Pthreads Programming

Computers are just as busy as the rest of us nowadays. They have lots of tasks to do at once, and need some cleverness to get them all done at the same time.

That's why threads are seen more and more often as a new model for programming. Threads have been available for some time. The Mach operating system, the Distributed Computer Environment (DCE), and Windows NT all feature threads.

One advantage of most UNIX implementations, as well as DCE, is that they conform to a recently ratified POSIX standard (originally 1003.4a, now 1003.1c), which allows your programs to be portable between them. POSIX threads are commonly known as pthreads, after the word that starts all the names of the function calls. The standard is supported by Solaris, OSF/1, AIX, and several other UNIX-based operating systems.

The idea behind threads programming is to have multiple tasks running concurrently within the same program. They can share a single CPU as processes do, or take advantage of multiple CPUs when available. In either case, they provide a clean way to divide the tasks of a program while sharing data.

A window interface can read input on dozens of different buttons, each responsible for a separate task. A network server has to accept simultaneous calls from many clients, providing each with reasonable response time. A multiprocessor runs a number-crunching program on several CPUs at once, combining the results when all are done. All these kinds of applications can benefit from threads.

In this book you will learn not only what the pthread calls are, but when it is a good idea to use threads and how to make them efficient (which is the whole reason for using threads in the first place). The authors delves into performance issues, comparing threads to processes, contrasting kernel threads to user threads, and showing how to measure speed. He also describes in a simple, clear manner what all the advanced features are for, and how threads interact with the rest of the UNIX system.

Topics include:

• Basic design techniques
• Mutexes, conditions, and specialized synchronization techniques
• Scheduling, priorities, and other real-time issues
• Cancellation
• UNIX libraries and re-entrant routines
• Signals
• Debugging tips
• Measuring performance
• Special considerations for the Distributed Computing Environment (DCE)

Dick Buttlar is a consulting writer in the UNIX Engineering Group at Digital Equipment Corporation, where he recently completed his stint as project leader for the Digital UNIX cluster documentation. He specializes in programming documentation -- both user-level and kernel -- and, in a former life, wrote the device driver documentation for the VMS operating system. A few years ago, he managed the initial planning of the corporate- wide documentation effort for Digital's Alpha processor. He's worked for Wang Laboratories, Recal/Redac, North American Technologies, and the American Trial Lawyers Association, among other places. He has a B.A. in English from Boston College and an M.A. in English from the University of Wisconsin at Madison.

Brad Nichols is a free-lance do-anything-computerish-for-a-buck kind of guy who works out of Milford, NH. He earned a Bachelor of Science degree in mechanical engineering from the University of New Hampshire in 1985 and a Master of Science degree from Worcester Polytechnic Institute (WPI) in 1991. He started his computer career working on very hard hardware (fuel pumps and valves). He worked his way up through the hardware layers into software on projects involving embedded avionics systems at Textron Lycomming and United Technologies Hamilton Standard Division. Brad left these jobs to learn more about AI at WPI, but instead caught the Mach fever, and was introduced to threads programming in UNIX. While at WPI he also worked on an OSF/1 performance project for the Open Software Foundation (OSF). After attending WPI, Brad taught training seminars to software developers on the Mach kernel interfaces. He then joined Digital Equipment Corporation to work on the port of the OSF's Distributed Computing Environment's Distributed File System (OSFDCEDFSDU for short) to Digital UNIX. Now, Brad is once again on his own and spends most of his time teaching software engineers about technologies with much shorter acronyms -- such as Pthreads.