In the case of a cache miss, both the switched snooping protocol described earlier and the directory protocol in this case study perform the read or write operation as soon as possible. In particular, they do the operation as part of the transition to the stable state, rather than transitioning to the stable state and simply retrying the operation. This is not an optimization. Rather, to ensure forward progress, protocol implementations must ensure that they perform at least one CPU operation before relinquishing a block.
Suppose the coherence protocol implementation didn't do this. Explain how this might lead to live lock. Give a simple code example that could stimulate this behavior.