Luke Gorrie <luke@bluetail.com> writes:
Peter Siebel suggests using monitors. Now that I think about it, I have already defined (SUSPEND-THIS-THREAD) and (RESUME THREAD) primitives, which would be enough to build monitors with. Maybe that is the way to go.
I asked some guys at work how to do this. It turns out that mutexes are enough, and it can be done without those SUSPEND/RESUME primitives or monitors. "Bread and butter POSIX threads stuff." The algorithm is this: We define a global lock L, and a global variable WHO that is bound to the thread currently allowed to talk to Emacs. Every thread that wants to talk to Emacs loops: Acquire lock L: If I am WHO, do my processing. Release L The Swank thread's "processing" is to read and evaluate a command from Emacs, and then loop. That command may have the side-effect of reassigning WHO to another thread. The "processing" of all other threads is to conduct a conversation with Emacs and then reassign WHO back to the Swank thread. When a thread wants to be debugged, it goes until a loop waiting until it becomes WHO. When Emacs chooses to debug such a thread, it tells the Swank thread to assign WHO accordingly. When that thread finishes debugging, it reassigns WHO to the Swank thread. I'll implement this tomorrow unless a better way comes along. Cheers, Luke