can I use singleTon to create a globle lock?

For example, I create a singleTon lock class. Then I use the locker whatever I want, for example another singleTon

class SIN
{
public:
    static SIN& getSIN()
    {
        static SIN *sin = new SIN;
        return *sin;
    }

    void insertMap(const int& id,const string& str)
    {
        locker::getLocker().lock();
        subMap[id] = str;
        locker::getLocker().unlock();
        return;
    }

    string getStr(const int& id)
    {
        string str = "";
        locker::getLocker().lock();
        if(subMap.find(id) != subMap.end()){
            str = subMap[id];
        }
        locker::getLocker().unlock();
        return str;
    }
private:
    SIN(){}
    SIN(const SIN&) = delete;
    SIN& operator=(const SIN&) = delete;

private:
    map<int,string> subMap;
}

I don't find this usage in network, will there be any potential problems during using?