[Python-Dev] Re: Thread safety of deques (original) (raw)

Moore, Paul Paul.Moore at atosorigin.com
Tue Jul 20 10:24:03 CEST 2004

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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