_Mutex_base
template<_Lock_policy _Lp>
class _Mutex_base
{
protected:
enum { _S_need_barriers = 0 };
};
template<>
class _Mutex_base<_S_mutex : public __gnu_cxx::__mutex
{
protected:
enum { _S_need_barriers = 1 };
};template<_Lock_policy _Lp>
class _
