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Fix race condition with cancellation tokens in Read/Flush operations #59090

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Merged
ericstj merged 4 commits into from
Sep 15, 2021
Merged

Fix race condition with cancellation tokens in Read/Flush operations #59090

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5d9548e
Fix race condition with cancellation tokens in Read/Write operations
davidfowl Sep 14, 2021
71344e8
Add a debug assert to make sure there's no state change.
davidfowl Sep 14, 2021
a58956e
Add if debug
davidfowl Sep 15, 2021
efb0999
More if DEBUG
davidfowl Sep 15, 2021
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23 changes: 20 additions & 3 deletions src/libraries/System.IO.Pipelines/src/System/IO/Pipelines/PipeAwaitable.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -47,16 +47,33 @@ public void BeginOperation(CancellationToken cancellationToken, Action<object?>
{
cancellationToken.ThrowIfCancellationRequested();

_awaitableState |= AwaitableState.Running;

// Don't register if already completed, we would immediately unregistered in ObserveCancellation
if (cancellationToken.CanBeCanceled && !IsCompleted)
{
#if DEBUG
var previousAwaitableState = _awaitableState;
#endif

_cancellationTokenRegistration = cancellationToken.UnsafeRegister(callback, state);

// If we get back the default CancellationTokenRegistration then it means the
// callback synchronously and we can throw inline. This is safe because we haven't changed
// the state of the awaitable as yet.
if (_cancellationTokenRegistration == default(CancellationTokenRegistration))
{
#if DEBUG
Debug.Assert(previousAwaitableState == _awaitableState, "The awaitable state changed!");
#endif

cancellationToken.ThrowIfCancellationRequested();
}

#if (NETSTANDARD2_0 || NETFRAMEWORK)
_cancellationToken = cancellationToken;
#endif
_cancellationTokenRegistration = cancellationToken.UnsafeRegister(callback, state);
}

_awaitableState |= AwaitableState.Running;
}

[MethodImpl(MethodImplOptions.AggressiveInlining)]
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