[MacRuby-devel] Thread safety in apply example?

[Jordan K. Hubbard]

On Jan 24, 2011, at 8:00 AM, Alan Skipp wrote:

> The post was admittedly vague, but was more of an idea about a general purpose thread safe array class (in principle, this could apply to any mutable class). Perhaps implemented as a module that would redirect all method calls through a serial dispatch queue. This would mean that the array (or other mutable collection) could be mutated from multiple threads/queues without fear of bad things happening.

FWIW, we've tried this same approach experimentally (use a per-object serial queue behind the scenes to implement an async setter / sync getter model) over in CoreFoundation land, and it seemed to work reasonably well for the most part.  We ran into some compatibility issues with a few of the methods which just didn't lend themselves to a thread-safe object model, enough that we couldn't simply do this as a completely transparent solution, but it mostly Just Worked and I think MacRuby (or, for that matter, JRuby) could do something very similar and probably get away with it since Ruby arrays/hashes/strings aren't quite so inclined to hand pointers to their internal state around to clients of the API.   Laurent doesn't exactly agree with me since he's still focused on performance, but I think it should definitely be possible to declare a Ruby object as "contended" in some way such that everything then goes through a serial queue implicitly to access it - I'm not saying this should be true for every object, just the ones for which you need thread safety.

- Jordan