015 原子操作 旋转锁
以下代码个别情况下会出错 导致值为1
#define UNICODE #include <stdio.h> #include <tchar.h> #include <windows.h> #include <process.h> long gNum = 0; unsigned int __stdcall ThreadRun1(void* lParam) { //锁 //原子操作 //同一资源在同一时间只有一个线程能够访问 //系统级的操作 //在硬件里面设置了一些局限性 InterlockedExchangeAdd(&gNum,1); // gNum += 1; return 0; } unsigned int __stdcall ThreadRun2(void* lParam) { InterlockedExchangeAdd(&gNum,1); //gNum += 1; return 0; } int main() { HANDLE hThread[2]; hThread[0] = (HANDLE)_beginthreadex(nullptr,0,ThreadRun1,nullptr,0,nullptr); hThread[1] = (HANDLE)_beginthreadex(nullptr,0,ThreadRun2,hThread[0],0,nullptr); WaitForMultipleObjects(sizeof(hThread)/sizeof(HANDLE), hThread,TRUE, INFINITE); printf("gNum:%d",gNum); for(int i = 0; i<sizeof(hThread)/sizeof(HANDLE);++i) { CloseHandle(hThread[i]); } return 0; }
#define UNICODE #include <stdio.h> #include <tchar.h> #include <windows.h> #include <process.h> long gNum = 0; unsigned int __stdcall ThreadRun1(void* lParam) { //锁 //原子操作 //同一资源在同一时间只有一个线程能够访问 //系统级的操作 //在硬件里面设置了一些局限性 gNum += 1; return 0; } unsigned int __stdcall ThreadRun2(void* lParam) {gNum += 1; return 0; } int main() { HANDLE hThread[2]; hThread[0] = (HANDLE)_beginthreadex(nullptr,0,ThreadRun1,nullptr,0,nullptr); hThread[1] = (HANDLE)_beginthreadex(nullptr,0,ThreadRun2,hThread[0],0,nullptr); WaitForMultipleObjects(sizeof(hThread)/sizeof(HANDLE), hThread,TRUE, INFINITE); printf("gNum:%d",gNum); for(int i = 0; i<sizeof(hThread)/sizeof(HANDLE);++i) { CloseHandle(hThread[i]); } return 0; }
出错的原因
下面是加硬件锁代码
1 #define UNICODE 2 #include <stdio.h> 3 #include <tchar.h> 4 #include <windows.h> 5 #include <process.h> 6 7 long gNum = 0; 8 unsigned int __stdcall ThreadRun1(void* lParam) 9 { 10 //锁 11 //原子操作 12 //同一资源在同一时间只有一个线程能够访问 13 //系统级的操作 14 //在硬件里面设置了一些局限性 15 InterlockedExchangeAdd(&gNum,1); 16 // gNum += 1; 17 return 0; 18 } 19 20 unsigned int __stdcall ThreadRun2(void* lParam) 21 { 22 InterlockedExchangeAdd(&gNum,1); 23 //gNum += 1; 24 return 0; 25 } 26 int main() 27 { 28 HANDLE hThread[2]; 29 hThread[0] = (HANDLE)_beginthreadex(nullptr,0,ThreadRun1,nullptr,0,nullptr); 30 hThread[1] = (HANDLE)_beginthreadex(nullptr,0,ThreadRun2,hThread[0],0,nullptr); 31 WaitForMultipleObjects(sizeof(hThread)/sizeof(HANDLE), hThread,TRUE, INFINITE); 32 printf("gNum:%d",gNum); 33 for(int i = 0; i<sizeof(hThread)/sizeof(HANDLE);++i) 34 { 35 CloseHandle(hThread[i]); 36 } 37 return 0; 38 }
1 #define UNICODE 2 #include <stdio.h> 3 #include <tchar.h> 4 #include <windows.h> 5 #include <process.h> 6 7 long gNum = 0; 8 BOOL bUseing = FALSE; 9 10 //线程的饥饿 11 //线程优先级 12 //CPU 13 //调度区 14 // 1 31 15 // 2 31 16 // 3 30 饥饿 可能永远得不到执行 17 unsigned int __stdcall ThreadRun1(void* lParam) 18 { 19 //锁 20 //原子操作 21 //同一资源在同一时间只有一个线程能够访问 22 //系统级的操作 23 //在硬件里面设置了一些局限性 24 while(InterlockedExchange((long*)&bUseing, TRUE) != TRUE) //旋转锁 25 Sleep(0); 26 27 //..... 上锁后的代码 线程安全 绝对安全的 28 InterlockedExchange((long*)&bUseing, FALSE); 29 // gNum += 1; 30 return 0; 31 } 32 33 unsigned int __stdcall ThreadRun2(void* lParam) 34 { 35 //InterlockedExchangeAdd(&gNum,1); 36 //gNum += 1; 37 while(InterlockedExchange((long*)&bUseing, TRUE) != TRUE) 38 Sleep(0); 39 40 //..... 上锁后的代码 线程安全 41 42 InterlockedExchange((long*)&bUseing, FALSE); 43 return 0; 44 } 45 int main() 46 { 47 HANDLE hThread[2]; 48 hThread[0] = (HANDLE)_beginthreadex(nullptr,0,ThreadRun1,nullptr,0,nullptr); 49 hThread[1] = (HANDLE)_beginthreadex(nullptr,0,ThreadRun2,hThread[0],0,nullptr); 50 WaitForMultipleObjects(sizeof(hThread)/sizeof(HANDLE), hThread,TRUE, INFINITE); 51 printf("gNum:%d",gNum); 52 for(int i = 0; i<sizeof(hThread)/sizeof(HANDLE);++i) 53 { 54 CloseHandle(hThread[i]); 55 } 56 return 0; 57 }
