Strange behaviour

[imadabh]

Hi all

I am trying to learn synchronization/multithreading. I have written a small snippet of code. After running for around 30 minutes, this code ends up in a deadlock. I am trying to figure out a reason. any help will be really appreciated. Thanks. Following is the code

package rollerdemo;

//Simulate a roller coaster, as in exercise 3.5 of Magee and Kramer.

import java.util.concurrent.CyclicBarrier;
import java.util.concurrent.BrokenBarrierException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

//This thread deals with the passengers arriving at random intervals.

class TurnstileBarrier implements Runnable
{  
	private ControlBarrier controlBarrier;
	private CyclicBarrier cyclicBarrier;

	TurnstileBarrier(ControlBarrier controlBarrier, CyclicBarrier cyclicBarrier) {  
		this.controlBarrier = controlBarrier;
		this.cyclicBarrier = cyclicBarrier;
	}

	public void run(){  
		try {
			controlBarrier.welcomePassenger();
			cyclicBarrier.await();
			
		} catch (InterruptedException e) { 
			Thread.currentThread().interrupt();			
		} catch (BrokenBarrierException e) { 
			Thread.currentThread().interrupt();			
		} finally {
			
		}
	}
}

class RollerBarrier
{  
	public static int NUMBER_OF_PASSENGERS_PER_CAR = 20;
	public static void main(String[] args) throws InterruptedException
	{
		final ControlBarrier controlBarrier = new ControlBarrier();
		
		Runnable carBarrier = new Runnable() {
			public void run(){  
				controlBarrier.departCar();
			}
		};
		
		CyclicBarrier barrier = new CyclicBarrier(NUMBER_OF_PASSENGERS_PER_CAR, carBarrier);

		ExecutorService pool = Executors.newFixedThreadPool(NUMBER_OF_PASSENGERS_PER_CAR);
		while(true)
			pool.execute(new TurnstileBarrier(controlBarrier,barrier));


		
	}
}

// The Control class represents the state of the controller, and the actions
// which can be performed. 

class ControlBarrier
{  
	private long queued = 0;
	private long carsSent = 0;
	private long numberOfPassengersTravelledToday = 0;
	
	ControlBarrier()
	{  
		queued = 0;
		carsSent = 0;
		numberOfPassengersTravelledToday = 0;
	}
	synchronized void welcomePassenger() {
		System.out.format("Welcoming Passenger %d%n", ++queued);
		++numberOfPassengersTravelledToday;
	}
	synchronized void departCar() {
		queued = queued - RollerBarrier.NUMBER_OF_PASSENGERS_PER_CAR;
		System.out.format("The car %d is going now and the number of passengers travelled so far with us is %d%n", ++carsSent, numberOfPassengersTravelledToday);
	}
}

[imadabh]

I am using Ubunutu 10.04 as my OS and jdk 1.6 to run the code.