Debugging Mutex and Locks

When there are multiple Mutex's in the program, it may be required to find if a particular thread is locked far longer than necessary. This can cause problems and the output may not be what is expected.

To get round this, I took an old example from here and modified it to help me print some debugging info.

I modified the printSomething() in Singleton.h to add a sleep as follows:

  void printSomething(char *name, int count)
 {
   Lock guard(mutex_);
   Sleep(10);
   Lock guard2(mutex_);
   std::cout << name << " loop " << count << std::endl;
 }

and I modified the Mutex.h as follows:

//Example from http://www.relisoft.com/Win32/active.html
#if !defined _MUTEX_H_
#define _MUTEX_H_

class Mutex
{
   friend class Lock;
public:
   Mutex () { InitializeCriticalSection (& _critSection); }
   ~Mutex () { DeleteCriticalSection (& _critSection); }
private:
   void Acquire ()
   {
     DWORD start = GetTickCount();
     EnterCriticalSection (& _critSection);
     DWORD elapsed = GetTickCount() - start;
     if (elapsed > 15)
     {
       //Debugging Info
        std::cout<<"Debugging Info: Waited at mutex for "<<elapsed<<std::endl;
     }
   }
   void Release ()
   {
       LeaveCriticalSection (& _critSection);
   }

   CRITICAL_SECTION _critSection;
};

#endif 

The output is as follows:

The small problem with the above approach is that if a Thread is deadlocked, we may not get the debug output as we would have to kill the process.