I've tried running the test suite with Python 3.8.0a3 (on Fedora 30, pytest-cov master, pytest==4.5.0, coverage==4.5.3). While digging into failures I noticed the following race condition.
Solving it doesn't quite fix the tests for me, but I believe it's valid.
cleanup() and the signal handler _signal_cleanup_handler() can enter an infinite recursion if a signal is delivered at the wrong time.
Trace when cleanup is called (with _cleanup_in_progress False and _pending_signal None):
_cleanup_in_progress = True- a signal is delivered now
_signal_cleanup_handler runs_cleanup_in_progress is True, so the handler only sets _pending_signal
_cleanup(_active_cov) runs_active_cov = None_cleanup_in_progress = False_pending_signal is set, so we call _signal_cleanup_handler(), with _cleanup_in_progress False and _pending_signal set:
_cleanup_in_progress is False, so we call cleanup():
_cleanup_in_progress = True_cleanup(_active_cov)_active_cov = None_cleanup_in_progress = False_pending_signal is still set, so call _signal_cleanup_handler(), again with _cleanup_in_progress False and _pending_signal set. This leads to infinite recursion.
The solution could be setting _cleanup_in_progress = False after the if _pending_signal block, or setting _pending_signal = None before calling _signal_cleanup_handler.
I'm not very familiar with the code and what it's trying to do, so I don't know what a good fix would be (if any).
I've tried running the test suite with Python 3.8.0a3 (on Fedora 30, pytest-cov master, pytest==4.5.0, coverage==4.5.3). While digging into failures I noticed the following race condition.
Solving it doesn't quite fix the tests for me, but I believe it's valid.
cleanup()and the signal handler_signal_cleanup_handler()can enter an infinite recursion if a signal is delivered at the wrong time.Trace when
cleanupis called (with_cleanup_in_progressFalse and_pending_signalNone):_cleanup_in_progress = True_signal_cleanup_handlerruns_cleanup_in_progressis True, so the handler only sets_pending_signal_cleanup(_active_cov)runs_active_cov = None_cleanup_in_progress = False_pending_signalis set, so we call_signal_cleanup_handler(), with_cleanup_in_progressFalse and_pending_signalset:_cleanup_in_progressis False, so we callcleanup():_cleanup_in_progress = True_cleanup(_active_cov)_active_cov = None_cleanup_in_progress = False_pending_signalis still set, so call_signal_cleanup_handler(), again with_cleanup_in_progressFalse and_pending_signalset. This leads to infinite recursion.The solution could be setting
_cleanup_in_progress = Falseafter theif _pending_signalblock, or setting_pending_signal = Nonebefore calling_signal_cleanup_handler.I'm not very familiar with the code and what it's trying to do, so I don't know what a good fix would be (if any).