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Make LinkedCancellationTokenSource register itself weakly #91679

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TimLovellSmith wants to merge 1 commit into from
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Make LinkedCancellationTokenSource register itself weakly #91679

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13 changes: 8 additions & 5 deletions src/libraries/System.Private.CoreLib/src/System/Threading/CancellationTokenSource.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -883,7 +883,7 @@ private sealed class Linked1CancellationTokenSource : CancellationTokenSource

internal Linked1CancellationTokenSource(CancellationToken token1)
{
_reg1 = token1.UnsafeRegister(LinkedNCancellationTokenSource.s_linkedTokenCancelDelegate, this);
_reg1 = token1.UnsafeRegister(LinkedNCancellationTokenSource.s_linkedTokenCancelDelegate, new WeakReference(this));
}

protected override void Dispose(bool disposing)
Expand All @@ -905,8 +905,8 @@ private sealed class Linked2CancellationTokenSource : CancellationTokenSource

internal Linked2CancellationTokenSource(CancellationToken token1, CancellationToken token2)
{
_reg1 = token1.UnsafeRegister(LinkedNCancellationTokenSource.s_linkedTokenCancelDelegate, this);
_reg2 = token2.UnsafeRegister(LinkedNCancellationTokenSource.s_linkedTokenCancelDelegate, this);
_reg1 = token1.UnsafeRegister(LinkedNCancellationTokenSource.s_linkedTokenCancelDelegate, new WeakReference(this));
_reg2 = token2.UnsafeRegister(LinkedNCancellationTokenSource.s_linkedTokenCancelDelegate, new WeakReference(this));
}

protected override void Dispose(bool disposing)
Expand All @@ -924,8 +924,11 @@ protected override void Dispose(bool disposing)

private sealed class LinkedNCancellationTokenSource : CancellationTokenSource
{
internal static readonly Action<object?> s_linkedTokenCancelDelegate = static s =>
internal static readonly Action<object?> s_linkedTokenCancelDelegate = static wr =>
{
Debug.Assert(wr is WeakReference, $"Expected {typeof(WeakReference)}, got {wr}");
object? s = ((WeakReference)wr).Target;
if (s is null) return;
Debug.Assert(s is CancellationTokenSource, $"Expected {typeof(CancellationTokenSource)}, got {s}");
((CancellationTokenSource)s).NotifyCancellation(throwOnFirstException: false); // skip ThrowIfDisposed() check in Cancel()
};
Expand All @@ -939,7 +942,7 @@ internal LinkedNCancellationTokenSource(CancellationToken[] tokens)
{
if (tokens[i].CanBeCanceled)
{
_linkingRegistrations[i] = tokens[i].UnsafeRegister(s_linkedTokenCancelDelegate, this);
_linkingRegistrations[i] = tokens[i].UnsafeRegister(s_linkedTokenCancelDelegate, new WeakReference(this));
}
// Empty slots in the array will be default(CancellationTokenRegistration), which are nops to Dispose.
// Based on usage patterns, such occurrences should also be rare, such that it's not worth resizing
Expand Down