Nrthugu

This code works fine, it acquires the one semaphore entry

static void Main(string args)

{

    Semaphore semaphore = new Semaphore(1, 1, "sem1");



    semaphore.WaitOne();



    Console.WriteLine("Press any Key to release semaphore");

    Console.ReadKey();



    semaphore.Release();

}

but this one waits on the WaitOne() method.

static void Main(string args)

{

    Semaphore semaphore = new Semaphore(0, 1, "sem1");



    semaphore.WaitOne();



    Console.WriteLine("Press any Key to release semaphore");

    Console.ReadKey();



    semaphore.Release();

}

Am I missing something basic here? Thanks

You are setting the amount of available requests to zero and then trying to acquire the semaphore. Since there are no available requests, the thread will hang on the semaphore and wait for some other thread to release it.

Think of the semaphore as an integer S. When you WaitOne, two things can happen

• If S is greater than zero, decrease it by one.


• If S is equal to zero, suspend the thread until it's not zero.

In the first example, you initialize it to one and then acquire.
In the second, you initialize it to zero, so the thread waits. And it waits indefinitely, since there are no other threads to release the semaphore.