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8a61b71eee
gh-142975: During GC, mark frozen objects with a merged zero refcount for destruction (GH-143156)
(cherry picked from commit 8611f74e08)
Co-authored-by: Peter Bierma <zintensitydev@gmail.com>
99 lines
2.7 KiB
Python
99 lines
2.7 KiB
Python
import unittest
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import threading
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from threading import Thread
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from unittest import TestCase
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import gc
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from test.support import threading_helper
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class MyObj:
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pass
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@threading_helper.requires_working_threading()
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class TestGC(TestCase):
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def test_get_objects(self):
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event = threading.Event()
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def gc_thread():
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for i in range(100):
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o = gc.get_objects()
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event.set()
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def mutator_thread():
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while not event.is_set():
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o1 = MyObj()
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o2 = MyObj()
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o3 = MyObj()
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o4 = MyObj()
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gcs = [Thread(target=gc_thread)]
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mutators = [Thread(target=mutator_thread) for _ in range(4)]
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with threading_helper.start_threads(gcs + mutators):
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pass
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def test_get_referrers(self):
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NUM_GC = 2
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NUM_MUTATORS = 4
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b = threading.Barrier(NUM_GC + NUM_MUTATORS)
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event = threading.Event()
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obj = MyObj()
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def gc_thread():
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b.wait()
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for i in range(100):
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o = gc.get_referrers(obj)
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event.set()
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def mutator_thread():
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b.wait()
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while not event.is_set():
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d1 = { "key": obj }
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d2 = { "key": obj }
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d3 = { "key": obj }
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d4 = { "key": obj }
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gcs = [Thread(target=gc_thread) for _ in range(NUM_GC)]
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mutators = [Thread(target=mutator_thread) for _ in range(NUM_MUTATORS)]
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with threading_helper.start_threads(gcs + mutators):
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pass
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def test_freeze_object_in_brc_queue(self):
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# GH-142975: Freezing objects in the BRC queue could result in some
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# objects having a zero refcount without being deallocated.
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class Weird:
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# We need a destructor to trigger the check for object resurrection
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def __del__(self):
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pass
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# This is owned by the main thread, so the subthread will have to increment
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# this object's reference count.
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weird = Weird()
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def evil():
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gc.freeze()
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# Decrement the reference count from this thread, which will trigger the
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# slow path during resurrection and add our weird object to the BRC queue.
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nonlocal weird
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del weird
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# Collection will merge the object's reference count and make it zero.
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gc.collect()
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# Unfreeze the object, making it visible to the GC.
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gc.unfreeze()
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gc.collect()
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thread = Thread(target=evil)
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thread.start()
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thread.join()
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if __name__ == "__main__":
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unittest.main()
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