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COSC 350 System Software (Lab #10)

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COSC 350 System Software
1
COSC 350 System Software (Lab #10)
Task#1
Write complete two C programs “msgQsnd.c” and “msgQrcv.c” to communicate through
message queue .
msgQsnd.c:
• Create a message queue with rw-r-r. To create a message queue, use existing file name
“msgQsnd.c for creating a key value.
• Ask a message “ two integers value” and send to the message queue.
• Keep asking a message until EOF (Ctr-D)
• Remove the message queue with termination.
msgQrcv.c:
• Receive a message (two integers) from the message queue created by msgQsnd.c.
• Calculate sum of two integers and display result on standard output.
• keep reading a message until EOF
What is producer Consumer Problem
• Two processes share a common, fixed-sized buffer size 10.
• Producer puts information into the buffer, and consumer takes it out.
Troubles arises
• When the producer wants to put a new item in the buffer, but it is already full.
• When the consumer tries to take an item from the buffer, but buffer is already empty.
COSC 350 System Software, Spring 2021
2
Solutions for each case
• When the producer wants to put a new item in the buffer, but it is already full.
o Solution – producer is going to sleep, awakened by customer when customer has
removed on or more items.
• When the consumer tries to take an item from the buffer, but buffer is already empty.
o Solution – customer is going to sleep, awakened by the producer when producer puts
one or more information into the buffer.
Task #2 Write a complete C program to simulate producer consumer problems without using
semaphores. Just simulate previous algorithms with count variables. And shows the race condition
problems.
• You need create two threads to simulate: producer and consumer
Task #3: Write a complete C program to simulate producer consumer problems with semaphores.
• You need create two threads: producer and consumer.
• You need use semaphores: two countable semaphore for empty and full and one binary
semaphore mutex for mutual exclusion in the algorithm
• You need find out a way to demonstrate your program works properly.
• You need use ftok(), semget(), semctl() and semop() system calls for semaphores.
Algorithms for Solving Producer Customer Problem using semaphores