Proposed Changes

I used the implementation further in some very high concurrent scenarios and ran into token problems with the manual reset implementation under the cover. I have concluded the original version I tweaked had some races that we collectively missed.

The race condition occurs in WaitAsync() where the IsSet check and valueTaskSource.Version capture happen at different moments without synchronization, allowing Set() or Reset() to execute between these operations and change the state. If Reset() is called after the IsSet check passes but before the ValueTask is created, the version becomes stale and the awaited task will never complete because it references the old version while the ManualResetValueTaskSourceCore has been reset. Additionally, the gap between checking IsSet and updating state in both Set() and Reset() creates windows where multiple threads can pass the initial checks simultaneously, leading to operations being performed on inconsistent state.

This implementation passed my concurrency tests, but it doesn't hurt if the original involved reviewers give this another review@lukebakken@paulomorgado@bollhals

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