Embodiments of the present invention disclose an approach for inserting code into a running thread of execution. A computer sets a first set of bits to a first value, wherein the first value indicates that a first set of instructions should be inserted onto a stack. The computer executes a second set of instructions associated with a first safepoint, wherein the second set of instructions comprises one or more instructions to determine if the first set of bits is set to the first value. The computer determines that the first set of bits is set to the first value, and the computer inserts the first set of instructions onto the stack.