171 ;;Quote: an upcall calls a higher level function across protection boundaries; an alternative to asynchronous signals

171+;;Quote: upcalls usually call a higher level function through a procedure variable

171 ;;Quote: organize a layer as tasks made of subroutines; all interfaces are subroutine calls instead of intertask communication

174 ;;Quote: rewriting a downcall protocol as upcalls improved performance and code size by 5-10x

174 ;;Quote: an upcall may asks questions about its service; e.g., ask for further data to append to an outgoing packet

175 ;;Quote: if organize modules as multi-tasks, can delay task division until later; otherwise the initial architecture determines the tasks

177 ;;Quote: with upcalls, need to separate client data from the level's data; the later must be consistent and unlocked before an upcall occurs

177 ;;Quote: if an upcall fails, need to recover the calling task; the simple solution is to fail; i.e., tasks are expendable

177 ;;Quote: with upcalls, need to either disallow recursive downcalls, restrict downcalls to simple actions/queuing, or restrict downcalls to setting flags

178 ;;Quote: define task priority as its deadline in microseconds; better than priority levels since easily understood

179 ;;Quote: deadline promotion -- a task with a short deadline can promote a task with a long deadline if it holds a locked monitor