Fix race condition in cleanup of collectible thread static variables

[davidwrighton]

There was a race condition where we could have collected all of the managed state of a LoaderAllocator, but not yet started cleaning up the actual LoaderAllocator object in native code. If a thread which had a TLS variable defined in a code associated with a collectible loader allocator was terminated at that point, then the runtime would crash.

The fix is to detect if the LoaderAllocator managed state is still alive, and if so, do not attempt to clean it up.

Attached is a test case which is a reduced version of a stress test used to examine the issue

Fixes #110837

[Copilot]

Copilot reviewed 1 out of 4 changed files in this pull request and generated 2 comments.

Files not reviewed (3)

• src/coreclr/vm/threadstatics.cpp: Language not supported
• src/tests/Loader/CollectibleAssemblies/Statics/CollectibleTLSStaticCollection.csproj: Language not supported
• src/tests/issues.targets: Language not supported

Comments suppressed due to low confidence (3)

src/tests/Loader/CollectibleAssemblies/Statics/CollectibleTLSStaticCollection.cs:16

• [nitpick] The variable name 'UseTLSStaticFromLoaderAllocator' is long and not very descriptive. Consider renaming it to something more concise and descriptive.

Action? UseTLSStaticFromLoaderAllocator = null;

src/tests/Loader/CollectibleAssemblies/Statics/CollectibleTLSStaticCollection.cs:17

• [nitpick] The variable name 'IsLoaderAllocatorLive' suggests a boolean, but it is a GCHandle. Consider renaming it to something more appropriate, like 'loaderAllocatorHandle'.

GCHandle IsLoaderAllocatorLive;

src/tests/Loader/CollectibleAssemblies/Statics/CollectibleTLSStaticCollection.cs:96

• The test method 'TestEntryPoint' does not assert any conditions. It should include assertions to verify the expected behavior.

[Fact]
public static void TestEntryPoint()