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"""
Various tests for synchronization primitives.
"""
import sys
import time
from _thread import start_new_thread, TIMEOUT_MAX
import threading
import unittest
import weakref
from test import support
def _wait():
# A crude wait/yield function not relying on synchronization primitives.
time.sleep(0.01)
class Bunch(object):
"""
A bunch of threads.
"""
def __init__(self, f, n, wait_before_exit=False):
"""
Construct a bunch of `n` threads running the same function `f`.
If `wait_before_exit` is True, the threads won't terminate until
do_finish() is called.
"""
self.f = f
self.n = n
self.started = []
self.finished = []
self._can_exit = not wait_before_exit
self.wait_thread = support.wait_threads_exit()
self.wait_thread.__enter__()
def task():
tid = threading.get_ident()
self.started.append(tid)
try:
f()
finally:
self.finished.append(tid)
while not self._can_exit:
_wait()
try:
for i in range(n):
start_new_thread(task, ())
except:
self._can_exit = True
raise
def wait_for_started(self):
while len(self.started) < self.n:
_wait()
def wait_for_finished(self):
while len(self.finished) < self.n:
_wait()
# Wait for threads exit
self.wait_thread.__exit__(None, None, None)
def do_finish(self):
self._can_exit = True
class BaseTestCase(unittest.TestCase):
def setUp(self):
self._threads = support.threading_setup()
def tearDown(self):
support.threading_cleanup(*self._threads)
support.reap_children()
def assertTimeout(self, actual, expected):
# The waiting and/or time.time() can be imprecise, which
# is why comparing to the expected value would sometimes fail
# (especially under Windows).
self.assertGreaterEqual(actual, expected * 0.6)
# Test nothing insane happened
self.assertLess(actual, expected * 10.0)
class BaseLockTests(BaseTestCase):
"""
Tests for both recursive and non-recursive locks.
"""
def test_constructor(self):
lock = self.locktype()
del lock
def test_repr(self):
lock = self.locktype()
self.assertRegex(repr(lock), "<unlocked .* object (.*)?at .*>")
del lock
def test_locked_repr(self):
lock = self.locktype()
lock.acquire()
self.assertRegex(repr(lock), "<locked .* object (.*)?at .*>")
del lock
def test_acquire_destroy(self):
lock = self.locktype()
lock.acquire()
del lock
def test_acquire_release(self):
lock = self.locktype()
lock.acquire()
lock.release()
del lock
def test_try_acquire(self):
lock = self.locktype()
self.assertTrue(lock.acquire(False))
lock.release()
def test_try_acquire_contended(self):
lock = self.locktype()
lock.acquire()
result = []
def f():
result.append(lock.acquire(False))
Bunch(f, 1).wait_for_finished()
self.assertFalse(result[0])
lock.release()
def test_acquire_contended(self):
lock = self.locktype()
lock.acquire()
N = 5
def f():
lock.acquire()
lock.release()
b = Bunch(f, N)
b.wait_for_started()
_wait()
self.assertEqual(len(b.finished), 0)
lock.release()
b.wait_for_finished()
self.assertEqual(len(b.finished), N)
def test_with(self):
lock = self.locktype()
def f():
lock.acquire()
lock.release()
def _with(err=None):
with lock:
if err is not None:
raise err
_with()
# Check the lock is unacquired
Bunch(f, 1).wait_for_finished()
self.assertRaises(TypeError, _with, TypeError)
# Check the lock is unacquired
Bunch(f, 1).wait_for_finished()
def test_thread_leak(self):
# The lock shouldn't leak a Thread instance when used from a foreign
# (non-threading) thread.
lock = self.locktype()
def f():
lock.acquire()
lock.release()
n = len(threading.enumerate())
# We run many threads in the hope that existing threads ids won't
# be recycled.
Bunch(f, 15).wait_for_finished()
if len(threading.enumerate()) != n:
# There is a small window during which a Thread instance's
# target function has finished running, but the Thread is still
# alive and registered. Avoid spurious failures by waiting a
# bit more (seen on a buildbot).
time.sleep(0.4)
self.assertEqual(n, len(threading.enumerate()))
def test_timeout(self):
lock = self.locktype()
# Can't set timeout if not blocking
self.assertRaises(ValueError, lock.acquire, 0, 1)
# Invalid timeout values
self.assertRaises(ValueError, lock.acquire, timeout=-100)
self.assertRaises(OverflowError, lock.acquire, timeout=1e100)
self.assertRaises(OverflowError, lock.acquire, timeout=TIMEOUT_MAX + 1)
# TIMEOUT_MAX is ok
lock.acquire(timeout=TIMEOUT_MAX)
lock.release()
t1 = time.time()
self.assertTrue(lock.acquire(timeout=5))
t2 = time.time()
# Just a sanity test that it didn't actually wait for the timeout.
self.assertLess(t2 - t1, 5)
results = []
def f():
t1 = time.time()
results.append(lock.acquire(timeout=0.5))
t2 = time.time()
results.append(t2 - t1)
Bunch(f, 1).wait_for_finished()
self.assertFalse(results[0])
self.assertTimeout(results[1], 0.5)
def test_weakref_exists(self):
lock = self.locktype()
ref = weakref.ref(lock)
self.assertIsNotNone(ref())
def test_weakref_deleted(self):
lock = self.locktype()
ref = weakref.ref(lock)
del lock
self.assertIsNone(ref())
class LockTests(BaseLockTests):
"""
Tests for non-recursive, weak locks
(which can be acquired and released from different threads).
"""
def test_reacquire(self):
# Lock needs to be released before re-acquiring.
lock = self.locktype()
phase = []
def f():
lock.acquire()
phase.append(None)
lock.acquire()
phase.append(None)
with support.wait_threads_exit():
start_new_thread(f, ())
while len(phase) == 0:
_wait()
_wait()
self.assertEqual(len(phase), 1)
lock.release()
while len(phase) == 1:
_wait()
self.assertEqual(len(phase), 2)
def test_different_thread(self):
# Lock can be released from a different thread.
lock = self.locktype()
lock.acquire()
def f():
lock.release()
b = Bunch(f, 1)
b.wait_for_finished()
lock.acquire()
lock.release()
def test_state_after_timeout(self):
# Issue #11618: check that lock is in a proper state after a
# (non-zero) timeout.
lock = self.locktype()
lock.acquire()
self.assertFalse(lock.acquire(timeout=0.01))
lock.release()
self.assertFalse(lock.locked())
self.assertTrue(lock.acquire(blocking=False))
class RLockTests(BaseLockTests):
"""
Tests for recursive locks.
"""
def test_reacquire(self):
lock = self.locktype()
lock.acquire()
lock.acquire()
lock.release()
lock.acquire()
lock.release()
lock.release()
def test_release_unacquired(self):
# Cannot release an unacquired lock
lock = self.locktype()
self.assertRaises(RuntimeError, lock.release)
lock.acquire()
lock.acquire()
lock.release()
lock.acquire()
lock.release()
lock.release()
self.assertRaises(RuntimeError, lock.release)
def test_release_save_unacquired(self):
# Cannot _release_save an unacquired lock
lock = self.locktype()
self.assertRaises(RuntimeError, lock._release_save)
lock.acquire()
lock.acquire()
lock.release()
lock.acquire()
lock.release()
lock.release()
self.assertRaises(RuntimeError, lock._release_save)
def test_different_thread(self):
# Cannot release from a different thread
lock = self.locktype()
def f():
lock.acquire()
b = Bunch(f, 1, True)
try:
self.assertRaises(RuntimeError, lock.release)
finally:
b.do_finish()
b.wait_for_finished()
def test__is_owned(self):
lock = self.locktype()
self.assertFalse(lock._is_owned())
lock.acquire()
self.assertTrue(lock._is_owned())
lock.acquire()
self.assertTrue(lock._is_owned())
result = []
def f():
result.append(lock._is_owned())
Bunch(f, 1).wait_for_finished()
self.assertFalse(result[0])
lock.release()
self.assertTrue(lock._is_owned())
lock.release()
self.assertFalse(lock._is_owned())
class EventTests(BaseTestCase):
"""
Tests for Event objects.
"""
def test_is_set(self):
evt = self.eventtype()
self.assertFalse(evt.is_set())
evt.set()
self.assertTrue(evt.is_set())
evt.set()
self.assertTrue(evt.is_set())
evt.clear()
self.assertFalse(evt.is_set())
evt.clear()
self.assertFalse(evt.is_set())
def _check_notify(self, evt):
# All threads get notified
N = 5
results1 = []
results2 = []
def f():
results1.append(evt.wait())
results2.append(evt.wait())
b = Bunch(f, N)
b.wait_for_started()
_wait()
self.assertEqual(len(results1), 0)
evt.set()
b.wait_for_finished()
self.assertEqual(results1, [True] * N)
self.assertEqual(results2, [True] * N)
def test_notify(self):
evt = self.eventtype()
self._check_notify(evt)
# Another time, after an explicit clear()
evt.set()
evt.clear()
self._check_notify(evt)
def test_timeout(self):
evt = self.eventtype()
results1 = []
results2 = []
N = 5
def f():
results1.append(evt.wait(0.0))
t1 = time.time()
r = evt.wait(0.5)
t2 = time.time()
results2.append((r, t2 - t1))
Bunch(f, N).wait_for_finished()
self.assertEqual(results1, [False] * N)
for r, dt in results2:
self.assertFalse(r)
self.assertTimeout(dt, 0.5)
# The event is set
results1 = []
results2 = []
evt.set()
Bunch(f, N).wait_for_finished()
self.assertEqual(results1, [True] * N)
for r, dt in results2:
self.assertTrue(r)
def test_set_and_clear(self):
# Issue #13502: check that wait() returns true even when the event is
# cleared before the waiting thread is woken up.
evt = self.eventtype()
results = []
timeout = 0.250
N = 5
def f():
results.append(evt.wait(timeout * 4))
b = Bunch(f, N)
b.wait_for_started()
time.sleep(timeout)
evt.set()
evt.clear()
b.wait_for_finished()
self.assertEqual(results, [True] * N)
def test_reset_internal_locks(self):
# ensure that condition is still using a Lock after reset
evt = self.eventtype()
with evt._cond:
self.assertFalse(evt._cond.acquire(False))
evt._reset_internal_locks()
with evt._cond:
self.assertFalse(evt._cond.acquire(False))
class ConditionTests(BaseTestCase):
"""
Tests for condition variables.
"""
def test_acquire(self):
cond = self.condtype()
# Be default we have an RLock: the condition can be acquired multiple
# times.
cond.acquire()
cond.acquire()
cond.release()
cond.release()
lock = threading.Lock()
cond = self.condtype(lock)
cond.acquire()
self.assertFalse(lock.acquire(False))
cond.release()
self.assertTrue(lock.acquire(False))
self.assertFalse(cond.acquire(False))
lock.release()
with cond:
self.assertFalse(lock.acquire(False))
def test_unacquired_wait(self):
cond = self.condtype()
self.assertRaises(RuntimeError, cond.wait)
def test_unacquired_notify(self):
cond = self.condtype()
self.assertRaises(RuntimeError, cond.notify)
def _check_notify(self, cond):
# Note that this test is sensitive to timing. If the worker threads
# don't execute in a timely fashion, the main thread may think they
# are further along then they are. The main thread therefore issues
# _wait() statements to try to make sure that it doesn't race ahead
# of the workers.
# Secondly, this test assumes that condition variables are not subject
# to spurious wakeups. The absence of spurious wakeups is an implementation
# detail of Condition Cariables in current CPython, but in general, not
# a guaranteed property of condition variables as a programming
# construct. In particular, it is possible that this can no longer
# be conveniently guaranteed should their implementation ever change.
N = 5
ready = []
results1 = []
results2 = []
phase_num = 0
def f():
cond.acquire()
ready.append(phase_num)
result = cond.wait()
cond.release()
results1.append((result, phase_num))
cond.acquire()
ready.append(phase_num)
result = cond.wait()
cond.release()
results2.append((result, phase_num))
b = Bunch(f, N)
b.wait_for_started()
# first wait, to ensure all workers settle into cond.wait() before
# we continue. See issues #8799 and #30727.
while len(ready) < 5:
_wait()
ready.clear()
self.assertEqual(results1, [])
# Notify 3 threads at first
cond.acquire()
cond.notify(3)
_wait()
phase_num = 1
cond.release()
while len(results1) < 3:
_wait()
self.assertEqual(results1, [(True, 1)] * 3)
self.assertEqual(results2, [])
# make sure all awaken workers settle into cond.wait()
while len(ready) < 3:
_wait()
# Notify 5 threads: they might be in their first or second wait
cond.acquire()
cond.notify(5)
_wait()
phase_num = 2
cond.release()
while len(results1) + len(results2) < 8:
_wait()
self.assertEqual(results1, [(True, 1)] * 3 + [(True, 2)] * 2)
self.assertEqual(results2, [(True, 2)] * 3)
# make sure all workers settle into cond.wait()
while len(ready) < 5:
_wait()
# Notify all threads: they are all in their second wait
cond.acquire()
cond.notify_all()
_wait()
phase_num = 3
cond.release()
while len(results2) < 5:
_wait()
self.assertEqual(results1, [(True, 1)] * 3 + [(True,2)] * 2)
self.assertEqual(results2, [(True, 2)] * 3 + [(True, 3)] * 2)
b.wait_for_finished()
def test_notify(self):
cond = self.condtype()
self._check_notify(cond)
# A second time, to check internal state is still ok.
self._check_notify(cond)
def test_timeout(self):
cond = self.condtype()
results = []
N = 5
def f():
cond.acquire()
t1 = time.time()
result = cond.wait(0.5)
t2 = time.time()
cond.release()
results.append((t2 - t1, result))
Bunch(f, N).wait_for_finished()
self.assertEqual(len(results), N)
for dt, result in results:
self.assertTimeout(dt, 0.5)
# Note that conceptually (that"s the condition variable protocol)
# a wait() may succeed even if no one notifies us and before any
# timeout occurs. Spurious wakeups can occur.
# This makes it hard to verify the result value.
# In practice, this implementation has no spurious wakeups.
self.assertFalse(result)
def test_waitfor(self):
cond = self.condtype()
state = 0
def f():
with cond:
result = cond.wait_for(lambda : state==4)
self.assertTrue(result)
self.assertEqual(state, 4)
b = Bunch(f, 1)
b.wait_for_started()
for i in range(4):
time.sleep(0.01)
with cond:
state += 1
cond.notify()
b.wait_for_finished()
def test_waitfor_timeout(self):
cond = self.condtype()
state = 0
success = []
def f():
with cond:
dt = time.time()
result = cond.wait_for(lambda : state==4, timeout=0.1)
dt = time.time() - dt
self.assertFalse(result)
self.assertTimeout(dt, 0.1)
success.append(None)
b = Bunch(f, 1)
b.wait_for_started()
# Only increment 3 times, so state == 4 is never reached.
for i in range(3):
time.sleep(0.01)
with cond:
state += 1
cond.notify()
b.wait_for_finished()
self.assertEqual(len(success), 1)
class BaseSemaphoreTests(BaseTestCase):
"""
Common tests for {bounded, unbounded} semaphore objects.
"""
def test_constructor(self):
self.assertRaises(ValueError, self.semtype, value = -1)
self.assertRaises(ValueError, self.semtype, value = -sys.maxsize)
def test_acquire(self):
sem = self.semtype(1)
sem.acquire()
sem.release()
sem = self.semtype(2)
sem.acquire()
sem.acquire()
sem.release()
sem.release()
def test_acquire_destroy(self):
sem = self.semtype()
sem.acquire()
del sem
def test_acquire_contended(self):
sem = self.semtype(7)
sem.acquire()
N = 10
sem_results = []
results1 = []
results2 = []
phase_num = 0
def f():
sem_results.append(sem.acquire())
results1.append(phase_num)
sem_results.append(sem.acquire())
results2.append(phase_num)
b = Bunch(f, 10)
b.wait_for_started()
while len(results1) + len(results2) < 6:
_wait()
self.assertEqual(results1 + results2, [0] * 6)
phase_num = 1
for i in range(7):
sem.release()
while len(results1) + len(results2) < 13:
_wait()
self.assertEqual(sorted(results1 + results2), [0] * 6 + [1] * 7)
phase_num = 2
for i in range(6):
sem.release()
while len(results1) + len(results2) < 19:
_wait()
self.assertEqual(sorted(results1 + results2), [0] * 6 + [1] * 7 + [2] * 6)
# The semaphore is still locked
self.assertFalse(sem.acquire(False))
# Final release, to let the last thread finish
sem.release()
b.wait_for_finished()
self.assertEqual(sem_results, [True] * (6 + 7 + 6 + 1))
def test_try_acquire(self):
sem = self.semtype(2)
self.assertTrue(sem.acquire(False))
self.assertTrue(sem.acquire(False))
self.assertFalse(sem.acquire(False))
sem.release()
self.assertTrue(sem.acquire(False))
def test_try_acquire_contended(self):
sem = self.semtype(4)
sem.acquire()
results = []
def f():
results.append(sem.acquire(False))
results.append(sem.acquire(False))
Bunch(f, 5).wait_for_finished()
# There can be a thread switch between acquiring the semaphore and
# appending the result, therefore results will not necessarily be
# ordered.
self.assertEqual(sorted(results), [False] * 7 + [True] * 3 )
def test_acquire_timeout(self):
sem = self.semtype(2)
self.assertRaises(ValueError, sem.acquire, False, timeout=1.0)
self.assertTrue(sem.acquire(timeout=0.005))
self.assertTrue(sem.acquire(timeout=0.005))
self.assertFalse(sem.acquire(timeout=0.005))
sem.release()
self.assertTrue(sem.acquire(timeout=0.005))
t = time.time()
self.assertFalse(sem.acquire(timeout=0.5))
dt = time.time() - t
self.assertTimeout(dt, 0.5)
def test_default_value(self):
# The default initial value is 1.
sem = self.semtype()
sem.acquire()
def f():
sem.acquire()
sem.release()
b = Bunch(f, 1)
b.wait_for_started()
_wait()
self.assertFalse(b.finished)
sem.release()
b.wait_for_finished()
def test_with(self):
sem = self.semtype(2)
def _with(err=None):
with sem:
self.assertTrue(sem.acquire(False))
sem.release()
with sem:
self.assertFalse(sem.acquire(False))
if err:
raise err
_with()
self.assertTrue(sem.acquire(False))
sem.release()
self.assertRaises(TypeError, _with, TypeError)
self.assertTrue(sem.acquire(False))
sem.release()
class SemaphoreTests(BaseSemaphoreTests):
"""
Tests for unbounded semaphores.
"""
def test_release_unacquired(self):
# Unbounded releases are allowed and increment the semaphore's value
sem = self.semtype(1)
sem.release()
sem.acquire()
sem.acquire()
sem.release()
class BoundedSemaphoreTests(BaseSemaphoreTests):
"""
Tests for bounded semaphores.
"""
def test_release_unacquired(self):
# Cannot go past the initial value
sem = self.semtype()
self.assertRaises(ValueError, sem.release)
sem.acquire()
sem.release()
self.assertRaises(ValueError, sem.release)
class BarrierTests(BaseTestCase):
"""
Tests for Barrier objects.
"""
N = 5
defaultTimeout = 2.0
def setUp(self):
self.barrier = self.barriertype(self.N, timeout=self.defaultTimeout)
def tearDown(self):
self.barrier.abort()
def run_threads(self, f):
b = Bunch(f, self.N-1)
f()
b.wait_for_finished()
def multipass(self, results, n):
m = self.barrier.parties
self.assertEqual(m, self.N)
for i in range(n):
results[0].append(True)
self.assertEqual(len(results[1]), i * m)
self.barrier.wait()
results[1].append(True)
self.assertEqual(len(results[0]), (i + 1) * m)
self.barrier.wait()
self.assertEqual(self.barrier.n_waiting, 0)
self.assertFalse(self.barrier.broken)
def test_barrier(self, passes=1):
"""
Test that a barrier is passed in lockstep
"""
results = [[],[]]
def f():
self.multipass(results, passes)
self.run_threads(f)
def test_barrier_10(self):
"""
Test that a barrier works for 10 consecutive runs
"""
return self.test_barrier(10)
def test_wait_return(self):
"""
test the return value from barrier.wait
"""
results = []
def f():
r = self.barrier.wait()
results.append(r)
self.run_threads(f)
self.assertEqual(sum(results), sum(range(self.N)))
def test_action(self):
"""
Test the 'action' callback
"""
results = []
def action():
results.append(True)
barrier = self.barriertype(self.N, action)
def f():
barrier.wait()
self.assertEqual(len(results), 1)
self.run_threads(f)
def test_abort(self):
"""
Test that an abort will put the barrier in a broken state
"""
results1 = []
results2 = []
def f():
try:
i = self.barrier.wait()
if i == self.N//2:
raise RuntimeError
self.barrier.wait()
results1.append(True)
except threading.BrokenBarrierError:
results2.append(True)
except RuntimeError:
self.barrier.abort()
pass
self.run_threads(f)
self.assertEqual(len(results1), 0)
self.assertEqual(len(results2), self.N-1)
self.assertTrue(self.barrier.broken)
def test_reset(self):
"""
Test that a 'reset' on a barrier frees the waiting threads
"""
results1 = []
results2 = []
results3 = []
def f():
i = self.barrier.wait()
if i == self.N//2:
# Wait until the other threads are all in the barrier.
while self.barrier.n_waiting < self.N-1:
time.sleep(0.001)
self.barrier.reset()
else:
try:
self.barrier.wait()
results1.append(True)
except threading.BrokenBarrierError:
results2.append(True)
# Now, pass the barrier again
self.barrier.wait()
results3.append(True)
self.run_threads(f)
self.assertEqual(len(results1), 0)
self.assertEqual(len(results2), self.N-1)
self.assertEqual(len(results3), self.N)
def test_abort_and_reset(self):
"""
Test that a barrier can be reset after being broken.
"""
results1 = []
results2 = []
results3 = []
barrier2 = self.barriertype(self.N)
def f():
try:
i = self.barrier.wait()
if i == self.N//2:
raise RuntimeError
self.barrier.wait()
results1.append(True)
except threading.BrokenBarrierError:
results2.append(True)
except RuntimeError:
self.barrier.abort()
pass
# Synchronize and reset the barrier. Must synchronize first so
# that everyone has left it when we reset, and after so that no
# one enters it before the reset.
if barrier2.wait() == self.N//2:
self.barrier.reset()
barrier2.wait()
self.barrier.wait()
results3.append(True)
self.run_threads(f)
self.assertEqual(len(results1), 0)
self.assertEqual(len(results2), self.N-1)
self.assertEqual(len(results3), self.N)
def test_timeout(self):
"""
Test wait(timeout)
"""
def f():
i = self.barrier.wait()
if i == self.N // 2:
# One thread is late!
time.sleep(1.0)
# Default timeout is 2.0, so this is shorter.
self.assertRaises(threading.BrokenBarrierError,
self.barrier.wait, 0.5)
self.run_threads(f)
def test_default_timeout(self):
"""
Test the barrier's default timeout
"""
# create a barrier with a low default timeout
barrier = self.barriertype(self.N, timeout=0.3)
def f():
i = barrier.wait()
if i == self.N // 2:
# One thread is later than the default timeout of 0.3s.
time.sleep(1.0)
self.assertRaises(threading.BrokenBarrierError, barrier.wait)
self.run_threads(f)
def test_single_thread(self):
b = self.barriertype(1)
b.wait()
b.wait()