# spin_rw_mutex Class

## Summary

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

## Syntax

    class spin_rw_mutex;

## Header

    #include "tbb/spin_rw_mutex.h"

## 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..

## Members

See ReaderWriterMutex concept.

Parent topic: Mutexes

## See Also

ReaderWriterMutex Concept