的boost :: shared_mutex多读/单写互斥 [英] boost::shared_mutex multiple-reader / single-writer mutex

问题描述

我想使用boost :: shared_mutex实现多读/单写互斥。我的问题是相当简单的，有可能是一个线程来获得读者访问shared_mutex，当另一个线程试图锁定该shared_mutex写？例如，我有10个线程，只有一个可以写，

I am trying to use boost::shared_mutex to implement a multiple-reader / single-writer mutex. My question is fairly simple, is it possible for a thread to gain reader access to a shared_mutex, when another thread tries to lock that shared_mutex for writing? For example, I have 10 threads, only one of them can write,

• 线程1对是shared_mutex一个shared_lock并尝试读取
  东西


• 2线设在该shared_mutex一个shared_lock并尝试读取
  东西


• 3线设在该shared_mutex一个unique_lock并尝试写东西


• 螺纹4具有上shared_mutex一个shared_lock并尝试读取
  东西


• 螺纹5对是shared_mutex一个shared_lock并尝试读取
  东西

该shared_mutex目前赞同线程2 ，我的问题是，是否有可能的螺纹4 可以获得读访问该shared_mutex，之前的线程锁定3 能写？是否有可能为一个读/写互斥曾经进入一个饥饿的情况下，例如，100读者V.S. 1作家？

The shared_mutex is currently shared locked by thread 2, my question is whether it is possible that thread 4 can gain read access to that shared_mutex, before thread 3 can write? Is it possible for a reader/writer mutex ever gets into a starvation situation, e.g., 100 reader v.s. 1 writer?

感谢。

推荐答案

显然，的boost :: shared_mutex 离开的公平策略到执行。它可以是公平的，读者过作家或作家在阅读器等等，这取决于它是为您的特定版本，它有可能是作家，可以饿死。

Apparently the boost::shared_mutex leaves the fairness policy up to the implementation. It can be either fair, reader-over-writer or writer-over-reader so depending on which it is for your particular version it's possible that the writer can be starved.

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