class MultiQueueBarrier {
      * which restricts the set of allowed queues for the barrier.
      */
     public MultiQueueBarrier(int queueCount) {
+        if(queueCount == 0) {
+            throw new IllegalArgumentException("queueCount was 0");
+        }
         this.latch = new CountDownLatch(queueCount);
         this.queues = null;
+        this.count = queueCount;
     }
 
     /**
      * Creates a new MultiQueueBarrier for the given queues.
      */
     public MultiQueueBarrier(CLCommandQueue... allowedQueues) {
+        if(allowedQueues.length == 0) {
+            throw new IllegalArgumentException("allowedQueues was empty");
+        }
         this.latch = new CountDownLatch(allowedQueues.length);
+        this.count = allowedQueues.length;
 
         HashSet<CLCommandQueue> set = new HashSet<CLCommandQueue>(allowedQueues.length);
         for (CLCommandQueue queue : allowedQueues) {
@@ -49,7 +59,9 @@ public class MultiQueueBarrier {
         checkQueue(queue);
 
         queue.putBarrier();
-        latch.countDown();
+        synchronized(this) {
+            latch.countDown();
+        }
         return this;
     }
 
@@ -62,7 +74,9 @@ public class MultiQueueBarrier {
         checkQueue(queue);
 
         queue.putWaitForEvents(events, true);
-        latch.countDown();
+        synchronized(this) {
+            latch.countDown();
+        }
         return this;
     }
 
@@ -73,6 +87,7 @@ public class MultiQueueBarrier {
      */
     public MultiQueueBarrier await() throws InterruptedException {
         latch.await();
+        rebuildBarrierIfBroken();
         return this;
     }
     
@@ -83,15 +98,30 @@ public class MultiQueueBarrier {
      */
     public MultiQueueBarrier await(long timeout, TimeUnit unit) throws InterruptedException {
         latch.await(timeout, unit);
+        rebuildBarrierIfBroken();
         return this;
     }
     
     /**
-     * Cancels this barrier and unblocks all waiting threads.
+     * Resets this barrier and unblocks all waiting threads.
      */
-    public void cancelBarrier() {
-        while(latch.getCount() > 0)
-            latch.countDown();
+    public void resetBarrier() {
+        synchronized(this) {
+            while(latch.getCount() > 0) {
+                latch.countDown();
+            }
+            // thats OK. Another Thread can not rebuild the barrier since we have the lock.
+            // we have to rebuid it here in case there was no thread waiting.
+            latch = new CountDownLatch(count);
+        }
+    }
+
+    private void rebuildBarrierIfBroken() {
+        synchronized (this) {
+            if (latch.getCount() == 0) {
+                latch = new CountDownLatch(count);
+            }
+        }
     }
 
     /**