With this practical book, you will attain a solid understanding of threads and will discover how to put this powerful mode of programming to work in real-world applications.
The primary advantage of threaded programming is that it enables your applications to accomplish more than one task at the same time by using the number-crunching power of multiprocessor parallelism and by automatically exploiting I/O concurrency in your code, even on a single processor machine. The result: applications that are faster, more responsive to users, and often easier to maintain. Threaded programming is particularly well suited to network programming where it helps alleviate the bottleneck of slow network I/O.
This book offers an in-depth description of the IEEE operating system interface standard, POSIX (Portable Operating System Interface) threads, commonly called Pthreads. Written for experienced C programmers, but assuming no previous knowledge of threads, the book explains basic concepts such as asynchronous programming, the lifecycle of a thread, and synchronization. You then move to more advanced topics such as attributes objects, thread-specific data, and realtime scheduling. An entire chapter is devoted to "real code," with a look at barriers, read/write locks, the work queue manager, and how to utilize existing libraries. In addition, the book tackles one of the thorniest problems faced by thread programmers-debugging-with valuable suggestions on how to avoid code errors and performance problems from the outset.
Numerous annotated examples are used to illustrate real-world concepts. A Pthreads mini-reference and a look at future standardization are also included.
2.2.5 Recycling
2.2.5 Recycling
If the thread was created with the detachstate attribute set to PTHREAD_ CREATE_DETACHED (see Section 5.2.3), or if the thread or some other thread has already called pthread_detach for the thread's identifier, then the thread is immediately recycled when it becomes terminated.
If the thread has not been detached when it terminates, it remains in the terminated state until the thread's pthread_t identifier is passed to pthread_detach or pthread_join. When either function returns, the thread cannot be accessed again. In lifecycle.c, for example, the thread that had run thread_routine will be recycled by the time the main thread returns from the pthread_join call at line 23.
Recycling releases any system or process resources that weren't released at termination. That includes the storage used for the thread's return value, the stack, memory used to store register state, and so forth. Some of these resources may have been released at termination; it is important to remember that none of it should be accessed from any other thread after termination. For example, if a thread passes a pointer to its stack storage to another thread through shared data, you should treat that information as obsolete from the time the thread that owns the stack terminates.
