[Python-Dev] GIL removal question

[Rene Nejsum]

Thank you for the clarification, I should have been more precise...

On 12/08/2011, at 23.38, Guido van Rossum wrote:

> On Fri, Aug 12, 2011 at 12:57 PM, Rene Nejsum <rene at stranden.com> wrote:
>> I think I understand the background and need for GIL. Without it Python
>> programs would have been cluttered with lock/synchronized statements and
>> C-extensions would be harder to write.
> 
> No, sorry, the first half of this is incorrect: with or without the
> GIL *Python* code would need the same amount of fine-grained locking.
> (The part about C extensions is correct.) I am butting in because this
> is a common misunderstanding that really needs to be squashed whenever
> it is aired -- the GIL does *not* help Python code to synchronize. A
> thread-switch can occur between any two bytecode opcodes. Without the
> GIL, atomic operations (e.g. dict lookups that doesn't require
> evaluation of __eq__ or __hash__ implemented in Python) are still
> supposed to be atomic.
> 
> -- 
> --Guido van Rossum (python.org/~guido)