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[release/8.0] Fix crash when calling AssemblyLoadContext.Unload twice #91346

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Aug 30, 2023
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[release/8.0] Fix crash when calling AssemblyLoadContext.Unload twice #91346

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c0b25cd
Fix crash when calling AssemblyLoadContext.Unload twice
janvorli Aug 29, 2023
531f09e
Add regression test
janvorli Aug 30, 2023
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29 changes: 18 additions & 11 deletions src/libraries/System.Private.CoreLib/src/System/Runtime/Loader/AssemblyLoadContext.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -135,25 +135,32 @@ private void InitiateUnload()
{
RaiseUnloadEvent();

InternalState previousState;

// When in Unloading state, we are not supposed to be called on the finalizer
// as the native side is holding a strong reference after calling Unload
lock (_unloadLock)
{
Debug.Assert(_state == InternalState.Alive);

var thisStrongHandle = GCHandle.Alloc(this, GCHandleType.Normal);
var thisStrongHandlePtr = GCHandle.ToIntPtr(thisStrongHandle);
// The underlying code will transform the original weak handle
// created by InitializeLoadContext to a strong handle
PrepareForAssemblyLoadContextRelease(_nativeAssemblyLoadContext, thisStrongHandlePtr);
previousState = _state;
if (previousState == InternalState.Alive)
{
var thisStrongHandle = GCHandle.Alloc(this, GCHandleType.Normal);
var thisStrongHandlePtr = GCHandle.ToIntPtr(thisStrongHandle);
// The underlying code will transform the original weak handle
// created by InitializeLoadContext to a strong handle
PrepareForAssemblyLoadContextRelease(_nativeAssemblyLoadContext, thisStrongHandlePtr);

_state = InternalState.Unloading;
_state = InternalState.Unloading;
}
}

Dictionary<long, WeakReference<AssemblyLoadContext>> allContexts = AllContexts;
lock (allContexts)
if (previousState == InternalState.Alive)
{
allContexts.Remove(_id);
Dictionary<long, WeakReference<AssemblyLoadContext>> allContexts = AllContexts;
lock (allContexts)
{
allContexts.Remove(_id);
}
}
}

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19 changes: 18 additions & 1 deletion src/libraries/System.Runtime.Loader/tests/CollectibleAssemblyLoadContextTest.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -16,12 +16,16 @@ public partial class AssemblyLoadContextTest
// Tests related to Collectible assemblies

[MethodImpl(MethodImplOptions.NoInlining)]
static void CreateAndLoadContext(CollectibleChecker checker)
static void CreateAndLoadContext(CollectibleChecker checker, bool unloadTwice = false)
{
var alc = new ResourceAssemblyLoadContext(true);
checker.SetAssemblyLoadContext(0, alc);

alc.Unload();
if (unloadTwice)
{
alc.Unload();
}

// Check that any attempt to load an assembly after an explicit Unload will fail
Assert.Throws<InvalidOperationException>(() => alc.LoadFromAssemblyPath(Path.GetFullPath("none.dll")));
Expand All @@ -39,6 +43,19 @@ public static void Unload_CollectibleWithNoAssemblyLoaded()
checker.GcAndCheck();
}

[Fact]
[ActiveIssue("https://github.com/mono/mono/issues/15142", TestRuntimes.Mono)]
public static void DoubleUnload_CollectibleWithNoAssemblyLoaded()
{
// Use a collectible ALC + Unload
// Check that we receive the Unloading event

var checker = new CollectibleChecker(1);
CreateAndLoadContext(checker, unloadTwice: true);
checker.GcAndCheck();
}


[ConditionalFact(typeof(PlatformDetection), nameof(PlatformDetection.IsPreciseGcSupported))]
public static void Finalizer_CollectibleWithNoAssemblyLoaded()
{
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