/**
 * Show an example of deadlock.
 *
 * On Linux, set LD_ASSUME_KERNEL to 2.4.1:
 * csh: setenv LD_ASSUME_KERNEL 2.4.1
 * bash: export LD_ASSUME_KERNEL=2.4.1
 *
 * Run with "java Account"
 * On deadlock, use ^Z to suspend.
 * Use "ps" to find process ids of Java threads.
 * Invoke "jstack pid" on any of the pids listed
 *
 * @author Godmar Back gback@cs.vt.edu, Feb 2006
 */
public class Account {
  private int amount;
  private String name;

  Account(String name, int amount) {
    this.name = name;
    this.amount = amount;
  }

  void transferTo(Account that, int amount) {
    synchronized (this) { // lock this account
      synchronized (that) { // lock other account
        System.out.println("Transfering $" + amount 
              + " from " + this.name + " to " + that.name);
        this.amount -= amount;
        that.amount += amount;
      }
    }
  }

  public static void main(String []av) throws Exception {
    final Account acc1 = new Account("acc1", 10000);
    final Account acc2 = new Account("acc2", 10000);

    Thread t = new Thread() {
      public void run() {
        for (int i = 0; i < 100000; i++) 
          acc1.transferTo(acc2, 20);
      }
    };
    t.start();

    for (int i = 0; i < 100000; i++) 
      acc2.transferTo(acc1, 20);

    t.join();
  }
}