The Solaris 7 kernel is multithreaded to make effective use of symmetric shared-memory multiprocessor computers. All parts of the kernel, including STREAMS modules and drivers, must ensure data integrity in a multiprocessing environment. For the most part, developers must ensure that concurrently running kernel threads do not attempt to manipulate the same data at the same time. The STREAMS framework provides multithreaded (MT) STREAMS perimeters, which allows the developer control over the level of concurrency allowed in a module. The DDI/DKI provides several advisory locks for protecting data. See Chapter 12, MultiThreaded STREAMS for more information.