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concurrencylockingmutexsemaphore

What is the difference between lock, mutex and semaphore?

I've heard these words related to concurrent programming, but what's the difference between lock, mutex and semaphore?

Solution

  • A lock allows only one thread to enter the part that's locked and the lock is not shared with any other processes.

    A mutex is the same as a lock but it can be system wide (shared by multiple processes).

    A semaphore does the same as a mutex but allows x number of threads to enter, this can be used for example to limit the number of cpu, io or ram intensive tasks running at the same time.

    For a more detailed post about the differences between mutex and semaphore read here.

    You also have read/write locks that allows either unlimited number of readers or 1 writer at any given time.

    The descriptions are from a .NET perspective and might not be 100% accurate for all OS/Languages.