Thanks for the explanation, Peter, and for accompanying me on this journey into the unknown. Your description of enqueue is what chouser explained to me too.
Someday I have to write some code with a queue named eat so that eat will pop itself. Cheers, Michael On May 26, 5:54 pm, Peter Schuller <peter.schul...@infidyne.com> wrote: > > Where is Action's execute method called in the event the queue is not > > empty? > > If the agent's queue was non-empty from the perspective of enqueue(), > that means one of the following is true: > > (1) A previous enqueue() has already scheduled the execution of an > action, but it has not yet begun running. > (2) doRun() is running but has not yet completed its CAS loop at the end. > > In either case, once doRun() runs and reaches its CAS loop, it will > detect that the queue is non-empty and schedule the next action. This > is the: > > if(error == null && next.q.count() > 0) > ((Action) next.q.peek()).execute(); > } > > which appears towards the end of doRun(). Next is the atomically > obtained (through CAS looping) queue, after it popped itself. > > Another way to look at it might be that the queue can be in two > relevant states at any point in time: > > * empty > * non-empty > > In the non-empty state, doRun() is continuously responsible for > re-scheduling itself. In the empty state, enqueue() is responsible for > scheduling it. Because of the use of CAS loops, the transition from > "empty" to "non-empty" can be atomically detected by enqueue(), > allowing it to determine whether or not it was responsible for such a > state transition, in which case it schedules the action for execution. > > -- > / Peter Schuller -- You received this message because you are subscribed to the Google Groups "Clojure" group. To post to this group, send email to clojure@googlegroups.com Note that posts from new members are moderated - please be patient with your first post. To unsubscribe from this group, send email to clojure+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/clojure?hl=en
