Multithreaded Programming Guide

Multithreaded Programming Guide

Term	Definition
Process	The UNIX environment (such as file descriptors, user ID, and so on) created with the fork(2) system call, which is set up to run a program.
Thread	A sequence of instructions executed within the context of a process.
pthreads (POSIX threads)	A POSIX 1003.1c compliant threads interface.
Solaris threads	A Sun MicrosystemsTM threads interface that is not POSIX compliant. A predecessor of pthreads.
Single-threaded	Restricting access to a single thread.
Multithreaded	Allowing access to two or more threads.
User- or Application-level threads	Threads managed by the threads library routines in user (as opposed to kernel) space.
Lightweight processes	Threads in the kernel that execute kernel code and system calls (also called LWPs).
Bound threads	Threads that are permanently bound to LWPs.
Unbound threads	A default Solaris thread that context switches very quickly without kernel support.
Attribute object	Contains opaque data types and related manipulation functions used to standardize some of the configurable aspects of POSIX threads, mutual exclusion locks (mutexes), and condition variables.
Mutual exclusion locks	Functions that lock and unlock access to shared data.
Condition variables	Functions that block threads until a change of state.
Counting semaphore	A memory-based synchronization mechanism.
Parallelism	A condition that arises when at least two threads are executing simultaneously.
Concurrency	A condition that exists when at least two threads are making progress. A more generalized form of parallelism that can include time-slicing as a form of virtual parallelism.

并行与并发

并行：两个或两个以上的线程同时在执行
并发：两个或两个以上线程处在运行状态中

并发与并行的区别在于并发情况下，同一时间点只能执行一个线程，多个线程轮流执行，而并行则是同时执行多个，齐头并进。