C ++ 11线程实现后端

问题描述

我从某处了解到，使用 PThreads OpenMP 在Linux系统中，尽管它们对我来说似乎完全不同。考虑到 C ++ 11 线程和 PThreads 之间的（相对）相似之处，我想知道，

I have read from somewhere that OpenMP is implemented using PThreads in Linux systems although they seem quite different to me. Considering the (relative) similarities between C++11 threads and PThreads I was wondering,

有人知道是否使用 PThreads 实现了 C ++ 11 线程或 gcc 或 clang 中的任何其他多线程库？

Does anyone know if C++11 threads implemented using PThreads or any other multithreading library in gcc or clang?

推荐答案

C ++ 2011多线程有多个部分：

There are multiple parts of C++ 2011 multi-threading:

1. 高级-像 std :: thread ， std :: mutex ， std :: condition_variable 等。这些抽象是针对libc ++（c族的本机库）和libstdc ++（gcc的本机库）的pthreads实现的。 libstdc ++使用间接寻址（ gthr.h ），可用于例如为单线程实现添加内容。从不同的同步类的来源来看，这是很明显的。


2. pthreads不提供较低级别的同步工具，即原子和各种内存可见性控件。看来gcc和clang都使用编译器内置程序来实现这些功能，它们可能会创建合适的指令。但是，我还没有找到这两个代码的实际代码。


3. 在库中实现功能还不够：需要防止编译器在同步期间对指令重新排序原语，它需要使值在适当的位置可见。

1. Higher-level abstractions like std::thread, std::mutex, std::condition_variable, etc. These abstractions are implemented in terms of pthreads for both libc++ (clang's native library) and libstdc++ (gcc's native library). libstdc++ uses an indirection (gthr.h) which can be used to, e.g., stub things out for a single threaded implementation. This is quite obvious from the source of the different synchronization classes.
2. The lower-level synchronization facilities, i.e., atomics and the various memory visibility controls, are not available from pthreads. It seems both gcc and clang implement these using compiler build-ins which probably create suitable instructions. I haven't tracked down the actual code for either of these, however.
3. It isn't sufficient to implement things in the library: the compiler needs to be prevented from reordering instruction across synchronization primitives and it needs to make values visible in appropriate locations.

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