OS Part 3 (Inter Process Communication)

Question 1

How does the kernel facilitate communication between processes?

Answer 1

Kernel sets up shared memory (distinct location from processes own memory) so that processes can both read input/output from each other.

Question 2

What is the “critical region”?

Answer 2

Any time a process is actively accessing shared memory.

Question 3

What are the 4 conditions needed to allow processes to communicate with one another correctly and efficiently?

Answer 3

1. No two processes simultaneously in their critical
   regions.
2. No assumptions made about number or speed of
   CPU(s)
3. No process outside a critical region may block
   another process.
4. No process should wait forever to enter its critical
   region.

Question 4

What is the “critical region”?

Answer 4

Any time a process is actively accessing shared memory.

Question 5

What is “busy waiting”?

Answer 5

When a process takes up CPU resources by constantly checking (e.g infinite while loop) if it can access shared data.

Question 6

What three values are tracked with Dijkstra’s Semaphores?

Answer 6

1. “Full”, which counts the number of slots that are in use.
2. “Empty”, which counts the number of slots that are free.
3. “Mutex”, which guards the buffer ensuring mutual exclusion.