The mutex class is a synchronization primitive that can be used to protect shared data from being simultaneously accessed by multiple threads. Added since C++ 11. mutex offers exclusive, non-recursive ownership semantics:

A calling thread owns a mutex from the time that it successfully calls either lock or try_lock until it calls unlock.
When a thread owns a mutex, all other threads will block (for calls to lock) or receive a false return value (for try_lock) if they attempt to claim ownership of the mutex.
A calling thread must not own the mutex prior to calling lock or try_lock. 

The behavior of a program is undefined if a mutex is destroyed while still owned by any threads, or a thread terminates while owning a mutex. The mutex class satisfies all requirements of Mutex and StandardLayoutType.

std::mutex is neither copyable nor movable.

Member types Member type Definition native_handle_type(optional) implementation-defined Member functions (constructor) constructs the mutex (public member function) (destructor) destroys the mutex (public member function) operator= [deleted] not copy-assignable (public member function) Locking lock locks the mutex, blocks if the mutex is not available (public member function) try_lock tries to lock the mutex, returns if the mutex is not available (public member function) unlock unlocks the mutex (public member function) Native handle native_handle returns the underlying implementation-defined native handle object (public member function) Notes

std::mutex is usually not accessed directly: std::unique_lock, std::lock_guard, or std::scoped_lock (since C++17) manage locking in a more exception-safe manner.