修改线程中的数据 [英] Modifying data in threads

问题描述

我有一个类的结构如下：

I have a class with the following structure:

class Nginx_sender
{
    private:
        std::vector<std::string> mMessagesBuffer;
        boost::mutex mMutex;

       void SendMessage(const std::string &msg)
       {
           mMutex.lock();
           mMessagesBuffer.push_back(msg);
           mMutex.unlock();

           std::cout << "Vector size: " << mMessagesBuffer.size() << std::endl;
       }

       void NewThreadFunction()
       {
          while(true) {
            mMutex.lock();
            if (mMessagesBuffer.size() >= 1) std::cout << ">=1\n";
            mMutex.unlock();

            boost::this_thread::sleep(boost::posix_time::milliseconds(200));
          }
       }
};

int main()
{
   Nginx_sender *NginxSenderHandle;
   boost::thread sender(boost::bind(&Nginx_sender::NewThreadFunction, &NginxSenderHandle));
   // ...
}

NewThreadFunction 正在新线程中运行，它检查 mMessagesBuffer 的大小。现在我调用 main 函数中的任何地方： NginxSenderHandle-> SendMessage（Test）;

NewThreadFunction is running in new thread and it checks the size of mMessagesBuffer. Now I call anywhere in main function: NginxSenderHandle->SendMessage("Test");

这显示了：第一次， 2

但是！ NewThreadFunction 它总是== 0.为什么会是？

But! In NewThreadFunction it's always == 0. Why could it be?

推荐答案

我敢打赌编译器缓存一些mMessagesBuffer内部在线程本地缓存。请尝试在mMessagesBuffer中添加volatile关键字，以停用此类优化。

I bet compiler is caching some of mMessagesBuffer internals in thread-local cache. Try adding 'volatile' keyword to mMessagesBuffer to disable such optimizations.

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