synchronize threads

[weixj2003ld]

I create two threads,and they share class A;

class A
{
    public:
       void method_1()
      {
           QMutexLocker locker(&mutex);
             ......
              method_2();
             ......
      }
      void method_2()
     {
             QMutexLocker locker(&mutex);//Does this code need?
                ........           
     }
    public:
           mutable QMutex mutex;
 
}

class A
{
    public:
       void method_1()
      {
           QMutexLocker locker(&mutex);
             ......
              method_2();
             ......
      }
      void method_2()
     {
             QMutexLocker locker(&mutex);//Does this code need?
                ........           
     }
    public:
           mutable QMutex mutex;
      
}

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I do not know the second locker is need or not,please please tell me.