What is Critical Section in Operating System
Critical Section in Operating System
What is Critical Section in Operating System In this article, we will explore the concept of the critical section in an operating system, why it’s important, and how operating systems manage access to shared resources. The critical section refers to a segment of code where shared resources, like variables, files, or data structures, are accessed and modified.
If multiple processes or threads attempt to enter the critical section simultaneously, it can lead to conflicts, data inconsistency, or even system crashes.
Critical section
Critical Section is any piece of code that is shared between different processes. If more than one process tries to operate in critical section we can reach to undesired output or else if one process starts to operate in critical section and does not release it then it may lead to deadlock, therefore, a single process is allowed to enter at a time. Whenever a process has entered a critical section, it doesn’t allow other processes to enter it by locking it for time being.
First, we have an entry section where each process checks whether the critical section is lock-free or not. If there is a lock then the process needs to wait else if there is no lock then the current process acquires the lock and enters the critical section. Once the process has been executed it releases the lock it has acquired. Whenever the next process comes it acquires the lock and then moves inside the critical section.
Necessary and sufficient conditions for a solution to the critical section problem:
- Mutual Exclusion: Only a single process is allowed to enter a critical section at a time. If a process pi is executing in its critical section then no other process is allowed to enter the critical section at that time.
- Progress: a process operating outside of its critical section cannot prevent other processes from entering theirs; processes attempting to enter their critical sections simultaneously must decide which process enters eventually.
- Bounded Waiting: a process attempting to enter its critical region will be able to do so eventually
Key Points:
- Critical sections are used in multi threaded and multi process systems to manage concurrent access to shared resources.
- If a process enters a critical section and never releases the lock (due to a bug or failure), it may lead to deadlock, where other processes wait indefinitely.
- Proper design of critical sections is essential for building reliable concurrent and parallel applications.
- Synchronization methods must ensure mutual exclusion, progress, and bounded waiting important properties in process synchronization.
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Real-life example
Bathroom: At a time only a single person can use the bathroom. Whenever a person enters the bathroom, he/she locks the bathroom so that no other person can enter it. Any other person who wants to use the bathroom needs to wait outside till the person comes out. Here washroom is an example of a critical section and people are examples of the process.
Pseudocode of Critical Section Problem
while(true){
// entry section
process_entered=1;
//loop until process_eneterd in 0
while(process_entered);
// critical section
// exit section
process_entered=0
// remainder section
} Advantages and Disadvantages of Critical Section in Operating System
| Advantages | Disadvantages |
| Ensures that shared resources are accessed in a controlled manner, preventing data corruption and maintaining integrity. | Increased contention and waiting time when multiple processes need to access the critical section. |
| Provides mechanisms like semaphores and mutexes that allow processes to synchronize effectively, avoiding race conditions. | If not properly managed, can lead to deadlock, where processes are stuck waiting for each other indefinitely. |
| Enables processes to work concurrently without interfering with each other, improving system performance. | If critical sections are too long or complex, they can become bottlenecks, reducing overall system efficiency. |
| Guarantees that each process eventually gets its turn to access the critical section, ensuring fairness. | Processes may experience starvation if the scheduling algorithm does not allocate time for all processes fairly. |
| With proper design, critical sections can be structured to prevent deadlocks, ensuring smooth system operation. | Improper design or priority inversion can lead to deadlocks where processes are blocked permanently. |
| The concept of critical sections is simple and easy to implement using basic locking mechanisms like mutexes or semaphores. | Implementing and managing locks in complex systems can be error-prone and lead to bugs like race conditions or lock contention. |
To wrap up
Critical Section in an operating system is essential for managing concurrent access to shared resources, ensuring data integrity and preventing race conditions. Proper synchronization mechanisms like semaphores and mutexes help achieve mutual exclusion, progress, and bounded waiting. While critical sections prevent data corruption, they can also introduce issues like deadlock, starvation, or bottlenecks if not managed correctly. Therefore, careful design and implementation are crucial to maintain system efficiency and reliability in multi threaded and multi process environments.
FAQs
Semaphores are used to control access to the critical section by signaling whether it is available or occupied, thus preventing race conditions.
The critical section is where shared resources are accessed, while the remainder section contains non-critical operations that do not interfere with other processes.
Long critical sections increase contention, leading to higher waiting times for processes and potential performance bottlenecks.
No, only one process is allowed to enter a critical section at a time to maintain mutual exclusion and prevent data corruption.
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