STREAMS Programming Guide

Message Queues

Each stream head, driver, and module has its own pair of queues, one queue for the read side and one queue for the write side. Messages are ordered into queues, generally on a first-in, first-out basis (FIFO), according to priorities associated with them. Kernel-level details of queues are covered in Structure of a Message Queue.

Figure 1–2 Messages Passing Using Queues

Diagram shows downstream and upstream message passing
between components of a stream.