gh-108277: Make test_os tolerate 10 ms diff for timerfd on Android emulators (#117223)

Author: mhsmith

Lib/test/test_os.py

@@ -13,6 +13,7 @@
 import locale
 import os
 import pickle
+import platform
 import select
 import selectors
 import shutil
@@ -4085,9 +4086,15 @@ def test_eventfd_select(self):
 @unittest.skipUnless(hasattr(os, 'timerfd_create'), 'requires os.timerfd_create')
 @support.requires_linux_version(2, 6, 30)
 class TimerfdTests(unittest.TestCase):
- # Tolerate a difference of 1 ms
- CLOCK_RES_NS = 1_000_000
- CLOCK_RES = CLOCK_RES_NS * 1e-9
+ # 1 ms accuracy is reliably achievable on every platform except Android
+ # emulators, where we allow 10 ms (gh-108277).
+ if sys.platform == "android" and platform.android_ver().is_emulator:
+ CLOCK_RES_PLACES = 2
+ else:
+ CLOCK_RES_PLACES = 3
+
+ CLOCK_RES = 10 ** -CLOCK_RES_PLACES
+ CLOCK_RES_NS = 10 ** (9 - CLOCK_RES_PLACES)
 
  def timerfd_create(self, *args, **kwargs):
  fd = os.timerfd_create(*args, **kwargs)
@@ -4109,18 +4116,18 @@ def test_timerfd_initval(self):
 
  # 1st call
  next_expiration, interval2 = os.timerfd_settime(fd, initial=initial_expiration, interval=interval)
- self.assertAlmostEqual(interval2, 0.0, places=3)
- self.assertAlmostEqual(next_expiration, 0.0, places=3)
+ self.assertAlmostEqual(interval2, 0.0, places=self.CLOCK_RES_PLACES)
+ self.assertAlmostEqual(next_expiration, 0.0, places=self.CLOCK_RES_PLACES)
 
  # 2nd call
  next_expiration, interval2 = os.timerfd_settime(fd, initial=initial_expiration, interval=interval)
- self.assertAlmostEqual(interval2, interval, places=3)
- self.assertAlmostEqual(next_expiration, initial_expiration, places=3)
+ self.assertAlmostEqual(interval2, interval, places=self.CLOCK_RES_PLACES)
+ self.assertAlmostEqual(next_expiration, initial_expiration, places=self.CLOCK_RES_PLACES)
 
  # timerfd_gettime
  next_expiration, interval2 = os.timerfd_gettime(fd)
- self.assertAlmostEqual(interval2, interval, places=3)
- self.assertAlmostEqual(next_expiration, initial_expiration, places=3)
+ self.assertAlmostEqual(interval2, interval, places=self.CLOCK_RES_PLACES)
+ self.assertAlmostEqual(next_expiration, initial_expiration, places=self.CLOCK_RES_PLACES)
 
  def test_timerfd_non_blocking(self):
  fd = self.timerfd_create(time.CLOCK_REALTIME, flags=os.TFD_NONBLOCK)
@@ -4174,8 +4181,8 @@ def test_timerfd_interval(self):
 
  # timerfd_gettime
  next_expiration, interval2 = os.timerfd_gettime(fd)
- self.assertAlmostEqual(interval2, interval, places=3)
- self.assertAlmostEqual(next_expiration, initial_expiration, places=3)
+ self.assertAlmostEqual(interval2, interval, places=self.CLOCK_RES_PLACES)
+ self.assertAlmostEqual(next_expiration, initial_expiration, places=self.CLOCK_RES_PLACES)
 
  count = 3
  t = time.perf_counter()
@@ -4206,8 +4213,8 @@ def test_timerfd_TFD_TIMER_ABSTIME(self):
  # timerfd_gettime
  # Note: timerfd_gettime returns relative values even if TFD_TIMER_ABSTIME is specified.
  next_expiration, interval2 = os.timerfd_gettime(fd)
- self.assertAlmostEqual(interval2, interval, places=3)
- self.assertAlmostEqual(next_expiration, offset, places=3)
+ self.assertAlmostEqual(interval2, interval, places=self.CLOCK_RES_PLACES)
+ self.assertAlmostEqual(next_expiration, offset, places=self.CLOCK_RES_PLACES)
 
  t = time.perf_counter()
  count_signaled = self.read_count_signaled(fd)