CSC 553 - Operating Systems

Dr. R. M. Siegfried

Assignment #5 - p. 248/5.1, Semaphores vs Monitors

Due Tuesday, October 10, 2023

5.1

Demonstrate the correct of Dekker's Algorithm:

1. Show that mutual exclusion is enforced. Hint: Show that when P_i enters its critical section, the following expression is true:

    flag[i] and ( not flag[1 - i])
   

2. Show that a process requiring access to its critical section will not be delayed indefinitely. Hint: Consider the following cases: (1) a single process is attempted to enter the critical section; (2) both processes are attempting to enter the critical section, and (2a) turn = 0 and (2b) turn = 0 and flag[0] = true.

Semaphores vs Monitor

In class, we discussed semaphores and monitor, it was said that semaphores are generally regarded as lower level operations than monitors. Why would we view in this way? Give one example that illustrates why this would be true?

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