1. A computer program making a computer execute: determining, when a task other than an operating system task operated cooperatively with a process executed under a control of an operating system requests a cooperative operation to the operating system task and is set in a wait state, whether a priority of the task is higher than a priority of other task set in a wait state by requesting a cooperative operation to the operating system task; and making, when the priority of the task is determined to be higher than the priority of the other task, the operating system task and a process under control of the operating system operated cooperatively with the task succeed the priority of the task.