1. A method to filter operations in a processing system that includes multiple thread units for concurrent execution of a plurality of threads, comprising: for a memory location to be accessed by a first thread unit executing a set of atomic instructions, determining the value of a hardware indicator private to the first thread unit, wherein the hardware indicator is to indicate whether the memory location has been accessed by the thread during current execution of the set of atomic instructions; performing, responsive to the hardware indicator being a value that indicates no prior access of the memory location by the thread during the current execution of the set of atomic instructions, one or more instructions to enforce atomicity of the execution of the set of instructions with respect to at least one other atomic transaction of one other of the plurality of threads, wherein the one or more instructions includes one or more instructions to modify the contents of the hardware indicator; declining, responsive to the indicator being a value that indicates prior access of the memory location by the thread during the current execution of the set of atomic instructions, to execution the one or more instructions to enforce atomicity.