Deadlock Problem

• A set of blocked processes each holding a resource and waiting to acquire a resource held by another process in the set.
• Example

1. System has 2 tape drives.
2. P1 and P2 each hold one tape drive and each needs another one.

• Example

1. semaphores A and B, initialized to 1

    P0     P1

wait (A);  wait(B)

wait (B);  wait(A)