In version 2 of the interface under the schedule system call, it says that the call can be used be schedulers. However, in the next sentence it goes on to say that the calling thread must reside in the same address space as the scheduler. Also, it goes on to say that an error code will be set if the calling thread is not the scheduler. So is the "schedule" system call made by the scheduler or by a thread that simply resides in the same address space as the scheduler?