这样的单件模式是线程安全的吗?该怎么解决

#include<windows.h>
#include <iostream>
using namespace std;


CRITICAL_SECTION g_cs;

template<typename T>
class Singleton
{
    
public: 

    static T& Instance()
    {
         static T& sg = MakeInstance();
         return sg;
    }

protected:

    static T& MakeInstance()
    {
        EnterCriticalSection(&g_cs);
        static T& sg = T();    
        LeaveCriticalSection(&g_cs);
        return sg; 
    }

    Singleton()    {}

    Singleton(const Singleton&){}

    ~Singleton(){}

};

class SingleA: public Singleton<SingleA>        //一个具体的单件类.
{
    friend Singleton;
    
    SingleA()
    {
        cout<<"Hello SingleA"<<endl;
    }
};

int main()
{
    
    InitializeCriticalSection(&g_cs);

    SingleA& s1=SingleA::Instance();
    SingleA& s2=SingleA::Instance();
    
    DeleteCriticalSection(&g_cs);

}