Dan Sugalski wrote: > For a copying collector to work, all the mutators must be blocked, > and arguably all readers should be blocked as well.
True of non-moving collectors, too. Or, let me put it this way: non- copying *GC* (the sweep or copy phase) can be threadsafe, but the mark phase is never threadsafe. The method in which marking is not threadsafe is a bit more pathological (i.e., it's not the common case as it is with the copying collector), but a standard tracing DOD cannot be correct when competeting with mutators. It WILL collect non- garbage (those are MUTATORS, remember), and the result WILL be Heizenbugs and crashes. Some of what I've written up addresses why. It's pretty simple to demonstrate a single case to prove the point, but I don't feel like re-creating the ASCII art right now. :) I'll send that section when I get out of the office. parrot will have to be able to suspend all threads in the environment. Unfortunate, but really quite unavoidable. > Oh, arguably it can't avoid deadlock at all, what with vtable methods > having access to the full environment. I can live with deadlocks, > only because there's no real alternative. But PMC implementations have to fall inside of the trusted environment, so that's not really a failure. Of course uncooperative code can break a cooperative algorithm. :) -- Gordon Henriksen IT Manager ICLUBcentral Inc. [EMAIL PROTECTED]
