https://www.cnblogs.com/52php/p/5861372.html (一系列)
https://blog.csdn.net/ljianhui/article/details/10253345
https://blog.csdn.net/adorable_/article/details/80465790
https://blog.csdn.net/qq_31073871/article/details/80922258
https://blog.csdn.net/adorable_/article/details/80465790
https://www.cnblogs.com/love-avrlinux/p/3618848.html (信號量)
https://blog.csdn.net/ypt523/article/details/79958188
https://blog.csdn.net/liushengxi_root/article/details/88778810#IO_60
圖片摘自:https://www.cnblogs.com/tp-16b/p/8987697.html