> You make local changes (on your processor, which has its local copy of memory). You then commit (write fence/atomic operation). No one else can see your changes until they update from source control and get the latest version (read fence).
That's actually not really true, what you are describing is a non-coherent system.
On a cc system, once a store is no longer speculative, it is guaranteed to be flushed out of the store buffer into the cache, and a load that reaches the cache layer is guaranteed to see the last version of the data that was stored in that memory location by any coherent agent in the system.
As pointed out elsethread, you need load barriers specifically to order your loads, so they are needed for ordering, not visibility.
The way that barriers contribute to visibility (and the reason that they need to be paired) is by giving conditionally guarantees: T: S.1; #StoreStore; S.2 T2: L2 #LoadLoad L.1. If T2 observers from its first load at memory location .2 the value stored by S.2, then it is guaranteed that L.1 will observer the value stored by S.1. So cache coherency plus purely local load and store barriers give you the global Acquire/Release model.
That's actually not really true, what you are describing is a non-coherent system.
On a cc system, once a store is no longer speculative, it is guaranteed to be flushed out of the store buffer into the cache, and a load that reaches the cache layer is guaranteed to see the last version of the data that was stored in that memory location by any coherent agent in the system.
As pointed out elsethread, you need load barriers specifically to order your loads, so they are needed for ordering, not visibility.
The way that barriers contribute to visibility (and the reason that they need to be paired) is by giving conditionally guarantees: T: S.1; #StoreStore; S.2 T2: L2 #LoadLoad L.1. If T2 observers from its first load at memory location .2 the value stored by S.2, then it is guaranteed that L.1 will observer the value stored by S.1. So cache coherency plus purely local load and store barriers give you the global Acquire/Release model.