Under the circumstances that a lock object which performs a restriction control on an exclusive use of a sharable resource is granting a second information processor a right of prior use of the sharable resource over a first information processor, a time length of exclusive use during which the sharable resource is exclusively used by the second information processor is measured when an attempt to acquire the right of prior use requested by the first information processor for the lock object fails, and least two standby operations are set, the at least two standby operations being carried out by the first information processor until the right of prior use of the sharable resource granted to the second information processor is no longer valid, and the time length of exclusive use is compared to a decision threshold value preset for evaluation of the time length of exclusive use so that one of the standby operations suitable for a comparison result is selected.