挥发性和多线程？ [英] volatile and multithreading?

问题描述

在以下code：

#include <pthread.h>
#include <unistd.h>
#include <stdio.h>

pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
int ready = 0;

wait()
{
    int i;
    do
    {
        usleep(1000);
        pthead_mutex_lock(&mutex);
        i = ready;
        pthread_mutex_unlock(&mutex);
    } while (i == 0);   
    printf("Finished\n");
}

signal()
{
    pthead_mutex_lock(&mutex);
    ready = 1;
    pthread_mutex_unlock(&mutex);
}

我们产卵两个线程，我们调用wait在一个线程，然后调用另一个信号我们也让编译器优化大举

We spawn two threads we call wait in one thread and then call signal in the other We also get the compiler to optimize aggressively.

现在将在code像预期的那样还是会我们需要准备挥发性得到这个工作？将不同的编译器和库不同的方式处理这个？

Now will the code behave as expected or will we need to make ready volatile to get this to work? Will different compilers and libraries handle this differently?

编辑：我希望有可能是一个圆形的互斥功能，将prevent优化自身周围或编译器一般不全面优化的函数调用

I am hoping that there might be something round the mutex functions that will prevent optimization around itself or that the compiler generally does not optimize round function calls.

注意：我没有编译和测试code呢，会做，所以当我有机会

Note: I have not compiled and tested the code yet, will do so when I have a chance.

推荐答案

从内核君王一些观点：

http://kernel.org/doc/Documentation/volatile-considered- harmful.txt

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