What is the minimum number of locks required to cause a deadlock in a system?

For a deadlock to occur in a system, at least two locks and two processes (or threads) that attempt to acquire them are necessary.

A classic example:

• Process A acquires lock 1 and tries to acquire lock 2.
• Process B acquires lock 2 and tries to acquire lock 1.

Both processes are waiting for the lock held by the other, and neither can continue — a deadlock occurs.

Thus, the minimum number of locks for a deadlock is 2.