Can't stop a thread blocked on a socket read.

Platform Solaris:


Included is a test case that demonstrates the fact that you can't stop
a thread that is blocked on a socket read.



import java.net.*;

public class Timeout implements Runnable
{
public static void main(String args[])
{
try
{
TestThread th = new TestThread();
th.run();
th.join();

// (We never get here -- this is the bug)
System.out.println("TestThread has stopped!");
}
catch( Exception e ) { };
}

public void run()
{
}
}

class TestThread extends Thread
{
public void run()
{
try
{
DatagramSocket s = new DatagramSocket();
DatagramPacket packet = new DatagramPacket(new byte[100],100);

// Create a ThreadKiller object to kill this thread in 5 seconds.
// We are blocking on the DatagramSocket.receive() function, which
// we don't expect to ever receive a packet in this demonstration.
// When the ThreadKiller kicks in and calls stop on this thread,
// it has no effect. It should stop the thread This is the bug.
//
System.out.println("Waiting for packet (timeout in 5 seconds)...");

ThreadKiller killer = new ThreadKiller(this,5000);
killer.start();
s.receive(packet);
killer.Dismiss();

System.out.println("Exiting TestThread.run()");
}
catch( Exception e ){ };
}
}

/*
** Thread class to kill other threads after a timeout occurs.
** The thread sleeps for the specified amount of milliseconds;
** when it wakes up it kills the target thread unless the
** Dismiss function is called.
*/
class ThreadKiller extends Thread
{
boolean fDismissed = false;
long fDuration = 5000;
Thread fTarget = null;

/***
* Constructor
* @param targetThread The thread to kill
* @param msDuration The amount of time that will elapse before the
* target thread is killed.
*/
ThreadKiller( Thread targetThread, long msDuration )
{
super("ThreadKiller");
fDuration=msDuration;
fTarget=targetThread;
}

/*
** Thread execution.
*/
public void run()
{
try
{
System.out.println("Waking up in "+fDuration+" ms");
sleep(fDuration);
}
catch( InterruptedException e )
{
System.out.println("ThreadKiller.run: Exception: "+e);
}

if( !fDismissed && fTarget != null ) {
System.out.println("Stopping thread: "+fTarget);
fTarget.stop();
}
}

/*
** Call to dismiss this thread; when it wakes up it will not kill the
** target thread.
*/
public void Dismiss()
{
System.out.println("Dismissed");
fDismissed=true;
}
}