MFC（学习笔记） - 多线程同步

一、win32线程创建与互斥

创建线程

HANDLE WINAPI CreateThread(
  _In_opt_  LPSECURITY_ATTRIBUTES  lpThreadAttributes,
  _In_      SIZE_T                 dwStackSize,
  _In_      LPTHREAD_START_ROUTINE lpStartAddress,
  _In_opt_  LPVOID                 lpParameter,
  _In_      DWORD                  dwCreationFlags,
  _Out_opt_ LPDWORD                lpThreadId
);

参数介绍：

1、线程安全属性，一般为NULL

2、线程栈大小：一般为0，取默认大小

3、线程的函数名：顾名思义，如果为类内的函数，则设为static即可

4、线程的参数：可以传递一个结构体指针，没有则为NULL

5、创建的标记：一般设为0

6、线程的ID：如非必须，设为NULL

互斥锁

HANDLE WINAPI CreateMutex(
  _In_opt_ LPSECURITY_ATTRIBUTES lpMutexAttributes,
  _In_     BOOL                  bInitialOwner,
  _In_opt_ LPCTSTR               lpName
);

参数介绍：

1、互斥锁安全属性：一般为NULL

2、互斥锁默认是否有信号：一般为FALSE，表示无人拥有此信号，TRUE表示信号已被人拥有，不可再获取

3、互斥锁名称：一般为NULL，由于此锁为内核对象，进程间互斥的话，需要命名

注：互斥锁，谁拥有，谁释放；多次拥有，需要多次释放；谁创建时，参数为TRUE，谁拥有；

卖票例子：

int ticket = 10;
HANDLE hMutex;

DWORD WINAPI Thread1(LPVOID param) {
	while (TRUE)
	{
		WaitForSingleObject(hMutex, INFINITE);
		Sleep(500);
		if (ticket > 0)
			cout << "线程1：" << ticket-- << endl;
		else
			break;
		ReleaseMutex(hMutex);
		
	}
	return TRUE;
}
DWORD WINAPI Thread2(LPVOID param) {
	while (TRUE)
	{
		WaitForSingleObject(hMutex, INFINITE);
		Sleep(500);
		if (ticket > 0)
			cout << "线程2：" << ticket-- << endl;
		else
			break;
		ReleaseMutex(hMutex);
	}
	return TRUE;
}
int main()
{
	HANDLE hTread1 = CreateThread(NULL, 0, Thread1, NULL,0, NULL);
	HANDLE hTread2 = CreateThread(NULL, 0, Thread2, NULL,0, NULL);
	CloseHandle(hTread1);
	CloseHandle(hTread2);
	hMutex = CreateMutex(NULL, FALSE, NULL);
	getchar();
	return 0;
}

注：MFC中封装了CMutex类

#include "afxmt.h"
CMutex mt;
mt.Lock();
mt.Unlock();

二、内核对象——事件

HANDLE WINAPI CreateEvent(
  _In_opt_ LPSECURITY_ATTRIBUTES lpEventAttributes,
  _In_     BOOL                  bManualReset,
  _In_     BOOL                  bInitialState,
  _In_opt_ LPCTSTR               lpName
);

参数介绍：

1、事件安全属性：一般为NULL，即默认

2、是否人工重置：TRUE代表由人工重置为初始信号，FALSE代表自动重置为初始信号

3、事件的初始信号：TRUE表示有信号，FALSE表示无信号

4、事件的名称：与上面的mutex一样

同样的卖票例子：

// ThreadTest.cpp : 定义控制台应用程序的入口点。
//

#include "stdafx.h"

int ticket = 10;
HANDLE hEvent;

DWORD WINAPI Thread1(LPVOID param) {
	while (TRUE)
	{
		WaitForSingleObject(hEvent, INFINITE);
		Sleep(500);
		if (ticket > 0)
			cout << "线程1：" << ticket-- << endl;
		else
			break;
		SetEvent(hEvent);

	}
	return TRUE;
}
DWORD WINAPI Thread2(LPVOID param) {
	while (TRUE)
	{
		WaitForSingleObject(hEvent, INFINITE);
		Sleep(500);
		if (ticket > 0)
			cout << "线程2：" << ticket-- << endl;
		else
			break;
		SetEvent(hEvent);
	}
	return TRUE;
}
int main()
{
	HANDLE hTread1 = CreateThread(NULL, 0, Thread1, NULL, 0, NULL);
	HANDLE hTread2 = CreateThread(NULL, 0, Thread2, NULL, 0, NULL);
	CloseHandle(hTread1);
	CloseHandle(hTread2);
	hEvent = CreateEvent(NULL,FALSE, FALSE, NULL);
	SetEvent(hEvent);
	getchar();
	return 0;
}

三、临界区

一共四个函数

void WINAPI InitializeCriticalSection(
  _Out_ LPCRITICAL_SECTION lpCriticalSection
);

void WINAPI EnterCriticalSection(
  _Inout_ LPCRITICAL_SECTION lpCriticalSection
);

void WINAPI LeaveCriticalSection(
  _Inout_ LPCRITICAL_SECTION lpCriticalSection
);

void WINAPI DeleteCriticalSection(
  _Inout_ LPCRITICAL_SECTION lpCriticalSection
);

卖票的例子：

// ThreadTest.cpp : 定义控制台应用程序的入口点。
//

#include "stdafx.h"

int ticket = 10;
CRITICAL_SECTION g_cs;

DWORD WINAPI Thread1(LPVOID param) {
	while (TRUE)
	{
		EnterCriticalSection(&g_cs);
		if (ticket > 0)
			cout << "线程1：" << ticket-- << endl;
		else
			break;
		LeaveCriticalSection(&g_cs);
		Sleep(500);
	}
	return TRUE;
}
DWORD WINAPI Thread2(LPVOID param) {
	while (TRUE)
	{
		EnterCriticalSection(&g_cs);
		if (ticket > 0)
			cout << "线程2：" << ticket-- << endl;
		else
			break;
		LeaveCriticalSection(&g_cs);
		Sleep(500);
	}
	return TRUE;
}
int main()
{
	HANDLE hTread1 = CreateThread(NULL, 0, Thread1, NULL, 0, NULL);
	HANDLE hTread2 = CreateThread(NULL, 0, Thread2, NULL, 0, NULL);
	CloseHandle(hTread1);
	CloseHandle(hTread2);
	InitializeCriticalSection(&g_cs);
	getchar();
	DeleteCriticalSection(&g_cs);
	return 0;
}

注：c++封装好的临界区类critical_section，简单好用如下：

#include "concrt.h"
using namespace concurrency;
critical_section g_cs;
g_cs.lock();
g_cs.unlock();