[Python-Dev] test_fork1 on SMP?

[Tim Peters]

[Thomas Wouters]
> ...
> And anyway, I thought the test_fork1 test tested for fork() behaviour in
> threads. It spawns a thread,

Four threads, actually.

> fork()s one of those threads,

It forks "the main" thread, which is in addition to the four it spawns.

> and tests to see if the other threads still exist after the fork(),
> in the new child. The entire test is done in Python code, so how
> the scheduler and/or race conditions come into play isn't too
> obvious to me. Except of course the whole test if flawed.

The test uses loops and time.sleep instead of proper synchronization, so its
behavior is at best probabilistic, depending entirely on timing accidents
(*likely* accidents, but accidents all the same).  But I don't have a
machine here that supports fork at all, so I can't run it, and I don't know
how it fails on the machines it fails on.  If it's failing with a thread
exiting with a non-zero exit code, then I'd say the timing uncertainties in
the *Python* code are irrelevant, and it's the failing platform's fork
implementation that's broken.