Hi all,

As there was recently not much work on the proposal, I'd like us to define some next steps to move towards finalizing threading support in WebAssembly.

A brief summary of the current state:

• a number of ambiguities around wasi_thread_spawn host call was clarified
• tests have been added
• tooling support:
  • partial implementation of pthread API in WASI libc
  • a PR to enable threads in Rust: https://github.com/rust-lang/rust/pull/112922/files
• Runtime support:
  • Wasmtime
  • WAMR
  • ... ?
• Open questions:
  • should threads be terminated on exiting from start function: return from _start #21
  • should the memory be exported from the module: should memory be exported as well? #22
  • do we need wasi_thread_exit(): Is wasi_thread_exit needed? #7
  • do we need API for querying a max thread count: Query the maximum available parallelism #31
  • should the proposal be included in wasi_snapshot_preview1: change module name to wasi_snapshot_preview1 #47

I think there are two possible ways we can move forward with the proposal:

1. we keep the proposal in its current stage (phase 1) and start work on a proposal for adding threading to WebAssembly (possibly as an extension to the threads proposal.
2. we continue the work on this proposal - define phase 2 advancement criteria (I think we're close), resolve all the remaining questions, define the release plan.

My personal opinion is that we should progress with wasi-threads proposal and accept the risk it becomes deprecated in the distant future (if ever) by WebAssembly threads - this approach will enable a number of use cases in short/mid-term that are currently blocked by lack of standardization of threading in the WASI ecosystem. There's already been a lot of discussions on open questions, and it feels like some of them only need a summary and updated documentation before closing, and some of them can be even resolved as follow-ups after this proposal.

I'm looking for others' feedback on that before taking any next steps.
cc @sunfishcode @abrown @sbc100 @AlexEne @yamt