std::shared_lock::owns_lock (3) Linux Manual Page
std::shared_lock<Mutex>::owns_lock – std::shared_lock<Mutex>::owns_lock Synopsis bool owns_lock() const noexcept; (since C++14) Checks whether *this owns a locked mutex or not. Parameters (none) Return value true if *this has an associated mutex and has acquired shared ownership of it, false otherwise. See also tests whether the lock owns its associated mutex operator_bool (public member function)
