Disclosed is an information processing apparatus that has an update procedure semaphore, and a generation management information as management information of a shared data area that requires exclusion control. The generation management information specifies one item of generation information of the shared data area. As generation information provided for every generation, the apparatus has a reference-count measuring counter, a semaphore for updating generation information, a pointer for pointing to old generation information, and a pointer for pointing to the substance of the shared data area. In a case where the latest shared data is updated, a duplicate of the latest shared data area is created, new generation information corresponding to the duplicated shared data area is generated, data in the duplicated shared data area is updated and generation information, which corresponds to the shared data area after the updating thereof, is registered as the latest generation information.