30 Thread support library [thread]

30.4 Mutual exclusion [thread.mutex]

30.4.2 Locks [thread.lock]

30.4.2.3 Class template shared_lock [thread.lock.shared]

30.4.2.3.4 shared_lock 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.