A method and central processing unit supporting atomic access of shared data by a sequence of memory access operations. A processor status flag is reset. A processor executes, subsequent to the setting of the processor status flag, a sequence of program instructions with instructions accessing a subset of shared data contained within its local cache. During execution of the sequence of program instructions and in response to a modification by another processor of the subset of shared data, the processor status flag is set. Subsequent to the executing the sequence of program instructions and based upon the state of the processor status flag, either a first program processing or a second program processing is executed. In some examples the first program processing includes storing results data into the local cache and the second program processing includes discarding the results data.