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Difference between Binary Semaphore and Mutex

Last Updated : 21 Sep, 2023
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Binary Semaphore and Mutex are both synchronization mechanisms used in concurrent programming to control access to shared resources and prevent race conditions. However, they have different characteristics and use cases

Binary Semaphore

Binary semaphores are semaphores that can only assume the values 0 and 1. They are used for implementing the locks by using signaling mechanisms to achieve mutual exclusion. Here, if the value of the semaphore is 0, it means it is locked, so the lock is unavailable. If the value of the semaphore is 1 it means it is unlocked, so, the lock is available in binary semaphore.

Binary Semaphore

Binary Semaphore

Mutex

A mutex provides mutual exclusion, either the producer or consumer can have the key (mutex) and proceed with their work. As long as the buffer is filled by producer, the consumer needs to wait, and vice versa. At any point in time, only one thread can work with the entire buffer. The concept can be generalized using semaphore.

IMAGE OF MUTEX

Difference Between Binary Semaphore and Mutex

Binary Semaphore Mutex
Its functions based up on signalling mechanism Its functions based up on locking mechanism
The thread which is having higher priority than current thread can also release binary semaphore and take lock. The thread which has acquired mutex can only release Mutex when it exits from critical section.
Semaphore value is changed according to wait () and signal () operations. Mutex values can be modified just as locked or unlocked.
Multiple number of threads can acquire binary semaphore at a time concurrently. Only one thread can acquire mutex at a time
Binary semaphore have no ownership. There is ownership associated with mutex because only owner can release the lock.
They are faster than mutex because any other thread/process can unlock binary semaphore. They are slower than binary semaphores because only thread which has acquired must release the lock.
If you have number of instances for resource it is better to use Binary semaphore. If you have single instance for resource it is better to use mutex.

Conclusion

In essence, both binary semaphores and mutexes help manage access to shared resources in a multi-threaded environment, but their primary difference lies in their intended use cases. Binary semaphores are often used for signaling and coordination between threads, while mutexes are focused on providing mutual exclusion to ensure thread-safe access to critical sections.

Frequently Asked Questions

Q1: When is a Binary Semaphore useful?

Answer:

Binary Semaphores are useful when you need to coordinate between multiple threads to control access to a shared resource. They are often used to signal whether a resource is available for use or to manage access to a critical section.

Q2: What is the purpose of a Mutex?

Answer:

A Mutex is used to provide mutual exclusion, ensuring that only one thread can enter a critical section of code at a time. This prevents conflicts and data inconsistencies that can occur when multiple threads access shared resources concurrently.

Q3: Can a Mutex be locked multiple times by the same thread?

Answer:

Yes, a Mutex can be locked multiple times by the same thread, but it needs to be unlocked an equivalent number of times before other threads can acquire the Mutex.


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