# spin_rw_mutex Class¶

## Summary¶

Class that models ReaderWriterMutex Concept that is unfair and not scalable.

## Syntax¶

class spin_rw_mutex;


## Description¶

A spin_rw_mutex models the ReaderWriterMutex Concept. A spin_rw_mutex is not scalable, fair, or recursive. It is ideal when the lock is lightly contended and is held for only a few machine instructions. If a thread has to wait to acquire a spin_rw_mutex, it busy waits, which can degrade system performance if the wait is long. However, if the wait is typically short, a spin_rw_mutex significantly improves performance compared to other mutexes..