1. A computer program product comprising at least one computer-usable storage medium having computer-usable program code for making a desirable modification to a site in a code region forming part of a computer program during execution of the computer program by a plurality of threads, the computer program product comprising: computer-usable program code for providing identical modification instructions to each thread for modifying the site in the code region, wherein the modification instructions direct each thread to make the desirable modification, without use of a self-loop, using an idempotent atomic instruction, wherein the idempotent atomic instruction is generated to ensure that the desirable modification does not cross a patching boundary by NOP insertion.