02.22.2021
Homework #1
An operating system’s pid manager is responsible for managing process identifiers. When a process is first created, it is assigned a unique pid by the pid manager. The pid is returned to the pid manager when the process completes execution, and the manager may later reassign this pid. Process identifiers must be unique; no two active processes may have the same pid.
Use the following constants to identify the range of possible pid values:
#define MIN_PID 300 #define MAX_PID 5000
You may use any data structure of your choice to represent the availability of process identifiers. One strategy is to adopt what Linux has done and use a bitmap in which a value of 0 at position i indicates that a process id of value i is available and a value of 1 indicates that the process id is currently in use.
Implement the following API for obtaining and releasing a pid:
• int allocate_map(void) – Creates and initializes a data structure for representing pids; returns -1 if unsuccessful and 1 if successful • int allocate_pid(void) – Allocates and returns a pid; returns -1 if if unable to allocate a pid (all pids are in use) • void release_pid(int_pid) – Releases a pid.
03.12.2021
Homework #2
Write a multithreaded program that tests your solution to HW#1. You will create several threads – for example, 100 – and each thread will request a pid, sleep for a random period of time, and then release the pid. (Sleeping for a random period approximates the typical pid usage in which a pid is assigned to a new process, the process executes and terminates, and the pid is released on the process’ termination). On UNIX and Linux systems, sleeping is accomplished through the sleep() function, which is passed an integer value representing the number of seconds to sleep.
04.01.2021
Homework #3
Programming Exercise 3.20 required you to design a PID manager that allocated a unique process identifier to each process. Exercise 4.20 required you to modify your solution to Exercise 3.20 by writing a program that created a number of threads that requested and released process identifiers. Now modify your solution to Exercise 4.20 by ensuring that the data structure used to represent the availability of process identifiers is safe from race conditions. Use Pthreads mutex locks. Please note. If you used mutex locks in your solution to HW #2, please resubmit to get credit for HW#3.