std::shared_lock::shared_lock (3) Linux Manual Page

std::shared_lock<Mutex>::~shared_lock – std::shared_lock<Mutex>::~shared_lock

Synopsis

~shared_lock(); (since C++14)
Destroys the lock.
If *this has an associated mutex ((mutex() returns a non-null pointer) and has acquired ownership of it (owns() returns true), the mutex is unlocked by calling unlock_shared().