gh-110697: test_os TimerfdTests uses selectors (#110789)

Replace select.epoll() with selectors.DefaultSelector to support
FreeBSD 14 and newer.

* Merge common code between test_timerfd_epoll()
  test_timerfd_ns_epoll().
* Replace "_ = func()" with "func()".
* Add TimerfdTests.read_count_signaled() method.

1 files changed, 67 insertions, 102 deletions

diff --git a/Lib/test/test_os.py b/Lib/test/test_os.py
index 398393b..c23de4d 100644
--- a/Lib/test/test_os.py
+++ b/Lib/test/test_os.py
@@ -14,6 +14,7 @@ import locale
 import os
 import pickle
 import select
+import selectors
 import shutil
 import signal
 import socket
@@ -3940,6 +3941,11 @@ class TimerfdTests(unittest.TestCase):
         self.addCleanup(os.close, fd)
         return fd
 
+    def read_count_signaled(self, fd):
+        # read 8 bytes
+        data = os.read(fd, 8)
+        return int.from_bytes(data, byteorder=sys.byteorder)
+
     def test_timerfd_initval(self):
         fd = self.timerfd_create(time.CLOCK_REALTIME)
 
@@ -3962,25 +3968,22 @@ class TimerfdTests(unittest.TestCase):
         self.assertAlmostEqual(next_expiration, initial_expiration, places=3)
 
     def test_timerfd_non_blocking(self):
-        size = 8  # read 8 bytes
         fd = self.timerfd_create(time.CLOCK_REALTIME, flags=os.TFD_NONBLOCK)
 
         # 0.1 second later
         initial_expiration = 0.1
-        _, _ = os.timerfd_settime(fd, initial=initial_expiration, interval=0)
+        os.timerfd_settime(fd, initial=initial_expiration, interval=0)
 
         # read() raises OSError with errno is EAGAIN for non-blocking timer.
         with self.assertRaises(OSError) as ctx:
-            _ = os.read(fd, size)
+            self.read_count_signaled(fd)
         self.assertEqual(ctx.exception.errno, errno.EAGAIN)
 
         # Wait more than 0.1 seconds
         time.sleep(initial_expiration + 0.1)
 
         # confirm if timerfd is readable and read() returns 1 as bytes.
-        n = os.read(fd, size)
-        count_signaled = int.from_bytes(n, byteorder=sys.byteorder)
-        self.assertEqual(count_signaled, 1)
+        self.assertEqual(self.read_count_signaled(fd), 1)
 
     def test_timerfd_negative(self):
         one_sec_in_nsec = 10**9
@@ -3995,17 +3998,16 @@ class TimerfdTests(unittest.TestCase):
             for flags in test_flags:
                 with self.subTest(flags=flags, initial=initial, interval=interval):
                     with self.assertRaises(OSError) as context:
-                        _, _ = os.timerfd_settime(fd, flags=flags, initial=initial, interval=interval)
+                        os.timerfd_settime(fd, flags=flags, initial=initial, interval=interval)
                     self.assertEqual(context.exception.errno, errno.EINVAL)
 
                     with self.assertRaises(OSError) as context:
                         initial_ns = int( one_sec_in_nsec * initial )
                         interval_ns = int( one_sec_in_nsec * interval )
-                        _, _ = os.timerfd_settime_ns(fd, flags=flags, initial=initial_ns, interval=interval_ns)
+                        os.timerfd_settime_ns(fd, flags=flags, initial=initial_ns, interval=interval_ns)
                     self.assertEqual(context.exception.errno, errno.EINVAL)
 
     def test_timerfd_interval(self):
-        size = 8  # read 8 bytes
         fd = self.timerfd_create(time.CLOCK_REALTIME)
 
         # 1 second
@@ -4013,7 +4015,7 @@ class TimerfdTests(unittest.TestCase):
         # 0.5 second
         interval = 0.5
 
-        _, _ = os.timerfd_settime(fd, initial=initial_expiration, interval=interval)
+        os.timerfd_settime(fd, initial=initial_expiration, interval=interval)
 
         # timerfd_gettime
         next_expiration, interval2 = os.timerfd_gettime(fd)
@@ -4023,9 +4025,7 @@ class TimerfdTests(unittest.TestCase):
         count = 3
         t = time.perf_counter()
         for _ in range(count):
-            n = os.read(fd, size)
-            count_signaled = int.from_bytes(n, byteorder=sys.byteorder)
-            self.assertEqual(count_signaled, 1)
+            self.assertEqual(self.read_count_signaled(fd), 1)
         t = time.perf_counter() - t
 
         total_time = initial_expiration + interval * (count - 1)
@@ -4033,12 +4033,9 @@ class TimerfdTests(unittest.TestCase):
 
         # wait 3.5 time of interval
         time.sleep( (count+0.5) * interval)
-        n = os.read(fd, size)
-        count_signaled = int.from_bytes(n, byteorder=sys.byteorder)
-        self.assertEqual(count_signaled, count)
+        self.assertEqual(self.read_count_signaled(fd), count)
 
     def test_timerfd_TFD_TIMER_ABSTIME(self):
-        size = 8  # read 8 bytes
         fd = self.timerfd_create(time.CLOCK_REALTIME)
 
         now = time.clock_gettime(time.CLOCK_REALTIME)
@@ -4049,7 +4046,7 @@ class TimerfdTests(unittest.TestCase):
         # not interval timer
         interval = 0
 
-        _, _ = os.timerfd_settime(fd, flags=os.TFD_TIMER_ABSTIME, initial=initial_expiration, interval=interval)
+        os.timerfd_settime(fd, flags=os.TFD_TIMER_ABSTIME, initial=initial_expiration, interval=interval)
 
         # timerfd_gettime
         # Note: timerfd_gettime returns relative values even if TFD_TIMER_ABSTIME is specified.
@@ -4058,15 +4055,13 @@ class TimerfdTests(unittest.TestCase):
         self.assertAlmostEqual(next_expiration, offset, places=3)
 
         t = time.perf_counter()
-        n = os.read(fd, size)
-        count_signaled = int.from_bytes(n, byteorder=sys.byteorder)
+        count_signaled = self.read_count_signaled(fd)
         t = time.perf_counter() - t
         self.assertEqual(count_signaled, 1)
 
         self.assertGreater(t, offset - self.CLOCK_RES)
 
     def test_timerfd_select(self):
-        size = 8  # read 8 bytes
         fd = self.timerfd_create(time.CLOCK_REALTIME, flags=os.TFD_NONBLOCK)
 
         rfd, wfd, xfd = select.select([fd], [fd], [fd], 0)
@@ -4077,56 +4072,74 @@ class TimerfdTests(unittest.TestCase):
         # every 0.125 second
         interval = 0.125
 
-        _, _ = os.timerfd_settime(fd, initial=initial_expiration, interval=interval)
+        os.timerfd_settime(fd, initial=initial_expiration, interval=interval)
 
         count = 3
         t = time.perf_counter()
         for _ in range(count):
             rfd, wfd, xfd = select.select([fd], [fd], [fd], initial_expiration + interval)
             self.assertEqual((rfd, wfd, xfd), ([fd], [], []))
-            n = os.read(fd, size)
-            count_signaled = int.from_bytes(n, byteorder=sys.byteorder)
-            self.assertEqual(count_signaled, 1)
+            self.assertEqual(self.read_count_signaled(fd), 1)
         t = time.perf_counter() - t
 
         total_time = initial_expiration + interval * (count - 1)
         self.assertGreater(t, total_time)
 
-    def test_timerfd_epoll(self):
-        size = 8  # read 8 bytes
+    def check_timerfd_poll(self, nanoseconds):
         fd = self.timerfd_create(time.CLOCK_REALTIME, flags=os.TFD_NONBLOCK)
 
-        ep = select.epoll()
-        ep.register(fd, select.EPOLLIN)
-        self.addCleanup(ep.close)
+        selector = selectors.DefaultSelector()
+        selector.register(fd, selectors.EVENT_READ)
+        self.addCleanup(selector.close)
 
+        sec_to_nsec = 10 ** 9
         # 0.25 second
-        initial_expiration = 0.25
+        initial_expiration_ns = sec_to_nsec // 4
         # every 0.125 second
-        interval = 0.125
+        interval_ns = sec_to_nsec // 8
 
-        _, _ = os.timerfd_settime(fd, initial=initial_expiration, interval=interval)
+        if nanoseconds:
+            os.timerfd_settime_ns(fd,
+                                  initial=initial_expiration_ns,
+                                  interval=interval_ns)
+        else:
+            os.timerfd_settime(fd,
+                               initial=initial_expiration_ns / sec_to_nsec,
+                               interval=interval_ns / sec_to_nsec)
 
         count = 3
-        t = time.perf_counter()
+        if nanoseconds:
+            t = time.perf_counter_ns()
+        else:
+            t = time.perf_counter()
         for i in range(count):
-            timeout_margin = interval
+            timeout_margin_ns = interval_ns
             if i == 0:
-                timeout = initial_expiration + interval + timeout_margin
+                timeout_ns = initial_expiration_ns + interval_ns + timeout_margin_ns
             else:
-                timeout = interval + timeout_margin
-            # epoll timeout is in seconds.
-            events = ep.poll(timeout)
-            self.assertEqual(events, [(fd, select.EPOLLIN)])
-            n = os.read(fd, size)
-            count_signaled = int.from_bytes(n, byteorder=sys.byteorder)
-            self.assertEqual(count_signaled, 1)
+                timeout_ns = interval_ns + timeout_margin_ns
 
-        t = time.perf_counter() - t
+            ready = selector.select(timeout_ns / sec_to_nsec)
+            self.assertEqual(len(ready), 1, ready)
+            event = ready[0][1]
+            self.assertEqual(event, selectors.EVENT_READ)
 
-        total_time = initial_expiration + interval * (count - 1)
-        self.assertGreater(t, total_time)
-        ep.unregister(fd)
+            self.assertEqual(self.read_count_signaled(fd), 1)
+
+        total_time = initial_expiration_ns + interval_ns * (count - 1)
+        if nanoseconds:
+            dt = time.perf_counter_ns() - t
+            self.assertGreater(dt, total_time)
+        else:
+            dt = time.perf_counter() - t
+            self.assertGreater(dt, total_time / sec_to_nsec)
+        selector.unregister(fd)
+
+    def test_timerfd_poll(self):
+        self.check_timerfd_poll(False)
+
+    def test_timerfd_ns_poll(self):
+        self.check_timerfd_poll(True)
 
     def test_timerfd_ns_initval(self):
         one_sec_in_nsec = 10**9
@@ -4153,7 +4166,6 @@ class TimerfdTests(unittest.TestCase):
         self.assertAlmostEqual(next_expiration_ns, initial_expiration_ns, delta=limit_error)
 
     def test_timerfd_ns_interval(self):
-        size = 8  # read 8 bytes
         one_sec_in_nsec = 10**9
         limit_error = one_sec_in_nsec // 10**3
         fd = self.timerfd_create(time.CLOCK_REALTIME)
@@ -4163,7 +4175,7 @@ class TimerfdTests(unittest.TestCase):
         # every 0.5 second
         interval_ns = one_sec_in_nsec // 2
 
-        _, _ = os.timerfd_settime_ns(fd, initial=initial_expiration_ns, interval=interval_ns)
+        os.timerfd_settime_ns(fd, initial=initial_expiration_ns, interval=interval_ns)
 
         # timerfd_gettime
         next_expiration_ns, interval_ns2 = os.timerfd_gettime_ns(fd)
@@ -4173,9 +4185,7 @@ class TimerfdTests(unittest.TestCase):
         count = 3
         t = time.perf_counter_ns()
         for _ in range(count):
-            n = os.read(fd, size)
-            count_signaled = int.from_bytes(n, byteorder=sys.byteorder)
-            self.assertEqual(count_signaled, 1)
+            self.assertEqual(self.read_count_signaled(fd), 1)
         t = time.perf_counter_ns() - t
 
         total_time_ns = initial_expiration_ns + interval_ns * (count - 1)
@@ -4183,13 +4193,10 @@ class TimerfdTests(unittest.TestCase):
 
         # wait 3.5 time of interval
         time.sleep( (count+0.5) * interval_ns / one_sec_in_nsec)
-        n = os.read(fd, size)
-        count_signaled = int.from_bytes(n, byteorder=sys.byteorder)
-        self.assertEqual(count_signaled, count)
+        self.assertEqual(self.read_count_signaled(fd), count)
 
 
     def test_timerfd_ns_TFD_TIMER_ABSTIME(self):
-        size = 8  # read 8 bytes
         one_sec_in_nsec = 10**9
         limit_error = one_sec_in_nsec // 10**3
         fd = self.timerfd_create(time.CLOCK_REALTIME)
@@ -4202,7 +4209,7 @@ class TimerfdTests(unittest.TestCase):
         # not interval timer
         interval_ns = 0
 
-        _, _ = os.timerfd_settime_ns(fd, flags=os.TFD_TIMER_ABSTIME, initial=initial_expiration_ns, interval=interval_ns)
+        os.timerfd_settime_ns(fd, flags=os.TFD_TIMER_ABSTIME, initial=initial_expiration_ns, interval=interval_ns)
 
         # timerfd_gettime
         # Note: timerfd_gettime returns relative values even if TFD_TIMER_ABSTIME is specified.
@@ -4211,15 +4218,13 @@ class TimerfdTests(unittest.TestCase):
         self.assertLess(abs(next_expiration_ns - offset_ns),  limit_error)
 
         t = time.perf_counter_ns()
-        n = os.read(fd, size)
-        count_signaled = int.from_bytes(n, byteorder=sys.byteorder)
+        count_signaled = self.read_count_signaled(fd)
         t = time.perf_counter_ns() - t
         self.assertEqual(count_signaled, 1)
 
         self.assertGreater(t, offset_ns - self.CLOCK_RES_NS)
 
     def test_timerfd_ns_select(self):
-        size = 8  # read 8 bytes
         one_sec_in_nsec = 10**9
 
         fd = self.timerfd_create(time.CLOCK_REALTIME, flags=os.TFD_NONBLOCK)
@@ -4232,59 +4237,19 @@ class TimerfdTests(unittest.TestCase):
         # every 0.125 second
         interval_ns = one_sec_in_nsec // 8
 
-        _, _ = os.timerfd_settime_ns(fd, initial=initial_expiration_ns, interval=interval_ns)
+        os.timerfd_settime_ns(fd, initial=initial_expiration_ns, interval=interval_ns)
 
         count = 3
         t = time.perf_counter_ns()
         for _ in range(count):
             rfd, wfd, xfd = select.select([fd], [fd], [fd], (initial_expiration_ns + interval_ns) / 1e9 )
             self.assertEqual((rfd, wfd, xfd), ([fd], [], []))
-            n = os.read(fd, size)
-            count_signaled = int.from_bytes(n, byteorder=sys.byteorder)
-            self.assertEqual(count_signaled, 1)
+            self.assertEqual(self.read_count_signaled(fd), 1)
         t = time.perf_counter_ns() - t
 
         total_time_ns = initial_expiration_ns + interval_ns * (count - 1)
         self.assertGreater(t, total_time_ns)
 
-    def test_timerfd_ns_epoll(self):
-        size = 8  # read 8 bytes
-        one_sec_in_nsec = 10**9
-        fd = self.timerfd_create(time.CLOCK_REALTIME, flags=os.TFD_NONBLOCK)
-
-        ep = select.epoll()
-        ep.register(fd, select.EPOLLIN)
-        self.addCleanup(ep.close)
-
-        # 0.25 second
-        initial_expiration_ns = one_sec_in_nsec // 4
-        # every 0.125 second
-        interval_ns = one_sec_in_nsec // 8
-
-        _, _ = os.timerfd_settime_ns(fd, initial=initial_expiration_ns, interval=interval_ns)
-
-        count = 3
-        t = time.perf_counter_ns()
-        for i in range(count):
-            timeout_margin_ns = interval_ns
-            if i == 0:
-                timeout_ns = initial_expiration_ns + interval_ns + timeout_margin_ns
-            else:
-                timeout_ns = interval_ns + timeout_margin_ns
-
-            # epoll timeout is in seconds.
-            events = ep.poll(timeout_ns / one_sec_in_nsec)
-            self.assertEqual(events, [(fd, select.EPOLLIN)])
-            n = os.read(fd, size)
-            count_signaled = int.from_bytes(n, byteorder=sys.byteorder)
-            self.assertEqual(count_signaled, 1)
-
-        t = time.perf_counter_ns() - t
-
-        total_time = initial_expiration_ns + interval_ns * (count - 1)
-        self.assertGreater(t, total_time)
-        ep.unregister(fd)
-
 class OSErrorTests(unittest.TestCase):
     def setUp(self):
         class Str(str):