[MacRuby-devel] Thread safety in apply example?

[Charles Oliver Nutter]

On Mon, Jan 24, 2011 at 10:24 AM, Matt Massicotte <massicotte at apple.com> wrote:
> My guess is that most problems need a thread-safe mechanism, where manipulating an array is just one part of a more complex system.  Pushing the details of the thread-safety into the array just hides the problem, and will likely trade more locking for possibly simpler code.
>
> Which could be a very good trade, don't get me wrong.  I'm not trying to knock your implementation at all.

In some cases, it's a great trade. It's just not a trade-off you want
to make for *all* access, which is why concurrent-threaded Ruby impls
like JRuby and MacRuby don't make that guarantee for Array, Hash, etc.
Of course, regular C Ruby isn't concurrent-threaded, so they have had
little motivation to do *anything* to improve the state of concurrent
programming on Ruby, like adding thread-safe collections or simpler
synchronization mechanisms.

> I think the actual underlying problem here is Queue#apply's rdoc entry.  Manipulating a non-thread-safe data structure (which is all of Foundation's collection classes) in an apply is a bug and even worse a conceptual error.  Where do you open bugs on the dispatch gem?

Queue#apply is actually defined in gcd.c in MacRuby's code, so this
would be a MacRuby bug. I'd have filed it, but I wasn't sure if I was
missing something about MacRuby's Array and thread-safety.

- Charlie