线程

线程管理

线程创建

#include 
#include 


DWORD WINAPI ThreadProc(LPVOID lpParam)
{
    int i=0;
    
    while(i<20)
    {
        printf("I am form a thread,count= %d \n",i++);
    }
    return 0;
}


int main(int argc,char* argv[])
{
    HANDLE hThread;  
    DWORD dwThreadId;


    hThread = ::CreateThread(NULL,NULL,ThreadProc,NULL,0,&dwThreadId);
    printf("Id = %d \n",dwThreadId);

    ::WaitForSingleObject(hThread,INFINITE);        //等待线程结束
    ::CloseHandle(hThread);                     //关闭句柄

    return 0;
}

优先级管理

线程之间存在优先级问题,如下解决

#include 
#include 

DWORD WINAPI ThreadIdle(LPVOID lpParam)
{
    int i=0;
    while(i++<10)
        printf("Idle Thread runing \n");

    return 0;
}

DWORD WINAPI ThreadNormal(LPVOID lpParam)
{
    int i=0;
    while(i++ < 10)
        printf("Normal Thread runing \n");

    return 0;
}

int main(int argc,char* argv[])
{
    DWORD dwThreadId;
    HANDLE h[2];

    h[0]=::CreateThread(NULL,0,ThreadIdle,NULL,CREATE_SUSPENDED,&dwThreadId);   //暂停态线程
    ::SetThreadPriority(h[0],THREAD_PRIORITY_IDLE);         //优先级(空闲)
    ::ResumeThread(h[0]);

    h[1]=::CreateThread(NULL,0,ThreadNormal,NULL,0,&dwThreadId);    //默认的Normal

    ::WaitForMultipleObjects(2,h,TRUE,INFINITE);        //等待多线程结束


    ::CloseHandle(h[0]);
    ::CloseHandle(h[1]);

    return 0;
}

线程同步

多个线程同时访问一段数据,会产生奇怪的问题,由此引入临界区
可把注释部分删除观察现象

#include 
#include 
#include 

int g_nCount1=0;
int g_nCount2=0;

BOOL g_bContinue=TRUE;
CRITICAL_SECTION g_cs;

UINT _stdcall ThreadFunc(LPVOID);

int main(int argc,char* argv[])
{
    UINT uId;
    HANDLE h[2];

    ::InitializeCriticalSection(&g_cs); //临界区声明

    h[0]=(HANDLE)::_beginthreadex(NULL,0,ThreadFunc,NULL,0,&uId);
    h[1]=(HANDLE)::_beginthreadex(NULL,0,ThreadFunc,NULL,0,&uId);
    
    Sleep(1000);
    g_bContinue=FALSE;

    ::WaitForMultipleObjects(2,h,TRUE,INFINITE);



    ::CloseHandle(h[1]);
    ::CloseHandle(h[2]);
    ::DeleteCriticalSection(&g_cs);     删除临界区

    printf("gCount1= %d\n",g_nCount1);
    printf("gCount2= %d\n",g_nCount2);

    return 0;
}

UINT _stdcall ThreadFunc(LPVOID)
{
    while(g_bContinue)
    {
        ::EnterCriticalSection(&g_cs);      //进入临界区
        g_nCount1++;
        g_nCount2++;
        ::LeaveCriticalSection(&g_cs);      //离开临界区
    }

    return 0;
}