mirror of
https://github.com/home-assistant/core
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75 lines
2.3 KiB
Python
75 lines
2.3 KiB
Python
"""Monkey patch Python to work around issues causing segfaults.
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Under heavy threading operations that schedule calls into
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the asyncio event loop, Task objects are created. Due to
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a bug in Python, GC may have an issue when switching between
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the threads and objects with __del__ (which various components
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in HASS have).
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This monkey-patch removes the weakref.Weakset, and replaces it
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with an object that ignores the only call utilizing it (the
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Task.__init__ which calls _all_tasks.add(self)). It also removes
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the __del__ which could trigger the future objects __del__ at
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unpredictable times.
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The side-effect of this manipulation of the Task is that
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Task.all_tasks() is no longer accurate, and there will be no
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warning emitted if a Task is GC'd while in use.
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Related Python bugs:
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- https://bugs.python.org/issue26617
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"""
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import sys
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from typing import Any
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def patch_weakref_tasks() -> None:
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"""Replace weakref.WeakSet to address Python 3 bug."""
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# pylint: disable=no-self-use, protected-access
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import asyncio.tasks
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class IgnoreCalls:
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"""Ignore add calls."""
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def add(self, other: Any) -> None:
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"""No-op add."""
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return
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asyncio.tasks.Task._all_tasks = IgnoreCalls() # type: ignore
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try:
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del asyncio.tasks.Task.__del__
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except: # noqa: E722 pylint: disable=bare-except
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pass
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def disable_c_asyncio() -> None:
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"""Disable using C implementation of asyncio.
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Required to be able to apply the weakref monkey patch.
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Requires Python 3.6+.
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"""
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class AsyncioImportFinder:
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"""Finder that blocks C version of asyncio being loaded."""
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PATH_TRIGGER = '_asyncio'
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def __init__(self, path_entry: str) -> None:
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if path_entry != self.PATH_TRIGGER:
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raise ImportError()
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def find_module(self, fullname: str, path: Any = None) -> None:
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"""Find a module."""
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if fullname == self.PATH_TRIGGER:
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# We lint in Py35, exception is introduced in Py36
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# pylint: disable=undefined-variable
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raise ModuleNotFoundError() # type: ignore # noqa
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sys.path_hooks.append(AsyncioImportFinder)
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sys.path.insert(0, AsyncioImportFinder.PATH_TRIGGER)
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try:
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import _asyncio # noqa
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except ImportError:
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pass
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