[TIP] How do you unit test threading classes?

[Laurens Van Houtven]

Hi Javier


On 06 Jun 2014, at 12:22, Javier Domingo Cansino <javier.domingo at fon.com> wrote:

> I do use locks, and the GIL does somehow make sure that nothing will
> happen between lines (unless you are doing several things on each
> line).

While this is technically true, you don’t have to try particularly hard to "do several things on one line". Calling a method on an object? Two opcodes, probably three (to get the object on the stack in the first place):

In [2]: def f(x):
   ...:     return x.bit_length()
   ...:

In [3]: dis(f)
  2           0 LOAD_FAST                0 (x)
              3 LOAD_ATTR                0 (bit_length)
              6 CALL_FUNCTION            0 (0 positional, 0 keyword pair)
              9 RETURN_VALUE

> The idea would be to have an utility like the following:
> 
> while obj.function_being_checked:
>    do_thread_safety_checks()
> 
> It could maybe iterate between unlocks of the GIL…

I don’t know of anything like this in Python. The automated safety checkers I do know of wouldn’t really work either.

hth
lvh
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