def test_demotion_no_waiters(self):
lock = RWLock()
try:
with lock.exclusive:
lock.acquireRead()
finally:
lock.release()
def test_wakeup_all_blocked_readers(self):
lock = RWLock()
readers = 10
ready = Barrier(readers + 1)
done = Barrier(readers + 1)
threads = []
def slow_reader():
ready.wait(2)
with lock.shared:
time.sleep(0.5)
done.wait(2)
try:
with lock.exclusive:
# Start all readers
for i in range(readers):
t = start_thread(slow_reader)
threads.append(t)
# Wait until all readers are ready
ready.wait(0.5)
# Ensure that all readers are blocked
time.sleep(0.5)
# Releasing the write lock should wake up all the readers, holding
# the lock for about 0.5 seconds.
with self.assertNotRaises():
done.wait(2)
finally:
for t in threads:
t.join()
def test_fifo(self):
lock = RWLock()
threads = []
try:
with lock.shared:
writer = LockingThread(lock.exclusive)
writer.start()
threads.append(writer)
if not writer.ready.wait(2):
raise RuntimeError("Timeout waiting for writer thread")
# Writer must block
self.assertFalse(writer.acquired.wait(1))
reader = LockingThread(lock.shared)
reader.start()
threads.append(reader)
if not reader.ready.wait(1):
raise RuntimeError("Timeout waiting for reader thread")
# Reader must block
self.assertFalse(reader.acquired.wait(1))
# Writer should get in before the reader
self.assertTrue(writer.acquired.wait(1))
writer.done.set()
self.assertTrue(reader.acquired.wait(1))
finally:
for t in threads:
t.stop()
def test_release_other_thread_write_lock(self):
lock = RWLock()
writer = LockingThread(lock.exclusive)
with utils.running(writer):
if not writer.acquired.wait(2):
raise RuntimeError("Timeout waiting for writer thread")
self.assertRaises(RuntimeError, lock.release)
def test_release_other_thread_read_lock(self):
lock = RWLock()
reader = LockingThread(lock.shared)
with utils.running(reader):
if not reader.acquired.wait(2):
raise RuntimeError("Timeout waiting for reader thread")
self.assertRaises(RuntimeError, lock.release)
def test_demotion_with_blocked_reader(self):
lock = RWLock()
reader = LockingThread(lock.shared)
try:
with lock.exclusive:
reader.start()
reader.ready.wait()
# Ensure that reader is blocked
if reader.acquired.wait(0.5):
raise RuntimeError("Reader could acquire the lock while "
"holding a write lock")
lock.acquireRead()
# I hold both a read lock and a write lock now
# I released the write lock. Having read lock, reader should get
# the lock.
self.assertTrue(reader.acquired.wait(0.5),
"Reader could not acuire the lock")
finally:
lock.release()
reader.stop()
def test_exclusive_context_blocks_reader(self):
lock = RWLock()
reader = LockingThread(lock.shared)
try:
with lock.exclusive:
reader.start()
if not reader.ready.wait(2):
raise RuntimeError("Timeout waiting for reader thread")
# Reader must block
self.assertFalse(reader.acquired.wait(1))
finally:
reader.stop()
def test_shared_context_blocks_writer(self):
lock = RWLock()
writer = LockingThread(lock.exclusive)
try:
with lock.shared:
writer.start()
if not writer.ready.wait(2):
raise RuntimeError("Timeout waiting for writer thread")
# Writer must block
self.assertFalse(writer.acquired.wait(1))
finally:
writer.stop()
def test_demotion_with_blocked_writer(self):
lock = RWLock()
writer = LockingThread(lock.exclusive)
try:
with lock.exclusive:
writer.start()
writer.ready.wait()
# Ensure that writer is blocked
if writer.acquired.wait(0.5):
raise RuntimeError("Writer could acquire the lock while "
"holding a write lock")
lock.acquireRead()
# I hold both a read lock and a write lock now
# I release the write lock. Having read lock, writer must block
self.assertFalse(
writer.acquired.wait(0.5),
"Writer acquired the lock while holding a read "
"lock")
finally:
lock.release()
try:
# Writer must acquire now
self.assertTrue(writer.acquired.wait(0.5))
finally:
writer.stop()
def test_demotion_no_waiters(self):
lock = RWLock()
try:
with lock.exclusive:
lock.acquireRead()
finally:
lock.release()
def test_concurrent_readers(self):
lock = RWLock()
readers = []
try:
for i in range(5):
t = LockingThread(lock.shared)
t.start()
readers.append(t)
for t in readers:
self.assertTrue(t.acquired.wait(1))
finally:
for t in readers:
t.stop()
def test_wakeup_blocked_reader(self):
lock = RWLock()
writer = LockingThread(lock.exclusive)
with utils.running(writer):
if not writer.acquired.wait(2):
raise RuntimeError("Timeout waiting for writer thread")
reader = LockingThread(lock.shared)
with utils.running(reader):
if not reader.ready.wait(2):
raise RuntimeError("Timeout waiting for reader thread")
self.assertFalse(reader.acquired.wait(1))
writer.done.set()
self.assertTrue(reader.acquired.wait(2))
def test_fairness(self, writers, readers):
lock = RWLock()
ready = Barrier(writers + readers + 1)
done = threading.Event()
reads = [0] * readers
writes = [0] * writers
threads = []
def read(slot):
ready.wait()
while not done.is_set():
with lock.shared:
reads[slot] += 1
def write(slot):
ready.wait()
while not done.is_set():
with lock.exclusive:
writes[slot] += 1
try:
for i in range(readers):
t = start_thread(read, i)
threads.append(t)
for i in range(writers):
t = start_thread(write, i)
threads.append(t)
ready.wait(5)
time.sleep(1)
finally:
done.set()
for t in threads:
t.join()
print()
# TODO: needed to work around bug in expandPermutations when using
# decorated test methods.
print("writers: %d readers: %d" % (writers, readers))
avg_writes, med_writes, min_writes, max_writes = stats(writes)
print("writes avg=%.2f med=%d min=%d max=%d" %
(avg_writes, med_writes, min_writes, max_writes))
avg_reads, med_reads, min_reads, max_reads = stats(reads)
print("reads avg=%.2f med=%d min=%d max=%d" %
(avg_reads, med_reads, min_reads, max_reads))
avg_all = stats(writes + reads)[0]
self.assertAlmostEqual(avg_reads, avg_writes, delta=avg_all / 10)
def test_demotion_with_blocked_writer(self):
lock = RWLock()
writer = LockingThread(lock.exclusive)
try:
with lock.exclusive:
writer.start()
writer.ready.wait()
# Ensure that writer is blocked
if writer.acquired.wait(0.5):
raise RuntimeError("Writer could acquire the lock while "
"holding a write lock")
lock.acquireRead()
# I hold both a read lock and a write lock now
# I release the write lock. Having read lock, writer must block
self.assertFalse(writer.acquired.wait(0.5),
"Writer acquired the lock while holding a read "
"lock")
finally:
lock.release()
try:
# Writer must acquire now
self.assertTrue(writer.acquired.wait(0.5))
finally:
writer.stop()
def test_demotion_with_blocked_reader(self):
lock = RWLock()
reader = LockingThread(lock.shared)
try:
with lock.exclusive:
reader.start()
reader.ready.wait()
# Ensure that reader is blocked
if reader.acquired.wait(0.5):
raise RuntimeError("Reader could acquire the lock while "
"holding a write lock")
lock.acquireRead()
# I hold both a read lock and a write lock now
# I released the write lock. Having read lock, reader shold get the
# lock.
self.assertTrue(reader.acquired.wait(0.5),
"Reader could not acuire the lock")
finally:
lock.release()
reader.stop()
def test_promotion_forbidden(self):
lock = RWLock()
with lock.shared:
self.assertRaises(RuntimeError, lock.acquireWrite)
def test_shared_context_allows_reader(self):
lock = RWLock()
with lock.shared:
reader = LockingThread(lock.shared)
with utils.running(reader):
self.assertTrue(reader.acquired.wait(1))
def test_recursive_write_lock(self):
lock = RWLock()
with lock.exclusive:
with lock.exclusive:
pass
def test_recursive_read_lock(self):
lock = RWLock()
with lock.shared:
with lock.shared:
pass
