1. A multiprocessor system comprising: a plurality of processors; a power supply device that individually supplies power to the processors; and a shared memory that stores a plurality of threads, each thread being executed by one of the plurality of processors, wherein the shared memory includes: a thread pool in which threads each having waiting events are registered in association with the numbers of the waiting events; and a thread queue in which threads having no waiting event are registered, and wherein the plurality of processors include: one or more first processors each acquiring a first thread from the thread queue and executing the first thread when power is supplied from the power supply device; a second processor that updates the number of waiting events of a second thread, which is registered in the thread pool, having completion of required procedure for the second thread by the first thread as a waiting event and registers the second thread to the thread queue when the number of the waiting events of the second thread is zero; and a third processor that individually stops or resumes supply of power from the power supply device to the first processors based on the number of threads that are registered in the thread queue and the number of threads of which the number of waiting events is a first threshold value or less.