Fix an unexpected RejectedExecutionException

- Ensure to run all remaining tasks before marking the executor as
  'shut down'.

transport/src/main/java/io/netty/channel/SingleThreadEventExecutor.java

@@ -91,16 +91,35 @@ public abstract class SingleThreadEventExecutor extends AbstractExecutorService
                 try {
                     SingleThreadEventExecutor.this.run();
                 } finally {
-                    synchronized (stateLock) {
-                        state = 3;
-                    }
                     try {
-                        cancelScheduledTasks();
-                        runShutdownHooks();
-                        cleanup();
+                        // Run all remaining tasks and shutdown hooks.
+                        try {
+                            cleanupTasks();
+                        } finally {
+                            synchronized (stateLock) {
+                                state = 3;
+                            }
+                        }
+                        cleanupTasks();
                     } finally {
-                        threadLock.release();
-                        assert taskQueue.isEmpty();
+                        try {
+                            cleanup();
+                        } finally {
+                            threadLock.release();
+                            assert taskQueue.isEmpty();
+                        }
+                    }
+                }
+            }
+
+            private void cleanupTasks() {
+                for (;;) {
+                    boolean ran = false;
+                    cancelScheduledTasks();
+                    ran |= runAllTasks();
+                    ran |= runShutdownHooks();
+                    if (!ran && !hasTasks()) {
+                        break;
                     }
                 }
             }
@@ -196,15 +215,22 @@ public abstract class SingleThreadEventExecutor extends AbstractExecutorService
         return taskQueue.remove(task);
     }
 
-    protected void runAllTasks() {
+    protected boolean runAllTasks() {
+        boolean ran = false;
         for (;;) {
             final Runnable task = pollTask();
             if (task == null) {
                 break;
             }
 
-            task.run();
+            try {
+                task.run();
+                ran = true;
+            } catch (Throwable t) {
+                logger.warn("A task raised an exception.", t);
+            }
         }
+        return ran;
     }
 
     protected abstract void run();
@@ -251,7 +277,8 @@ public abstract class SingleThreadEventExecutor extends AbstractExecutorService
         }
     }
 
-    private void runShutdownHooks() {
+    private boolean runShutdownHooks() {
+        boolean ran = false;
         // Note shutdown hooks can add / remove shutdown hooks.
         while (!shutdownHooks.isEmpty()) {
             List<Runnable> copy = new ArrayList<Runnable>(shutdownHooks);
@@ -259,11 +286,13 @@ public abstract class SingleThreadEventExecutor extends AbstractExecutorService
             for (Runnable task: copy) {
                 try {
                     task.run();
+                    ran = true;
                 } catch (Throwable t) {
                     logger.warn("Shutdown hook raised an exception.", t);
                 }
             }
         }
+        return ran;
     }
 
     @Override
@@ -358,7 +387,7 @@ public abstract class SingleThreadEventExecutor extends AbstractExecutorService
     }
 
     private static void reject() {
-        throw new RejectedExecutionException("event loop shut down");
+        throw new RejectedExecutionException("event executor shut down");
     }
 
     @Override