The RWCriticalSection class is primarily intended for use in the Microsoft Win32 environment. In this environment, the class encapsulates the Win32 critical section mechanism, which is an efficient form of mutual exclusion based on a spin-lock. Spin-locks do not block a thread while waiting to acquire ownership of the critical section. A waiting thread spins in a polling loop until the section is released.

A critical section is more efficient than a mutex when little competition exists for a lock because the Win32 mutex acquisition requires kernel intervention even when the mutex is not currently owned by another thread.

In environments other than Win32, this class is implemented as a mutex. This allows a Win32 version of an application to realize the performance benefits of a critical section, but also allows that same code to be ported to platforms that do not have a critical section mechanism.