edfa10d607
This commit includes a set of changes that add initial support for `wasi-threads` to Wasmtime:
* feat: remove mutability from the WasiCtx Table
This patch adds interior mutability to the WasiCtx Table and the Table elements.
Major pain points:
* `File` only needs `RwLock<cap_std::fs::File>` to implement
`File::set_fdflags()` on Windows, because of [1]
* Because `File` needs a `RwLock` and `RwLock*Guard` cannot
be hold across an `.await`, The `async` from
`async fn num_ready_bytes(&self)` had to be removed
* Because `File` needs a `RwLock` and `RwLock*Guard` cannot
be dereferenced in `pollable`, the signature of
`fn pollable(&self) -> Option<rustix::fd::BorrowedFd>`
changed to `fn pollable(&self) -> Option<Arc<dyn AsFd + '_>>`
[1] da238e324e/src/fs/fd_flags.rs (L210-L217)
* wasi-threads: add an initial implementation
This change is a first step toward implementing `wasi-threads` in
Wasmtime. We may find that it has some missing pieces, but the core
functionality is there: when `wasi::thread_spawn` is called by a running
WebAssembly module, a function named `wasi_thread_start` is found in the
module's exports and called in a new instance. The shared memory of the
original instance is reused in the new instance.
This new WASI proposal is in its early stages and details are still
being hashed out in the [spec] and [wasi-libc] repositories. Due to its
experimental state, the `wasi-threads` functionality is hidden behind
both a compile-time and runtime flag: one must build with `--features
wasi-threads` but also run the Wasmtime CLI with `--wasm-features
threads` and `--wasi-modules experimental-wasi-threads`. One can
experiment with `wasi-threads` by running:
```console
$ cargo run --features wasi-threads -- \
--wasm-features threads --wasi-modules experimental-wasi-threads \
<a threads-enabled module>
```
Threads-enabled Wasm modules are not yet easy to build. Hopefully this
is resolved soon, but in the meantime see the use of
`THREAD_MODEL=posix` in the [wasi-libc] repository for some clues on
what is necessary. Wiggle complicates things by requiring the Wasm
memory to be exported with a certain name and `wasi-threads` also
expects that memory to be imported; this build-time obstacle can be
overcome with the `--import-memory --export-memory` flags only available
in the latest Clang tree. Due to all of this, the included tests are
written directly in WAT--run these with:
```console
$ cargo test --features wasi-threads -p wasmtime-cli -- cli_tests
```
[spec]: https://github.com/WebAssembly/wasi-threads
[wasi-libc]: https://github.com/WebAssembly/wasi-libc
This change does not protect the WASI implementations themselves from
concurrent access. This is already complete in previous commits or left
for future commits in certain cases (e.g., wasi-nn).
* wasi-threads: factor out process exit logic
As is being discussed [elsewhere], either calling `proc_exit` or
trapping in any thread should halt execution of all threads. The
Wasmtime CLI already has logic for adapting a WebAssembly error code to
a code expected in each OS. This change factors out this logic to a new
function, `maybe_exit_on_error`, for use within the `wasi-threads`
implementation.
This will work reasonably well for CLI users of Wasmtime +
`wasi-threads`, but embedders will want something better in the future:
when a `wasi-threads` threads fails, they may not want their application
to exit. Handling this is tricky, because it will require cancelling the
threads spawned by the `wasi-threads` implementation, something that is
not trivial to do in Rust. With this change, we defer that work until
later in order to provide a working implementation of `wasi-threads` for
experimentation.
[elsewhere]: https://github.com/WebAssembly/wasi-threads/pull/17
* review: work around `fd_fdstat_set_flags`
In order to make progress with wasi-threads, this change temporarily
works around limitations induced by `wasi-common`'s
`fd_fdstat_set_flags` to allow `&mut self` use in the implementation.
Eventual resolution is tracked in
https://github.com/bytecodealliance/wasmtime/issues/5643. This change
makes several related helper functions (e.g., `set_fdflags`) take `&mut
self` as well.
* test: use `wait`/`notify` to improve `threads.wat` test
Previously, the test simply executed in a loop for some hardcoded number
of iterations. This changes uses `wait` and `notify` and atomic
operations to keep track of when the spawned threads are done and join
on the main thread appropriately.
* various fixes and tweaks due to the PR review
---------
Signed-off-by: Harald Hoyer <harald@profian.com>
Co-authored-by: Harald Hoyer <harald@profian.com>
Co-authored-by: Alex Crichton <alex@alexcrichton.com>
wasmtime-wasi-nn
This crate enables support for the wasi-nn API in Wasmtime. Currently it contains an implementation of wasi-nn using OpenVINO™ but in the future it could support multiple machine learning backends. Since the wasi-nn API is expected to be an optional feature of WASI, this crate is currently separate from the wasi-common crate. This crate is experimental and its API, functionality, and location could quickly change.
Use
Use the Wasmtime APIs to instantiate a Wasm module and link in the WasiNn implementation as follows:
let wasi_nn = WasiNn::new(&store, WasiNnCtx::new()?);
wasi_nn.add_to_linker(&mut linker)?;
Build
This crate should build as usual (i.e. cargo build) but note that using an existing installation of OpenVINO™, rather
than building from source, will drastically improve the build times. See the openvino crate for more information
Example
An end-to-end example demonstrating ML classification is included in examples:
tests/wasi-nn-rust-bindingscontains ergonomic bindings for writing Rust code against the wasi-nn APIstests/classification-examplecontains a standalone Rust project that uses the wasi-nn APIs and is compiled to thewasm32-wasitarget using thewasi-nn-rust-bindings
Run the example from the Wasmtime project directory:
ci/run-wasi-nn-example.sh