Critical Section | Critical Section Problem

Critical Section-

 

Before you go through this article, make sure that you have gone through the previous article on Process Synchronization.

 

We have discussed-

  • Process Synchronization controls the execution of processes running concurrently so as to produce the consistent results.
  • Critical section is a part of the program where shared resources are accessed by the process.

 

Critical Section Problem-

 

  • If multiple processes access the critical section concurrently, then results produced might be inconsistent.
  • This problem is called as critical section problem.

 

Synchronization Mechanisms-

 

Synchronization mechanisms allow the processes to access critical section in a synchronized manner to avoid the inconsistent results.

 

For every critical section in the program, a synchronization mechanism adds-

  • An entry section before the critical section
  • An exit section after the critical section

 

 

Entry Section-

 

  • It acts as a gateway for a process to enter inside the critical section.
  • It ensures that only one process is present inside the critical section at any time.
  • It does not allow any other process to enter inside the critical section if one process is already present inside it.

 

Exit Section-

 

  • It acts as an exit gate for a process to leave the critical section.
  • When a process takes exit from the critical section, some changes are made so that other processes can enter inside the critical section.

 

Criteria For Synchronization Mechanisms-

 

Any synchronization mechanism proposed to handle the critical section problem should meet the following criteria-

 

 

  1. Mutual Exclusion
  2. Progress
  3. Bounded Wait
  4. Architectural Neutral

 

1. Mutual Exclusion-

 

The mechanism must ensure-

  • The processes access the critical section in a mutual exclusive manner.
  • Only one process is present inside the critical section at any time.
  • No other process can enter the critical section until the process already present inside it completes.

 

2. Progress-

 

The mechanism must ensure-

  • An entry of a process inside the critical section is not dependent on the entry of another process inside the critical section.
  • A process can freely enter inside the critical section if there is no other process present inside it.
  • A process enters the critical section only if it wants to enter.
  • A process is not forced to enter inside the critical section if it does not want to enter.

 

3. Bounded Wait-

 

The mechanism should ensure-

  • The wait of a process to enter the critical section is bounded.
  • A process gets to enter the critical section before its wait gets over.

 

4. Architectural Neutral-

 

The mechanism should ensure-

  • It can run on any architecture without any problem.
  • There is no dependency on the architecture.

 

Important Notes-

 

Note-01:

 

  • Mutual Exclusion and Progress are the mandatory criteria.
  • They must be fulfilled by all the synchronization mechanisms.

 

Note-02:

 

  • Bounded waiting and Architectural neutrality are the optional criteria.
  • However, it is recommended to meet these criteria if possible.

 

To gain better understanding of Critical Section in OS,

Watch this Video Lecture

 

Next Article- Lock Variable | Synchronization Mechanism

 

Get more notes and other study material of Operating System.

Watch video lectures by visiting our YouTube channel LearnVidFun.

Summary
Critical Section | Critical Section Problem
Article Name
Critical Section | Critical Section Problem
Description
Critical Section in OS is a part of the program where shared resources are accessed by the processes. Critical Section Problem arises when multiple processes access the critical section at the same time.
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Publisher Name
Gate Vidyalay
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