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[3.10] gh-90155: Fix bug in asyncio.Semaphore and strengthen FIFO guarantee (GH-93222)#97020
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…antee (pythonGH-93222)The main problem was that an unluckily timed task cancellation could causethe semaphore to be stuck. There were also doubts about strict FIFO orderingof tasks allowed to pass.The Semaphore implementation was rewritten to be more similar to Lock.Many tests for edge cases (including cancellation) were added.(cherry picked from commit24e0379)Co-authored-by: Cyker Way <cykerway@gmail.com>
gvanrossum approved these changesSep 22, 2022
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miss-islington commentedSep 22, 2022
Status check is done, and it's a success ✅. |
altendky added a commit to Chia-Network/chia-blockchain that referenced this pull requestOct 15, 2022
We access the `._waiters` private attribute of the Python asyncio`Semaphore` class. This was changed in Python 3.10.8 (and other versions)to be initialized to `None` instead of an empty deque. Our existingunconditional length checks failed on the new `None` default. This seemsto block syncing.python/cpython#97020https://github.com/python/cpython/compare/v3.10.7..v3.10.8#diff-0fee1befb15023abc0dad2623effa93a304946796929f6cb445d11a57821e737Reported traceback:```python-traceback2022-10-12T20:03:59.367 full_node full_node_server : INFO Connected with full_node {'host': '65.34.144.6', 'port': 8444}2022-10-12T20:03:59.370 full_node full_node_server : ERROR Exception: object of type 'NoneType' has no len(), {'host': '65.34.144.6', 'port': 8444}. Traceback (most recent call last):File "/home/summa/chia-blockchain/chia/server/server.py", line 598, in wrapped_coroutineresult = await coroutineFile "/home/summa/chia-blockchain/chia/full_node/full_node_api.py", line 114, in new_peakwaiter_count = len(self.full_node.new_peak_sem._waiters)TypeError: object of type 'NoneType' has no len()2022-10-12T20:03:59.371 full_node full_node_server : ERROR Exception: object of type 'NoneType' has no len() <class 'TypeError'>, closing connection {'host': '65.34.144.6', 'port': 8444}. Traceback (most recent call last):File "/home/summa/chia-blockchain/chia/server/server.py", line 608, in api_callresponse: Optional[Message] = await asyncio.wait_for(wrapped_coroutine(), timeout=timeout)File "/usr/lib/python3.10/asyncio/tasks.py", line 408, in wait_forreturn await futFile "/home/summa/chia-blockchain/chia/server/server.py", line 605, in wrapped_coroutineraise eFile "/home/summa/chia-blockchain/chia/server/server.py", line 598, in wrapped_coroutineresult = await coroutineFile "/home/summa/chia-blockchain/chia/full_node/full_node_api.py", line 114, in new_peakwaiter_count = len(self.full_node.new_peak_sem._waiters)TypeError: object of type 'NoneType' has no len()2022-10-12T20:03:59.487 full_node full_node_server : INFO Connection closed: 65.34.144.6, node id: 506fe4c05ce6b72bb707471842e552307c7a547aa9ba981175db5c08fa3e47e6```
wallentx pushed a commit to Chia-Network/chia-blockchain that referenced this pull requestOct 17, 2022
We access the `._waiters` private attribute of the Python asyncio`Semaphore` class. This was changed in Python 3.10.8 (and other versions)to be initialized to `None` instead of an empty deque. Our existingunconditional length checks failed on the new `None` default. This seemsto block syncing.python/cpython#97020https://github.com/python/cpython/compare/v3.10.7..v3.10.8#diff-0fee1befb15023abc0dad2623effa93a304946796929f6cb445d11a57821e737Reported traceback:```python-traceback2022-10-12T20:03:59.367 full_node full_node_server : INFO Connected with full_node {'host': '65.34.144.6', 'port': 8444}2022-10-12T20:03:59.370 full_node full_node_server : ERROR Exception: object of type 'NoneType' has no len(), {'host': '65.34.144.6', 'port': 8444}. Traceback (most recent call last):File "/home/summa/chia-blockchain/chia/server/server.py", line 598, in wrapped_coroutineresult = await coroutineFile "/home/summa/chia-blockchain/chia/full_node/full_node_api.py", line 114, in new_peakwaiter_count = len(self.full_node.new_peak_sem._waiters)TypeError: object of type 'NoneType' has no len()2022-10-12T20:03:59.371 full_node full_node_server : ERROR Exception: object of type 'NoneType' has no len() <class 'TypeError'>, closing connection {'host': '65.34.144.6', 'port': 8444}. Traceback (most recent call last):File "/home/summa/chia-blockchain/chia/server/server.py", line 608, in api_callresponse: Optional[Message] = await asyncio.wait_for(wrapped_coroutine(), timeout=timeout)File "/usr/lib/python3.10/asyncio/tasks.py", line 408, in wait_forreturn await futFile "/home/summa/chia-blockchain/chia/server/server.py", line 605, in wrapped_coroutineraise eFile "/home/summa/chia-blockchain/chia/server/server.py", line 598, in wrapped_coroutineresult = await coroutineFile "/home/summa/chia-blockchain/chia/full_node/full_node_api.py", line 114, in new_peakwaiter_count = len(self.full_node.new_peak_sem._waiters)TypeError: object of type 'NoneType' has no len()2022-10-12T20:03:59.487 full_node full_node_server : INFO Connection closed: 65.34.144.6, node id: 506fe4c05ce6b72bb707471842e552307c7a547aa9ba981175db5c08fa3e47e6```
wallentx pushed a commit to Chia-Network/chia-blockchain that referenced this pull requestNov 6, 2022
* treat Semaphore._waiters as length zero when it is NoneWe access the `._waiters` private attribute of the Python asyncio`Semaphore` class. This was changed in Python 3.10.8 (and other versions)to be initialized to `None` instead of an empty deque. Our existingunconditional length checks failed on the new `None` default. This seemsto block syncing.python/cpython#97020https://github.com/python/cpython/compare/v3.10.7..v3.10.8#diff-0fee1befb15023abc0dad2623effa93a304946796929f6cb445d11a57821e737Reported traceback:```python-traceback2022-10-12T20:03:59.367 full_node full_node_server : INFO Connected with full_node {'host': '65.34.144.6', 'port': 8444}2022-10-12T20:03:59.370 full_node full_node_server : ERROR Exception: object of type 'NoneType' has no len(), {'host': '65.34.144.6', 'port': 8444}. Traceback (most recent call last):File "/home/summa/chia-blockchain/chia/server/server.py", line 598, in wrapped_coroutineresult = await coroutineFile "/home/summa/chia-blockchain/chia/full_node/full_node_api.py", line 114, in new_peakwaiter_count = len(self.full_node.new_peak_sem._waiters)TypeError: object of type 'NoneType' has no len()2022-10-12T20:03:59.371 full_node full_node_server : ERROR Exception: object of type 'NoneType' has no len() <class 'TypeError'>, closing connection {'host': '65.34.144.6', 'port': 8444}. Traceback (most recent call last):File "/home/summa/chia-blockchain/chia/server/server.py", line 608, in api_callresponse: Optional[Message] = await asyncio.wait_for(wrapped_coroutine(), timeout=timeout)File "/usr/lib/python3.10/asyncio/tasks.py", line 408, in wait_forreturn await futFile "/home/summa/chia-blockchain/chia/server/server.py", line 605, in wrapped_coroutineraise eFile "/home/summa/chia-blockchain/chia/server/server.py", line 598, in wrapped_coroutineresult = await coroutineFile "/home/summa/chia-blockchain/chia/full_node/full_node_api.py", line 114, in new_peakwaiter_count = len(self.full_node.new_peak_sem._waiters)TypeError: object of type 'NoneType' has no len()2022-10-12T20:03:59.487 full_node full_node_server : INFO Connection closed: 65.34.144.6, node id: 506fe4c05ce6b72bb707471842e552307c7a547aa9ba981175db5c08fa3e47e6```* add LimitedSemaphore
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The main problem was that an unluckily timed task cancellation could cause
the semaphore to be stuck. There were also doubts about strict FIFO ordering
of tasks allowed to pass.
The Semaphore implementation was rewritten to be more similar to Lock.
Many tests for edge cases (including cancellation) were added.
(cherry picked from commit24e0379)
Co-authored-by: Cyker Waycykerway@gmail.com