[Python-checkins] bpo-29255: Wait in KqueueSelector.select when no fds are registered (GH-19508)
Russell Davis
webhook-mailer at python.org
Wed Apr 15 14:57:14 EDT 2020
https://github.com/python/cpython/commit/ba1bcffe5cafc1bb0ac6fdf9ecef51e75e342707
commit: ba1bcffe5cafc1bb0ac6fdf9ecef51e75e342707
branch: master
author: Russell Davis <551404+russelldavis at users.noreply.github.com>
committer: GitHub <noreply at github.com>
date: 2020-04-15T11:57:06-07:00
summary:
bpo-29255: Wait in KqueueSelector.select when no fds are registered (GH-19508)
Also partially fixes bpo-25680 (there's still a discrepancy in behavior
on Windows that needs to be fixed).
files:
A Misc/NEWS.d/next/Library/2020-04-14-11-31-07.bpo-29255.4EcyIN.rst
M Lib/selectors.py
M Lib/test/test_selectors.py
diff --git a/Lib/selectors.py b/Lib/selectors.py
index a9a0801ef0713..90251dc34a0b3 100644
--- a/Lib/selectors.py
+++ b/Lib/selectors.py
@@ -552,7 +552,10 @@ def unregister(self, fileobj):
def select(self, timeout=None):
timeout = None if timeout is None else max(timeout, 0)
- max_ev = len(self._fd_to_key)
+ # If max_ev is 0, kqueue will ignore the timeout. For consistent
+ # behavior with the other selector classes, we prevent that here
+ # (using max). See https://bugs.python.org/issue29255
+ max_ev = max(len(self._fd_to_key), 1)
ready = []
try:
kev_list = self._selector.control(None, max_ev, timeout)
diff --git a/Lib/test/test_selectors.py b/Lib/test/test_selectors.py
index 31611224dc71e..c449155c4b49f 100644
--- a/Lib/test/test_selectors.py
+++ b/Lib/test/test_selectors.py
@@ -543,6 +543,19 @@ def test_register_bad_fd(self):
with self.assertRaises(KeyError):
s.get_key(bad_f)
+ def test_empty_select_timeout(self):
+ # Issues #23009, #29255: Make sure timeout is applied when no fds
+ # are registered.
+ s = self.SELECTOR()
+ self.addCleanup(s.close)
+
+ t0 = time()
+ self.assertEqual(s.select(1), [])
+ t1 = time()
+ dt = t1 - t0
+ # Tolerate 2.0 seconds for very slow buildbots
+ self.assertTrue(0.8 <= dt <= 2.0, dt)
+
@unittest.skipUnless(hasattr(selectors, 'DevpollSelector'),
"Test needs selectors.DevpollSelector")
diff --git a/Misc/NEWS.d/next/Library/2020-04-14-11-31-07.bpo-29255.4EcyIN.rst b/Misc/NEWS.d/next/Library/2020-04-14-11-31-07.bpo-29255.4EcyIN.rst
new file mode 100644
index 0000000000000..18fbddf2cee73
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2020-04-14-11-31-07.bpo-29255.4EcyIN.rst
@@ -0,0 +1 @@
+Wait in `KqueueSelector.select` when no fds are registered
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