02. Process Management

Process Management

1. Processes and Threads

Process: the execution of a program, the basic unit of resource allocation and scheduling
Process states: ready, running, blocked, and their transitions
Process control: creation, termination, switching
Process organization: PCB (Process Control Block)
Process communication: shared memory, message passing, pipes
Thread: execution unit within a process, shares resources, lightweight
Multithreading models: user-level threads, kernel-level threads

2. Processor Scheduling

Basic concepts: scheduling objects, timing, switching
Scheduling criteria: CPU utilization, turnaround time, response time, etc.
Scheduling types: preemptive, non-preemptive
Typical algorithms: First-Come-First-Served (FCFS), Shortest Job First (SJF), Round Robin (RR), Priority Scheduling, Multilevel Feedback Queue

3. Synchronization and Mutual Exclusion

Critical section, mutual exclusion, synchronization
Software methods: Peterson’s algorithm, etc.
Hardware methods: interrupt disabling, Test-and-Set, etc.
Semaphore (P/V operations), monitors
Classic synchronization problems: producer-consumer, readers-writers, dining philosophers

4. Deadlock

Deadlock concept: processes are permanently blocked due to resource competition
Deadlock handling strategies: prevention, avoidance, detection and recovery
Deadlock prevention: break the four necessary conditions
Deadlock avoidance: Banker’s algorithm
Deadlock detection and recovery

Exercises

Briefly describe the difference between a process and a thread.
What are the three basic states of a process and their transition conditions?
What are the characteristics of FCFS, SJF, and RR scheduling algorithms?
What is a semaphore? What do P/V operations mean?
What are the four necessary conditions for deadlock? How can deadlock be avoided?

Reference Answers

1. Difference between process and thread

A process is a unit of resource allocation, a thread is a unit of scheduling, and threads share process resources.

2. Three process states and transitions

Ready (waiting for CPU), running (using CPU), blocked (waiting for resources); transitions are caused by scheduling, I/O, events, etc.

3. Scheduling algorithm characteristics

FCFS: simple, easy to implement, long jobs may starve; SJF: shortest average turnaround time, hard to predict job length; RR: fair, fast response, suitable for time-sharing systems

4. Semaphore and P/V operations

Semaphore is used for synchronization and mutual exclusion; P operation requests a resource, V operation releases a resource

5. Deadlock conditions and avoidance

Mutual exclusion, no preemption, hold and wait, circular wait; avoidance methods: break conditions, Banker’s algorithm

上一章节 01. Operating System Overview Understand the basic concepts, characteristics, functions, and history of operating systems, as well as their runtime environment and architecture. 下一章节 03. Memory Management Master the basic principles of memory management, contiguous and non-contiguous allocation, virtual memory, and page replacement algorithms.