Programming with POSIX® Threads

This book assumes that you are an experienced programmer, familiar with developing code for an operating system in "the UNIX family" using the ANSI C language. I have tried not to assume that you have any experience with threads or other forms of asynchronous programming. The Introduction chapter provides a general overview of the terms and concepts you'll need for the rest of the book. If you don't want to read the Introduction first, that's fine, but if you ever feel like you're "missing something" you might try skipping back to get introduced.

Along the way you'll find examples and simple analogies for everything. In the end I hope that you'll be able to continue comfortably threading along on your own. Have fun, and "happy threading."

About the author

I have been involved in the Pthreads standard since it began, although I stayed at home for the first few meetings. I was finally forced to spend a grueling week in the avalanche-proof concrete bunker at the base of Snowbird ski resort in Utah, watching hard-working standards representatives from around the world wax their skis. This was very distracting, because I had expected a standards meeting to be a formal and stuffy environment. As a result of this misunderstanding, I was forced to rent ski equipment instead of using my own.

After the Pthreads standard went into balloting, I worked on additional thread synchronization interfaces and multiprocessor issues with several POSIX working groups. I also helped to define the Aspen threads extensions, which were fast-tracked into X/Open XSH5.

I have worked at Digital Equipment Corporation for (mumble, mumble) years, in various locations throughout Massachusetts and New Hampshire. I was one of the creators of Digital's own threading architecture, and I designed (and implemented much of) the Pthreads interfaces on Digital UNIX 4.0. I have been helping people develop and debug threaded code for more than eight years.

My unofficial motto is "Better Living Through Concurrency." Threads are not sliced bread, but then, we're programmers, not bakers, so we do what we can.

Acknowledgments

This is the part where I write the stuff that I'd like to see printed, and that my friends and coworkers want to see. You probably don't care, and I promise not to be annoyed if you skip over it—but if you're curious, by all means read on.

No project such as this book can truly be accomplished by a single person, despite the fact that only one name appears on the cover. I could have written a book about threads without any help—I know a great deal about threads, and I am at least reasonably competent at written communication. However, the result would not have been this book, and this book is better than that hypothetical work could possibly have been.

Thanks first and foremost to my manager Jean Fullerton, who gave me the time and encouragement to write this book on the job—and thanks to the rest of the DECthreads team who kept things going while I wrote, including Brian Keane, Webb Scales, Jacqueline Berg, Richard Love, Peter Portante, Brian Silver, Mark Simons, and Steve Johnson.

Thanks to Garret Swart who, while he was with Digital at the Systems Research Center, got us involved with POSIX. Thanks to Nawaf Bitar who worked with Garret to create, literally overnight, the first draft of what became Pthreads, and who became POSIX thread evangelist through the difficult period of getting everyone to understand just what the heck this threading thing was all about anyway. Without Garret, and especially Nawaf, Pthreads might not exist, and certainly wouldn't be as good as it is. (The lack of perfection is not their responsibility—that's the way life is.)

Thanks to everyone who contributed to the design of cma, Pthreads, UNLX98, and to the users of DCE threads and DECthreads, for all the help, thought-provoking discourse, and assorted skin-thickening exercises, including Andrew Birrell, Paul Borman, Bob Conti, Bill Cox, Jeff Denham, Peter Gilbert, Rick Greer, Mike Grier, Kevin Harris, Ken Hobday, Mike Jones, Steve Kleiman, Bob Knighten, Leslie Lamport, Doug Locke, Paula Long, Finnbarr P. Murphy, Bill Noyce, Simon Patience, Harold Seigel, Al Simons, Jim Woodward, and John Zolnowsky.

Many thanks to all those who patiently reviewed the drafts of this book (and even to those who didn't seem so patient at times). Brian Kernighan, Rich Stevens, Dave Brownell, Bill Gallmeister, Ilan Ginzburg, Will Morse, Bryan O'Sullivan, Bob Robillard, Dave Ruddock, Bil Lewis, and many others suggested or motivated improvements in structure and detail—and provided additional skin-thickening exercises to keep me in shape. Devang Shah and Bart Smaalders answered some Solaris questions, and Bryan O'Sullivan suggested what became the "bailing programmers" analogy.