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Add epoch interruption to WASM engine for cooperative yielding (#32806)

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Prevent extensions from blocking async threads by enabling epoch
interruption with 100ms intervals. Extensions will yield control back to
the executor regularly during Future::poll operations.

Addresses the
[discussion](https://github.com/zed-industries/zed/discussions/24515)
that goes into depth on why this is important when enabling async
support with Wasmtime.

Release Notes:

- N/A
This commit is contained in:
Ben Brandt 2025-06-17 15:43:17 +02:00 • committed by GitHub
parent 4bbb7b5c2f
commit acb0210d26
No known key found for this signature in database
GPG key ID: B5690EEEBB952194
11 changed files with 93 additions and 43 deletions
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55
crates/extension_host/src/wasm_host.rs
View file

@ -19,7 +19,7 @@ use futures::{
},
future::BoxFuture,
};
use gpui::{App, AsyncApp, BackgroundExecutor, Task};
use gpui::{App, AsyncApp, BackgroundExecutor, Task, Timer};
use http_client::HttpClient;
use language::LanguageName;
use lsp::LanguageServerName;
@ -28,7 +28,8 @@ use node_runtime::NodeRuntime;
use release_channel::ReleaseChannel;
use semantic_version::SemanticVersion;
use std::borrow::Cow;
use std::sync::LazyLock;
use std::sync::{LazyLock, OnceLock};
use std::time::Duration;
use std::{
path::{Path, PathBuf},
sync::Arc,
@ -487,18 +488,52 @@ type ExtensionCall = Box<
dyn Send + for<'a> FnOnce(&'a mut Extension, &'a mut Store<WasmState>) -> BoxFuture<'a, ()>,
>;
fn wasm_engine() -> wasmtime::Engine {
static WASM_ENGINE: LazyLock<wasmtime::Engine> = LazyLock::new(|| {
fn wasm_engine(executor: &BackgroundExecutor) -> wasmtime::Engine {
static WASM_ENGINE: OnceLock<wasmtime::Engine> = OnceLock::new();
WASM_ENGINE
.get_or_init(|| {
let mut config = wasmtime::Config::new();
config.wasm_component_model(true);
config.async_support(true);
config
.enable_incremental_compilation(cache_store())
.unwrap();
wasmtime::Engine::new(&config).unwrap()
});
// Async support introduces the issue that extension execution happens during `Future::poll`,
// which could block an async thread.
// https://docs.rs/wasmtime/latest/wasmtime/struct.Config.html#execution-in-poll
//
// Epoch interruption is a lightweight mechanism to allow the extensions to yield control
// back to the executor at regular intervals.
config.epoch_interruption(true);
WASM_ENGINE.clone()
let engine = wasmtime::Engine::new(&config).unwrap();
// It might be safer to do this on a non-async thread to make sure it makes progress
// regardless of if extensions are blocking.
// However, due to our current setup, this isn't a likely occurrence and we'd rather
// not have a dedicated thread just for this. If it becomes an issue, we can consider
// creating a separate thread for epoch interruption.
let engine_ref = engine.weak();
executor
.spawn(async move {
// Somewhat arbitrary interval, as it isn't a guaranteed interval.
// But this is a rough upper bound for how long the extension execution can block on
// `Future::poll`.
const EPOCH_INTERVAL: Duration = Duration::from_millis(100);
let mut timer = Timer::interval(EPOCH_INTERVAL);
while let Some(_) = timer.next().await {
// Exit the loop and thread once the engine is dropped.
let Some(engine) = engine_ref.upgrade() else {
break;
};
engine.increment_epoch();
}
})
.detach();
engine
})
.clone()
}
fn cache_store() -> Arc<IncrementalCompilationCache> {
@ -523,7 +558,7 @@ impl WasmHost {
}
});
Arc::new(Self {
engine: wasm_engine(),
engine: wasm_engine(cx.background_executor()),
fs,
work_dir,
http_client,
@ -558,8 +593,12 @@ impl WasmHost {
host: this.clone(),
},
);
// Store will yield after 1 tick, and get a new deadline of 1 tick after each yield.
store.set_epoch_deadline(1);
store.epoch_deadline_async_yield_and_update(1);
let mut extension = Extension::instantiate_async(
&executor,
&mut store,
this.release_channel,
zed_api_version,

23
crates/extension_host/src/wasm_host/wit.rs
View file

@ -9,6 +9,7 @@ mod since_v0_5_0;
mod since_v0_6_0;
use dap::DebugRequest;
use extension::{DebugTaskDefinition, KeyValueStoreDelegate, WorktreeDelegate};
use gpui::BackgroundExecutor;
use language::LanguageName;
use lsp::LanguageServerName;
use release_channel::ReleaseChannel;
@ -39,9 +40,10 @@ pub use latest::{
pub use since_v0_0_4::LanguageServerConfig;
pub fn new_linker(
executor: &BackgroundExecutor,
f: impl Fn(&mut Linker<WasmState>, fn(&mut WasmState) -> &mut WasmState) -> Result<()>,
) -> Linker<WasmState> {
let mut linker = Linker::new(&wasm_engine());
let mut linker = Linker::new(&wasm_engine(executor));
wasmtime_wasi::add_to_linker_async(&mut linker).unwrap();
f(&mut linker, wasi_view).unwrap();
linker
@ -109,6 +111,7 @@ pub enum Extension {
impl Extension {
pub async fn instantiate_async(
executor: &BackgroundExecutor,
store: &mut Store<WasmState>,
release_channel: ReleaseChannel,
version: SemanticVersion,
@ -121,7 +124,7 @@ impl Extension {
authorize_access_to_unreleased_wasm_api_version(release_channel)?;
let extension =
latest::Extension::instantiate_async(store, component, latest::linker())
latest::Extension::instantiate_async(store, component, latest::linker(executor))
.await
.context("failed to instantiate wasm extension")?;
Ok(Self::V0_6_0(extension))
@ -129,7 +132,7 @@ impl Extension {
let extension = since_v0_5_0::Extension::instantiate_async(
store,
component,
since_v0_5_0::linker(),
since_v0_5_0::linker(executor),
)
.await
.context("failed to instantiate wasm extension")?;
@ -138,7 +141,7 @@ impl Extension {
let extension = since_v0_4_0::Extension::instantiate_async(
store,
component,
since_v0_4_0::linker(),
since_v0_4_0::linker(executor),
)
.await
.context("failed to instantiate wasm extension")?;
@ -147,7 +150,7 @@ impl Extension {
let extension = since_v0_3_0::Extension::instantiate_async(
store,
component,
since_v0_3_0::linker(),
since_v0_3_0::linker(executor),
)
.await
.context("failed to instantiate wasm extension")?;
@ -156,7 +159,7 @@ impl Extension {
let extension = since_v0_2_0::Extension::instantiate_async(
store,
component,
since_v0_2_0::linker(),
since_v0_2_0::linker(executor),
)
.await
.context("failed to instantiate wasm extension")?;
@ -165,7 +168,7 @@ impl Extension {
let extension = since_v0_1_0::Extension::instantiate_async(
store,
component,
since_v0_1_0::linker(),
since_v0_1_0::linker(executor),
)
.await
.context("failed to instantiate wasm extension")?;
@ -174,7 +177,7 @@ impl Extension {
let extension = since_v0_0_6::Extension::instantiate_async(
store,
component,
since_v0_0_6::linker(),
since_v0_0_6::linker(executor),
)
.await
.context("failed to instantiate wasm extension")?;
@ -183,7 +186,7 @@ impl Extension {
let extension = since_v0_0_4::Extension::instantiate_async(
store,
component,
since_v0_0_4::linker(),
since_v0_0_4::linker(executor),
)
.await
.context("failed to instantiate wasm extension")?;
@ -192,7 +195,7 @@ impl Extension {
let extension = since_v0_0_1::Extension::instantiate_async(
store,
component,
since_v0_0_1::linker(),
since_v0_0_1::linker(executor),
)
.await
.context("failed to instantiate wasm extension")?;

5
crates/extension_host/src/wasm_host/wit/since_v0_0_1.rs
View file

@ -3,6 +3,7 @@ use crate::wasm_host::WasmState;
use crate::wasm_host::wit::since_v0_0_4;
use anyhow::Result;
use extension::{ExtensionLanguageServerProxy, WorktreeDelegate};
use gpui::BackgroundExecutor;
use language::BinaryStatus;
use semantic_version::SemanticVersion;
use std::sync::{Arc, OnceLock};
@ -23,9 +24,9 @@ wasmtime::component::bindgen!({
pub type ExtensionWorktree = Arc<dyn WorktreeDelegate>;
pub fn linker() -> &'static Linker<WasmState> {
pub fn linker(executor: &BackgroundExecutor) -> &'static Linker<WasmState> {
static LINKER: OnceLock<Linker<WasmState>> = OnceLock::new();
LINKER.get_or_init(|| super::new_linker(Extension::add_to_linker))
LINKER.get_or_init(|| super::new_linker(executor, Extension::add_to_linker))
}
impl From<DownloadedFileType> for latest::DownloadedFileType {

5
crates/extension_host/src/wasm_host/wit/since_v0_0_4.rs
View file

@ -2,6 +2,7 @@ use super::latest;
use crate::wasm_host::WasmState;
use anyhow::Result;
use extension::WorktreeDelegate;
use gpui::BackgroundExecutor;
use semantic_version::SemanticVersion;
use std::sync::{Arc, OnceLock};
use wasmtime::component::{Linker, Resource};
@ -21,9 +22,9 @@ wasmtime::component::bindgen!({
pub type ExtensionWorktree = Arc<dyn WorktreeDelegate>;
pub fn linker() -> &'static Linker<WasmState> {
pub fn linker(executor: &BackgroundExecutor) -> &'static Linker<WasmState> {
static LINKER: OnceLock<Linker<WasmState>> = OnceLock::new();
LINKER.get_or_init(|| super::new_linker(Extension::add_to_linker))
LINKER.get_or_init(|| super::new_linker(executor, Extension::add_to_linker))
}
impl From<DownloadedFileType> for latest::DownloadedFileType {

5
crates/extension_host/src/wasm_host/wit/since_v0_0_6.rs
View file

@ -2,6 +2,7 @@ use super::{latest, since_v0_1_0};
use crate::wasm_host::WasmState;
use anyhow::Result;
use extension::WorktreeDelegate;
use gpui::BackgroundExecutor;
use semantic_version::SemanticVersion;
use std::sync::{Arc, OnceLock};
use wasmtime::component::{Linker, Resource};
@ -27,9 +28,9 @@ mod settings {
pub type ExtensionWorktree = Arc<dyn WorktreeDelegate>;
pub fn linker() -> &'static Linker<WasmState> {
pub fn linker(executor: &BackgroundExecutor) -> &'static Linker<WasmState> {
static LINKER: OnceLock<Linker<WasmState>> = OnceLock::new();
LINKER.get_or_init(|| super::new_linker(Extension::add_to_linker))
LINKER.get_or_init(|| super::new_linker(executor, Extension::add_to_linker))
}
impl From<Command> for latest::Command {

5
crates/extension_host/src/wasm_host/wit/since_v0_1_0.rs
View file

@ -7,6 +7,7 @@ use async_tar::Archive;
use extension::{ExtensionLanguageServerProxy, KeyValueStoreDelegate, WorktreeDelegate};
use futures::{AsyncReadExt, lock::Mutex};
use futures::{FutureExt as _, io::BufReader};
use gpui::BackgroundExecutor;
use language::LanguageName;
use language::{BinaryStatus, language_settings::AllLanguageSettings};
use project::project_settings::ProjectSettings;
@ -48,9 +49,9 @@ pub type ExtensionWorktree = Arc<dyn WorktreeDelegate>;
pub type ExtensionKeyValueStore = Arc<dyn KeyValueStoreDelegate>;
pub type ExtensionHttpResponseStream = Arc<Mutex<::http_client::Response<AsyncBody>>>;
pub fn linker() -> &'static Linker<WasmState> {
pub fn linker(executor: &BackgroundExecutor) -> &'static Linker<WasmState> {
static LINKER: OnceLock<Linker<WasmState>> = OnceLock::new();
LINKER.get_or_init(|| super::new_linker(Extension::add_to_linker))
LINKER.get_or_init(|| super::new_linker(executor, Extension::add_to_linker))
}
impl From<Command> for latest::Command {

5
crates/extension_host/src/wasm_host/wit/since_v0_2_0.rs
View file

@ -1,6 +1,7 @@
use crate::wasm_host::WasmState;
use anyhow::Result;
use extension::{KeyValueStoreDelegate, ProjectDelegate, WorktreeDelegate};
use gpui::BackgroundExecutor;
use semantic_version::SemanticVersion;
use std::sync::{Arc, OnceLock};
use wasmtime::component::{Linker, Resource};
@ -36,9 +37,9 @@ pub type ExtensionWorktree = Arc<dyn WorktreeDelegate>;
pub type ExtensionProject = Arc<dyn ProjectDelegate>;
pub type ExtensionKeyValueStore = Arc<dyn KeyValueStoreDelegate>;
pub fn linker() -> &'static Linker<WasmState> {
pub fn linker(executor: &BackgroundExecutor) -> &'static Linker<WasmState> {
static LINKER: OnceLock<Linker<WasmState>> = OnceLock::new();
LINKER.get_or_init(|| super::new_linker(Extension::add_to_linker))
LINKER.get_or_init(|| super::new_linker(executor, Extension::add_to_linker))
}
impl From<Command> for latest::Command {

5
crates/extension_host/src/wasm_host/wit/since_v0_3_0.rs
View file

@ -1,6 +1,7 @@
use crate::wasm_host::WasmState;
use anyhow::Result;
use extension::{KeyValueStoreDelegate, ProjectDelegate, WorktreeDelegate};
use gpui::BackgroundExecutor;
use semantic_version::SemanticVersion;
use std::sync::{Arc, OnceLock};
use wasmtime::component::{Linker, Resource};
@ -36,9 +37,9 @@ pub type ExtensionWorktree = Arc<dyn WorktreeDelegate>;
pub type ExtensionProject = Arc<dyn ProjectDelegate>;
pub type ExtensionKeyValueStore = Arc<dyn KeyValueStoreDelegate>;
pub fn linker() -> &'static Linker<WasmState> {
pub fn linker(executor: &BackgroundExecutor) -> &'static Linker<WasmState> {
static LINKER: OnceLock<Linker<WasmState>> = OnceLock::new();
LINKER.get_or_init(|| super::new_linker(Extension::add_to_linker))
LINKER.get_or_init(|| super::new_linker(executor, Extension::add_to_linker))
}
impl From<CodeLabel> for latest::CodeLabel {

5
crates/extension_host/src/wasm_host/wit/since_v0_4_0.rs
View file

@ -1,6 +1,7 @@
use crate::wasm_host::WasmState;
use anyhow::Result;
use extension::{KeyValueStoreDelegate, ProjectDelegate, WorktreeDelegate};
use gpui::BackgroundExecutor;
use semantic_version::SemanticVersion;
use std::sync::{Arc, OnceLock};
use wasmtime::component::{Linker, Resource};
@ -36,9 +37,9 @@ pub type ExtensionWorktree = Arc<dyn WorktreeDelegate>;
pub type ExtensionProject = Arc<dyn ProjectDelegate>;
pub type ExtensionKeyValueStore = Arc<dyn KeyValueStoreDelegate>;
pub fn linker() -> &'static Linker<WasmState> {
pub fn linker(executor: &BackgroundExecutor) -> &'static Linker<WasmState> {
static LINKER: OnceLock<Linker<WasmState>> = OnceLock::new();
LINKER.get_or_init(|| super::new_linker(Extension::add_to_linker))
LINKER.get_or_init(|| super::new_linker(executor, Extension::add_to_linker))
}
impl From<CodeLabel> for latest::CodeLabel {

5
crates/extension_host/src/wasm_host/wit/since_v0_5_0.rs
View file

@ -1,6 +1,7 @@
use crate::wasm_host::WasmState;
use anyhow::Result;
use extension::{KeyValueStoreDelegate, ProjectDelegate, WorktreeDelegate};
use gpui::BackgroundExecutor;
use semantic_version::SemanticVersion;
use std::sync::{Arc, OnceLock};
use wasmtime::component::{Linker, Resource};
@ -38,9 +39,9 @@ pub type ExtensionWorktree = Arc<dyn WorktreeDelegate>;
pub type ExtensionProject = Arc<dyn ProjectDelegate>;
pub type ExtensionKeyValueStore = Arc<dyn KeyValueStoreDelegate>;
pub fn linker() -> &'static Linker<WasmState> {
pub fn linker(executor: &BackgroundExecutor) -> &'static Linker<WasmState> {
static LINKER: OnceLock<Linker<WasmState>> = OnceLock::new();
LINKER.get_or_init(|| super::new_linker(Extension::add_to_linker))
LINKER.get_or_init(|| super::new_linker(executor, Extension::add_to_linker))
}
impl From<CodeLabel> for latest::CodeLabel {

6
crates/extension_host/src/wasm_host/wit/since_v0_6_0.rs
View file

@ -18,7 +18,7 @@ use extension::{
};
use futures::{AsyncReadExt, lock::Mutex};
use futures::{FutureExt as _, io::BufReader};
use gpui::SharedString;
use gpui::{BackgroundExecutor, SharedString};
use language::{BinaryStatus, LanguageName, language_settings::AllLanguageSettings};
use project::project_settings::ProjectSettings;
use semantic_version::SemanticVersion;
@ -59,9 +59,9 @@ pub type ExtensionProject = Arc<dyn ProjectDelegate>;
pub type ExtensionKeyValueStore = Arc<dyn KeyValueStoreDelegate>;
pub type ExtensionHttpResponseStream = Arc<Mutex<::http_client::Response<AsyncBody>>>;
pub fn linker() -> &'static Linker<WasmState> {
pub fn linker(executor: &BackgroundExecutor) -> &'static Linker<WasmState> {
static LINKER: OnceLock<Linker<WasmState>> = OnceLock::new();
LINKER.get_or_init(|| super::new_linker(Extension::add_to_linker))
LINKER.get_or_init(|| super::new_linker(executor, Extension::add_to_linker))
}
impl From<Range> for std::ops::Range<usize> {