Apparatus, system, and method for cache synchronization

A system to synchronize cache data of cascading caches within a multi-tier system, the system comprising:

• an upstream node of an upstream tier, the upstream nodes having source data and comprising a processor and a storage device;
• an intermediate node of an intermediate tier coupled to the upstream node, wherein the intermediate tier comprises a processor and a storage device and is downstream of the upstream tier, the intermediate node coupled to a first cache having the source data from the upstream node cached thereon;
• a downstream node of a downstream tier coupled to the intermediate node, wherein the downstream tier comprises a processor and a storage device and is downstream of the intermediate tier, the downstream node coupled to a second cache having data from the first cache, including the source data from the upstream node, cached thereon;
• and
• a caching apparatus coupled to the intermediate node, the caching apparatus synchronizing the cached data on the second cache with the cached data on the first cache prior to synchronizing the cached data on the first cache with the source data by performing the steps of:
• receiving a first pre-synchronization call from the upstream node to the intermediate node, the first pre-synchronization call providing advance notice to the intermediate node of an impending synchronization call;
• preventing the second cache caching data from the first cache coupled in response to the receiving of the first pre-synchronization call while the first cache remains unlocked until locked in response to the receiving of a first synchronization call-back from the upstream node;
• sending a second pre-synchronization call from the intermediate node to the downstream node in response to the receiving of the first pre-synchronization call;
• sending a second pre-synchronization acknowledgement from the downstream node to the intermediate node in response to the receiving of the second pre-synchronization call;
• receiving a second pre-synchronization acknowledgement from the downstream node;
• sending a second synchronization call-back from the intermediate node to the downstream node in response to receiving the second pre-synchronization acknowledgement by the intermediate node;
• locking the second cache in response to the receiving of the second synchronization call-back;
• synchronizing the second cache with the first cache in response to locking the second cache;
• unlocking the second cache in response to synchronizing the second cache with the first cache;
• sending a first synchronization completion from the downstream node to the intermediate node in response to synchronizing the second cache with the first cache;
• sending a first pre-synchronization acknowledgement from the intermediate node to the upstream node in response to the receiving of the first synchronization completion;
• sending the first synchronization call-back from the upstream module to the intermediate node in response to the receiving of the first pre-synchronization acknowledgement;
• locking the first cache in response to the receiving of the first synchronization call-back from the upstream node;
• synchronizing source data on the upstream node with cached data on the first cache after the first cache is locked;
• unlocking the first cache in response to synchronizing the source data;
• sending a second synchronization completion from the intermediate node to the upstream node in response to synchronizing the source data with the cached data;
• sending a post synchronization call-back from the upstream module to the intermediate node in response to the second synchronization completion;
• receiving the post synchronization call-back at the intermediate node;
• allowing caching by the second cache in response to the receiving of the post synchronization call-back;
• sending a post synchronization acknowledgment from the intermediate node to the upstream node;
• and
• allowing the first cache to cache data from the source data in response to the receiving of the post synchronization acknowledgement.

A computer readable storage medium tangibly embodying a semiconductor device storing a program of executable code executed by a processor to perform operations to synchronize cache data of cascading caches within a multi-tier system, the operations comprising:

• receiving a first pre-synchronization call from an upstream node of an upstream tier coupled to an intermediate node of an intermediate tier, the first pre-synchronization call providing advance notice to the intermediate node of an impending synchronization call;
• preventing a second cache coupled to a downstream node of a downstream tier caching data from a first cache coupled to the intermediate node in response to the receiving of the first pre-synchronization call while the first cache remains unlocked until locked in response to the receiving of a first synchronization call-back from the upstream node;
• sending a second pre-synchronization call from the intermediate node to the downstream node in response to the receiving of the first pre-synchronization call;
• sending a second pre-synchronization acknowledgement from the downstream node to the intermediate node in response to the receiving of the second pre-synchronization call;
• receiving a second pre-synchronization acknowledgement from the downstream node;
• sending a second synchronization call-back from the intermediate node to the downstream node in response to receiving the second pre-synchronization acknowledgement by the intermediate node;
• locking the second cache in response to the second synchronization call-back;
• synchronizing the second cache with the first cache in response to locking the second cache;
• unlocking the second cache in response to synchronizing the second cache with the first cache;
• sending a synchronization completion from the downstream node to the intermediate node in response to synchronizing the second cache with the first cache;
• sending a first pre-synchronization acknowledgement from the intermediate node to the upstream node in response to the receiving of the synchronization completion;
• sending the first synchronization call-back from the upstream module to the intermediate node in response to the receiving of the first pre-synchronization acknowledgement;
• locking the first cache in response to the receiving of the first synchronization call-back from the upstream node;
• synchronizing source data on the upstream node with cached data on the first cache after the first cache is locked;
• unlocking the first cache in response to synchronizing the source data;
• sending a first synchronization completion from the intermediate node to the upstream node in response to synchronizing the source data with the cached data;
• sending a post synchronization call-back from the upstream module to the intermediate node in response to the receiving of the first synchronization completion;
• receiving the post synchronization call-back at the intermediate node;
• allowing caching by the second cache in response to the receiving of the post synchronization call-back;
• sending a post synchronization acknowledgment from the intermediate node to the upstream node;
• and
• allowing the first cache to cache data from the source data in response to the receiving of the post synchronization acknowledgement.

A method for synchronizing cache data of cascading caches within a multi-tier system, the method comprising:

• receiving a first pre-synchronization call from an upstream node of an upstream tier coupled to an intermediate node of an intermediate tier, the first pre-synchronization call providing advance notice to the intermediate node of an impending synchronization call;
• preventing by use of a processor, a second cache coupled to a downstream node of a downstream tier caching data from a first cache coupled to the intermediate node in response to the first pre-synchronization call while the first cache remains unlocked until locked in response to a first synchronization call-back from the upstream node;
• sending a second pre-synchronization call from the intermediate node to the downstream node in response to the receiving of the first pre-synchronization call;
• sending a second pre-synchronization acknowledgement from the downstream node to the intermediate node in response to the receiving of the second pre-synchronization call;
• receiving a second pre-synchronization acknowledgement from the downstream node;
• sending a second synchronization call-back from the intermediate node to the downstream node in response to receiving the second pre-synchronization acknowledgement;
• locking the second cache in response to the second synchronization call-back;
• synchronizing, by use of a processor, the second cache with the first cache in response to locking the second cache;
• unlocking the second cache in response to synchronizing the second cache with the first cache;
• sending a synchronization completion from the downstream node to the intermediate node in response to synchronizing the second cache with the first cache;
• sending a first pre-synchronization acknowledgement from the intermediate node to the upstream node in response to the receiving of the synchronization completion;
• sending the first synchronization call-back from the upstream module to the intermediate node in response to the receiving of the first pre-synchronization acknowledgement;
• locking the first cache in response to the receiving of the first synchronization call-back from the upstream node;
• synchronizing, by use of a processor, source data on the upstream node with cached data on the first cache after the first cache is locked;
• unlocking the first cache in response to synchronizing the source data;
• sending a synchronization completion from the intermediate node to the upstream node in response to synchronizing the source data with the cached data;
• sending a post synchronization call-back from the upstream module to the intermediate node in response to the receiving of the synchronization completion;
• receiving the post synchronization call-back at the intermediate node;
• allowing caching by the second cache in response to the receiving of the post synchronization call-back;
• sending a post synchronization acknowledgment from the intermediate node to the upstream node;
• and
• allowing the first cache to cache data from the source data in response to the receiving of the post synchronization acknowledgement.