考虑线程安全且效率高的单例C++代码

本文即考虑了线程安全，又保证了效率，代码为单例，语言为C++，代码如下：

#include <iostream>

using namespace std;

void Lock()
{
    //some mutex code
}

void UnLock()
{
    //some mutex code
}

class Singleton{
public:
    static Singleton* GetInstance()
    {
        if (m_Instance == NULL)                // 如果已经创建了单例，那么就不用每次进去加锁了
        {
            Lock();
            if (m_Instance == NULL)
            {
                m_Instance = new Singleton();
            }
            UnLock();
        }
        return m_Instance;
    }

    static void DeleteInstance()
    {
        if (m_Instance)
        {
            Lock();
            if (m_Instance)
            {
                delete m_Instance;
                m_Instance = NULL;
            }
            UnLock();
        }
    }

    void TestPrint()
    {
        cout<<"lala"<<endl;
    }
private:
    static Singleton* m_Instance;

    Singleton(){}
    ~Singleton(){}
};

Singleton* Singleton::m_Instance = NULL;

int main()
{
    Singleton::GetInstance()->TestPrint();
    return 1;
}