Professional Multicore Programming: Design and Implementation for C++ Developers

Chapter 6. Multithreading

	They come from a much older version of the matrix, but like so many back then, they caused more problems than they solved.
	--Persephone, Matrix Reloaded

In Chapter 5, we examined how concurrency in a C++ program can be accomplished by decomposing your program into either multiple processes or multiple threads. We discussed a process, which is a unit of work created by the operating system. We explained the POSIX API for process management and the several system calls that can be used to create processes: fork(), fork-exec(), system(), and posix_spawn(). We showed you how to build C++ interface components, interface classes, and declarative interfaces that can be used to simplify part of the POSIX API for process management. In the chapter we cover:

• What is a thread?

• The pthread API for thread management

• Thread scheduling and priorities

• Thread contention scope

• Extending the thread_object to encapsulate thread attribute functionality

What Is a Thread?

A thread is a sequence or stream of executable code within a process that is scheduled for execution by the operating system on a processor or core. All processes have a primary thread. The primary thread is a process's flow of control or thread of execution. A process with multiple threads has as many flows of controls as there are threads. Each thread executes independently and concurrently with its own sequence of instructions. A process with multiple threads is multithreaded. There are user-level threads and kernel-level ...