The SunOS 5.x operating system is fully multithreaded, able to make effective use of the available parallelism of a symmetric shared-memory multiprocessor computer. All kernel subsystems are multithreaded: scheduler, virtual memory, file systems, block/character/STREAMS I/O, networking protocols, and device drivers.
MT STREAMS requires you to use some new concepts and terminology. These concepts apply not only to STREAMS drivers, but to all device drivers in the SunOS 5.x system. For more a complete description of these terms, see Writing Device Drivers. Additionally, see Chapter 1, Overview of STREAMS of this guide for definitions, and Chapter 8, Messages - Kernel Level for elements of MT drivers.
You need to understand the following terms and ideas.
a sequence of instructions executed within context of a process
a mechanism to restrict access to data structures
restricting access to a single thread
allowing two or more threads access
two or more CPUs concurrently executing the OS
suspending execution for the next thread to run
portion of code that is single threaded
exclusive access to a data element by a single thread at one time
kernel event synchronization primitives
memory based synchronization mechanism
data lock allowing one writer or many readers at one time
on specific event, call module function