To understand the importance of condition variables, let's examine a producer-consumer scenario.

Suppose we have two threads: one serving as a producer and the other as a consumer. The producer's function is to generate a value, while the consumer's is to utilize that value. The key requirement is for the consumer thread to wait until a value has been produced.

At first glance, this might seem easily achievable using a mutex. However, a deeper analysis reveals an inherent inefficiency in the correct solution: busy-waiting.

Here is an example of an inefficient implementation.