>
>
> That's quite an interesting idea. I do think a lot of production Python
> code implicitly depends on the GIL and would need rework for multicore.
> For example, code that expects "n += 1" to be atomic, because the
> CPython bytecode interpreter won't switch threads in the middle of it.
> --
>
Yes it will. The interpreter may switch threads between any of these
bytecode instructions.
In [8]: dis.dis(compile('n += 1', '', 'single'))
1 0 LOAD_NAME 0 (n)
3 LOAD_CONST 0 (1)
6 INPLACE_ADD
7 STORE_NAME 0 (n)
10 LOAD_CONST 1 (None)
13 RETURN_VALUE
Proof:
In [15]: n = 0
In [16]: class Foo(threading.Thread):
....: def run(self):
....: global n
....: for i in range(10000):
....: n += 1
....:
....:
In [17]: threads = [Foo() for i in range(5)]
In [18]: for thread in threads:
....: thread.start()
....:
....:
In [19]: n
Out[19]: 37433
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