Fix race condition with cancellation tokens in Read/Flush operations … #61500
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@davidfowl we will need to add the packaging changes here https://github.com/dotnet/runtime/blob/release/6.0/docs/project/library-servicing.md can you please add those ? example 96c5ebf this is part of the aspnetcore as well so @safern while validation please make sure the assembly versions are correct here. cc @ericstj |
halter73
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Nov 12, 2021
…59090) * Fix race condition with cancellation tokens in Read/Write operations - There's a tight race where UnsafeRegister can fire inline and then ReadAsync never completes. This is because the cancellation token property has not been assigned yet so the callback noops. This change checks the result of the UnsafeRegister operation to see if ran synchronously and throws if it did. We also move any state transitions to after these checks to make sure the PipeAwaitable state doesn't change before throwing. * Add a debug assert to make sure there's no state change. * Add if debug * More if DEBUG
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safern
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Nov 15, 2021
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Backport of #59090 to release/6.0
Customer Impact
@AArnott reported a race condition with PipeReader where the ReadAsync operation could hang in some hard to reproduce cases when used with a cancellation token. The race resulting in hangs in various usages of pipelines in https://github.com/AArnott/Nerdbank.Streams (which is used in VS).
Testing
Manual testing. It's very hard to write a unit test for this scenario. Also verified by @AArnott
Risk
Low. The change was made to only affect a very narrow case (synchronous completion). Asserts were added to make sure existing invariants weren't broken.