是std :: ifstream线程安全&无锁？ [英] Is std::ifstream thread-safe & lock-free?

问题描述

我打算使用std :: ifstream执行从许多线程读取单个文件的打开。我的关注是如果std :: ifstream是线程安全&无锁？

更多详细信息：

1. 我在Ubuntu上使用g ++ 4.4 &


$ b p>提前感谢！

解决方案

请参阅 http://gcc.gnu.org/onlinedocs/libstdc++/manual/using_concurrency.html 。





在编写该手册页面时，GCC的标准库推迟了操作系统的C stdio文件缓冲。他们避免保持状态在C FILE 结构之外，并通过它实现一定程度的安全。





由于C stdio库在最后一个I / O操作周围的文件中实现单个范围的缓冲区，我没有看到无锁实现。必须对文件上的操作进行连续处理。也许无缓冲模式可以帮助;这是比我现在想做的更多的研究。




I intend to perform opening for reading a single file from many threads using std::ifstream. My concern is if std::ifstream is thread-safe & lock-free?

More details:

1. I use g++ 4.4 on Ubuntu & Windows XP, 4.0 on Leopard.
2. Each thread creates its own instance of std::ifstream

Thanks in advance!

解决方案

See http://gcc.gnu.org/onlinedocs/libstdc++/manual/using_concurrency.html.

As of the writing of that manual page, GCC's standard library defers to the operating system's C stdio file buffering. They avoid keeping state outside the C FILE structure and achieve some level of safety through it.

Since the C stdio library implements a buffer of a single range within the file around the last I/O operation, I don't see how a lock-free implementation is possible. The operations on a file must be processed serially. Perhaps unbuffered mode could help; that's a little more research than I'd like to do right now.

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