How do you Implement a Barrier using Semaphores?

To implement a barrier using semaphores, you can use two semaphores: one to count the number of threads that have reached the barrier and another to block threads until the required number has arrived. Initialize a semaphore to zero, which will signal when all threads have reached the barrier. Each thread increments a counter as it arrives; once the counter reaches the limit, the semaphore is released to wake all waiting threads. Threads that arrive after reaching the limit wait on the semaphore until they are released, ensuring they proceed together.