《Operating System Concepts》学习第 29 天，p309-p330 总结，总计 22 页。

一、技术总结

1.Python 中的并发编程

(1)semaphore

class threading.Semaphore(value=1)。

(2)condition variable

class threading.Condition(lock=None)

书上使用的是 Java, 因本人在开发工作中使用的是 Python, 所以补充一些 Python 相关的内容。平时都没注意到这些(Python 官方文档：The Python Standard Library » Concurrent Execution » threading — Thread-based parallelism)，是我孤陋寡闻了。当然，现在只是知道了，还是不知道应用场景是什么，何时使用。

2.memory transaction

A type of memory supporting memory transactions.

3.dead lock

(1)定义

The state in which two processes or threads are stuck waiting for an event that can only be caused by one of the processes or threads.

(2)Necessary Conditions

1)Mutual exclusion

2)Hold and wait

3)No preemption

4)Circular wait

二、英语总结(生词：2)

1.coherency

(1)coherence: co-("together") + haerere("to adhere, stick")

u. sth logically or structurally connected and consistent(连贯性)。

(2)coherence vs coherency

两者意思一样，暂时没看出有啥区别，先记录。

1)However, HTM does require that existing cache hierarchies and cache coherency protocols be modified to support transactional memory(《Operating System Concepts》第 312 页)。

2)Discuss, with examples, how the problem of maintaining coherence of cached data manifests itself in the following processing environments:

a.Single-processor systems

b.Multiprocessor systems

c.Distributed systems

2.a priori

adj/adv. presupposed by experience(凭经验预设的)，两个词组合形成一个形容词。

示例：Note that the resources must be claimed a priori in the system(《Operating System Concepts》第 333 页)。

关于英语的注解同步更新汇总到 https://github.com/codists/English-In-CS-Books 仓库。

三、其它

第 7 章(Synchronization Examples)简评：本章介绍了 synchronization 在 POSIX 系统、在 Java 中的应用。

四、参考资料

1. 编程

(1) Abraham Silberschatz，Peter Baer Galvin，Greg Gagne《Operating System Concepts》：https://book.douban.com/subject/30272539/

2. 英语

(1) Etymology Dictionary：https://www.etymonline.com

(2) Cambridge Dictionary：https://dictionary.cambridge.org

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