Difference Between Semaphore and Mutex

In this post, we will understand the difference between a semaphore and a mutex −

Semaphore

• It is used in the signalling mechanism.

• It is an integer variable.

• The ‘wait’ and ‘signal’ operations can be used to modify a semaphore.

• If no resources are available, the process requires that a resource that needs to be executed has to ‘wait’.

• The process will have to ‘wait’ until the count of the semaphore is higher than 0.

• Multiple program threads can be used with a semaphore.

• The value of a semaphore can be changed by any process that releases or obtains the resource.

• There are different kinds of semaphores: Counting semaphore and Binary semaphore.

• The value of a semaphore can be changed using ‘wait’ operation and ‘signal’ operation.

• The process is occupied if all resources are used.

• The process requesting the resource uses the ‘wait’ operation and blocks itself until the count of the semaphore becomes greater than 1.

Mutex

• It is used in locking mechanism.

• It is an object.

• It is modified by that process (only) that requests or releases a resource.

• If the mutex is locked, then the process will have to wait.

• The process is kept in a queue when mutex s locked.

• This can be accessed only after the mutex has been unlocked.

• Multiple program threads can be used in mutex (but not simultaneously).

• The lock on the object can be released by the process only, which would have obtained the lock on it.

• It doesn’t have any subtypes.

• The object is either locked or unlocked.

• If the object has already been locked, the process that requests the resources will wait.

• It will be queued by the system before the lock has been released.