xfstests | filesystem testing suite ( mirror of kernel.org repository

This is an obvious issue with the xfstests tool, and has nothing to do with Python or fork calls themselves, as you took care to document

It could help, for example, if xfstests embeds its own python interpreter, calling fork will fork the test suite itself, and it might decide to redo the current-running test from start. (As opposed from calling for from a standalone script that forks only the state of the Python interpreter. So, even if unexpected, this could hardly be called a faulty behavior.

The bad news is that you won't get an easy workaround if yur original intent is to parallelise test executions - or make a test which execute concurrent code to trigger situations you want to test. Higher level calls, such as subprocess or multiprocessing, and even executor pools with concurrent.futures all will call fork in the lower level layers.

You should check if they work, or lead to this behavior. If they work, it means they take care of the corner-case you had hist with your use case and should be preferred in place of a bare fork.

If they don't, as I suspect, the workaround for the case of having code intentionally running in parallel for your tests will include a worker running outside the control of xfstests - something using Celery would do, if you set it up correctly:

• the tasks that run in parallel should have no other sideeffects than your desired one, and not use any functionality of whatever xfstests make available for your tests (special libraries, loggers, etc...) - not even an import statement including these.
• You run the workers using celery, in parallel to your test suite
• your main thread, running inside the test suite coordinats the calls and waits for the workers to complete - optionally making intermediate asserts on the external resource (e.g. filesystem) that you want to measure at carefully timed moments.

If you just want to run tests in parallel, just check the xfstests docs themselves on how to do it, from the "outside" of a test-suite written in Python.