Make it more clear in the javadocs that you should use *Later methods to

send upstream events from a ChannelDownstreamHandler

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

@@ -56,6 +56,10 @@ package io.netty.channel;
  * <p>
  * You will also find various helper methods in {@link Channels} to be useful
  * to generate and send an artificial or manipulated event.
+ * <p>
+ * <strong>Caution:</strong> 
+ * <p>
+ * Use the *Later(..) methods of the {@link Channels} class if you want to send an upstream event from a {@link ChannelDownstreamHandler} otherwise you may run into threading issues.
  *
  * <h3>State management</h3>
  *

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

@@ -49,6 +49,12 @@ import java.net.SocketAddress;
  *         <strong>super.handleDownstream(ctx, e);</strong>
  *     }
  * }</pre>
+ * 
+ * <p>
+ * <strong>Caution:</strong> 
+ * <p>
+ * Use the *Later(..) methods of the {@link Channels} class if you want to send an upstream event from a {@link ChannelDownstreamHandler} otherwise you may run into threading issues.
+ *
  */
 public class SimpleChannelDownstreamHandler implements ChannelDownstreamHandler {