Ready stateready

Execution status running

blocking state block

five-state process model

The two state transitions, blocking state -> running state and ready state -> blocking state, cannot occur.

End user needs: Modify, inspect processes

The needs of the parent process: modify and coordinate the child process

The need for swapping: buffering memory

The need for load regulation: ensuring the execution of real-time tasks

As a symbol of the basic unit of independent operation

Able to achieve intermittent operation mode

Provide information needed for process management

Provide information needed for process scheduling

Implement synchronization and communication with other processes

process identifier

processor status

Process scheduling information

process control information

How process control blocks are organized

support function

Resource management function

System state, management state, kernel state

user state, eye state

parent process

child process

User login

job scheduling

Provide services

application request

1. Apply for blank PCB

2. Allocate the new process the resources it needs to run

3.Initialize process block PCB

4. If the process ready queue can accommodate the new process, insert the new process into the ready queue.

Events that cause process termination

process termination process

Events that cause processes to block and wake up

Process blocking process (blocking itself)

Process wake-up process (the system or other processes wake themselves up)

suspend

active

Two forms of constraints

critical resources

Partition

Rules that synchronization mechanisms should follow

Software synchronization mechanism: None of them solves the problem of waiting for rights, and some methods can also cause deadlocks.

Hardware synchronization mechanism

semaphore mechanism

producer-consumer problem

Philosophers' dining problem

Reader-Writer Problem

Communication based on shared data structures

Communication method based on shared storage area

advanced communications

advanced communications

Method classification

Two basic properties of processes

The time and space overhead required for concurrent execution of programs

Inter-process communication is inefficient

Separate the two attributes of resource allocation and scheduling

The process is the unit of system resource allocation, and the thread is the unit of processor scheduling.

A thread represents a control point of a process and can execute a series of instructions. Usually, corresponds to a function of the application

The decomposition of processes into threads also enables efficient utilization of multi-processor and multi-core computers

basic unit of scheduling

Concurrency

Status: running, blocked, ready

Threads have a certain life span

A process can create threads, and a thread can create another child thread.

Mutual exclusion and synchronization still exist when multiple threads execute concurrently

Kernel supports thread KST

User-level thread ULT

Combination method

A process is a basic unit that can own resources

Multiple threads can execute concurrently

The process is no longer an executable entity

Three states of thread running

Thread control block TCB