Simplified NioWorker.register() - it was too complex

src/main/java/org/jboss/netty/channel/socket/nio/NioWorker.java

@@ -70,12 +70,12 @@ class NioWorker implements Runnable {
     private final int bossId;
     private final int id;
     private final Executor executor;
-    private final AtomicBoolean started = new AtomicBoolean();
+    private boolean started;
     private volatile Thread thread;
     volatile Selector selector;
     private final AtomicBoolean wakenUp = new AtomicBoolean();
     private final ReadWriteLock selectorGuard = new ReentrantReadWriteLock();
-    private final Object shutdownLock = new Object();
+    private final Object startStopLock = new Object();
     private final Queue<Runnable> registerTaskQueue = new LinkedTransferQueue<Runnable>();
     private final Queue<Runnable> writeTaskQueue = new LinkedTransferQueue<Runnable>();
 
@@ -86,59 +86,55 @@ class NioWorker implements Runnable {
     }
 
     void register(NioSocketChannel channel, ChannelFuture future) {
-        boolean firstChannel;
-        Selector selector;
-        for (;;) {
-            firstChannel = started.compareAndSet(false, true);
-            if (firstChannel) {
-                boolean success = false;
-                try {
-                    synchronized (shutdownLock) {
-                        this.selector = selector = Selector.open();
-                    }
-                    success = true;
-                } catch (IOException e) {
-                    throw new ChannelException(
-                            "Failed to create a selector.", e);
-                } finally {
-                    if (!success) {
-                        started.compareAndSet(true, false);
-                    }
-                }
-                
-                break;
-            } else {
-                selector = this.selector;
-                if (selector == null) {
-                    do {
-                        Thread.yield();
-                        selector = this.selector;
-                    } while (selector == null && started.get());
-                    
-                    if (selector != null && selector.isOpen()) {
-                        break;
-                    }
-                } else {
-                    break;
-                }
-            }
-        }
         
         boolean server = !(channel instanceof NioClientSocketChannel);
         Runnable registerTask = new RegisterTask(channel, future, server);
-        synchronized (shutdownLock) {
+        Selector selector;
-            registerTaskQueue.offer(registerTask);
+
-        }
+        synchronized (startStopLock) {
-        if (wakenUp.compareAndSet(false, true)) {
+            if (!started) {
-            selector.wakeup();
+                // Open a selector if this worker didn't start yet.
+                try {
+                    this.selector = selector = Selector.open();
+                } catch (Throwable t) {
+                    throw new ChannelException(
+                            "Failed to create a selector.", t);
                 }
                 
-        if (firstChannel) {
+                // Start the worker thread with the new Selector.
                 String threadName =
                     (server ? "New I/O server worker #"
                             : "New I/O client worker #") + bossId + '-' + id;
 
+                boolean success = false;
+                try {
                     executor.execute(new ThreadRenamingRunnable(this, threadName));
+                    success = true;
+                } finally {
+                    if (!success) {
+                        // Release the Selector if the execution fails.
+                        try {
+                            selector.close();
+                        } catch (Throwable t) {
+                            logger.warn("Failed to close a selector.", t);
+                        }
+                        this.selector = selector = null;
+                        // The method will return to the caller at this point.
+                    }
+                }
+            } else {
+                // Use the existing selector if this worker has been started.
+                selector = this.selector;
+            }
+            
+            assert selector != null && selector.isOpen();
+
+            started = true;
+            registerTaskQueue.offer(registerTask);
+        }
+
+        if (wakenUp.compareAndSet(false, true)) {
+            selector.wakeup();
         }
     }
 
@@ -176,9 +172,9 @@ class NioWorker implements Runnable {
                     if (shutdown ||
                         executor instanceof ExecutorService && ((ExecutorService) executor).isShutdown()) {
 
-                        synchronized (shutdownLock) {
+                        synchronized (startStopLock) {
                             if (registerTaskQueue.isEmpty() && selector.keys().isEmpty()) {
-                                started.set(false);
+                                started = false;
                                 try {
                                     selector.close();
                                 } catch (IOException e) {
@@ -203,7 +199,8 @@ class NioWorker implements Runnable {
                 logger.warn(
                         "Unexpected exception in the selector loop.", t);
 
-                // Prevent possible consecutive immediate failures.
+                // Prevent possible consecutive immediate failures that lead to
+                // excessive CPU consumption.
                 try {
                     Thread.sleep(1000);
                 } catch (InterruptedException e) {