Avoiding deadlock is obviously something we would want to ensure. In addition to the points covered in the Locking guidelines section, there is one more key point, which is that the order in which multiple locks are taken matters; keeping the lock ordering consistent throughout will provide protection against deadlocks.
To understand why, let's re-look at the ABBA deadlock scenario we just covered (refer to the preceding table). Look at the table again: notice that thread A takes lock L1 and then attempts to take lock L2, while thread B does the opposite. We shall now represent this scenario, but with a key caveat: lock ordering! This time, we shall have a lock ordering rule; it could be as simple as this: first, take lock ...
