25.互斥锁

• 创建互斥锁

  SRWLOCK g_lock;

  注意一个线程仅能锁定资源一次，不能多次锁定资源

• 读取期间锁定数据,数据无法被外部线程修改

  AcquireSRWLockShared(&g_lock);

• 释放互斥锁

  AcquireSRWLockShared(&g_lock);

完整代码:(一个进程读,是个进程写,读的时候不能写,写的时候不能读)

#include <stdio.h>
#include <stdlib.h>
#include <Windows.h>

int num = 6400000;
SRWLOCK g_lock;
// 注意一个线程仅能锁定资源一次，不能多次锁定资源
DWORD WINAPI read(void*p)
{
    AcquireSRWLockShared(&g_lock);//读取期间，锁定数据，数据无法被修改
    int i = 0;
    while (1)
    {
        Sleep(1000);
        printf("
第%d秒num=%d",i, num);

        if (i==20)
        {
            break;
        }
        i++;
    }
    ReleaseSRWLockShared(&g_lock);

}

//写数据
DWORD WINAPI write(void *p)
{
    AcquireSRWLockExclusive(&g_lock);//锁定写入，
    printf("
开始写入");
    for (int i = 0; i < 100000; i++)
    {
        num--;
    }
    ReleaseSRWLockExclusive(&g_lock);//
    printf("
结束写入");

}


void main()
{
    InitializeSRWLock(&g_lock);//初始化


    CreateThread(NULL, 0, read, NULL, 0, NULL);


    HANDLE hd[64];
    for (int i = 0; i < 64; i++)
    {
        hd[i] = CreateThread(NULL, 0, write, NULL, 0, NULL);
    }

    WaitForMultipleObjects(64, hd, TRUE, INFINITE);

    printf("
 last=%d", num);







    system("pause");
}