Threading plus multiprocessing plus cv2 error

[Stephane Tougard]

On 2020-08-30, Chris Angelico <rosuav at gmail.com> wrote:
>> I'm not even that makes sense, how 2 processes can share a thread ?
>>
> They can't. However, they can share a Thread object, which is the
> Python representation of a thread. That can lead to confusion, and
> possibly the OP's error (I don't know for sure, I'm just positing).

A fork() is a copy of a process in a new process. If this process has a
thread (or several), they are part of the copy and the new process has
those threads as well.

Unless there is a memory sharing between those processes, what happens
on one thread in the first process is totally independant of what
happens in the copy of this thread in the other process.

I'm not specialist on multi-threading in Python, but it should not
change anything. Both processes (father and child) don't share the same
thread, each one has its own copy of the thread.