A data processing system implements a weak consistency memory model for a distributed shared memory system. The data processing system concurrently executes, on a plurality of processor cores, one or more transactional memory instructions within a memory transaction and one or more non-transactional memory instructions. The one or more non-transactional memory instructions include a non-transactional store instruction. The data processing system commits the memory transaction to the distributed shared memory system only in response to enforcement of causality of the non-transactional store instruction with respect to the memory transaction.