threading and iterator crashing interpreter

[Gabriel Genellina]

En Sun, 11 Mar 2007 09:47:34 -0300, Janto Dreijer <jantod at gmail.com>  
escribió:

> As far as I can tell I'm not running it from restricted mode
> explicitly.

This error is rather strange then:

> > RuntimeError: instance.__dict__ not accessible in restricted mode

"restricted mode" means that the current builtins are not the standard  
builtins.


> The reason I'm doing the random.choice() is so I don't have a handle
> ("session" in this case) that would prevent it from being garbage
> collected. I am not bothered by the Python-level Exceptions. I am
> bothered by the interpreter throwing a segfault. What I suspect is
> happening is the Session object is deallocated, while it still has a
> reference from within the iterator.

But on your code Session objects are never deleted; they stay inside  
System.sessions. Having an extra reference (the session variable) doesnt  
matter.

> It's quite difficult to reproduce these bugs consistently. You might
> need to run it a few times.

At least, the problem of using the same generator from different threads  
still remains, if you don't use my modified code. In general, when using  
multiple threads you always need some way to syncronize access to shared  
objects. You are lucky with Sessions because append is an atomic operation  
on lists; for more information see  
http://effbot.org/pyfaq/what-kinds-of-global-value-mutation-are-thread-safe.htm

-- 
Gabriel Genellina