Simple Deadlock Examples

Maybe a simple bank situation.

class Account {
  double balance;

  void withdraw(double amount){
     balance -= amount;
  } 

  void deposit(double amount){
     balance += amount;
  } 

   void transfer(Account from, Account to, double amount){
        sync(from);
        sync(to);

        from.withdraw(amount);
        to.deposit(amount);

        release(to);
        release(from);
    }

}

Obviously, should there be two threads which attempt to run transfer(a, b) and transfer(b, a) at the same time, then a deadlock is going to occur because they try to acquire the resources in reverse order.

This code is also great for looking at solutions to the deadlock as well.