1. A computer program product for a processor to support multiple execution of threads in parallel, the computer program product comprising: one or more computer-readable storage media and program instructions stored on the one or more computer-readable storage media, the program instructions comprising: program instructions to determine that processing of a first thread of a plurality of threads is suspended due to limited availability of a first processing resource, wherein the processor supports execution of the plurality of threads in parallel; program instructions to obtain a first lock on a second processing resource that is substitutable substitute for the first processing resource during processing of the first thread, wherein the second processing resource is included as part of a component that is external to the processor, wherein the component supports a number of threads that is less than the plurality of threads, and wherein the processing of the first thread is suspended until the first lock is available; program instructions to process the first thread using the second processing resource, wherein the processor includes a shared register to support mapping of a portion of the plurality of threads to the component, and wherein that portion of the plurality of threads is equal to, at most, the number of threads that are supported by component; program instructions to determine whether the first thread has been processed; and program instructions to respond to a determination that the first thread has been processed, by releasing the first lock on the second processing resource.