Cooperative Task Management Without Manual Stack Management

Cooperative task management can provide program architects with ease of reasoning about concurrency issues. This property is often espoused by those who recommend ``event-driven'' programming over ``multithreaded'' programming. Those terms conflate several issues. In this paper, we clarify the issues, and show how one can get the best of both worlds: reason more simply about concurrency in the way ``event-driven'' advocates recommend, while preserving the readability and maintainability of code associated with ``multithreaded'' programming.

We identify the source of confusion about the two programming styles as a conflation of two concepts: task management and stack management. Those two concerns define a two-axis space in which ``multithreaded'' and ``event-driven'' programming are diagonally opposite; there is a third ``sweet spot'' in the space that combines the advantages of both programming styles. We point out pitfalls in both alternative forms of stack management, manual and automatic, and we supply techniques that mitigate the danger in the automatic case. Finally, we exhibit adaptors that enable automatic stack management code and manual stack management code to interoperate in the same code base.