2d26c29e67
Deadlock can occur when a reader X waits for pending writers to be empty but the reader X already owns a read lock (since it will then wait for pending writers to be empty which it will never be, since pending writers is only empty when there are no readers - but since the current thread X is getting another read lock it result in deadlock for the reader and deadlock for the writer). Closes-Bug: #1276868 Change-Id: Ibe13eafa4bd0bc817e8bfe3cf303c54298778b37
288 lines
9.2 KiB
Python
288 lines
9.2 KiB
Python
# -*- coding: utf-8 -*-
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# vim: tabstop=4 shiftwidth=4 softtabstop=4
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# Copyright (C) 2014 Yahoo! Inc. All Rights Reserved.
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#
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# Licensed under the Apache License, Version 2.0 (the "License"); you may
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# not use this file except in compliance with the License. You may obtain
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# a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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# License for the specific language governing permissions and limitations
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# under the License.
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import collections
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import threading
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import time
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from concurrent import futures
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from taskflow import test
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from taskflow.utils import lock_utils
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def _find_overlaps(times, start, end):
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overlaps = 0
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for (s, e) in times:
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if s >= start and e <= end:
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overlaps += 1
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return overlaps
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def _spawn_variation(readers, writers, max_workers=None):
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start_stops = collections.deque()
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lock = lock_utils.ReaderWriterLock()
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def read_func():
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with lock.read_lock():
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start_stops.append(('r', time.time(), time.time()))
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def write_func():
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with lock.write_lock():
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start_stops.append(('w', time.time(), time.time()))
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if max_workers is None:
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max_workers = max(0, readers) + max(0, writers)
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if max_workers > 0:
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with futures.ThreadPoolExecutor(max_workers=max_workers) as e:
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for i in range(0, readers):
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e.submit(read_func)
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for i in range(0, writers):
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e.submit(write_func)
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writer_times = []
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reader_times = []
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for (t, start, stop) in list(start_stops):
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if t == 'w':
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writer_times.append((start, stop))
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else:
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reader_times.append((start, stop))
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return (writer_times, reader_times)
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class ReadWriteLockTest(test.TestCase):
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def test_writer_abort(self):
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lock = lock_utils.ReaderWriterLock()
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self.assertFalse(lock.owner)
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def blow_up():
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with lock.write_lock():
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self.assertEqual(lock.WRITER, lock.owner)
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raise RuntimeError("Broken")
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self.assertRaises(RuntimeError, blow_up)
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self.assertFalse(lock.owner)
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def test_reader_abort(self):
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lock = lock_utils.ReaderWriterLock()
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self.assertFalse(lock.owner)
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def blow_up():
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with lock.read_lock():
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self.assertEqual(lock.READER, lock.owner)
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raise RuntimeError("Broken")
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self.assertRaises(RuntimeError, blow_up)
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self.assertFalse(lock.owner)
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def test_double_reader_abort(self):
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lock = lock_utils.ReaderWriterLock()
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activated = collections.deque()
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def double_bad_reader():
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with lock.read_lock():
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with lock.read_lock():
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raise RuntimeError("Broken")
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def happy_writer():
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with lock.write_lock():
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activated.append(lock.owner)
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with futures.ThreadPoolExecutor(max_workers=20) as e:
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for i in range(0, 20):
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if i % 2 == 0:
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e.submit(double_bad_reader)
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else:
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e.submit(happy_writer)
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self.assertEqual(10, len([a for a in activated if a == 'w']))
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def test_double_reader_writer(self):
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lock = lock_utils.ReaderWriterLock()
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activated = collections.deque()
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active = threading.Event()
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def double_reader():
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with lock.read_lock():
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active.set()
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while lock.pending_writers == 0:
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time.sleep(0.001)
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with lock.read_lock():
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activated.append(lock.owner)
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def happy_writer():
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with lock.write_lock():
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activated.append(lock.owner)
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reader = threading.Thread(target=double_reader)
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reader.start()
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active.wait()
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writer = threading.Thread(target=happy_writer)
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writer.start()
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reader.join()
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writer.join()
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self.assertEqual(2, len(activated))
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self.assertEqual(['r', 'w'], list(activated))
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def test_reader_chaotic(self):
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lock = lock_utils.ReaderWriterLock()
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activated = collections.deque()
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def chaotic_reader(blow_up):
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with lock.read_lock():
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if blow_up:
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raise RuntimeError("Broken")
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else:
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activated.append(lock.owner)
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def happy_writer():
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with lock.write_lock():
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activated.append(lock.owner)
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with futures.ThreadPoolExecutor(max_workers=20) as e:
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for i in range(0, 20):
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if i % 2 == 0:
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e.submit(chaotic_reader, blow_up=bool(i % 4 == 0))
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else:
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e.submit(happy_writer)
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writers = [a for a in activated if a == 'w']
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readers = [a for a in activated if a == 'r']
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self.assertEqual(10, len(writers))
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self.assertEqual(5, len(readers))
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def test_writer_chaotic(self):
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lock = lock_utils.ReaderWriterLock()
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activated = collections.deque()
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def chaotic_writer(blow_up):
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with lock.write_lock():
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if blow_up:
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raise RuntimeError("Broken")
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else:
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activated.append(lock.owner)
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def happy_reader():
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with lock.read_lock():
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activated.append(lock.owner)
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with futures.ThreadPoolExecutor(max_workers=20) as e:
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for i in range(0, 20):
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if i % 2 == 0:
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e.submit(chaotic_writer, blow_up=bool(i % 4 == 0))
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else:
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e.submit(happy_reader)
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writers = [a for a in activated if a == 'w']
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readers = [a for a in activated if a == 'r']
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self.assertEqual(5, len(writers))
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self.assertEqual(10, len(readers))
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def test_single_reader_writer(self):
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results = []
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lock = lock_utils.ReaderWriterLock()
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with lock.read_lock():
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self.assertTrue(lock.is_reader())
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self.assertEqual(0, len(results))
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with lock.write_lock():
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results.append(1)
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self.assertTrue(lock.is_writer())
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with lock.read_lock():
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self.assertTrue(lock.is_reader())
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self.assertEqual(1, len(results))
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self.assertFalse(lock.is_reader())
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self.assertFalse(lock.is_writer())
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def test_reader_to_writer(self):
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lock = lock_utils.ReaderWriterLock()
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def writer_func():
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with lock.write_lock():
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pass
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with lock.read_lock():
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self.assertRaises(RuntimeError, writer_func)
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self.assertFalse(lock.is_writer())
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self.assertFalse(lock.is_reader())
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self.assertFalse(lock.is_writer())
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def test_writer_to_reader(self):
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lock = lock_utils.ReaderWriterLock()
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def reader_func():
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with lock.read_lock():
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pass
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with lock.write_lock():
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self.assertRaises(RuntimeError, reader_func)
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self.assertFalse(lock.is_reader())
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self.assertFalse(lock.is_reader())
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self.assertFalse(lock.is_writer())
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def test_double_writer(self):
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lock = lock_utils.ReaderWriterLock()
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with lock.write_lock():
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self.assertFalse(lock.is_reader())
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self.assertTrue(lock.is_writer())
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with lock.write_lock():
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self.assertTrue(lock.is_writer())
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self.assertTrue(lock.is_writer())
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self.assertFalse(lock.is_reader())
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self.assertFalse(lock.is_writer())
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def test_double_reader(self):
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lock = lock_utils.ReaderWriterLock()
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with lock.read_lock():
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self.assertTrue(lock.is_reader())
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self.assertFalse(lock.is_writer())
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with lock.read_lock():
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self.assertTrue(lock.is_reader())
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self.assertTrue(lock.is_reader())
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self.assertFalse(lock.is_reader())
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self.assertFalse(lock.is_writer())
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def test_multi_reader_multi_writer(self):
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writer_times, reader_times = _spawn_variation(10, 10)
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self.assertEqual(10, len(writer_times))
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self.assertEqual(10, len(reader_times))
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for (start, stop) in writer_times:
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self.assertEqual(0, _find_overlaps(reader_times, start, stop))
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self.assertEqual(1, _find_overlaps(writer_times, start, stop))
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for (start, stop) in reader_times:
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self.assertEqual(0, _find_overlaps(writer_times, start, stop))
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def test_multi_reader_single_writer(self):
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writer_times, reader_times = _spawn_variation(9, 1)
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self.assertEqual(1, len(writer_times))
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self.assertEqual(9, len(reader_times))
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start, stop = writer_times[0]
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self.assertEqual(0, _find_overlaps(reader_times, start, stop))
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def test_multi_writer(self):
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writer_times, reader_times = _spawn_variation(0, 10)
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self.assertEqual(10, len(writer_times))
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self.assertEqual(0, len(reader_times))
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for (start, stop) in writer_times:
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self.assertEqual(1, _find_overlaps(writer_times, start, stop))
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