[Python-Dev] Re: Thread safety of deques

[Moore, Paul]

From: Aahz
> On Mon, Jul 19, 2004, Phillip J. Eby wrote:
>>
>> However, anything that calls back into Python code isn't necessarily 
>> atomic, and in general, almost anything can call back into Python code.
>
> Yup.

>> For example, the seemingly harmless dictionary item assignment can call 
>> back into Python for a custom type's __hash__ and __eq__ methods, so could 
>> it be that a thread switch could actually occur during this statement:
>> 
>>     foo[bar] = baz
>> 
>> if 'bar' has such custom methods?  Maybe I'm wrong, and the GIL is still 
>> held in such a case, but I'm not sure *how*.

> No, it isn't.

Hmm. I think that makes the point fairly well - thread safety is subtle, and
not to be taken lightly. Whether that was Raymond's point or mine, I'm less
sure :-)

I'll take Raymond's suggestion and see if I can come up with a relatively
succinct description of thread safety which would be suitable as a glossary
entry.

Paul.


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