锁机制: 1. https://www.cnblogs.com/aaronLinux/p/5890924.html (常见spin_lock) 2. https://blog.youkuaiyun.com/morixinguan/article/details/69666642 (下半部) 3. http://www.360doc.com/content/19/1121/17/7632576_874602462.shtml