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Fix access violation exception on shutdown #2386

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lostmsu merged 4 commits into from
Aug 6, 2024
+26 −8
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Fix access violation exception on shutdown #2386

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4e5afdf
Fix access violation exception on shutdown (#1977)
Frawak May 13, 2024
6f0f671
Restrict first garbage collection
Frawak May 13, 2024
c99cdf3
Throw exception trying to add a reflected object after the hashset is…
Frawak Jul 8, 2024
6cdd6d7
Move reflected object creation block
Frawak Aug 5, 2024
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Fix access violation exception on shutdown (#1977) 
When nulling the GC handles on shutdown the reference count of all objects pointed to by the IntPtr in the `CLRObject.reflectedObjects` are zero.
This caused an exception in some scenarios because `Runtime.PyObject_TYPE(reflectedClrObject)` is called while the reference counter is at zero.

After `TypeManager.RemoveTypes();` is called in the `Runtime.Shutdown()` method, reference count decrements to zero do not invoke `ClassBase.tp_clear` for managed objects anymore which normally is responsible for removing references from `CLRObject.reflectedObjects`. Collecting objects referenced in `CLRObject.reflectedObjects` only after leads to an unstable state in which the reference count for these object addresses is zero while still maintaining them to be used for further pseudo-cleanup. In that time, the memory could have been reclaimed already which leads to the exception.
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@Frawak
Frawak committed May 13, 2024
commit 4e5afdf973e29f1ae50413aa0cc092f2a03df68f
1 change: 1 addition & 0 deletions AUTHORS.md
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Expand Up @@ -38,6 +38,7 @@
- Dmitriy Se ([@dmitriyse](https://github.com/dmitriyse))
- Félix Bourbonnais ([@BadSingleton](https://github.com/BadSingleton))
- Florian Treurniet ([@ftreurni](https://github.com/ftreurni))
- Frank Witscher ([@Frawak](https://github.com/Frawak))
- He-chien Tsai ([@t3476](https://github.com/t3476))
- Inna Wiesel ([@inna-w](https://github.com/inna-w))
- Ivan Cronyn ([@cronan](https://github.com/cronan))
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2 changes: 2 additions & 0 deletions CHANGELOG.md
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Expand Up @@ -23,6 +23,7 @@ This document follows the conventions laid out in [Keep a CHANGELOG][].

- Fixed RecursionError for reverse operators on C# operable types from python. See #2240
- Fixed probing for assemblies in `sys.path` failing when a path in `sys.path` has invalid characters. See #2376
- Fixed possible access violation exception on shutdown. See ([#1977][i1977])

## [3.0.3](https://github.com/pythonnet/pythonnet/releases/tag/v3.0.3) - 2023-10-11

Expand Down Expand Up @@ -970,3 +971,4 @@ This version improves performance on benchmarks significantly compared to 2.3.
[i1481]: https://github.com/pythonnet/pythonnet/issues/1481
[i1672]: https://github.com/pythonnet/pythonnet/pull/1672
[i2311]: https://github.com/pythonnet/pythonnet/issues/2311
[i1977]: https://github.com/pythonnet/pythonnet/issues/1977
5 changes: 3 additions & 2 deletions src/runtime/Runtime.cs
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Expand Up @@ -278,6 +278,8 @@ internal static void Shutdown()
ClearClrModules();
RemoveClrRootModule();

TryCollectingGarbage(MaxCollectRetriesOnShutdown, forceBreakLoops: true);

NullGCHandles(ExtensionType.loadedExtensions);
ClassManager.RemoveClasses();
TypeManager.RemoveTypes();
Expand All @@ -295,8 +297,7 @@ internal static void Shutdown()
PyObjectConversions.Reset();

PyGC_Collect();
bool everythingSeemsCollected = TryCollectingGarbage(MaxCollectRetriesOnShutdown,
forceBreakLoops: true);
bool everythingSeemsCollected = TryCollectingGarbage(MaxCollectRetriesOnShutdown);
Debug.Assert(everythingSeemsCollected);

Finalizer.Shutdown();
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