US Patent 7950001 Method and apparatus for instrumentation in a multiprocessing environment

A method of instrumentation, preferably a computer implemented method for instrumentation, in a program which contains an original program. The original instruction is copied into a user address space which has an unused stack space. When a breakpoint is encountered the original instruction is executed out-of-line in the unused stack space by single stepping. Using this debugging in a multithreaded environment is advantageous as all threads will switch into the unused stack space and execute the breakpoint.