I found code online that displays how to use threads from a tutorial by redKyle. In the Race Condition tutorial, he basically shows how two threads are sent to a function. The objective of the function is to print . and # in sequence one hundred times each. He provides the code to get this to work, he does NOT provide the code for the mutex. I have modified the code to include the mutex so that to prevent one thread from accessing the variable that holds the last character printed while another thread is accessing it. I got the code to work. Great! However, I kept changing the sleep value between 1 and 50. The mutex code works fine. However, when i set sleep to 0 (or just comment it out) the mutex no longer works and the values are no longer printed in the correct manner (I no longer see 200 characters of strictly alternating # and . ).

该守则如下:

#include "stdafx.h"

#include <iostream>
#include <windows.h>
using namespace std;

static char lastChar= # ;

//define a mutex
HANDLE mutexHandle = NULL;

//flag to specify if thread has begun
bool threadStarted = false;

void threadProc(int *sleepVal, int *threadID)
{

    cout<<"sleepVal: "<<*sleepVal<<endl;

    for (int i=0; i<100; i++)
    {

        char currentChar;

        threadStarted = true;

        while(!threadStarted){}

        //lock mutex
        WaitForSingleObject(mutexHandle, INFINITE);

        if (lastChar ==  # )
            currentChar =  . ;
        else
            currentChar =  # ;

        Sleep(*sleepVal);

        lastChar = currentChar;

        ReleaseMutex(mutexHandle);

        threadStarted = false;


        //      cout<<"
SleepVal: "<<*sleepVal<<" at: "<<currentChar;
        cout<<currentChar;
    }//end for
}//end threadProc

int main()
{
    cout<<"Race conditions by redKlyde 
";

    int sleepVal1 = 50;
    int sleepVal2 = 30;

    //create mutex
    mutexHandle = CreateMutex(NULL, false, NULL);

    //create thread1
    HANDLE threadHandle;
    threadHandle = CreateThread(NULL, 0, (LPTHREAD_START_ROUTINE) threadProc, &sleepVal1, 0, NULL);

    //create thread2
    HANDLE threadHandle2;
    threadHandle2 = CreateThread(NULL, 0, (LPTHREAD_START_ROUTINE) threadProc, &sleepVal2, 0, NULL);

    WaitForSingleObject(threadHandle, INFINITE);
    WaitForSingleObject(threadHandle2, INFINITE);

    cout<<endl<<endl;

    CloseHandle(mutexHandle);

    system("pause");

    return 0;

}

因此,我的问题是:为什么不把mut子法 void倒。