single-threaded async/await · C#/.net-collaboration

Stream: C#/.net-collaboration

Topic: single-threaded async/await

Joel Dice (May 29 2024 at 16:43):

Is anybody here an expert on async/await in C#/.NET? I'm trying to support it in WASI using wasi:io/poll to drive await continuations, but my experiments so far implementing a custom SynchronizationContext and/or custom TaskScheduler aren't working.

All the examples I've found so far seem to assume there are at least two threads in play. I think it should be possible to do everything in a single thread, but I haven't figured out how to hook everything up.

Notification Bot (May 29 2024 at 17:36):

A message was moved here from #C#/.net-collaboration > replacing emsdk with wasi-sdk by Joel Dice.

Joel Dice (May 29 2024 at 17:37):

Nevermind, I figured it out. The key was to use TaskCreationOptions.AttachedToParent to ensure the child tasks finish before the parent task finishes.

Scott Waye (May 30 2024 at 09:44):

no problem, feel free to create noise :-)

Joel Dice (May 30 2024 at 19:19):

Ok, so I hit a real (i.e. not just self-inflicted) roadblock this time: https://github.com/dotnet/runtime/issues/102894
I'd love to get feedback on that from the .NET experts.

[wasi] `async`/`await` on WASI · Issue #102894 · dotnet/runtime

I've been working to support async/await in C# for doing concurrent I/O when targeting WASIp2. A key piece of that is the wasi:io/poll#poll function, which accepts an arbitrary number of pollable h...

Joel Dice (May 30 2024 at 22:19):

While I still think the above is a real issue, I worked around it by implementing my own WhenEach combinator. Here's an example that does concurrent outbound request streaming: https://github.com/dicej/dotnet9-wasi-http-example/blob/snapshot/App.cs

dotnet9-wasi-http-example/App.cs at snapshot · dicej/dotnet9-wasi-http-example

Contribute to dicej/dotnet9-wasi-http-example development by creating an account on GitHub.

Last updated: Dec 13 2025 at 20:04 UTC