33 Concurrency support library [thread]

33.9 Coordination types [thread.coord]

33.9.3 Barriers [thread.barrier] General [thread.barrier.general]

A barrier is a thread coordination mechanism whose lifetime consists of a sequence of barrier phases, where each phase allows at most an expected number of threads to block until the expected number of threads arrive at the barrier.
[Note 1: 
A barrier is useful for managing repeated tasks that are handled by multiple threads.
— end note]