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gh-109974: Fix threading lock_tests race conditions (#110057)

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Fix race conditions in test_threading lock tests. Wait until a
condition is met rather than using time.sleep() with a hardcoded
number of seconds.

* Replace sleeping loops with support.sleeping_retry() which raises
  an exception on timeout.
* Add wait_threads_blocked(nthread) which computes a sleep depending
  on the number of threads. Remove _wait() function.
* test_set_and_clear(): use a way longer Event.wait() timeout.
* BarrierTests.test_repr(): wait until the 2 threads are waiting for
  the barrier. Use a way longer timeout for Barrier.wait() timeout.
* test_thread_leak() no longer needs to count
  len(threading.enumerate()): Bunch uses
  threading_helper.wait_threads_exit() internally which does it in
  wait_for_finished().
* Add BaseLockTests.wait_phase() which implements a timeout.
  test_reacquire() and test_recursion_count() use wait_phase().
This commit is contained in:
Victor Stinner 2023-09-29 02:34:27 +02:00 committed by GitHub
parent 5fdcea7440
commit 4e356ad183
No known key found for this signature in database
GPG Key ID: 4AEE18F83AFDEB23
2 changed files with 226 additions and 124 deletions
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347
Lib/test/lock_tests.py
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@ -19,22 +19,24 @@ requires_fork = unittest.skipUnless(support.has_fork_support,
"(no _at_fork_reinit method)") "(no _at_fork_reinit method)")
def _wait(): def wait_threads_blocked(nthread):
# A crude wait/yield function not relying on synchronization primitives. # Arbitrary sleep to wait until N threads are blocked,
time.sleep(0.01) # like waiting for a lock.
time.sleep(0.010 * nthread)
class Bunch(object): class Bunch(object):
""" """
A bunch of threads. A bunch of threads.
""" """
def __init__(self, f, n, wait_before_exit=False): def __init__(self, func, nthread, wait_before_exit=False):
""" """
Construct a bunch of `n` threads running the same function `f`. Construct a bunch of `nthread` threads running the same function `func`.
If `wait_before_exit` is True, the threads won't terminate until If `wait_before_exit` is True, the threads won't terminate until
do_finish() is called. do_finish() is called.
""" """
self.f = f self.func = func
self.n = n self.nthread = nthread
self.started = [] self.started = []
self.finished = [] self.finished = []
self._can_exit = not wait_before_exit self._can_exit = not wait_before_exit
@ -45,26 +47,30 @@ class Bunch(object):
tid = threading.get_ident() tid = threading.get_ident()
self.started.append(tid) self.started.append(tid)
try: try:
f() func()
finally: finally:
self.finished.append(tid) self.finished.append(tid)
while not self._can_exit: for _ in support.sleeping_retry(support.SHORT_TIMEOUT):
_wait() if self._can_exit:
break
try: try:
for i in range(n): for i in range(nthread):
start_new_thread(task, ()) start_new_thread(task, ())
except: except:
self._can_exit = True self._can_exit = True
raise raise
def wait_for_started(self): def wait_for_started(self):
while len(self.started) < self.n: for _ in support.sleeping_retry(support.SHORT_TIMEOUT):
_wait() if len(self.started) >= self.nthread:
break
def wait_for_finished(self): def wait_for_finished(self):
while len(self.finished) < self.n: for _ in support.sleeping_retry(support.SHORT_TIMEOUT):
_wait() if len(self.finished) >= self.nthread:
break
# Wait for threads exit # Wait for threads exit
self.wait_thread.__exit__(None, None, None) self.wait_thread.__exit__(None, None, None)
@ -94,6 +100,12 @@ class BaseLockTests(BaseTestCase):
Tests for both recursive and non-recursive locks. 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): def test_constructor(self):
lock = self.locktype() lock = self.locktype()
del lock del lock
@ -138,15 +150,18 @@ class BaseLockTests(BaseTestCase):
def test_acquire_contended(self): def test_acquire_contended(self):
lock = self.locktype() lock = self.locktype()
lock.acquire() lock.acquire()
N = 5
def f(): def f():
lock.acquire() lock.acquire()
lock.release() lock.release()
# Threads block on lock.acquire()
N = 5
b = Bunch(f, N) b = Bunch(f, N)
b.wait_for_started() b.wait_for_started()
_wait() wait_threads_blocked(N)
self.assertEqual(len(b.finished), 0) self.assertEqual(len(b.finished), 0)
# Threads unblocked
lock.release() lock.release()
b.wait_for_finished() b.wait_for_finished()
self.assertEqual(len(b.finished), N) self.assertEqual(len(b.finished), N)
@ -174,17 +189,10 @@ class BaseLockTests(BaseTestCase):
def f(): def f():
lock.acquire() lock.acquire()
lock.release() lock.release()
n = len(threading.enumerate())
# We run many threads in the hope that existing threads ids won't # We run many threads in the hope that existing threads ids won't
# be recycled. # be recycled.
Bunch(f, 15).wait_for_finished() 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): def test_timeout(self):
lock = self.locktype() lock = self.locktype()
@ -242,15 +250,13 @@ class LockTests(BaseLockTests):
phase.append(None) phase.append(None)
with threading_helper.wait_threads_exit(): with threading_helper.wait_threads_exit():
# Thread blocked on lock.acquire()
start_new_thread(f, ()) start_new_thread(f, ())
while len(phase) == 0: self.wait_phase(phase, 1)
_wait()
_wait() # Thread unblocked
self.assertEqual(len(phase), 1)
lock.release() lock.release()
while len(phase) == 1: self.wait_phase(phase, 2)
_wait()
self.assertEqual(len(phase), 2)
def test_different_thread(self): def test_different_thread(self):
# Lock can be released from a different thread. # Lock can be released from a different thread.
@ -349,21 +355,20 @@ class RLockTests(BaseLockTests):
def f(): def f():
lock.acquire() lock.acquire()
phase.append(None) phase.append(None)
while len(phase) == 1:
_wait() self.wait_phase(phase, 2)
lock.release() lock.release()
phase.append(None) phase.append(None)
with threading_helper.wait_threads_exit(): with threading_helper.wait_threads_exit():
# Thread blocked on lock.acquire()
start_new_thread(f, ()) start_new_thread(f, ())
while len(phase) == 0: self.wait_phase(phase, 1)
_wait()
self.assertEqual(len(phase), 1)
self.assertEqual(0, lock._recursion_count()) self.assertEqual(0, lock._recursion_count())
# Thread unblocked
phase.append(None) phase.append(None)
while len(phase) == 2: self.wait_phase(phase, 3)
_wait()
self.assertEqual(len(phase), 3)
self.assertEqual(0, lock._recursion_count()) self.assertEqual(0, lock._recursion_count())
def test_different_thread(self): def test_different_thread(self):
@ -421,10 +426,14 @@ class EventTests(BaseTestCase):
def f(): def f():
results1.append(evt.wait()) results1.append(evt.wait())
results2.append(evt.wait()) results2.append(evt.wait())
# Threads blocked on first evt.wait()
b = Bunch(f, N) b = Bunch(f, N)
b.wait_for_started() b.wait_for_started()
_wait() wait_threads_blocked(N)
self.assertEqual(len(results1), 0) self.assertEqual(len(results1), 0)
# Threads unblocked
evt.set() evt.set()
b.wait_for_finished() b.wait_for_finished()
self.assertEqual(results1, [True] * N) self.assertEqual(results1, [True] * N)
@ -464,19 +473,22 @@ class EventTests(BaseTestCase):
self.assertTrue(r) self.assertTrue(r)
def test_set_and_clear(self): def test_set_and_clear(self):
# Issue #13502: check that wait() returns true even when the event is # gh-57711: check that wait() returns true even when the event is
# cleared before the waiting thread is woken up. # cleared before the waiting thread is woken up.
evt = self.eventtype() event = self.eventtype()
results = [] results = []
timeout = 0.250
N = 5
def f(): def f():
results.append(evt.wait(timeout * 4)) results.append(event.wait(support.LONG_TIMEOUT))
# Threads blocked on event.wait()
N = 5
b = Bunch(f, N) b = Bunch(f, N)
b.wait_for_started() b.wait_for_started()
time.sleep(timeout) wait_threads_blocked(N)
evt.set()
evt.clear() # Threads unblocked
event.set()
event.clear()
b.wait_for_finished() b.wait_for_finished()
self.assertEqual(results, [True] * N) self.assertEqual(results, [True] * N)
@ -533,15 +545,14 @@ class ConditionTests(BaseTestCase):
# Note that this test is sensitive to timing. If the worker threads # 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 # don't execute in a timely fashion, the main thread may think they
# are further along then they are. The main thread therefore issues # are further along then they are. The main thread therefore issues
# _wait() statements to try to make sure that it doesn't race ahead # wait_threads_blocked() statements to try to make sure that it doesn't
# of the workers. # race ahead of the workers.
# Secondly, this test assumes that condition variables are not subject # Secondly, this test assumes that condition variables are not subject
# to spurious wakeups. The absence of spurious wakeups is an implementation # to spurious wakeups. The absence of spurious wakeups is an implementation
# detail of Condition Variables in current CPython, but in general, not # detail of Condition Variables in current CPython, but in general, not
# a guaranteed property of condition variables as a programming # a guaranteed property of condition variables as a programming
# construct. In particular, it is possible that this can no longer # construct. In particular, it is possible that this can no longer
# be conveniently guaranteed should their implementation ever change. # be conveniently guaranteed should their implementation ever change.
N = 5
ready = [] ready = []
results1 = [] results1 = []
results2 = [] results2 = []
@ -550,57 +561,84 @@ class ConditionTests(BaseTestCase):
cond.acquire() cond.acquire()
ready.append(phase_num) ready.append(phase_num)
result = cond.wait() result = cond.wait()
cond.release() cond.release()
results1.append((result, phase_num)) results1.append((result, phase_num))
cond.acquire() cond.acquire()
ready.append(phase_num) ready.append(phase_num)
result = cond.wait() result = cond.wait()
cond.release() cond.release()
results2.append((result, phase_num)) results2.append((result, phase_num))
N = 5
b = Bunch(f, N) b = Bunch(f, N)
b.wait_for_started() b.wait_for_started()
# first wait, to ensure all workers settle into cond.wait() before # first wait, to ensure all workers settle into cond.wait() before
# we continue. See issues #8799 and #30727. # we continue. See issues #8799 and #30727.
while len(ready) < 5: for _ in support.sleeping_retry(support.SHORT_TIMEOUT):
_wait() if len(ready) >= N:
break
ready.clear() ready.clear()
self.assertEqual(results1, []) self.assertEqual(results1, [])
# Notify 3 threads at first # Notify 3 threads at first
count1 = 3
cond.acquire() cond.acquire()
cond.notify(3) cond.notify(count1)
_wait() wait_threads_blocked(count1)
# Phase 1
phase_num = 1 phase_num = 1
cond.release() cond.release()
while len(results1) < 3: for _ in support.sleeping_retry(support.SHORT_TIMEOUT):
_wait() if len(results1) >= count1:
self.assertEqual(results1, [(True, 1)] * 3) break
self.assertEqual(results1, [(True, 1)] * count1)
self.assertEqual(results2, []) self.assertEqual(results2, [])
# make sure all awaken workers settle into cond.wait()
while len(ready) < 3: # Wait until awaken workers are blocked on cond.wait()
_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 # Notify 5 threads: they might be in their first or second wait
cond.acquire() cond.acquire()
cond.notify(5) cond.notify(5)
_wait() wait_threads_blocked(N)
# Phase 2
phase_num = 2 phase_num = 2
cond.release() cond.release()
while len(results1) + len(results2) < 8: for _ in support.sleeping_retry(support.SHORT_TIMEOUT):
_wait() if len(results1) + len(results2) >= (N + count1):
self.assertEqual(results1, [(True, 1)] * 3 + [(True, 2)] * 2) break
self.assertEqual(results2, [(True, 2)] * 3)
# make sure all workers settle into cond.wait() count2 = N - count1
while len(ready) < 5: self.assertEqual(results1, [(True, 1)] * count1 + [(True, 2)] * count2)
_wait() 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 # Notify all threads: they are all in their second wait
cond.acquire() cond.acquire()
cond.notify_all() cond.notify_all()
_wait() wait_threads_blocked(N)
# Phase 3
phase_num = 3 phase_num = 3
cond.release() cond.release()
while len(results2) < 5: for _ in support.sleeping_retry(support.SHORT_TIMEOUT):
_wait() if len(results2) >= N:
self.assertEqual(results1, [(True, 1)] * 3 + [(True,2)] * 2) break
self.assertEqual(results2, [(True, 2)] * 3 + [(True, 3)] * 2) self.assertEqual(results1, [(True, 1)] * count1 + [(True, 2)] * count2)
self.assertEqual(results2, [(True, 2)] * count1 + [(True, 3)] * count2)
b.wait_for_finished() b.wait_for_finished()
def test_notify(self): def test_notify(self):
@ -611,19 +649,22 @@ class ConditionTests(BaseTestCase):
def test_timeout(self): def test_timeout(self):
cond = self.condtype() cond = self.condtype()
timeout = 0.5
results = [] results = []
N = 5
def f(): def f():
cond.acquire() cond.acquire()
t1 = time.monotonic() t1 = time.monotonic()
result = cond.wait(0.5) result = cond.wait(timeout)
t2 = time.monotonic() t2 = time.monotonic()
cond.release() cond.release()
results.append((t2 - t1, result)) results.append((t2 - t1, result))
N = 5
Bunch(f, N).wait_for_finished() Bunch(f, N).wait_for_finished()
self.assertEqual(len(results), N) self.assertEqual(len(results), N)
for dt, result in results: for dt, result in results:
self.assertTimeout(dt, 0.5) self.assertTimeout(dt, timeout)
# Note that conceptually (that"s the condition variable protocol) # Note that conceptually (that"s the condition variable protocol)
# a wait() may succeed even if no one notifies us and before any # a wait() may succeed even if no one notifies us and before any
# timeout occurs. Spurious wakeups can occur. # timeout occurs. Spurious wakeups can occur.
@ -636,13 +677,13 @@ class ConditionTests(BaseTestCase):
state = 0 state = 0
def f(): def f():
with cond: with cond:
result = cond.wait_for(lambda : state==4) result = cond.wait_for(lambda: state == 4)
self.assertTrue(result) self.assertTrue(result)
self.assertEqual(state, 4) self.assertEqual(state, 4)
b = Bunch(f, 1) b = Bunch(f, 1)
b.wait_for_started() b.wait_for_started()
for i in range(4): for i in range(4):
time.sleep(0.01) time.sleep(0.010)
with cond: with cond:
state += 1 state += 1
cond.notify() cond.notify()
@ -660,14 +701,16 @@ class ConditionTests(BaseTestCase):
self.assertFalse(result) self.assertFalse(result)
self.assertTimeout(dt, 0.1) self.assertTimeout(dt, 0.1)
success.append(None) success.append(None)
b = Bunch(f, 1) b = Bunch(f, 1)
b.wait_for_started() b.wait_for_started()
# Only increment 3 times, so state == 4 is never reached. # Only increment 3 times, so state == 4 is never reached.
for i in range(3): for i in range(3):
time.sleep(0.01) time.sleep(0.010)
with cond: with cond:
state += 1 state += 1
cond.notify() cond.notify()
b.wait_for_finished() b.wait_for_finished()
self.assertEqual(len(success), 1) self.assertEqual(len(success), 1)
@ -697,70 +740,107 @@ class BaseSemaphoreTests(BaseTestCase):
del sem del sem
def test_acquire_contended(self): def test_acquire_contended(self):
sem = self.semtype(7) sem_value = 7
sem = self.semtype(sem_value)
sem.acquire() sem.acquire()
N = 10
sem_results = [] sem_results = []
results1 = [] results1 = []
results2 = [] results2 = []
phase_num = 0 phase_num = 0
def f():
def func():
sem_results.append(sem.acquire()) sem_results.append(sem.acquire())
results1.append(phase_num) results1.append(phase_num)
sem_results.append(sem.acquire()) sem_results.append(sem.acquire())
results2.append(phase_num) results2.append(phase_num)
b = Bunch(f, 10)
def wait_count(count):
for _ in support.sleeping_retry(support.SHORT_TIMEOUT):
if len(results1) + len(results2) >= count:
break
# Phase 0
N = 10
b = Bunch(func, N)
b.wait_for_started() b.wait_for_started()
while len(results1) + len(results2) < 6: count1 = sem_value - 1
_wait() wait_count(count1)
self.assertEqual(results1 + results2, [0] * 6) self.assertEqual(results1 + results2, [0] * count1)
# Phase 1
phase_num = 1 phase_num = 1
for i in range(7): for i in range(sem_value):
sem.release() sem.release()
while len(results1) + len(results2) < 13: count2 = sem_value
_wait() wait_count(count1 + count2)
self.assertEqual(sorted(results1 + results2), [0] * 6 + [1] * 7) self.assertEqual(sorted(results1 + results2),
[0] * count1 + [1] * count2)
# Phase 2
phase_num = 2 phase_num = 2
for i in range(6): count3 = (sem_value - 1)
for i in range(count3):
sem.release() sem.release()
while len(results1) + len(results2) < 19: wait_count(count1 + count2 + count3)
_wait() self.assertEqual(sorted(results1 + results2),
self.assertEqual(sorted(results1 + results2), [0] * 6 + [1] * 7 + [2] * 6) [0] * count1 + [1] * count2 + [2] * count3)
# The semaphore is still locked # The semaphore is still locked
self.assertFalse(sem.acquire(False)) self.assertFalse(sem.acquire(False))
# Final release, to let the last thread finish # Final release, to let the last thread finish
count4 = 1
sem.release() sem.release()
b.wait_for_finished() b.wait_for_finished()
self.assertEqual(sem_results, [True] * (6 + 7 + 6 + 1)) self.assertEqual(sem_results,
[True] * (count1 + count2 + count3 + count4))
def test_multirelease(self): def test_multirelease(self):
sem = self.semtype(7) sem_value = 7
sem = self.semtype(sem_value)
sem.acquire() sem.acquire()
results1 = [] results1 = []
results2 = [] results2 = []
phase_num = 0 phase_num = 0
def f(): def func():
sem.acquire() sem.acquire()
results1.append(phase_num) results1.append(phase_num)
sem.acquire() sem.acquire()
results2.append(phase_num) results2.append(phase_num)
b = Bunch(f, 10)
def wait_count(count):
for _ in support.sleeping_retry(support.SHORT_TIMEOUT):
if len(results1) + len(results2) >= count:
break
# Phase 0
b = Bunch(func, 10)
b.wait_for_started() b.wait_for_started()
while len(results1) + len(results2) < 6: count1 = sem_value - 1
_wait() wait_count(count1)
self.assertEqual(results1 + results2, [0] * 6) self.assertEqual(results1 + results2, [0] * count1)
# Phase 1
phase_num = 1 phase_num = 1
sem.release(7) count2 = sem_value
while len(results1) + len(results2) < 13: sem.release(count2)
_wait() wait_count(count1 + count2)
self.assertEqual(sorted(results1 + results2), [0] * 6 + [1] * 7) self.assertEqual(sorted(results1 + results2),
[0] * count1 + [1] * count2)
# Phase 2
phase_num = 2 phase_num = 2
sem.release(6) count3 = sem_value - 1
while len(results1) + len(results2) < 19: sem.release(count3)
_wait() wait_count(count1 + count2 + count3)
self.assertEqual(sorted(results1 + results2), [0] * 6 + [1] * 7 + [2] * 6) self.assertEqual(sorted(results1 + results2),
[0] * count1 + [1] * count2 + [2] * count3)
# The semaphore is still locked # The semaphore is still locked
self.assertFalse(sem.acquire(False)) self.assertFalse(sem.acquire(False))
# Final release, to let the last thread finish # Final release, to let the last thread finish
sem.release() sem.release()
b.wait_for_finished() b.wait_for_finished()
@ -806,10 +886,14 @@ class BaseSemaphoreTests(BaseTestCase):
def f(): def f():
sem.acquire() sem.acquire()
sem.release() sem.release()
# Thread blocked on sem.acquire()
b = Bunch(f, 1) b = Bunch(f, 1)
b.wait_for_started() b.wait_for_started()
_wait() wait_threads_blocked(1)
self.assertFalse(b.finished) self.assertFalse(b.finished)
# Thread unblocked
sem.release() sem.release()
b.wait_for_finished() b.wait_for_finished()
@ -882,6 +966,7 @@ class BarrierTests(BaseTestCase):
def setUp(self): def setUp(self):
self.barrier = self.barriertype(self.N, timeout=self.defaultTimeout) self.barrier = self.barriertype(self.N, timeout=self.defaultTimeout)
def tearDown(self): def tearDown(self):
self.barrier.abort() self.barrier.abort()
@ -979,8 +1064,9 @@ class BarrierTests(BaseTestCase):
i = self.barrier.wait() i = self.barrier.wait()
if i == self.N//2: if i == self.N//2:
# Wait until the other threads are all in the barrier. # Wait until the other threads are all in the barrier.
while self.barrier.n_waiting < self.N-1: for _ in support.sleeping_retry(support.SHORT_TIMEOUT):
time.sleep(0.001) if self.barrier.n_waiting >= (self.N - 1):
break
self.barrier.reset() self.barrier.reset()
else: else:
try: try:
@ -1068,16 +1154,29 @@ class BarrierTests(BaseTestCase):
b.wait() b.wait()
def test_repr(self): def test_repr(self):
b = self.barriertype(3) barrier = self.barriertype(3)
self.assertRegex(repr(b), r"<\w+\.Barrier at .*: waiters=0/3>") timeout = support.LONG_TIMEOUT
self.assertRegex(repr(barrier), r"<\w+\.Barrier at .*: waiters=0/3>")
def f(): def f():
b.wait(3) barrier.wait(timeout)
bunch = Bunch(f, 2)
# Threads blocked on barrier.wait()
N = 2
bunch = Bunch(f, N)
bunch.wait_for_started() bunch.wait_for_started()
time.sleep(0.2) for _ in support.sleeping_retry(support.SHORT_TIMEOUT):
self.assertRegex(repr(b), r"<\w+\.Barrier at .*: waiters=2/3>") if barrier.n_waiting >= N:
b.wait(3) break
self.assertRegex(repr(barrier),
r"<\w+\.Barrier at .*: waiters=2/3>")
# Threads unblocked
barrier.wait(timeout)
bunch.wait_for_finished() bunch.wait_for_finished()
self.assertRegex(repr(b), r"<\w+\.Barrier at .*: waiters=0/3>") self.assertRegex(repr(barrier),
b.abort() r"<\w+\.Barrier at .*: waiters=0/3>")
self.assertRegex(repr(b), r"<\w+\.Barrier at .*: broken>")
# Abort the barrier
barrier.abort()
self.assertRegex(repr(barrier),
r"<\w+\.Barrier at .*: broken>")

3
Misc/NEWS.d/next/Tests/2023-09-29-00-19-21.gh-issue-109974.Sh_g-r.rst Normal file
View File

@ -0,0 +1,3 @@
Fix race conditions in test_threading lock tests. Wait until a condition is met
rather than using :func:`time.sleep` with a hardcoded number of seconds. Patch
by Victor Stinner.