FULL PRODUCT VERSION :
Mustang b59 fastdebug

ADDITIONAL OS VERSION INFORMATION :
XP SP 2

A DESCRIPTION OF THE PROBLEM :
I have a select loop, selector is blocked with one key, a socketchannel, interest set = 0. When another thread calls SocketChannel#close, the select wakes up, no keys selected. The loop spins several times until the connection is finally closed.

Thread state when select first wakes up:

Thread-0@d8 prio=5, in group "main", status: RUNNING
close0():-1, SocketDispatcher.java
preClose():44, SocketDispatcher.java
implCloseSelectableChannel():630, SocketChannelImpl.java
implCloseChannel():201, AbstractSelectableChannel.java
close():97, AbstractInterruptibleChannel.java
run():33, SelectBlocks.java

...

main@2 prio=5, in group "main", status: RUNNING
main():44, SelectBlocks.java



According to my understanding the selector shouldn't wake up at all. And certainly not spin.

I see a similar phenomenon on Solaris 10 / AMD x64.
No wakeup with 1.5_05, only one "spurious" wakeup with b59:

% uname -a
SunOS sol10sqa 5.10 Generic i86pc i386 i86pc

Accepted connection = java.nio.channels.SocketChannel[connected local=/10.2.2.22:56420 remote=/10.2.2.22:56421]
Closing connection
Closed connection
Selector: 0/1
Selector: 0/0


STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Run the attached program. It will open a connection to itself, select on it and close it after one second. It will print a line for each time select wakes up.


EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
JDK 1.5.0_05:

  Accepted connection = java.nio.channels.SocketChannel[connected local=/169.254.69.42:2632 remote=/169.254.69.42:2633]
Closing connection
  Closed connection
Selector: 0/0

ACTUAL -
  Accepted connection = java.nio.channels.SocketChannel[connected local=/169.254.69.42:2684 remote=/169.254.69.42:2685]
Closing connection
Selector: 0/1
Selector: 0/1
Selector: 0/1
Selector: 0/1
Selector: 0/1
Selector: 0/1
Selector: 0/1
Selector: 0/1
Selector: 0/1
Selector: 0/1
Selector: 0/1
Selector: 0/1
Selector: 0/1
Selector: 0/1
Selector: 0/1
Selector: 0/1
Selector: 0/1
Selector: 0/1
Selector: 0/1
Selector: 0/1
Selector: 0/1
Selector: 0/1
Selector: 0/1
Selector: 0/1
Selector: 0/1
Closed connection
Selector: 0/0


REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
/*
 * Copyright (c) 2005 Matthias Ernst, Hamburg. All rights reserved.
 */
package test.nio;


import java.io.IOException;
import java.net.Socket;
import java.nio.channels.Selector;
import java.nio.channels.ServerSocketChannel;
import java.nio.channels.SocketChannel;

public class SelectBlocks {
  public static void main(String[] args) throws IOException {
    ServerSocketChannel serverSocketChannel = ServerSocketChannel.open();
    serverSocketChannel.socket().bind(null);

    new Socket(serverSocketChannel.socket().getInetAddress(), serverSocketChannel.socket().getLocalPort());
    final SocketChannel connection = serverSocketChannel.accept();

    System.out.println("Accepted connection = " + connection);

    connection.configureBlocking(false);

    final Selector selector = Selector.open();
    connection.register(selector, 0);

    new Thread() {
      public void run() {
        try {
          Thread.sleep(1000);
          System.out.println("Closing connection");
          connection.close();
          System.out.println("Closed connection");
          selector.wakeup();
        } catch (Exception e) {
          e.printStackTrace();
        }
      }
    }.start();

    while(true) {
      selector.select();
      System.out.println("Selector: "+selector.selectedKeys().size()+"/"+selector.keys().size());
      selector.selectedKeys().clear();
    }
  }
}

---------- END SOURCE ----------