On Saturday, 25 February 2017 14:56:53 GMT Ralph Corderoy wrote:
> Although your code now has two threads, your first initial main one, and
> the one GPIO creates once you start wanting it to watch for interrupt
> events, there's still Python's GIL, Global Interpreter Lock, and the
> second thread's C code has to aquire it before it can run the Python
> code of your callback function, and then release it. Once released,
> Python code in your main thread, that was held up waiting for the lock,
> will continue.
>
> Does that explain the `isn't busy' behaviour?
Yes. And I kind of understood that. I have read about the GIL without
necessarily understanding it other than that it limits how many threads Python
can manage at once.
It's one reason why I thought multiprocessing might be needed, because I
understand that this gets over the problem with the GIL.
> Your callbacks will need a `gpio' or `channel' parameter else I'd expect
> an error when GPIO tries to call them.
I never tried it without one; if I copy code then I don't change anything that
doesn't look as if it needs changing :-)
--
Terry Coles
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