Deadlock and Starvation

• Deadlock – two or more processes are waiting indefinitely for an event that can be caused by only one of the waiting processes.
• Let S and Q be two semaphores initialized to 1

                P0           P1

            wait(S);    wait(Q);

            wait(Q);    wait(S);

                M                M

          signal(S);  signal(Q);

          signal(Q)  signal(S);

• Starvation  – indefinite blocking.  A process may never be removed from the semaphore queue in which it is suspended.