C++中多线程Singleton的实现

from http://blog.chinaunix.net/xmlrpc.php?r=blog/article&id=4281275&uid=26611383
/**********************************************

*******
g++ test.cpp
-lpthread****************

* *******************************************/

#include <iostream>

#include <pthread.h>

using namespace std;

template <class T>

class Singleton

{

public:

Singleton()

{

}

static T* GetInstance()

{

if(m_pInstance
==
NULL)

{

pthread_mutex_lock(&mutex);

if(m_pInstance
==
NULL)

{

T* temp
= new T;

m_pInstance = temp;

}

pthread_mutex_unlock(&mutex);

}

return m_pInstance;

}

private:

static T* m_pInstance;

static pthread_mutex_t mutex;

};

template<class T>

T* Singleton<T>::m_pInstance
= NULL;

template<class T>

pthread_mutex_t Singleton<T>::mutex;

class Test:public Singleton<Test>

{

public:

Test()

{

cout<<"Test::Test()."<<endl;

}

};

void* thread1(void*)

{

cout<<"In thread1."<<endl;

Test* test1
= Test::GetInstance();

}

void* thread2(void
*)

{

cout<<"In thread2."<<endl;

Test* test2
= Test::GetInstance();

}

int main()

{

const unsigned
int thread_num = 20;

pthread_t thread_id[thread_num];

for(unsigned
int i = 0; i<thread_num;i++)

{

pthread_create(&thread_id[i],
NULL, thread1,
NULL);

}

for(unsigned
int i = 0; i<thread_num;i++)

{

pthread_create(&thread_id[i],
NULL, thread2,
NULL);

}

sleep(1);

return 0;

}