sleeping barber problem

Etymology
By analogy with a barber who sleeps while not cutting hair, and whose customers wake him on arrival. Since actions such as entering the salon and looking around take variable amounts of time, this may lead to a situation where both barber and customer(s) are futilely waiting for each other.

Noun

 * 1)  A problem of interprocess communication and synchronization where one process responds to requests from multiple other threads and sleeps when not doing so. In some cases this may lead to an undesirable state where components are waiting for each other despite being ready.