30 Thread support library [thread]

30.4 Mutual exclusion [thread.mutex]

30.4.4 Locks [thread.lock]

30.4.4.4 Class template shared_­lock [thread.lock.shared]

30.4.4.4.4 Observers [thread.lock.shared.obs]

bool owns_lock() const noexcept;
Returns: owns.
explicit operator bool() const noexcept;
Returns: owns.
mutex_type* mutex() const noexcept;
Returns: pm.