[MacRuby-devel] Thread safety in apply example?

[Charles Oliver Nutter]

On Mon, Jan 24, 2011 at 11:39 AM, Jordan K. Hubbard <jkh at apple.com> wrote:
> 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 sh
>  ould be true for every object, just the ones for which you need thread safety.

I'd be extremely surprised if the overhead frrom making an object
thread safe with a queue wasn't much higher than simply synchronizing
all access with normal low-level locking primitives. It might be
useful to transparently proxy all calls targeting a specific object
through a queue-based delegator (as I believe you or someone has
rigged up in the Dispatch gem), but I'd be very surprised if it were a
good generally-applicable thread-safety mechanism for mutable state.

Sometimes you just need to use locks.

- Charlie