Mutex Vs Semaphore | Difference Between Semaphore and Mutex

Hello Friends! Today, here we will explain about key difference between Semaphore and Mutex in OS as well as Mutex Vs Semaphore in tabular comparisons with ease. This is unique post over the Internet. Making ensure that after reading this content; you will definitely fully aware about Mutex Vs Semaphore in Operating System without getting any hindrance.

Important Things about Semaphore and Mutex

Here are some important things to know about semaphores and mutexes in Operating System, including:

Difference Between Semaphore and Mutex


  • Binary state can be locked or unlocked
  • Ownership concept that requiring the same thread to release the mutex
  • A thread attempting to acquire a locked mutex is blocked until it is released.
  • May support recursive locking; whereas the thread can lock the mutex multiple times


  • Generalized synchronization mechanism for controlling access to the resource by multiple threads
  • Maintains a count that allowing multiple threads to access the resource up to a specified limit
  • It can be used for signaling between threads
  • Supports both blocking and non-blocking operations
  • No ownership concept; any thread can release the semaphore.
  • Well-suited for scenarios whereas the limited number of threads can access a resource concurrently or for signaling

What are Major Differences between Semaphore and Mutex?

In this section, we will cover the major differences in between the Semaphore and Mutex in operating system; below shown each one, you can check them:


Mutex is an object in a program that serves as a lock that is used to negotiate mutual exclusion among threads. It works as a programming concept that is frequently used to fix multi-threading problems. In concurrent programming, multiple threads/processes updating the shared resource (any variable, shared memory, etc.) may lead to unexpected results. Mutex makes ensuring that only one process/thread can enter into the critical section at a given time.

Also Read: Mutex in Operating System with Examples

Key Properties of Mutex include:

  • Guaranteed access to only one of the actors at once
  • Critical section is the part of the code that should not be executed by more than one thread at a time
  • Mutexes can be used to prevent race conditions; whereas the multiple threads try to access a shared resource at the same time

Benefits Are:

  • Ensures exclusive access to shared resources
  • Prevents data race conditions by allowing only one thread to access the critical section at a time
  • Provides a simple and effective mechanism for synchronization
  • Can be used across different processes in some inter-process communication scenarios

Drawbacks Are:

  • May lead to potential deadlocks if not used properly
  • Can introduce contention, especially in scenarios with frequent lock and unlock operations
  • Requires careful implementation to avoid priority inversion issues
  • Overuse of mutexes can lead to performance bottlenecks
  • Mutexes are specific to the particular platform or operating system, which can limit portability


Semaphore is a synchronization primitive used in computer science to control access to a common resource by multiple threads and avoid critical section conflicts. It is a variable or abstract data type that helps manage the access to a shared resource, and making ensure that only a limited number of threads can access it at a given time. Semaphores are often used to restrict the number of threads that can access some resource, such as a physical or virtual pool.

Also Read: What is Semaphore in OS? Types with Examples & Their Operations

Key Properties of Semaphore include:

  • Semaphore maintains a set of permits, with each acquire() blocking if necessary until a permit is available, and then taking it.
  • Each release () adds a permit, and it potentially releasing a blocking acquirer.
  • Semaphores are often used to restrict the number of threads that can access some resource, such as a physical or virtual pool.

Benefits Are:

  • Allows multiple threads to access the critical section simultaneously that is based on the semaphore count
  • Provides more flexibility as compared the mutexes in controlling access to shared resources
  • It can be used for signalling in between the threads or processes
  • Helps in avoiding busy waiting as threads can be put to sleep and awakened when a semaphore is signalled
  • Suitable for scenarios where a fixed number of resources are available

Drawbacks Are:

  • Increased complexity compared to mutexes that may lead to more error-prone code
  • Semaphores don’t inherently prevent priority inversion, and additional mechanisms may be needed to address this issue
  • Incorrect usage can result in race conditions and other synchronization problems
  • Debugging and understanding code with semaphores may be more challenging
  • Semaphore usage may lead to more difficult-to-diagnose issues, such as deadlocks and livelocks

Key Differences between Semaphore and Mutex

Here, we will show you remarkable key differences between semaphores and mutexes in tabular format:





Generalization of Mutex (more versatile)Specifically designed for mutual exclusion


Resource counting, signaling, synchronizationExclusive access to a shared resource


Can be initialized with a count greater than 1Typically binary (0 or 1)


Wait (P) and Signal (V)Lock and Unlock


May be released by a different task/threadMust be released by the same task/thread


System-wide or limited to a specific scopeTypically used within a single process

Wait Queue

Supports a waiting queue for multiple tasksTypically supports only one waiting task


More flexible, can be used for more complex scenariosSimpler, suitable for basic synchronization


More complex to use and understandSimpler and easier to use

Resource Handling

Can be used for managing multiple resourcesPrimarily used for managing one resource
ExampleManaging access to a pool of resourcesControlling access to a shared variable

 How Do Mutexes and Semaphores Help with Synchronization?

Mutexes and semaphores are synchronization approaches that are going to use for control access to shared resources in your computer programming. They helping out the prevent data inconsistency and corruption cause of the concurrent access to shared resources, efficiency of the system, and improve the performance. They also enable the coordination and communication among threads or processes; simplify the design and implementation of concurrent programs.

Mutex is a locking and unlocking mechanism, while a semaphore is a signaling mechanism. Mutexes allow only one process at a time to access a shared resource, providing mutual exclusion, while semaphores allow multiple processes to access a shared resource simultaneously, up to the limit set by the semaphore value.

Which One are Best from Semaphore and Mutex?

Both mutexes and semaphores have their own specific requirements and constraints of the system and the application. A mutex is better for a single shared resource, while a semaphore is better for multiple instances of a resource. Mutexes are lightweight and faster than semaphores.

Also Read: Server Operating System: Types, Examples, and Working

But they can be more costly due to the protection protocols associated with them. Semaphores are most flexible and able to handle more complex synchronization scenarios; but they can also serve the more complexity and overhead. In general, programmer can prefer mutex rather than creating a semaphore with a count of 1.

FAQs (Frequently Asked Questions)

What is difference between mutex and binary semaphore?

The main difference between a binary semaphore and a mutex is that a binary semaphore is a signaling mechanism, while a mutex is a locking mechanism. However, they can be used interchangeably in some cases. But they have different characteristics and behaviors.

What is the difference between spin lock and semaphore mutex?

Spin lock is a busy-waiting mechanism, whereas the thread waits in a loop until the lock is available, while a semaphore or mutex involves sleeping and signaling. Spin locks waste CPU while waiting, making them suitable for short waits; whereas semaphores are more efficient for longer waits.

How do mutexes and semaphores address issues like priority inversion?

Mutexes may lead to priority inversion, and additional mechanisms are needed to mitigate this problem. Semaphores, while not inherently addressing priority inversion, can be used with additional techniques to handle such issues more effectively.

Summing Up

Now at the end, we can hope that you have been completely educated about key difference between Semaphore and Mutex in OS as well as Mutex Vs Semaphore in tabular comparisons with ease. If this article is useful for you, then please share it along with your friends, family members or relatives over social media platforms like as Facebook, Instagram, Linked In, Twitter, and more.

If you have any experience, tips, tricks, or query regarding this issue? You can drop a comment!

Happy Learning!!

Leave a Reply

Your email address will not be published. Required fields are marked *