A method and data processing system are disclosed for concurrently loading a plurality of new modules while code of a plurality of modules of an original (i.e., currently running) computer program is loaded and executed on a computer system. The method may comprise allocating a module TLS block for each thread within an initial computer program, wherein the allocated module TLS blocks are large enough to hold all module thread variables that are loaded or to be loaded. The method further may comprise providing constant offsets between module TLS block pointers corresponding to the module TLS blocks and the module thread variables for all of the threads. The disclosed method may be used to add modules to the original computer program and/or to apply a concurrent patch by replacing one or more of the plurality of original computer program modules.