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lock_tests.py
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1265 lines (1075 loc) · 37.4 KB
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"""
Various tests for synchronization primitives.
"""
import gc
import sys
import time
from _thread import start_new_thread, TIMEOUT_MAX
import threading
import unittest
import weakref
from test import support
from test.support import threading_helper
requires_fork = unittest.skipUnless(support.has_fork_support,
"platform doesn't support fork "
"(no _at_fork_reinit method)")
def wait_threads_blocked(nthread):
# Arbitrary sleep to wait until N threads are blocked,
# like waiting for a lock.
time.sleep(0.010 * nthread)
class Bunch(object):
"""
A bunch of threads.
"""
def __init__(self, func, nthread, wait_before_exit=False):
"""
Construct a bunch of `nthread` threads running the same function `func`.
If `wait_before_exit` is True, the threads won't terminate until
do_finish() is called.
"""
self.func = func
self.nthread = nthread
self.started = []
self.finished = []
self.exceptions = []
self._can_exit = not wait_before_exit
self._wait_thread = None
def task(self):
tid = threading.get_ident()
self.started.append(tid)
try:
self.func()
except BaseException as exc:
self.exceptions.append(exc)
finally:
self.finished.append(tid)
for _ in support.sleeping_retry(support.SHORT_TIMEOUT):
if self._can_exit:
break
def __enter__(self):
self._wait_thread = threading_helper.wait_threads_exit(support.SHORT_TIMEOUT)
self._wait_thread.__enter__()
try:
for _ in range(self.nthread):
start_new_thread(self.task, ())
except:
self._can_exit = True
raise
for _ in support.sleeping_retry(support.SHORT_TIMEOUT):
if len(self.started) >= self.nthread:
break
return self
def __exit__(self, exc_type, exc_value, traceback):
for _ in support.sleeping_retry(support.SHORT_TIMEOUT):
if len(self.finished) >= self.nthread:
break
# Wait until threads completely exit according to _thread._count()
self._wait_thread.__exit__(None, None, None)
# Break reference cycle
exceptions = self.exceptions
self.exceptions = None
if exceptions:
raise ExceptionGroup(f"{self.func} threads raised exceptions",
exceptions)
def do_finish(self):
self._can_exit = True
class BaseTestCase(unittest.TestCase):
def setUp(self):
self._threads = threading_helper.threading_setup()
def tearDown(self):
threading_helper.threading_cleanup(*self._threads)
support.reap_children()
def assertTimeout(self, actual, expected):
# The waiting and/or time.monotonic() 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 wait_phase(self, phase, expected):
for _ in support.sleeping_retry(support.SHORT_TIMEOUT):
if len(phase) >= expected:
break
self.assertEqual(len(phase), expected)
def test_constructor(self):
lock = self.locktype()
del lock
def test_constructor_noargs(self):
self.assertRaises(TypeError, self.locktype, 1)
self.assertRaises(TypeError, self.locktype, x=1)
self.assertRaises(TypeError, self.locktype, 1, x=2)
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))
with Bunch(f, 1):
pass
self.assertFalse(result[0])
lock.release()
def test_acquire_contended(self):
lock = self.locktype()
lock.acquire()
def f():
lock.acquire()
lock.release()
N = 5
with Bunch(f, N) as bunch:
# Threads block on lock.acquire()
wait_threads_blocked(N)
self.assertEqual(len(bunch.finished), 0)
# Threads unblocked
lock.release()
self.assertEqual(len(bunch.finished), N)
def test_with(self):
lock = self.locktype()
def f():
lock.acquire()
lock.release()
def with_lock(err=None):
with lock:
if err is not None:
raise err
# Acquire the lock, do nothing, with releases the lock
with lock:
pass
# Check that the lock is unacquired
with Bunch(f, 1):
pass
# Acquire the lock, raise an exception, with releases the lock
with self.assertRaises(TypeError):
with lock:
raise TypeError
# Check that the lock is unacquired even if after an exception
# was raised in the previous "with lock:" block
with Bunch(f, 1):
pass
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()
# We run many threads in the hope that existing threads ids won't
# be recycled.
with Bunch(f, 15):
pass
def test_timeout(self):
lock = self.locktype()
# Can't set timeout if not blocking
self.assertRaises(ValueError, lock.acquire, False, 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.monotonic()
self.assertTrue(lock.acquire(timeout=5))
t2 = time.monotonic()
# Just a sanity test that it didn't actually wait for the timeout.
self.assertLess(t2 - t1, 5)
results = []
def f():
t1 = time.monotonic()
results.append(lock.acquire(timeout=0.5))
t2 = time.monotonic()
results.append(t2 - t1)
with Bunch(f, 1):
pass
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
gc.collect() # For PyPy or other GCs.
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 threading_helper.wait_threads_exit():
# Thread blocked on lock.acquire()
start_new_thread(f, ())
self.wait_phase(phase, 1)
# Thread unblocked
lock.release()
self.wait_phase(phase, 2)
def test_different_thread(self):
# Lock can be released from a different thread.
lock = self.locktype()
lock.acquire()
def f():
lock.release()
with Bunch(f, 1):
pass
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))
@requires_fork
def test_at_fork_reinit(self):
def use_lock(lock):
# make sure that the lock still works normally
# after _at_fork_reinit()
lock.acquire()
lock.release()
# unlocked
lock = self.locktype()
lock._at_fork_reinit()
use_lock(lock)
# locked: _at_fork_reinit() resets the lock to the unlocked state
lock2 = self.locktype()
lock2.acquire()
lock2._at_fork_reinit()
use_lock(lock2)
class RLockTests(BaseLockTests):
"""
Tests for recursive locks.
"""
def test_repr_count(self):
# see gh-134322: check that count values are correct:
# when a rlock is just created,
# in a second thread when rlock is acquired in the main thread.
lock = self.locktype()
self.assertIn("count=0", repr(lock))
self.assertIn("<unlocked", repr(lock))
lock.acquire()
lock.acquire()
self.assertIn("count=2", repr(lock))
self.assertIn("<locked", repr(lock))
result = []
def call_repr():
result.append(repr(lock))
with Bunch(call_repr, 1):
pass
self.assertIn("count=2", result[0])
self.assertIn("<locked", result[0])
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_locked(self):
lock = self.locktype()
self.assertFalse(lock.locked())
lock.acquire()
self.assertTrue(lock.locked())
lock.acquire()
self.assertTrue(lock.locked())
lock.release()
self.assertTrue(lock.locked())
lock.release()
self.assertFalse(lock.locked())
def test_locked_with_2threads(self):
# see gh-134323: check that a rlock which
# is acquired in a different thread,
# is still locked in the main thread.
result = []
rlock = self.locktype()
self.assertFalse(rlock.locked())
def acquire():
result.append(rlock.locked())
rlock.acquire()
result.append(rlock.locked())
with Bunch(acquire, 1):
pass
self.assertTrue(rlock.locked())
self.assertFalse(result[0])
self.assertTrue(result[1])
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_recursion_count(self):
lock = self.locktype()
self.assertEqual(0, lock._recursion_count())
lock.acquire()
self.assertEqual(1, lock._recursion_count())
lock.acquire()
lock.acquire()
self.assertEqual(3, lock._recursion_count())
lock.release()
self.assertEqual(2, lock._recursion_count())
lock.release()
lock.release()
self.assertEqual(0, lock._recursion_count())
phase = []
def f():
lock.acquire()
phase.append(None)
self.wait_phase(phase, 2)
lock.release()
phase.append(None)
with threading_helper.wait_threads_exit():
# Thread blocked on lock.acquire()
start_new_thread(f, ())
self.wait_phase(phase, 1)
self.assertEqual(0, lock._recursion_count())
# Thread unblocked
phase.append(None)
self.wait_phase(phase, 3)
self.assertEqual(0, lock._recursion_count())
def test_different_thread(self):
# Cannot release from a different thread
lock = self.locktype()
def f():
lock.acquire()
with Bunch(f, 1, True) as bunch:
try:
self.assertRaises(RuntimeError, lock.release)
finally:
bunch.do_finish()
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())
with Bunch(f, 1):
pass
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())
with Bunch(f, N):
# Threads blocked on first evt.wait()
wait_threads_blocked(N)
self.assertEqual(len(results1), 0)
# Threads unblocked
evt.set()
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.monotonic()
r = evt.wait(0.5)
t2 = time.monotonic()
results2.append((r, t2 - t1))
with Bunch(f, N):
pass
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()
with Bunch(f, N):
pass
self.assertEqual(results1, [True] * N)
for r, dt in results2:
self.assertTrue(r)
def test_set_and_clear(self):
# gh-57711: check that wait() returns true even when the event is
# cleared before the waiting thread is woken up.
event = self.eventtype()
results = []
def f():
results.append(event.wait(support.LONG_TIMEOUT))
N = 5
with Bunch(f, N):
# Threads blocked on event.wait()
wait_threads_blocked(N)
# Threads unblocked
event.set()
event.clear()
self.assertEqual(results, [True] * N)
@requires_fork
def test_at_fork_reinit(self):
# ensure that condition is still using a Lock after reset
evt = self.eventtype()
with evt._cond:
self.assertFalse(evt._cond.acquire(False))
evt._at_fork_reinit()
with evt._cond:
self.assertFalse(evt._cond.acquire(False))
def test_repr(self):
evt = self.eventtype()
self.assertRegex(repr(evt), r"<\w+\.Event at .*: unset>")
evt.set()
self.assertRegex(repr(evt), r"<\w+\.Event at .*: set>")
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_threads_blocked() 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 Variables 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.
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))
N = 5
with Bunch(f, N):
# first wait, to ensure all workers settle into cond.wait() before
# we continue. See issues #8799 and #30727.
for _ in support.sleeping_retry(support.SHORT_TIMEOUT):
if len(ready) >= N:
break
ready.clear()
self.assertEqual(results1, [])
# Notify 3 threads at first
count1 = 3
cond.acquire()
cond.notify(count1)
wait_threads_blocked(count1)
# Phase 1
phase_num = 1
cond.release()
for _ in support.sleeping_retry(support.SHORT_TIMEOUT):
if len(results1) >= count1:
break
self.assertEqual(results1, [(True, 1)] * count1)
self.assertEqual(results2, [])
# Wait until awaken workers are blocked on cond.wait()
for _ in support.sleeping_retry(support.SHORT_TIMEOUT):
if len(ready) >= count1 :
break
# Notify 5 threads: they might be in their first or second wait
cond.acquire()
cond.notify(5)
wait_threads_blocked(N)
# Phase 2
phase_num = 2
cond.release()
for _ in support.sleeping_retry(support.SHORT_TIMEOUT):
if len(results1) + len(results2) >= (N + count1):
break
count2 = N - count1
self.assertEqual(results1, [(True, 1)] * count1 + [(True, 2)] * count2)
self.assertEqual(results2, [(True, 2)] * count1)
# Make sure all workers settle into cond.wait()
for _ in support.sleeping_retry(support.SHORT_TIMEOUT):
if len(ready) >= N:
break
# Notify all threads: they are all in their second wait
cond.acquire()
cond.notify_all()
wait_threads_blocked(N)
# Phase 3
phase_num = 3
cond.release()
for _ in support.sleeping_retry(support.SHORT_TIMEOUT):
if len(results2) >= N:
break
self.assertEqual(results1, [(True, 1)] * count1 + [(True, 2)] * count2)
self.assertEqual(results2, [(True, 2)] * count1 + [(True, 3)] * count2)
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()
timeout = 0.5
results = []
def f():
cond.acquire()
t1 = time.monotonic()
result = cond.wait(timeout)
t2 = time.monotonic()
cond.release()
results.append((t2 - t1, result))
N = 5
with Bunch(f, N):
pass
self.assertEqual(len(results), N)
for dt, result in results:
self.assertTimeout(dt, timeout)
# 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)
with Bunch(f, 1):
for i in range(4):
time.sleep(0.010)
with cond:
state += 1
cond.notify()
def test_waitfor_timeout(self):
cond = self.condtype()
state = 0
success = []
def f():
with cond:
dt = time.monotonic()
result = cond.wait_for(lambda : state==4, timeout=0.1)
dt = time.monotonic() - dt
self.assertFalse(result)
self.assertTimeout(dt, 0.1)
success.append(None)
with Bunch(f, 1):
# Only increment 3 times, so state == 4 is never reached.
for i in range(3):
time.sleep(0.010)
with cond:
state += 1
cond.notify()
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_value = 7
sem = self.semtype(sem_value)
sem.acquire()
sem_results = []
results1 = []
results2 = []
phase_num = 0
def func():
sem_results.append(sem.acquire())
results1.append(phase_num)
sem_results.append(sem.acquire())
results2.append(phase_num)
def wait_count(count):
for _ in support.sleeping_retry(support.SHORT_TIMEOUT):
if len(results1) + len(results2) >= count:
break
N = 10
with Bunch(func, N):
# Phase 0
count1 = sem_value - 1
wait_count(count1)
self.assertEqual(results1 + results2, [0] * count1)
# Phase 1
phase_num = 1
for i in range(sem_value):
sem.release()
count2 = sem_value
wait_count(count1 + count2)
self.assertEqual(sorted(results1 + results2),
[0] * count1 + [1] * count2)
# Phase 2
phase_num = 2
count3 = (sem_value - 1)
for i in range(count3):
sem.release()
wait_count(count1 + count2 + count3)
self.assertEqual(sorted(results1 + results2),
[0] * count1 + [1] * count2 + [2] * count3)
# The semaphore is still locked
self.assertFalse(sem.acquire(False))
# Final release, to let the last thread finish
count4 = 1
sem.release()
self.assertEqual(sem_results,
[True] * (count1 + count2 + count3 + count4))
def test_multirelease(self):
sem_value = 7
sem = self.semtype(sem_value)
sem.acquire()
results1 = []
results2 = []
phase_num = 0
def func():
sem.acquire()
results1.append(phase_num)
sem.acquire()
results2.append(phase_num)
def wait_count(count):
for _ in support.sleeping_retry(support.SHORT_TIMEOUT):
if len(results1) + len(results2) >= count:
break
with Bunch(func, 10):
# Phase 0
count1 = sem_value - 1
wait_count(count1)
self.assertEqual(results1 + results2, [0] * count1)
# Phase 1
phase_num = 1
count2 = sem_value
sem.release(count2)
wait_count(count1 + count2)
self.assertEqual(sorted(results1 + results2),
[0] * count1 + [1] * count2)
# Phase 2
phase_num = 2
count3 = sem_value - 1
sem.release(count3)
wait_count(count1 + count2 + count3)
self.assertEqual(sorted(results1 + results2),
[0] * count1 + [1] * count2 + [2] * count3)
# The semaphore is still locked
self.assertFalse(sem.acquire(False))
# Final release, to let the last thread finish
sem.release()
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))
with Bunch(f, 5):
pass
# 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.monotonic()
self.assertFalse(sem.acquire(timeout=0.5))
dt = time.monotonic() - 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()
with Bunch(f, 1) as bunch:
# Thread blocked on sem.acquire()
wait_threads_blocked(1)
self.assertFalse(bunch.finished)
# Thread unblocked
sem.release()
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.