Re: Threads HOWTO?

[Johann Hibschman <jhibschman@...>]

On Jul 21, 2004, at 7:35 PM, Rici Lake wrote:

> On 21-Jul-04, at 5:39 PM, Johann Hibschman wrote:

> The giant interpreter lock does guarantee that the Lua internal 
> structures will remain coherent. But it does not at all guarantee that 
> individual threads will have a consistent view of the world, if they 
> share state with each other.

That's all right.  Anything in the global state would be immutable.

> where a is a global variable could generate unpredictable results. And 
> Lua does not provide any interpreter-visible synchronization 
> primitives which would let you prevent that. Of course, the problem 
> could be avoided by giving each thread its own globals environment, 
> but then one has to wonder what the point of using Lua threads was.

Hopefully immutable globals wouldn't require a global envt for each lua 
thread.

> Given all that, my inclination in threading Lua is not to; that is, to 
> keep a separate Lua instance for each thread and to do inter-thread 
> communication (if necessary) through a separate library.

Unfortunately, I'm trying to bolt-in a bit of scriptability to an 
application that creates computation threads all over the place.

I'm looking for a way to execute some lua code safely from inside some 
random thread, when I don't have the luxury of setting up a special 
thread-specific state at thread-creation time.  That's why I was 
looking at the idea of creating lua threads each time a chunk of code 
is executed.

Thanks for the comments,

-Johann