Merge pull request #122 from njsmith/119-workaround-improved

Different and better workaround for gh-119

trio/_core/tests/test_ki.py

@@ -367,13 +367,47 @@ async def main():
 def test_ki_wakes_us_up():
  assert threading.current_thread() == threading.main_thread()
 
+ # This test is flaky due to a race condition on Windows; see:
+ # https://github.com/python-trio/trio/issues/119
+ # https://bugs.python.org/issue30038
+ # I think the only fix is to wait for fixed CPython to be released, so in
+ # the mean time, on affected versions we send two signals (equivalent to
+ # hitting control-C twice). This works because the problem is that the C
+ # level signal handler does
+ #
+ # write-to-fd -> set-flags
+ #
+ # and we need
+ #
+ # set-flags -> write-to-fd
+ #
+ # so running the C level signal handler twice does
+ #
+ # write-to-fd -> set-flags -> write-to-fd -> set-flags
+ #
+ # which contains the desired sequence.
+ #
+ # Affected version of CPython include:
+ # - 3.5.3
+ # - 3.6.1
+ # Let's be optimistic and assume the next releases won't be affected...
+ buggy_wakeup_fd = False
+ import platform
+ if os.name == "nt" and platform.python_implementation() == "CPython":
+ if (3, 5, 0) <= sys.version_info < (3, 5, 4):
+ buggy_wakeup_fd = True
+ if (3, 6, 0) <= sys.version_info < (3, 6, 2):
+ buggy_wakeup_fd = True
+
  def kill_soon():
  # We want the signal to be raised after the main thread has entered
  # the IO manager blocking primitive. There really is no way to
  # deterministically interlock with that, so we have to use sleep and
  # hope it's long enough.
  time.sleep(1)
  ki_self()
+ if buggy_wakeup_fd:
+ ki_self()
 
  async def main():
  thread = threading.Thread(target=kill_soon)
@@ -386,34 +420,7 @@ async def main():
  finally:
  thread.join()
 
- # This is flaky due to a race condition; see:
- # https://github.com/python-trio/trio/issues/119
- # https://bugs.python.org/issue30038
- # I think the only fix is to wait for fixed CPython to be released, so in
- # the mean time, we give it 5 chances to pass.
- #
- # Affected version of CPython include:
- # - 3.5.3
- # - 3.6.1
- # Hopefully the next releases won't be affected...
- if (3, 5, 0) <= sys.version_info < (3, 5, 4):
- retries = 5
- elif (3, 6, 0) <= sys.version_info < (3, 6, 2):
- retries = 5
- else: # pragma: no cover
- retries = 1
- for _ in range(retries): # pragma: no branch
- # The actual test:
- start = time.time()
- try:
- # This shouldn't raise KeyboardInterrupt, but sometimes it does
- _core.run(main)
- except KeyboardInterrupt: # pragma: no cover
- # Try again
- continue
- end = time.time()
- assert 1.0 <= (end - start) < 2
- # Test passed!
- break
- else: # pragma: no cover
- assert False, "flaky test_ki_wakes_us_up failed 5 times in a row!"
+ start = time.time()
+ _core.run(main)
+ end = time.time()
+ assert 1.0 <= (end - start) < 2