Hi,
I really think the spin model is good. And in fact, I really think current sleep/wakeup/postnote code is good. However, this model makes the assumption that plan9 processes are really Machs and not coroutines. I think we need a larger model, which includes the scheduler. I mean a model that describes a set of processes (in spin meaning), picking one kind of coroutine objects from a run queue (shared by all spin processes) and then calling sleep/wakeup/postnote a few times before putting the coroutine object back to the run queue. These spin processes would represent the cpus (or Machs) while coroutine objects would represent the plan9 processes. I even think we don't have to simulate the fact these processes can be interrupted. Again, the change I proposed is not about sleep/wakeup/postnote, but because wakeup() is ready()'ing the awakened process while the mach on which sleep() runs is still holdind a pointer (up) to the awakened process and can later (in schedinit()) assumes it is safe to access (up)->state. Because of this, schedinit() can tries to call ready() on (up), because because (up)->state may have been changed to Running by a third mach entity. This change only updates schedinit() (and tries) to make (up)->state access safe when it happens after a sleep() is awakened. Phil;
in any event, given the long history with sleep/wakeup, changes should be justified with a promula model. the current model omits the spl* and the second lock. (http://swtch.com/spin/sleep_wakeup.txt). - erik
