Re: [PATCH v3] sched/fair: Add advisory flag for borrowing a timeslice (was: Pre-emption control for userspace)

- Request to borrow timeslice is not guranteed to be honored.
- If the task is allowed to borrow, kernel will inform the task
  of this. When this happens, task must yield the processor as soon
  as it completes its critical section.
- If the task fails to yield processor after being allowed to
  borrow, it is penalized by forcing it to skip its next time slot
  by the scheduler.
- Task is charged additional time for the borrowed timeslice as
  accumulated run time. This pushes it further down in consideration
  for the next task to run.