Operating System: Mutual Exclusion

Mutual Exclusion

• When one process uses a shared resource, other processes that need access to the same resource are excluded from using it simultaneously.
• Only one process can access a shared resource at a time, and all other processes must wait.

Critical Section

• The part of code in a process that accesses and uses a shared resource is called the critical section.
• Only one process can enter the critical section at a time to avoid undesirable events.

Process Concepts

• Process spawning occurs when the OS creates a process at the explicit request of another process.
• The process that spawns another process is referred to as the parent process, and the spawned process is referred to as the child process.

Semaphores

• A semaphore is an abstract data type that functions as a software synchronization tool to implement a solution to the critical section problem.
• Semaphores can be used to synchronize access to shared resources.

Producer-Consumer Problem

• The producer-consumer problem involves two processes: the producer process, which produces data items and inserts them in a buffer, and the consumer process, which removes data items from the buffer and consumes them.

Multi-Threading

• Multi-threading refers to the ability of an OS to support multiple, concurrent paths of execution within a single process.
• A thread is a unit of dispatching, and a process is a unit of resource ownership.

Context Switch

• When the OS interrupts an executing process, it carries out a context switch, changing the CPU from one process to another.
• The time it takes for this changeover is called the context switch time.

Deadlocks

• A deadlock is a state of indefinite waiting that processes may reach when competing for system resources or when attempting to communicate.
• Four conditions are necessary for the existence of a deadlock: mutual exclusion, hold and wait, no preemption, and circular wait.

Synchronization

• Synchronization is the coordination of activities of two or more processes that need to carry out certain activities, such as competing for resources in a mutually exclusive manner or cooperating in sequencing or ordering specific events.

Blocking and Unblocking

• A thread blocks when it waits for an event, saving its user registers, program counter, and stack pointers.
• A thread is unblocked when the event for which it was blocked occurs, and it is moved to the Ready queue.

Atomic Operations

• An atomic operation is a function or action implemented as a sequence of one or more instructions that appears to be indivisible, and no other process can see an intermediate state or interrupt the operation.