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79e7c2c426
Just after a task acquires a contended `Linearizer` lock, it sleeps. If the task is cancelled during this sleep, we need to release the lock. Signed-off-by: Sean Quah <seanq@element.io>
257 lines
8.4 KiB
Python
257 lines
8.4 KiB
Python
# Copyright 2016 OpenMarket Ltd
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# Copyright 2018 New Vector Ltd
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain 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,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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from typing import Hashable, Tuple
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from typing_extensions import Protocol
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from twisted.internet import defer, reactor
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from twisted.internet.base import ReactorBase
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from twisted.internet.defer import CancelledError, Deferred
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from synapse.logging.context import LoggingContext, current_context
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from synapse.util.async_helpers import Linearizer
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from tests import unittest
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class UnblockFunction(Protocol):
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def __call__(self, pump_reactor: bool = True) -> None:
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...
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class LinearizerTestCase(unittest.TestCase):
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def _start_task(
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self, linearizer: Linearizer, key: Hashable
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) -> Tuple["Deferred[None]", "Deferred[None]", UnblockFunction]:
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"""Starts a task which acquires the linearizer lock, blocks, then completes.
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Args:
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linearizer: The `Linearizer`.
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key: The `Linearizer` key.
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Returns:
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A tuple containing:
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* A cancellable `Deferred` for the entire task.
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* A `Deferred` that resolves once the task acquires the lock.
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* A function that unblocks the task. Must be called by the caller
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to allow the task to release the lock and complete.
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"""
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acquired_d: "Deferred[None]" = Deferred()
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unblock_d: "Deferred[None]" = Deferred()
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async def task() -> None:
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async with linearizer.queue(key):
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acquired_d.callback(None)
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await unblock_d
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d = defer.ensureDeferred(task())
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def unblock(pump_reactor: bool = True) -> None:
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unblock_d.callback(None)
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# The next task, if it exists, will acquire the lock and require a kick of
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# the reactor to advance.
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if pump_reactor:
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self._pump()
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return d, acquired_d, unblock
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def _pump(self) -> None:
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"""Pump the reactor to advance `Linearizer`s."""
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assert isinstance(reactor, ReactorBase)
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while reactor.getDelayedCalls():
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reactor.runUntilCurrent()
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def test_linearizer(self) -> None:
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"""Tests that a task is queued up behind an earlier task."""
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linearizer = Linearizer()
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key = object()
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_, acquired_d1, unblock1 = self._start_task(linearizer, key)
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self.assertTrue(acquired_d1.called)
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_, acquired_d2, unblock2 = self._start_task(linearizer, key)
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self.assertFalse(acquired_d2.called)
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# Once the first task is done, the second task can continue.
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unblock1()
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self.assertTrue(acquired_d2.called)
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unblock2()
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def test_linearizer_is_queued(self) -> None:
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"""Tests `Linearizer.is_queued`.
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Runs through the same scenario as `test_linearizer`.
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"""
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linearizer = Linearizer()
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key = object()
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_, acquired_d1, unblock1 = self._start_task(linearizer, key)
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self.assertTrue(acquired_d1.called)
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# Since the first task acquires the lock immediately, "is_queued" should return
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# false.
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self.assertFalse(linearizer.is_queued(key))
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_, acquired_d2, unblock2 = self._start_task(linearizer, key)
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self.assertFalse(acquired_d2.called)
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# Now the second task is queued up behind the first.
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self.assertTrue(linearizer.is_queued(key))
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unblock1()
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# And now the second task acquires the lock and nothing is in the queue again.
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self.assertTrue(acquired_d2.called)
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self.assertFalse(linearizer.is_queued(key))
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unblock2()
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self.assertFalse(linearizer.is_queued(key))
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def test_lots_of_queued_things(self) -> None:
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"""Tests lots of fast things queued up behind a slow thing.
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The stack should *not* explode when the slow thing completes.
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"""
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linearizer = Linearizer()
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key = ""
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async def func(i: int) -> None:
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with LoggingContext("func(%s)" % i) as lc:
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async with linearizer.queue(key):
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self.assertEqual(current_context(), lc)
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self.assertEqual(current_context(), lc)
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_, _, unblock = self._start_task(linearizer, key)
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for i in range(1, 100):
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defer.ensureDeferred(func(i))
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d = defer.ensureDeferred(func(1000))
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unblock()
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self.successResultOf(d)
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def test_multiple_entries(self) -> None:
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"""Tests a `Linearizer` with a concurrency above 1."""
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limiter = Linearizer(max_count=3)
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key = object()
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_, acquired_d1, unblock1 = self._start_task(limiter, key)
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self.assertTrue(acquired_d1.called)
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_, acquired_d2, unblock2 = self._start_task(limiter, key)
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self.assertTrue(acquired_d2.called)
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_, acquired_d3, unblock3 = self._start_task(limiter, key)
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self.assertTrue(acquired_d3.called)
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# These next two tasks have to wait.
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_, acquired_d4, unblock4 = self._start_task(limiter, key)
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self.assertFalse(acquired_d4.called)
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_, acquired_d5, unblock5 = self._start_task(limiter, key)
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self.assertFalse(acquired_d5.called)
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# Once the first task completes, the fourth task can continue.
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unblock1()
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self.assertTrue(acquired_d4.called)
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self.assertFalse(acquired_d5.called)
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# Once the third task completes, the fifth task can continue.
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unblock3()
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self.assertTrue(acquired_d5.called)
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# Make all tasks finish.
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unblock2()
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unblock4()
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unblock5()
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# The next task shouldn't have to wait.
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_, acquired_d6, unblock6 = self._start_task(limiter, key)
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self.assertTrue(acquired_d6)
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unblock6()
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def test_cancellation(self) -> None:
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"""Tests cancellation while waiting for a `Linearizer`."""
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linearizer = Linearizer()
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key = object()
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d1, acquired_d1, unblock1 = self._start_task(linearizer, key)
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self.assertTrue(acquired_d1.called)
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# Create a second task, waiting for the first task.
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d2, acquired_d2, _ = self._start_task(linearizer, key)
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self.assertFalse(acquired_d2.called)
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# Create a third task, waiting for the second task.
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d3, acquired_d3, unblock3 = self._start_task(linearizer, key)
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self.assertFalse(acquired_d3.called)
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# Cancel the waiting second task.
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d2.cancel()
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unblock1()
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self.successResultOf(d1)
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self.assertTrue(d2.called)
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self.failureResultOf(d2, CancelledError)
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# The third task should continue running.
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self.assertTrue(
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acquired_d3.called,
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"Third task did not get the lock after the second task was cancelled",
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)
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unblock3()
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self.successResultOf(d3)
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def test_cancellation_during_sleep(self) -> None:
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"""Tests cancellation during the sleep just after waiting for a `Linearizer`."""
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linearizer = Linearizer()
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key = object()
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d1, acquired_d1, unblock1 = self._start_task(linearizer, key)
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self.assertTrue(acquired_d1.called)
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# Create a second task, waiting for the first task.
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d2, acquired_d2, _ = self._start_task(linearizer, key)
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self.assertFalse(acquired_d2.called)
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# Create a third task, waiting for the second task.
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d3, acquired_d3, unblock3 = self._start_task(linearizer, key)
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self.assertFalse(acquired_d3.called)
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# Once the first task completes, cancel the waiting second task while it is
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# sleeping just after acquiring the lock.
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unblock1(pump_reactor=False)
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self.successResultOf(d1)
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d2.cancel()
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self._pump()
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self.assertTrue(d2.called)
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self.failureResultOf(d2, CancelledError)
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# The third task should continue running.
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self.assertTrue(
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acquired_d3.called,
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"Third task did not get the lock after the second task was cancelled",
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)
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unblock3()
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self.successResultOf(d3)
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