Add the following settings to your local.xml inside the <global>
node.
<global>
...
<cache_lock>
<enable>1</enable> <!-- If cache locking is enabled or not -->
<server>127.0.0.1</server> <!-- The Redis database IP -->
<port>6379</port> <!-- The Redis port -->
<database>0</database> <!-- The Redis Database to use -->
<password></password> <!-- The password of the Redis server -->
<timeout>2.5</timeout> <!-- The Redis timeout -->
<key>cache_lock</key> <!-- The name of lock in the Redis Database -->
<max_attempts>10</max_attempts> <!-- The maximum amount of times to retry the connection. Defaults to 10. -->
<retry_time>10000000</retry_time> <!-- The amount of microseconds to wait between checking the cache has generated. Defaults to 10000000 -->
</cache_lock>
</global>