std::shared_timed_mutex::lock (3) - Linux Manuals
void lock(); (since C++14)
Locks the mutex. If another thread has already locked the mutex, a call to lock will block execution until the lock is acquired.
If lock is called by a thread that already owns the mutex in any mode (shared or exclusive), the behavior is undefined.
Prior unlock() operations on the same mutex synchronize-with (as defined in std::memory_order) this operation.
Throws std::system_error when errors occur, including errors from the underlying operating system that would prevent lock from meeting its specifications. The mutex is not locked in the case of any exception being thrown.
lock() is usually not called directly: std::unique_lock and std::lock_guard are used to manage exclusive locking.
Shared mutexes do not support direct transition from shared to unique ownership mode: the shared lock has to be relinquished with unlock_shared() before exclusive ownership may be obtained with lock(). boost::upgrade_mutex may be used for this purpose.
This example shows how lock and unlock can be used to protect shared data.
// Run this code
try_lock (public member function)
unlock (public member function)