User-level scheduling in L4

Two ways to control scheduling:

Can use controller thread (with high MCP):
- uses thread_schedule to manipulate other threads,
- controlled threads run with zero MCP.
Can use user-level scheduler thread running at highest priority:
- L4 will always schedule this scheduler thread,
- Scheduler thread uses thread_switch() to give a time slice to some thread.
Preempters (unimplemented) would be used to inform scheduler of premptions.

Obvioulsy combinations of these are possible.

Gernot Heiser 2002-08-07