Signalling and Resource Counting Using Semaphores

Semaphores

The word semaphore means something that can be used for signaling, such as a flag or a light. In the example that follows, we will see how we can use semaphores for signaling different states that other threads can be waiting for.

A semaphore can also be used to control access to a resource, similarly to how a std::mutex restricts access to a critical section: