bpo-33613, test_semaphore_tracker_sigint: fix race condition by pablogsal · Pull Request #7850 · python/cpython

Fail `test_semaphore_tracker_sigint` if no warnings are expected and
one is received.

Fix race condition when the child receives SIGINT
before it can register signal handlers for it.

The race condition occurs when the parent calls
`_semaphore_tracker.ensure_running()` (which in turn spawns the
semaphore_tracker using `_posixsubprocess.fork_exec`), the child
registers the signal handlers and the parent tries to kill the child.
What seem to happen is that in some slow systems, the parent sends the
signal to kill the child before the child protects against the signal.

There is no reliable and portable solution for the parent to wait until
the child has register the signal handlers to send the signal to kill
the child so a `sleep` is introduced between the spawning of the child
and the parent sending the signal to give time to the child to register
the handlers.

…me process

… the same process

…runs in the same process

…esting runs in the same process