===How MESI protocol works:===

To ensure data consistency across multiple caches, multiprocessor-capable Intel® processors follow the MESI protocol.

The cache line would be signed ‘Exclusive’ as its first load. As the processor find the cache line is loaded by other processors. The access of cache line is changed to ‘Share’. If the processor stored a cache line marked as ‘Share’, the cache line is marked as ‘Modified’ and all other processors are sent an ‘Invalid’ cache line message. If the processor sees the same cache line which is now marked ‘Modified’ being accessed by another processor, the processor stores the cache line back to memory and marks its cache line as ‘Shared’.