ucontext的介绍
http://blog.csdn.net/qq910894904/article/details/41911175
协程的介绍
https://en.wikipedia.org/wiki/Coroutine
风云的c库
http://blog.codingnow.com/2012/07/c_coroutine.html
https://github.com/cloudwu/coroutine/
腾讯的开源c++库
https://code.csdn.net/Tencent/libco/tree/master
原文：http://www.cnblogs.com/woshare/p/5882744.html