wasmtime/runtime/component/concurrent.rs
1//! Runtime support for the Component Model Async ABI.
2//!
3//! This module and its submodules provide host runtime support for Component
4//! Model Async features such as async-lifted exports, async-lowered imports,
5//! streams, futures, and related intrinsics. See [the Async
6//! Explainer](https://github.com/WebAssembly/component-model/blob/main/design/mvp/Async.md)
7//! for a high-level overview.
8//!
9//! At the core of this support is an event loop which schedules and switches
10//! between guest tasks and any host tasks they create. Each
11//! `ComponentInstance` will have at most one event loop running at any given
12//! time, and that loop may be suspended and resumed by the host embedder using
13//! e.g. `Instance::run_concurrent`. The `ComponentInstance::poll_until`
14//! function contains the loop itself, while the
15//! `ComponentInstance::concurrent_state` field holds its state.
16//!
17//! # Public API Overview
18//!
19//! ## Top-level API (e.g. kicking off host->guest calls and driving the event loop)
20//!
21//! - `[Typed]Func::call_concurrent`: Start a host->guest call to an
22//! async-lifted or sync-lifted import, creating a guest task.
23//!
24//! - `Instance::run_concurrent`: Run the event loop for the specified instance,
25//! allowing any and all tasks belonging to that instance to make progress.
26//!
27//! - `Instance::spawn`: Run a background task as part of the event loop for the
28//! specified instance.
29//!
30//! - `Instance::{future,stream}`: Create a new Component Model `future` or
31//! `stream`; the read end may be passed to the guest.
32//!
33//! - `{Future,Stream}Reader::read` and `{Future,Stream}Writer::write`: read
34//! from or write to a future or stream, respectively.
35//!
36//! ## Host Task API (e.g. implementing concurrent host functions and background tasks)
37//!
38//! - `LinkerInstance::func_wrap_concurrent`: Register a concurrent host
39//! function with the linker. That function will take an `Accessor` as its
40//! first parameter, which provides access to the store and instance between
41//! (but not across) await points.
42//!
43//! - `Accessor::with`: Access the store, its associated data, and the current
44//! instance.
45//!
46//! - `Accessor::spawn`: Run a background task as part of the event loop for the
47//! specified instance. This is equivalent to `Instance::spawn` but more
48//! convenient to use in host functions.
49
50use crate::component::func::{self, Func, Options};
51use crate::component::{Component, ComponentInstanceId, HasData, HasSelf, Instance};
52use crate::fiber::{self, StoreFiber, StoreFiberYield};
53use crate::store::{StoreInner, StoreOpaque, StoreToken};
54use crate::vm::component::{
55 CallContext, ComponentInstance, InstanceFlags, ResourceTables, TransmitLocalState,
56};
57use crate::vm::{SendSyncPtr, VMFuncRef, VMMemoryDefinition, VMStore};
58use crate::{AsContext, AsContextMut, StoreContext, StoreContextMut, ValRaw};
59use anyhow::{Context as _, Result, anyhow, bail};
60use error_contexts::GlobalErrorContextRefCount;
61use futures::channel::oneshot;
62use futures::future::{self, Either, FutureExt};
63use futures::stream::{FuturesUnordered, StreamExt};
64use futures_and_streams::{FlatAbi, ReturnCode, TransmitHandle, TransmitIndex};
65use std::any::Any;
66use std::borrow::ToOwned;
67use std::boxed::Box;
68use std::cell::UnsafeCell;
69use std::collections::{BTreeMap, BTreeSet, HashMap, HashSet};
70use std::fmt;
71use std::future::Future;
72use std::marker::PhantomData;
73use std::mem::{self, ManuallyDrop, MaybeUninit};
74use std::ops::DerefMut;
75use std::pin::{Pin, pin};
76use std::ptr::{self, NonNull};
77use std::slice;
78use std::sync::Mutex;
79use std::task::{Context, Poll, Waker};
80use std::vec::Vec;
81use table::{Table, TableDebug, TableError, TableId};
82use wasmtime_environ::component::{
83 CanonicalOptions, CanonicalOptionsDataModel, ExportIndex, MAX_FLAT_PARAMS, MAX_FLAT_RESULTS,
84 OptionsIndex, PREPARE_ASYNC_NO_RESULT, PREPARE_ASYNC_WITH_RESULT,
85 RuntimeComponentInstanceIndex, StringEncoding, TypeComponentGlobalErrorContextTableIndex,
86 TypeComponentLocalErrorContextTableIndex, TypeFutureTableIndex, TypeStreamTableIndex,
87 TypeTupleIndex,
88};
89
90pub use abort::JoinHandle;
91pub use futures_and_streams::{
92 ErrorContext, FutureReader, FutureWriter, GuardedFutureReader, GuardedFutureWriter,
93 GuardedStreamReader, GuardedStreamWriter, ReadBuffer, StreamReader, StreamWriter, VecBuffer,
94 WriteBuffer,
95};
96pub(crate) use futures_and_streams::{
97 ResourcePair, lower_error_context_to_index, lower_future_to_index, lower_stream_to_index,
98};
99
100mod abort;
101mod error_contexts;
102mod futures_and_streams;
103mod table;
104pub(crate) mod tls;
105
106/// Constant defined in the Component Model spec to indicate that the async
107/// intrinsic (e.g. `future.write`) has not yet completed.
108const BLOCKED: u32 = 0xffff_ffff;
109
110/// Corresponds to `CallState` in the upstream spec.
111#[derive(Clone, Copy, Eq, PartialEq, Debug)]
112pub enum Status {
113 Starting = 0,
114 Started = 1,
115 Returned = 2,
116 StartCancelled = 3,
117 ReturnCancelled = 4,
118}
119
120impl Status {
121 /// Packs this status and the optional `waitable` provided into a 32-bit
122 /// result that the canonical ABI requires.
123 ///
124 /// The low 4 bits are reserved for the status while the upper 28 bits are
125 /// the waitable, if present.
126 pub fn pack(self, waitable: Option<u32>) -> u32 {
127 assert!(matches!(self, Status::Returned) == waitable.is_none());
128 let waitable = waitable.unwrap_or(0);
129 assert!(waitable < (1 << 28));
130 (waitable << 4) | (self as u32)
131 }
132}
133
134/// Corresponds to `EventCode` in the Component Model spec, plus related payload
135/// data.
136#[derive(Clone, Copy, Debug)]
137enum Event {
138 None,
139 Cancelled,
140 Subtask {
141 status: Status,
142 },
143 StreamRead {
144 code: ReturnCode,
145 pending: Option<(TypeStreamTableIndex, u32)>,
146 },
147 StreamWrite {
148 code: ReturnCode,
149 pending: Option<(TypeStreamTableIndex, u32)>,
150 },
151 FutureRead {
152 code: ReturnCode,
153 pending: Option<(TypeFutureTableIndex, u32)>,
154 },
155 FutureWrite {
156 code: ReturnCode,
157 pending: Option<(TypeFutureTableIndex, u32)>,
158 },
159}
160
161impl Event {
162 /// Lower this event to core Wasm integers for delivery to the guest.
163 ///
164 /// Note that the waitable handle, if any, is assumed to be lowered
165 /// separately.
166 fn parts(self) -> (u32, u32) {
167 const EVENT_NONE: u32 = 0;
168 const EVENT_SUBTASK: u32 = 1;
169 const EVENT_STREAM_READ: u32 = 2;
170 const EVENT_STREAM_WRITE: u32 = 3;
171 const EVENT_FUTURE_READ: u32 = 4;
172 const EVENT_FUTURE_WRITE: u32 = 5;
173 const EVENT_CANCELLED: u32 = 6;
174 match self {
175 Event::None => (EVENT_NONE, 0),
176 Event::Cancelled => (EVENT_CANCELLED, 0),
177 Event::Subtask { status } => (EVENT_SUBTASK, status as u32),
178 Event::StreamRead { code, .. } => (EVENT_STREAM_READ, code.encode()),
179 Event::StreamWrite { code, .. } => (EVENT_STREAM_WRITE, code.encode()),
180 Event::FutureRead { code, .. } => (EVENT_FUTURE_READ, code.encode()),
181 Event::FutureWrite { code, .. } => (EVENT_FUTURE_WRITE, code.encode()),
182 }
183 }
184}
185
186/// Corresponds to `CallbackCode` in the spec.
187mod callback_code {
188 pub const EXIT: u32 = 0;
189 pub const YIELD: u32 = 1;
190 pub const WAIT: u32 = 2;
191 pub const POLL: u32 = 3;
192}
193
194/// A flag indicating that the callee is an async-lowered export.
195///
196/// This may be passed to the `async-start` intrinsic from a fused adapter.
197const START_FLAG_ASYNC_CALLEE: u32 = wasmtime_environ::component::START_FLAG_ASYNC_CALLEE as u32;
198
199/// Provides access to either store data (via the `get` method) or the store
200/// itself (via [`AsContext`]/[`AsContextMut`]), as well as the component
201/// instance to which the current host task belongs.
202///
203/// See [`Accessor::with`] for details.
204pub struct Access<'a, T: 'static, D: HasData + ?Sized = HasSelf<T>> {
205 accessor: &'a Accessor<T, D>,
206 store: StoreContextMut<'a, T>,
207}
208
209impl<'a, T, D> Access<'a, T, D>
210where
211 D: HasData + ?Sized,
212 T: 'static,
213{
214 /// Get mutable access to the store data.
215 pub fn data_mut(&mut self) -> &mut T {
216 self.store.data_mut()
217 }
218
219 /// Get mutable access to the store data.
220 pub fn get(&mut self) -> D::Data<'_> {
221 let get_data = self.accessor.get_data;
222 get_data(self.data_mut())
223 }
224
225 /// Spawn a background task.
226 ///
227 /// See [`Accessor::spawn`] for details.
228 pub fn spawn(&mut self, task: impl AccessorTask<T, D, Result<()>>) -> JoinHandle
229 where
230 T: 'static,
231 {
232 self.accessor.instance.unwrap().spawn_with_accessor(
233 self.store.as_context_mut(),
234 self.accessor.clone_for_spawn(),
235 task,
236 )
237 }
238
239 /// Retrieve the component instance of the caller.
240 pub fn instance(&self) -> Instance {
241 self.accessor.instance()
242 }
243}
244
245impl<'a, T, D> AsContext for Access<'a, T, D>
246where
247 D: HasData + ?Sized,
248 T: 'static,
249{
250 type Data = T;
251
252 fn as_context(&self) -> StoreContext<'_, T> {
253 self.store.as_context()
254 }
255}
256
257impl<'a, T, D> AsContextMut for Access<'a, T, D>
258where
259 D: HasData + ?Sized,
260 T: 'static,
261{
262 fn as_context_mut(&mut self) -> StoreContextMut<'_, T> {
263 self.store.as_context_mut()
264 }
265}
266
267/// Provides scoped mutable access to store data in the context of a concurrent
268/// host task future.
269///
270/// This allows multiple host task futures to execute concurrently and access
271/// the store between (but not across) `await` points.
272///
273/// # Rationale
274///
275/// This structure is sort of like `&mut T` plus a projection from `&mut T` to
276/// `D::Data<'_>`. The problem this is solving, however, is that it does not
277/// literally store these values. The basic problem is that when a concurrent
278/// host future is being polled it has access to `&mut T` (and the whole
279/// `Store`) but when it's not being polled it does not have access to these
280/// values. This reflects how the store is only ever polling one future at a
281/// time so the store is effectively being passed between futures.
282///
283/// Rust's `Future` trait, however, has no means of passing a `Store`
284/// temporarily between futures. The [`Context`](std::task::Context) type does
285/// not have the ability to attach arbitrary information to it at this time.
286/// This type, [`Accessor`], is used to bridge this expressivity gap.
287///
288/// The [`Accessor`] type here represents the ability to acquire, temporarily in
289/// a synchronous manner, the current store. The [`Accessor::with`] function
290/// yields an [`Access`] which can be used to access [`StoreContextMut`], `&mut
291/// T`, or `D::Data<'_>`. Note though that [`Accessor::with`] intentionally does
292/// not take an `async` closure as its argument, instead it's a synchronous
293/// closure which must complete during on run of `Future::poll`. This reflects
294/// how the store is temporarily made available while a host future is being
295/// polled.
296///
297/// # Implementation
298///
299/// This type does not actually store `&mut T` nor `StoreContextMut<T>`, and
300/// this type additionally doesn't even have a lifetime parameter. This is
301/// instead a representation of proof of the ability to acquire these while a
302/// future is being polled. Wasmtime will, when it polls a host future,
303/// configure ambient state such that the `Accessor` that a future closes over
304/// will work and be able to access the store.
305///
306/// This has a number of implications for users such as:
307///
308/// * It's intentional that `Accessor` cannot be cloned, it needs to stay within
309/// the lifetime of a single future.
310/// * A futures is expected to, however, close over an `Accessor` and keep it
311/// alive probably for the duration of the entire future.
312/// * Different host futures will be given different `Accessor`s, and that's
313/// intentional.
314/// * The `Accessor` type is `Send` and `Sync` irrespective of `T` which
315/// alleviates some otherwise required bounds to be written down.
316///
317/// # Using `Accessor` in `Drop`
318///
319/// The methods on `Accessor` are only expected to work in the context of
320/// `Future::poll` and are not guaranteed to work in `Drop`. This is because a
321/// host future can be dropped at any time throughout the system and Wasmtime
322/// store context is not necessarily available at that time. It's recommended to
323/// not use `Accessor` methods in anything connected to a `Drop` implementation
324/// as they will panic and have unintended results. If you run into this though
325/// feel free to file an issue on the Wasmtime repository.
326pub struct Accessor<T: 'static, D = HasSelf<T>>
327where
328 D: HasData + ?Sized,
329{
330 token: StoreToken<T>,
331 get_data: fn(&mut T) -> D::Data<'_>,
332 instance: Option<Instance>,
333}
334
335/// A helper trait to take any type of accessor-with-data in functions.
336///
337/// This trait is similar to [`AsContextMut`] except that it's used when
338/// working with an [`Accessor`] instead of a [`StoreContextMut`]. The
339/// [`Accessor`] is the main type used in concurrent settings and is passed to
340/// functions such as [`Func::call_concurrent`] or [`FutureWriter::write`].
341///
342/// This trait is implemented for [`Accessor`] and `&T` where `T` implements
343/// this trait. This effectively means that regardless of the `D` in
344/// `Accessor<T, D>` it can still be passed to a function which just needs a
345/// store accessor.
346///
347/// Acquiring an [`Accessor`] can be done through [`Instance::run_concurrent`]
348/// for example or in a host function through
349/// [`Linker::func_wrap_concurrent`](crate::component::Linker::func_wrap_concurrent).
350pub trait AsAccessor {
351 /// The `T` in `Store<T>` that this accessor refers to.
352 type Data: 'static;
353
354 /// The `D` in `Accessor<T, D>`, or the projection out of
355 /// `Self::Data`.
356 type AccessorData: HasData + ?Sized;
357
358 /// Returns the accessor that this is referring to.
359 fn as_accessor(&self) -> &Accessor<Self::Data, Self::AccessorData>;
360}
361
362impl<T: AsAccessor + ?Sized> AsAccessor for &T {
363 type Data = T::Data;
364 type AccessorData = T::AccessorData;
365
366 fn as_accessor(&self) -> &Accessor<Self::Data, Self::AccessorData> {
367 T::as_accessor(self)
368 }
369}
370
371impl<T, D: HasData + ?Sized> AsAccessor for Accessor<T, D> {
372 type Data = T;
373 type AccessorData = D;
374
375 fn as_accessor(&self) -> &Accessor<T, D> {
376 self
377 }
378}
379
380// Note that it is intentional at this time that `Accessor` does not actually
381// store `&mut T` or anything similar. This distinctly enables the `Accessor`
382// structure to be both `Send` and `Sync` regardless of what `T` is (or `D` for
383// that matter). This is used to ergonomically simplify bindings where the
384// majority of the time `Accessor` is closed over in a future which then needs
385// to be `Send` and `Sync`. To avoid needing to write `T: Send` everywhere (as
386// you already have to write `T: 'static`...) it helps to avoid this.
387//
388// Note as well that `Accessor` doesn't actually store its data at all. Instead
389// it's more of a "proof" of what can be accessed from TLS. API design around
390// `Accessor` and functions like `Linker::func_wrap_concurrent` are
391// intentionally made to ensure that `Accessor` is ideally only used in the
392// context that TLS variables are actually set. For example host functions are
393// given `&Accessor`, not `Accessor`, and this prevents them from persisting
394// the value outside of a future. Within the future the TLS variables are all
395// guaranteed to be set while the future is being polled.
396//
397// Finally though this is not an ironclad guarantee, but nor does it need to be.
398// The TLS APIs are designed to panic or otherwise model usage where they're
399// called recursively or similar. It's hoped that code cannot be constructed to
400// actually hit this at runtime but this is not a safety requirement at this
401// time.
402const _: () = {
403 const fn assert<T: Send + Sync>() {}
404 assert::<Accessor<UnsafeCell<u32>>>();
405};
406
407impl<T> Accessor<T> {
408 /// Creates a new `Accessor` backed by the specified functions.
409 ///
410 /// - `get`: used to retrieve the store
411 ///
412 /// - `get_data`: used to "project" from the store's associated data to
413 /// another type (e.g. a field of that data or a wrapper around it).
414 ///
415 /// - `spawn`: used to queue spawned background tasks to be run later
416 ///
417 /// - `instance`: used to access the `Instance` to which this `Accessor`
418 /// (and the future which closes over it) belongs
419 pub(crate) fn new(token: StoreToken<T>, instance: Option<Instance>) -> Self {
420 Self {
421 token,
422 get_data: |x| x,
423 instance,
424 }
425 }
426}
427
428impl<T, D> Accessor<T, D>
429where
430 D: HasData + ?Sized,
431{
432 /// Run the specified closure, passing it mutable access to the store.
433 ///
434 /// This function is one of the main building blocks of the [`Accessor`]
435 /// type. This yields synchronous, blocking, access to store via an
436 /// [`Access`]. The [`Access`] implements [`AsContextMut`] in addition to
437 /// providing the ability to access `D` via [`Access::get`]. Note that the
438 /// `fun` here is given only temporary access to the store and `T`/`D`
439 /// meaning that the return value `R` here is not allowed to capture borrows
440 /// into the two. If access is needed to data within `T` or `D` outside of
441 /// this closure then it must be `clone`d out, for example.
442 ///
443 /// # Panics
444 ///
445 /// This function will panic if it is call recursively with any other
446 /// accessor already in scope. For example if `with` is called within `fun`,
447 /// then this function will panic. It is up to the embedder to ensure that
448 /// this does not happen.
449 pub fn with<R>(&self, fun: impl FnOnce(Access<'_, T, D>) -> R) -> R {
450 tls::get(|vmstore| {
451 fun(Access {
452 store: self.token.as_context_mut(vmstore),
453 accessor: self,
454 })
455 })
456 }
457
458 /// Changes this accessor to access `D2` instead of the current type
459 /// parameter `D`.
460 ///
461 /// This changes the underlying data access from `T` to `D2::Data<'_>`.
462 ///
463 /// Note that this is not a public or recommended API because it's easy to
464 /// cause panics with this by having two `Accessor` values live at the same
465 /// time. The returned `Accessor` does not refer to this `Accessor` meaning
466 /// that both can be used. You could, for example, call `Accessor::with`
467 /// simultaneously on both. That would cause a panic though.
468 ///
469 /// In short while there's nothing unsafe about this it's a footgun. It's
470 /// here for bindings generation where the provided accessor is transformed
471 /// into a new accessor and then this returned accessor is passed to
472 /// implementations.
473 ///
474 /// Note that one possible fix for this would be a lifetime parameter on
475 /// `Accessor` itself so the returned value could borrow from the original
476 /// value (or this could be `self`-by-value instead of `&mut self`) but in
477 /// attempting that it was found to be a bit too onerous in terms of
478 /// plumbing things around without a whole lot of benefit.
479 ///
480 /// In short, this works, but must be treated with care. The current main
481 /// user, bindings generation, treats this with care.
482 #[doc(hidden)]
483 pub fn with_data<D2: HasData>(&self, get_data: fn(&mut T) -> D2::Data<'_>) -> Accessor<T, D2> {
484 Accessor {
485 token: self.token,
486 get_data,
487 instance: self.instance,
488 }
489 }
490
491 /// Spawn a background task which will receive an `&Accessor<T, D>` and
492 /// run concurrently with any other tasks in progress for the current
493 /// instance.
494 ///
495 /// This is particularly useful for host functions which return a `stream`
496 /// or `future` such that the code to write to the write end of that
497 /// `stream` or `future` must run after the function returns.
498 ///
499 /// The returned [`JoinHandle`] may be used to cancel the task.
500 ///
501 /// # Panics
502 ///
503 /// Panics if called within a closure provided to the [`Accessor::with`]
504 /// function. This can only be called outside an active invocation of
505 /// [`Accessor::with`].
506 pub fn spawn(&self, task: impl AccessorTask<T, D, Result<()>>) -> JoinHandle
507 where
508 T: 'static,
509 {
510 let instance = self.instance.unwrap();
511 let accessor = self.clone_for_spawn();
512 self.with(|mut access| {
513 instance.spawn_with_accessor(access.as_context_mut(), accessor, task)
514 })
515 }
516
517 /// Retrieve the component instance of the caller.
518 pub fn instance(&self) -> Instance {
519 self.instance.unwrap()
520 }
521
522 fn clone_for_spawn(&self) -> Self {
523 Self {
524 token: self.token,
525 get_data: self.get_data,
526 instance: self.instance,
527 }
528 }
529}
530
531/// Represents a task which may be provided to `Accessor::spawn`,
532/// `Accessor::forward`, or `Instance::spawn`.
533// TODO: Replace this with `std::ops::AsyncFnOnce` when that becomes a viable
534// option.
535//
536// `AsyncFnOnce` is still nightly-only in latest stable Rust version as of this
537// writing (1.84.1), and even with 1.85.0-beta it's not possible to specify
538// e.g. `Send` and `Sync` bounds on the `Future` type returned by an
539// `AsyncFnOnce`. Also, using `F: Future<Output = Result<()>> + Send + Sync,
540// FN: FnOnce(&Accessor<T>) -> F + Send + Sync + 'static` fails with a type
541// mismatch error when we try to pass it an async closure (e.g. `async move |_|
542// { ... }`). So this seems to be the best we can do for the time being.
543pub trait AccessorTask<T, D, R>: Send + 'static
544where
545 D: HasData + ?Sized,
546{
547 /// Run the task.
548 fn run(self, accessor: &Accessor<T, D>) -> impl Future<Output = R> + Send;
549}
550
551/// Represents parameter and result metadata for the caller side of a
552/// guest->guest call orchestrated by a fused adapter.
553enum CallerInfo {
554 /// Metadata for a call to an async-lowered import
555 Async {
556 params: Vec<ValRaw>,
557 has_result: bool,
558 },
559 /// Metadata for a call to an sync-lowered import
560 Sync {
561 params: Vec<ValRaw>,
562 result_count: u32,
563 },
564}
565
566/// Indicates how a guest task is waiting on a waitable set.
567enum WaitMode {
568 /// The guest task is waiting using `task.wait`
569 Fiber(StoreFiber<'static>),
570 /// The guest task is waiting via a callback declared as part of an
571 /// async-lifted export.
572 Callback,
573}
574
575/// Represents the reason a fiber is suspending itself.
576#[derive(Debug)]
577enum SuspendReason {
578 /// The fiber is waiting for an event to be delivered to the specified
579 /// waitable set or task.
580 Waiting {
581 set: TableId<WaitableSet>,
582 task: TableId<GuestTask>,
583 },
584 /// The fiber has finished handling its most recent work item and is waiting
585 /// for another (or to be dropped if it is no longer needed).
586 NeedWork,
587 /// The fiber is yielding and should be resumed once other tasks have had a
588 /// chance to run.
589 Yielding { task: TableId<GuestTask> },
590}
591
592/// Represents a pending call into guest code for a given guest task.
593enum GuestCallKind {
594 /// Indicates there's an event to deliver to the task, possibly related to a
595 /// waitable set the task has been waiting on or polling.
596 DeliverEvent {
597 /// The waitable set the event belongs to, if any.
598 ///
599 /// If this is `None` the event will be waiting in the
600 /// `GuestTask::event` field for the task.
601 set: Option<TableId<WaitableSet>>,
602 },
603 /// Indicates that a new guest task call is pending and may be executed
604 /// using the specified closure.
605 Start(Box<dyn FnOnce(&mut dyn VMStore, Instance) -> Result<()> + Send + Sync>),
606}
607
608impl fmt::Debug for GuestCallKind {
609 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
610 match self {
611 Self::DeliverEvent { set } => f.debug_struct("DeliverEvent").field("set", set).finish(),
612 Self::Start(_) => f.debug_tuple("Start").finish(),
613 }
614 }
615}
616
617/// Represents a pending call into guest code for a given guest task.
618#[derive(Debug)]
619struct GuestCall {
620 task: TableId<GuestTask>,
621 kind: GuestCallKind,
622}
623
624impl GuestCall {
625 /// Returns whether or not the call is ready to run.
626 ///
627 /// A call will not be ready to run if either:
628 ///
629 /// - the (sub-)component instance to be called has already been entered and
630 /// cannot be reentered until an in-progress call completes
631 ///
632 /// - the call is for a not-yet started task and the (sub-)component
633 /// instance to be called has backpressure enabled
634 fn is_ready(&self, state: &mut ConcurrentState) -> Result<bool> {
635 let task_instance = state.get(self.task)?.instance;
636 let state = state.instance_state(task_instance);
637 let ready = match &self.kind {
638 GuestCallKind::DeliverEvent { .. } => !state.do_not_enter,
639 GuestCallKind::Start(_) => !(state.do_not_enter || state.backpressure),
640 };
641 log::trace!(
642 "call {self:?} ready? {ready} (do_not_enter: {}; backpressure: {})",
643 state.do_not_enter,
644 state.backpressure
645 );
646 Ok(ready)
647 }
648}
649
650/// Job to be run on a worker fiber.
651enum WorkerItem {
652 GuestCall(GuestCall),
653 Function(Mutex<Box<dyn FnOnce(&mut dyn VMStore, Instance) -> Result<()> + Send>>),
654}
655
656/// Represents state related to an in-progress poll operation (e.g. `task.poll`
657/// or `CallbackCode.POLL`).
658#[derive(Debug)]
659struct PollParams {
660 /// Identifies the polling task.
661 task: TableId<GuestTask>,
662 /// The waitable set being polled.
663 set: TableId<WaitableSet>,
664}
665
666/// Represents a pending work item to be handled by the event loop for a given
667/// component instance.
668enum WorkItem {
669 /// A host task to be pushed to `ConcurrentState::futures`.
670 PushFuture(Mutex<HostTaskFuture>),
671 /// A fiber to resume.
672 ResumeFiber(StoreFiber<'static>),
673 /// A pending call into guest code for a given guest task.
674 GuestCall(GuestCall),
675 /// A pending `task.poll` or `CallbackCode.POLL` operation.
676 Poll(PollParams),
677 /// A job to run on a worker fiber.
678 WorkerFunction(Mutex<Box<dyn FnOnce(&mut dyn VMStore, Instance) -> Result<()> + Send>>),
679}
680
681impl fmt::Debug for WorkItem {
682 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
683 match self {
684 Self::PushFuture(_) => f.debug_tuple("PushFuture").finish(),
685 Self::ResumeFiber(_) => f.debug_tuple("ResumeFiber").finish(),
686 Self::GuestCall(call) => f.debug_tuple("GuestCall").field(call).finish(),
687 Self::Poll(params) => f.debug_tuple("Poll").field(params).finish(),
688 Self::WorkerFunction(_) => f.debug_tuple("WorkerFunction").finish(),
689 }
690 }
691}
692
693impl ComponentInstance {
694 /// Handle the `CallbackCode` returned from an async-lifted export or its
695 /// callback.
696 ///
697 /// If `initial_call` is `true`, then the code was received from the
698 /// async-lifted export; otherwise, it was received from its callback.
699 fn handle_callback_code(
700 mut self: Pin<&mut Self>,
701 guest_task: TableId<GuestTask>,
702 runtime_instance: RuntimeComponentInstanceIndex,
703 code: u32,
704 initial_call: bool,
705 ) -> Result<()> {
706 let (code, set) = unpack_callback_code(code);
707
708 log::trace!("received callback code from {guest_task:?}: {code} (set: {set})");
709
710 let state = self.as_mut().concurrent_state_mut();
711 let task = state.get_mut(guest_task)?;
712
713 if task.lift_result.is_some() {
714 if code == callback_code::EXIT {
715 return Err(anyhow!(crate::Trap::NoAsyncResult));
716 }
717 if initial_call {
718 // Notify any current or future waiters that this subtask has
719 // started.
720 Waitable::Guest(guest_task).set_event(
721 state,
722 Some(Event::Subtask {
723 status: Status::Started,
724 }),
725 )?;
726 }
727 }
728
729 let get_set = |instance: Pin<&mut Self>, handle| {
730 if handle == 0 {
731 bail!("invalid waitable-set handle");
732 }
733
734 let set = instance.guest_tables().0[runtime_instance].waitable_set_rep(handle)?;
735
736 Ok(TableId::<WaitableSet>::new(set))
737 };
738
739 match code {
740 callback_code::EXIT => {
741 let task = state.get_mut(guest_task)?;
742 match &task.caller {
743 Caller::Host {
744 remove_task_automatically,
745 ..
746 } => {
747 if *remove_task_automatically {
748 log::trace!("handle_callback_code will delete task {guest_task:?}");
749 Waitable::Guest(guest_task).delete_from(state)?;
750 }
751 }
752 Caller::Guest { .. } => {
753 task.exited = true;
754 task.callback = None;
755 }
756 }
757 }
758 callback_code::YIELD => {
759 // Push this task onto the "low priority" queue so it runs after
760 // any other tasks have had a chance to run.
761 let task = state.get_mut(guest_task)?;
762 assert!(task.event.is_none());
763 task.event = Some(Event::None);
764 state.push_low_priority(WorkItem::GuestCall(GuestCall {
765 task: guest_task,
766 kind: GuestCallKind::DeliverEvent { set: None },
767 }));
768 }
769 callback_code::WAIT | callback_code::POLL => {
770 let set = get_set(self.as_mut(), set)?;
771 let state = self.concurrent_state_mut();
772
773 if state.get_mut(guest_task)?.event.is_some()
774 || !state.get_mut(set)?.ready.is_empty()
775 {
776 // An event is immediately available; deliver it ASAP.
777 state.push_high_priority(WorkItem::GuestCall(GuestCall {
778 task: guest_task,
779 kind: GuestCallKind::DeliverEvent { set: Some(set) },
780 }));
781 } else {
782 // No event is immediately available.
783 match code {
784 callback_code::POLL => {
785 // We're polling, so just yield and check whether an
786 // event has arrived after that.
787 state.push_low_priority(WorkItem::Poll(PollParams {
788 task: guest_task,
789 set,
790 }));
791 }
792 callback_code::WAIT => {
793 // We're waiting, so register to be woken up when an
794 // event is published for this waitable set.
795 //
796 // Here we also set `GuestTask::wake_on_cancel`
797 // which allows `subtask.cancel` to interrupt the
798 // wait.
799 let old = state.get_mut(guest_task)?.wake_on_cancel.replace(set);
800 assert!(old.is_none());
801 let old = state
802 .get_mut(set)?
803 .waiting
804 .insert(guest_task, WaitMode::Callback);
805 assert!(old.is_none());
806 }
807 _ => unreachable!(),
808 }
809 }
810 }
811 _ => bail!("unsupported callback code: {code}"),
812 }
813
814 Ok(())
815 }
816
817 /// Get the next pending event for the specified task and (optional)
818 /// waitable set, along with the waitable handle if applicable.
819 fn get_event(
820 mut self: Pin<&mut Self>,
821 guest_task: TableId<GuestTask>,
822 set: Option<TableId<WaitableSet>>,
823 ) -> Result<Option<(Event, Option<(Waitable, u32)>)>> {
824 let state = self.as_mut().concurrent_state_mut();
825
826 Ok(
827 if let Some(event) = state.get_mut(guest_task)?.event.take() {
828 log::trace!("deliver event {event:?} to {guest_task:?}");
829
830 Some((event, None))
831 } else if let Some((set, waitable)) = set
832 .and_then(|set| {
833 state
834 .get_mut(set)
835 .map(|v| v.ready.pop_first().map(|v| (set, v)))
836 .transpose()
837 })
838 .transpose()?
839 {
840 let common = waitable.common(state)?;
841 let handle = common.handle.unwrap();
842 let event = common.event.take().unwrap();
843
844 log::trace!(
845 "deliver event {event:?} to {guest_task:?} for {waitable:?} (handle {handle}); set {set:?}"
846 );
847
848 waitable.on_delivery(self, event);
849
850 Some((event, Some((waitable, handle))))
851 } else {
852 None
853 },
854 )
855 }
856
857 /// Implements the `waitable-set.new` intrinsic.
858 pub(crate) fn waitable_set_new(
859 mut self: Pin<&mut Self>,
860 caller_instance: RuntimeComponentInstanceIndex,
861 ) -> Result<u32> {
862 let set = self
863 .as_mut()
864 .concurrent_state_mut()
865 .push(WaitableSet::default())?;
866 let handle = self.guest_tables().0[caller_instance].waitable_set_insert(set.rep())?;
867 log::trace!("new waitable set {set:?} (handle {handle})");
868 Ok(handle)
869 }
870
871 /// Implements the `waitable-set.drop` intrinsic.
872 pub(crate) fn waitable_set_drop(
873 mut self: Pin<&mut Self>,
874 caller_instance: RuntimeComponentInstanceIndex,
875 set: u32,
876 ) -> Result<()> {
877 let rep = self.as_mut().guest_tables().0[caller_instance].waitable_set_remove(set)?;
878
879 log::trace!("drop waitable set {rep} (handle {set})");
880
881 let set = self
882 .concurrent_state_mut()
883 .delete(TableId::<WaitableSet>::new(rep))?;
884
885 if !set.waiting.is_empty() {
886 bail!("cannot drop waitable set with waiters");
887 }
888
889 Ok(())
890 }
891
892 /// Implements the `waitable.join` intrinsic.
893 pub(crate) fn waitable_join(
894 mut self: Pin<&mut Self>,
895 caller_instance: RuntimeComponentInstanceIndex,
896 waitable_handle: u32,
897 set_handle: u32,
898 ) -> Result<()> {
899 let waitable = Waitable::from_instance(self.as_mut(), caller_instance, waitable_handle)?;
900
901 let set = if set_handle == 0 {
902 None
903 } else {
904 let set =
905 self.as_mut().guest_tables().0[caller_instance].waitable_set_rep(set_handle)?;
906
907 Some(TableId::<WaitableSet>::new(set))
908 };
909
910 log::trace!(
911 "waitable {waitable:?} (handle {waitable_handle}) join set {set:?} (handle {set_handle})",
912 );
913
914 waitable.join(self.concurrent_state_mut(), set)
915 }
916
917 /// Implements the `subtask.drop` intrinsic.
918 pub(crate) fn subtask_drop(
919 mut self: Pin<&mut Self>,
920 caller_instance: RuntimeComponentInstanceIndex,
921 task_id: u32,
922 ) -> Result<()> {
923 self.as_mut().waitable_join(caller_instance, task_id, 0)?;
924
925 let (rep, is_host) =
926 self.as_mut().guest_tables().0[caller_instance].subtask_remove(task_id)?;
927
928 let concurrent_state = self.concurrent_state_mut();
929 let (waitable, expected_caller_instance, delete) = if is_host {
930 let id = TableId::<HostTask>::new(rep);
931 let task = concurrent_state.get(id)?;
932 if task.join_handle.is_some() {
933 bail!("cannot drop a subtask which has not yet resolved");
934 }
935 (Waitable::Host(id), task.caller_instance, true)
936 } else {
937 let id = TableId::<GuestTask>::new(rep);
938 let task = concurrent_state.get(id)?;
939 if task.lift_result.is_some() {
940 bail!("cannot drop a subtask which has not yet resolved");
941 }
942 if let Caller::Guest { instance, .. } = &task.caller {
943 (Waitable::Guest(id), *instance, task.exited)
944 } else {
945 unreachable!()
946 }
947 };
948
949 waitable.common(concurrent_state)?.handle = None;
950
951 if waitable.take_event(concurrent_state)?.is_some() {
952 bail!("cannot drop a subtask with an undelivered event");
953 }
954
955 if delete {
956 waitable.delete_from(concurrent_state)?;
957 }
958
959 // Since waitables can neither be passed between instances nor forged,
960 // this should never fail unless there's a bug in Wasmtime, but we check
961 // here to be sure:
962 assert_eq!(expected_caller_instance, caller_instance);
963 log::trace!("subtask_drop {waitable:?} (handle {task_id})");
964 Ok(())
965 }
966}
967
968impl Instance {
969 /// Enable or disable concurrent state debugging mode for e.g. integration
970 /// tests.
971 ///
972 /// This will avoid re-using deleted handles, making it easier to catch
973 /// e.g. "use-after-delete" and "double-delete" errors. It can also make
974 /// reading trace output easier since it ensures handles are never
975 /// repurposed.
976 #[doc(hidden)]
977 pub fn enable_concurrent_state_debug(&self, mut store: impl AsContextMut, enable: bool) {
978 self.id()
979 .get_mut(store.as_context_mut().0)
980 .concurrent_state_mut()
981 .table
982 .enable_debug(enable);
983 // TODO: do the same for the tables holding guest-facing handles
984 }
985
986 /// Assert that all the relevant tables and queues in the concurrent state
987 /// for this instance are empty.
988 ///
989 /// This is for sanity checking in integration tests
990 /// (e.g. `component-async-tests`) that the relevant state has been cleared
991 /// after each test concludes. This should help us catch leaks, e.g. guest
992 /// tasks which haven't been deleted despite having completed and having
993 /// been dropped by their supertasks.
994 #[doc(hidden)]
995 pub fn assert_concurrent_state_empty(&self, mut store: impl AsContextMut) {
996 let mut instance = self.id().get_mut(store.as_context_mut().0);
997 assert!(
998 instance
999 .as_mut()
1000 .guest_tables()
1001 .0
1002 .iter()
1003 .all(|(_, table)| table.is_empty())
1004 );
1005 let state = instance.concurrent_state_mut();
1006 assert!(state.table.is_empty(), "non-empty table: {:?}", state.table);
1007 assert!(state.high_priority.is_empty());
1008 assert!(state.low_priority.is_empty());
1009 assert!(state.guest_task.is_none());
1010 assert!(
1011 state
1012 .futures
1013 .get_mut()
1014 .unwrap()
1015 .as_ref()
1016 .unwrap()
1017 .is_empty()
1018 );
1019 assert!(
1020 state
1021 .instance_states
1022 .iter()
1023 .all(|(_, state)| state.pending.is_empty())
1024 );
1025 assert!(state.global_error_context_ref_counts.is_empty());
1026 }
1027
1028 /// Run the specified closure `fun` to completion as part of this instance's
1029 /// event loop.
1030 ///
1031 /// Like [`Self::run`], this will run `fun` as part of this instance's event
1032 /// loop until it yields a result _or_ there are no more tasks to run.
1033 /// Unlike [`Self::run`], `fun` is provided an [`Accessor`], which provides
1034 /// controlled access to the `Store` and its data.
1035 ///
1036 /// This function can be used to invoke [`Func::call_concurrent`] for
1037 /// example within the async closure provided here.
1038 ///
1039 /// # Example
1040 ///
1041 /// ```
1042 /// # use {
1043 /// # anyhow::{Result},
1044 /// # wasmtime::{
1045 /// # component::{ Component, Linker, Resource, ResourceTable},
1046 /// # Config, Engine, Store
1047 /// # },
1048 /// # };
1049 /// #
1050 /// # struct MyResource(u32);
1051 /// # struct Ctx { table: ResourceTable }
1052 /// #
1053 /// # async fn foo() -> Result<()> {
1054 /// # let mut config = Config::new();
1055 /// # let engine = Engine::new(&config)?;
1056 /// # let mut store = Store::new(&engine, Ctx { table: ResourceTable::new() });
1057 /// # let mut linker = Linker::new(&engine);
1058 /// # let component = Component::new(&engine, "")?;
1059 /// # let instance = linker.instantiate_async(&mut store, &component).await?;
1060 /// # let foo = instance.get_typed_func::<(Resource<MyResource>,), (Resource<MyResource>,)>(&mut store, "foo")?;
1061 /// # let bar = instance.get_typed_func::<(u32,), ()>(&mut store, "bar")?;
1062 /// instance.run_concurrent(&mut store, async |accessor| -> wasmtime::Result<_> {
1063 /// let resource = accessor.with(|mut access| access.get().table.push(MyResource(42)))?;
1064 /// let (another_resource,) = foo.call_concurrent(accessor, (resource,)).await?;
1065 /// let value = accessor.with(|mut access| access.get().table.delete(another_resource))?;
1066 /// bar.call_concurrent(accessor, (value.0,)).await?;
1067 /// Ok(())
1068 /// }).await??;
1069 /// # Ok(())
1070 /// # }
1071 /// ```
1072 pub async fn run_concurrent<T, R>(
1073 self,
1074 mut store: impl AsContextMut<Data = T>,
1075 fun: impl AsyncFnOnce(&Accessor<T>) -> R,
1076 ) -> Result<R>
1077 where
1078 T: Send + 'static,
1079 {
1080 check_recursive_run();
1081 let mut store = store.as_context_mut();
1082 let token = StoreToken::new(store.as_context_mut());
1083
1084 struct Dropper<'a, T: 'static, V> {
1085 store: StoreContextMut<'a, T>,
1086 value: ManuallyDrop<V>,
1087 }
1088
1089 impl<'a, T, V> Drop for Dropper<'a, T, V> {
1090 fn drop(&mut self) {
1091 tls::set(self.store.0, || {
1092 // SAFETY: Here we drop the value without moving it for the
1093 // first and only time -- per the contract for `Drop::drop`,
1094 // this code won't run again, and the `value` field will no
1095 // longer be accessible.
1096 unsafe { ManuallyDrop::drop(&mut self.value) }
1097 });
1098 }
1099 }
1100
1101 let accessor = &Accessor::new(token, Some(self));
1102 let dropper = &mut Dropper {
1103 store,
1104 value: ManuallyDrop::new(fun(accessor)),
1105 };
1106 // SAFETY: We never move `dropper` nor its `value` field.
1107 let future = unsafe { Pin::new_unchecked(dropper.value.deref_mut()) };
1108
1109 self.poll_until(dropper.store.as_context_mut(), future)
1110 .await
1111 }
1112
1113 /// Spawn a background task to run as part of this instance's event loop.
1114 ///
1115 /// The task will receive an `&Accessor<U>` and run concurrently with
1116 /// any other tasks in progress for the instance.
1117 ///
1118 /// Note that the task will only make progress if and when the event loop
1119 /// for this instance is run.
1120 ///
1121 /// The returned [`SpawnHandle`] may be used to cancel the task.
1122 pub fn spawn<U: 'static>(
1123 self,
1124 mut store: impl AsContextMut<Data = U>,
1125 task: impl AccessorTask<U, HasSelf<U>, Result<()>>,
1126 ) -> JoinHandle {
1127 let mut store = store.as_context_mut();
1128 let accessor = Accessor::new(StoreToken::new(store.as_context_mut()), Some(self));
1129 self.spawn_with_accessor(store, accessor, task)
1130 }
1131
1132 /// Internal implementation of `spawn` functions where a `store` is
1133 /// available along with an `Accessor`.
1134 fn spawn_with_accessor<T, D>(
1135 self,
1136 mut store: StoreContextMut<T>,
1137 accessor: Accessor<T, D>,
1138 task: impl AccessorTask<T, D, Result<()>>,
1139 ) -> JoinHandle
1140 where
1141 T: 'static,
1142 D: HasData + ?Sized,
1143 {
1144 let store = store.as_context_mut();
1145
1146 // Create an "abortable future" here where internally the future will
1147 // hook calls to poll and possibly spawn more background tasks on each
1148 // iteration.
1149 let (handle, future) =
1150 JoinHandle::run(async move { HostTaskOutput::Result(task.run(&accessor).await) });
1151 self.concurrent_state_mut(store.0)
1152 .push_future(Box::pin(async move {
1153 future.await.unwrap_or(HostTaskOutput::Result(Ok(())))
1154 }));
1155
1156 handle
1157 }
1158
1159 /// Run this instance's event loop.
1160 ///
1161 /// The returned future will resolve when either the specified future
1162 /// completes (in which case we return its result) or no further progress
1163 /// can be made (in which case we trap with `Trap::AsyncDeadlock`).
1164 async fn poll_until<T, R>(
1165 self,
1166 mut store: StoreContextMut<'_, T>,
1167 mut future: Pin<&mut impl Future<Output = R>>,
1168 ) -> Result<R>
1169 where
1170 T: Send,
1171 {
1172 loop {
1173 // Take `ConcurrentState::futures` out of the instance so we can
1174 // poll it while also safely giving any of the futures inside access
1175 // to `self`.
1176 let mut futures = self
1177 .concurrent_state_mut(store.0)
1178 .futures
1179 .get_mut()
1180 .unwrap()
1181 .take()
1182 .unwrap();
1183 let mut next = pin!(futures.next());
1184
1185 let result = future::poll_fn(|cx| {
1186 // First, poll the future we were passed as an argument and
1187 // return immediately if it's ready.
1188 if let Poll::Ready(value) = self.set_tls(store.0, || future.as_mut().poll(cx)) {
1189 return Poll::Ready(Ok(Either::Left(value)));
1190 }
1191
1192 // Next, poll `ConcurrentState::futures` (which includes any
1193 // pending host tasks and/or background tasks), returning
1194 // immediately if one of them fails.
1195 let next = match self.set_tls(store.0, || next.as_mut().poll(cx)) {
1196 Poll::Ready(Some(output)) => {
1197 match output {
1198 HostTaskOutput::Result(Err(e)) => return Poll::Ready(Err(e)),
1199 HostTaskOutput::Result(Ok(())) => {}
1200 HostTaskOutput::Function(fun) => {
1201 // Defer calling this function to a worker fiber
1202 // in case it involves calling a guest realloc
1203 // function as part of a lowering operation.
1204 //
1205 // TODO: This isn't necessary for _all_
1206 // `HostOutput::Function`s, so we could optimize
1207 // by adding another variant to `HostOutput` to
1208 // distinguish which ones need it and which
1209 // don't.
1210 self.concurrent_state_mut(store.0)
1211 .push_high_priority(WorkItem::WorkerFunction(Mutex::new(fun)))
1212 }
1213 }
1214 Poll::Ready(true)
1215 }
1216 Poll::Ready(None) => Poll::Ready(false),
1217 Poll::Pending => Poll::Pending,
1218 };
1219
1220 let mut instance = self.id().get_mut(store.0);
1221
1222 // Next, check the "high priority" work queue and return
1223 // immediately if it has at least one item.
1224 let state = instance.as_mut().concurrent_state_mut();
1225 let ready = mem::take(&mut state.high_priority);
1226 let ready = if ready.is_empty() {
1227 // Next, check the "low priority" work queue and return
1228 // immediately if it has at least one item.
1229 let ready = mem::take(&mut state.low_priority);
1230 if ready.is_empty() {
1231 return match next {
1232 Poll::Ready(true) => {
1233 // In this case, one of the futures in
1234 // `ConcurrentState::futures` completed
1235 // successfully, so we return now and continue
1236 // the outer loop in case there is another one
1237 // ready to complete.
1238 Poll::Ready(Ok(Either::Right(Vec::new())))
1239 }
1240 Poll::Ready(false) => {
1241 // Poll the future we were passed one last time
1242 // in case one of `ConcurrentState::futures` had
1243 // the side effect of unblocking it.
1244 if let Poll::Ready(value) =
1245 self.set_tls(store.0, || future.as_mut().poll(cx))
1246 {
1247 Poll::Ready(Ok(Either::Left(value)))
1248 } else {
1249 // In this case, there are no more pending
1250 // futures in `ConcurrentState::futures`,
1251 // there are no remaining work items, _and_
1252 // the future we were passed as an argument
1253 // still hasn't completed, meaning we're
1254 // stuck, so we return an error. The
1255 // underlying assumption is that `future`
1256 // depends on this component instance making
1257 // such progress, and thus there's no point
1258 // in continuing to poll it given we've run
1259 // out of work to do.
1260 //
1261 // Note that we'd also reach this point if
1262 // the host embedder passed e.g. a
1263 // `std::future::Pending` to
1264 // `Instance::run_concurrent`, in which case
1265 // we'd return a "deadlock" error even when
1266 // any and all tasks have completed
1267 // normally. However, that's not how
1268 // `Instance::run_concurrent` is intended
1269 // (and documented) to be used, so it seems
1270 // reasonable to lump that case in with
1271 // "real" deadlocks.
1272 //
1273 // TODO: Once we've added host APIs for
1274 // cancelling in-progress tasks, we can
1275 // return some other, non-error value here,
1276 // treating it as "normal" and giving the
1277 // host embedder a chance to intervene by
1278 // cancelling one or more tasks and/or
1279 // starting new tasks capable of waking the
1280 // existing ones.
1281 Poll::Ready(Err(anyhow!(crate::Trap::AsyncDeadlock)))
1282 }
1283 }
1284 // There is at least one pending future in
1285 // `ConcurrentState::futures` and we have nothing
1286 // else to do but wait for now, so we return
1287 // `Pending`.
1288 Poll::Pending => Poll::Pending,
1289 };
1290 } else {
1291 ready
1292 }
1293 } else {
1294 ready
1295 };
1296
1297 Poll::Ready(Ok(Either::Right(ready)))
1298 })
1299 .await;
1300
1301 // Put the `ConcurrentState::futures` back into the instance before
1302 // we return or handle any work items since one or more of those
1303 // items might append more futures.
1304 *self
1305 .concurrent_state_mut(store.0)
1306 .futures
1307 .get_mut()
1308 .unwrap() = Some(futures);
1309
1310 match result? {
1311 // The future we were passed as an argument completed, so we
1312 // return the result.
1313 Either::Left(value) => break Ok(value),
1314 // The future we were passed has not yet completed, so handle
1315 // any work items and then loop again.
1316 Either::Right(ready) => {
1317 for item in ready {
1318 self.handle_work_item(store.as_context_mut(), item).await?;
1319 }
1320 }
1321 }
1322 }
1323 }
1324
1325 /// Handle the specified work item, possibly resuming a fiber if applicable.
1326 async fn handle_work_item<T: Send>(
1327 self,
1328 store: StoreContextMut<'_, T>,
1329 item: WorkItem,
1330 ) -> Result<()> {
1331 log::trace!("handle work item {item:?}");
1332 match item {
1333 WorkItem::PushFuture(future) => {
1334 self.concurrent_state_mut(store.0)
1335 .futures
1336 .get_mut()
1337 .unwrap()
1338 .as_mut()
1339 .unwrap()
1340 .push(future.into_inner().unwrap());
1341 }
1342 WorkItem::ResumeFiber(fiber) => {
1343 self.resume_fiber(store.0, fiber).await?;
1344 }
1345 WorkItem::GuestCall(call) => {
1346 let state = self.concurrent_state_mut(store.0);
1347 if call.is_ready(state)? {
1348 self.run_on_worker(store, WorkerItem::GuestCall(call))
1349 .await?;
1350 } else {
1351 let task = state.get_mut(call.task)?;
1352 if !task.starting_sent {
1353 task.starting_sent = true;
1354 if let GuestCallKind::Start(_) = &call.kind {
1355 Waitable::Guest(call.task).set_event(
1356 state,
1357 Some(Event::Subtask {
1358 status: Status::Starting,
1359 }),
1360 )?;
1361 }
1362 }
1363
1364 let runtime_instance = state.get(call.task)?.instance;
1365 state
1366 .instance_state(runtime_instance)
1367 .pending
1368 .insert(call.task, call.kind);
1369 }
1370 }
1371 WorkItem::Poll(params) => {
1372 let state = self.concurrent_state_mut(store.0);
1373 if state.get_mut(params.task)?.event.is_some()
1374 || !state.get_mut(params.set)?.ready.is_empty()
1375 {
1376 // There's at least one event immediately available; deliver
1377 // it to the guest ASAP.
1378 state.push_high_priority(WorkItem::GuestCall(GuestCall {
1379 task: params.task,
1380 kind: GuestCallKind::DeliverEvent {
1381 set: Some(params.set),
1382 },
1383 }));
1384 } else {
1385 // There are no events immediately available; deliver
1386 // `Event::None` to the guest.
1387 state.get_mut(params.task)?.event = Some(Event::None);
1388 state.push_high_priority(WorkItem::GuestCall(GuestCall {
1389 task: params.task,
1390 kind: GuestCallKind::DeliverEvent {
1391 set: Some(params.set),
1392 },
1393 }));
1394 }
1395 }
1396 WorkItem::WorkerFunction(fun) => {
1397 self.run_on_worker(store, WorkerItem::Function(fun)).await?;
1398 }
1399 }
1400
1401 Ok(())
1402 }
1403
1404 /// Resume the specified fiber, giving it exclusive access to the specified
1405 /// store.
1406 async fn resume_fiber(self, store: &mut StoreOpaque, fiber: StoreFiber<'static>) -> Result<()> {
1407 let old_task = self.concurrent_state_mut(store).guest_task;
1408 log::trace!("resume_fiber: save current task {old_task:?}");
1409
1410 let fiber = fiber::resolve_or_release(store, fiber).await?;
1411
1412 let state = self.concurrent_state_mut(store);
1413
1414 state.guest_task = old_task;
1415 log::trace!("resume_fiber: restore current task {old_task:?}");
1416
1417 if let Some(mut fiber) = fiber {
1418 // See the `SuspendReason` documentation for what each case means.
1419 match state.suspend_reason.take().unwrap() {
1420 SuspendReason::NeedWork => {
1421 if state.worker.is_none() {
1422 state.worker = Some(fiber);
1423 } else {
1424 fiber.dispose(store);
1425 }
1426 }
1427 SuspendReason::Yielding { .. } => {
1428 state.push_low_priority(WorkItem::ResumeFiber(fiber));
1429 }
1430 SuspendReason::Waiting { set, task } => {
1431 let old = state
1432 .get_mut(set)?
1433 .waiting
1434 .insert(task, WaitMode::Fiber(fiber));
1435 assert!(old.is_none());
1436 }
1437 }
1438 }
1439
1440 Ok(())
1441 }
1442
1443 /// Execute the specified guest call on a worker fiber.
1444 async fn run_on_worker<T: Send>(
1445 self,
1446 store: StoreContextMut<'_, T>,
1447 item: WorkerItem,
1448 ) -> Result<()> {
1449 let worker = if let Some(fiber) = self.concurrent_state_mut(store.0).worker.take() {
1450 fiber
1451 } else {
1452 fiber::make_fiber(store.0, move |store| {
1453 loop {
1454 match self.concurrent_state_mut(store).worker_item.take().unwrap() {
1455 WorkerItem::GuestCall(call) => self.handle_guest_call(store, call)?,
1456 WorkerItem::Function(fun) => fun.into_inner().unwrap()(store, self)?,
1457 }
1458
1459 self.suspend(store, SuspendReason::NeedWork)?;
1460 }
1461 })?
1462 };
1463
1464 let worker_item = &mut self.concurrent_state_mut(store.0).worker_item;
1465 assert!(worker_item.is_none());
1466 *worker_item = Some(item);
1467
1468 self.resume_fiber(store.0, worker).await
1469 }
1470
1471 /// Execute the specified guest call.
1472 fn handle_guest_call(self, store: &mut dyn VMStore, call: GuestCall) -> Result<()> {
1473 match call.kind {
1474 GuestCallKind::DeliverEvent { set } => {
1475 let (event, waitable) =
1476 self.id().get_mut(store).get_event(call.task, set)?.unwrap();
1477 let state = self.concurrent_state_mut(store);
1478 let task = state.get_mut(call.task)?;
1479 let runtime_instance = task.instance;
1480 let handle = waitable.map(|(_, v)| v).unwrap_or(0);
1481
1482 log::trace!(
1483 "use callback to deliver event {event:?} to {:?} for {waitable:?}",
1484 call.task,
1485 );
1486
1487 let old_task = state.guest_task.replace(call.task);
1488 log::trace!(
1489 "GuestCallKind::DeliverEvent: replaced {old_task:?} with {:?} as current task",
1490 call.task
1491 );
1492
1493 self.maybe_push_call_context(store.store_opaque_mut(), call.task)?;
1494
1495 let state = self.concurrent_state_mut(store);
1496 state.enter_instance(runtime_instance);
1497
1498 let callback = state.get_mut(call.task)?.callback.take().unwrap();
1499
1500 let code = callback(store, self, runtime_instance, event, handle)?;
1501
1502 let state = self.concurrent_state_mut(store);
1503
1504 state.get_mut(call.task)?.callback = Some(callback);
1505
1506 state.exit_instance(runtime_instance)?;
1507
1508 self.maybe_pop_call_context(store.store_opaque_mut(), call.task)?;
1509
1510 self.id().get_mut(store).handle_callback_code(
1511 call.task,
1512 runtime_instance,
1513 code,
1514 false,
1515 )?;
1516
1517 self.concurrent_state_mut(store).guest_task = old_task;
1518 log::trace!("GuestCallKind::DeliverEvent: restored {old_task:?} as current task");
1519 }
1520 GuestCallKind::Start(fun) => {
1521 fun(store, self)?;
1522 }
1523 }
1524
1525 Ok(())
1526 }
1527
1528 /// Suspend the current fiber, storing the reason in
1529 /// `ConcurrentState::suspend_reason` to indicate the conditions under which
1530 /// it should be resumed.
1531 ///
1532 /// See the `SuspendReason` documentation for details.
1533 fn suspend(self, store: &mut dyn VMStore, reason: SuspendReason) -> Result<()> {
1534 log::trace!("suspend fiber: {reason:?}");
1535
1536 // If we're yielding or waiting on behalf of a guest task, we'll need to
1537 // pop the call context which manages resource borrows before suspending
1538 // and then push it again once we've resumed.
1539 let task = match &reason {
1540 SuspendReason::Yielding { task } | SuspendReason::Waiting { task, .. } => Some(*task),
1541 SuspendReason::NeedWork => None,
1542 };
1543
1544 let old_guest_task = if let Some(task) = task {
1545 self.maybe_pop_call_context(store, task)?;
1546 self.concurrent_state_mut(store).guest_task
1547 } else {
1548 None
1549 };
1550
1551 let suspend_reason = &mut self.concurrent_state_mut(store).suspend_reason;
1552 assert!(suspend_reason.is_none());
1553 *suspend_reason = Some(reason);
1554
1555 store.with_blocking(|_, cx| cx.suspend(StoreFiberYield::ReleaseStore))?;
1556
1557 if let Some(task) = task {
1558 self.concurrent_state_mut(store).guest_task = old_guest_task;
1559 self.maybe_push_call_context(store, task)?;
1560 }
1561
1562 Ok(())
1563 }
1564
1565 /// Push the call context for managing resource borrows for the specified
1566 /// guest task if it has not yet either returned a result or cancelled
1567 /// itself.
1568 fn maybe_push_call_context(
1569 self,
1570 store: &mut StoreOpaque,
1571 guest_task: TableId<GuestTask>,
1572 ) -> Result<()> {
1573 let task = self.concurrent_state_mut(store).get_mut(guest_task)?;
1574 if task.lift_result.is_some() {
1575 log::trace!("push call context for {guest_task:?}");
1576 let call_context = task.call_context.take().unwrap();
1577 store.component_resource_state().0.push(call_context);
1578 }
1579 Ok(())
1580 }
1581
1582 /// Pop the call context for managing resource borrows for the specified
1583 /// guest task if it has not yet either returned a result or cancelled
1584 /// itself.
1585 fn maybe_pop_call_context(
1586 self,
1587 store: &mut StoreOpaque,
1588 guest_task: TableId<GuestTask>,
1589 ) -> Result<()> {
1590 if self
1591 .concurrent_state_mut(store)
1592 .get(guest_task)?
1593 .lift_result
1594 .is_some()
1595 {
1596 log::trace!("pop call context for {guest_task:?}");
1597 let call_context = Some(store.component_resource_state().0.pop().unwrap());
1598 self.concurrent_state_mut(store)
1599 .get_mut(guest_task)?
1600 .call_context = call_context;
1601 }
1602 Ok(())
1603 }
1604
1605 /// Add the specified guest call to the "high priority" work item queue, to
1606 /// be started as soon as backpressure and/or reentrance rules allow.
1607 ///
1608 /// SAFETY: The raw pointer arguments must be valid references to guest
1609 /// functions (with the appropriate signatures) when the closures queued by
1610 /// this function are called.
1611 unsafe fn queue_call<T: 'static>(
1612 self,
1613 mut store: StoreContextMut<T>,
1614 guest_task: TableId<GuestTask>,
1615 callee: SendSyncPtr<VMFuncRef>,
1616 param_count: usize,
1617 result_count: usize,
1618 flags: Option<InstanceFlags>,
1619 async_: bool,
1620 callback: Option<SendSyncPtr<VMFuncRef>>,
1621 post_return: Option<SendSyncPtr<VMFuncRef>>,
1622 ) -> Result<()> {
1623 /// Return a closure which will call the specified function in the scope
1624 /// of the specified task.
1625 ///
1626 /// This will use `GuestTask::lower_params` to lower the parameters, but
1627 /// will not lift the result; instead, it returns a
1628 /// `[MaybeUninit<ValRaw>; MAX_FLAT_PARAMS]` from which the result, if
1629 /// any, may be lifted. Note that an async-lifted export will have
1630 /// returned its result using the `task.return` intrinsic (or not
1631 /// returned a result at all, in the case of `task.cancel`), in which
1632 /// case the "result" of this call will either be a callback code or
1633 /// nothing.
1634 ///
1635 /// SAFETY: `callee` must be a valid `*mut VMFuncRef` at the time when
1636 /// the returned closure is called.
1637 unsafe fn make_call<T: 'static>(
1638 store: StoreContextMut<T>,
1639 guest_task: TableId<GuestTask>,
1640 callee: SendSyncPtr<VMFuncRef>,
1641 param_count: usize,
1642 result_count: usize,
1643 flags: Option<InstanceFlags>,
1644 ) -> impl FnOnce(
1645 &mut dyn VMStore,
1646 Instance,
1647 ) -> Result<[MaybeUninit<ValRaw>; MAX_FLAT_PARAMS]>
1648 + Send
1649 + Sync
1650 + 'static
1651 + use<T> {
1652 let token = StoreToken::new(store);
1653 move |store: &mut dyn VMStore, instance: Instance| {
1654 let mut storage = [MaybeUninit::uninit(); MAX_FLAT_PARAMS];
1655 let task = instance.concurrent_state_mut(store).get_mut(guest_task)?;
1656 let may_enter_after_call = task.call_post_return_automatically();
1657 let lower = task.lower_params.take().unwrap();
1658
1659 lower(store, instance, &mut storage[..param_count])?;
1660
1661 let mut store = token.as_context_mut(store);
1662
1663 // SAFETY: Per the contract documented in `make_call's`
1664 // documentation, `callee` must be a valid pointer.
1665 unsafe {
1666 if let Some(mut flags) = flags {
1667 flags.set_may_enter(false);
1668 }
1669 crate::Func::call_unchecked_raw(
1670 &mut store,
1671 callee.as_non_null(),
1672 NonNull::new(
1673 &mut storage[..param_count.max(result_count)]
1674 as *mut [MaybeUninit<ValRaw>] as _,
1675 )
1676 .unwrap(),
1677 )?;
1678 if let Some(mut flags) = flags {
1679 flags.set_may_enter(may_enter_after_call);
1680 }
1681 }
1682
1683 Ok(storage)
1684 }
1685 }
1686
1687 // SAFETY: Per the contract described in this function documentation,
1688 // the `callee` pointer which `call` closes over must be valid when
1689 // called by the closure we queue below.
1690 let call = unsafe {
1691 make_call(
1692 store.as_context_mut(),
1693 guest_task,
1694 callee,
1695 param_count,
1696 result_count,
1697 flags,
1698 )
1699 };
1700
1701 let callee_instance = self.concurrent_state_mut(store.0).get(guest_task)?.instance;
1702 let fun = if callback.is_some() {
1703 assert!(async_);
1704
1705 Box::new(move |store: &mut dyn VMStore, instance: Instance| {
1706 let old_task = instance
1707 .concurrent_state_mut(store)
1708 .guest_task
1709 .replace(guest_task);
1710 log::trace!(
1711 "stackless call: replaced {old_task:?} with {guest_task:?} as current task"
1712 );
1713
1714 instance.maybe_push_call_context(store.store_opaque_mut(), guest_task)?;
1715
1716 instance
1717 .concurrent_state_mut(store)
1718 .enter_instance(callee_instance);
1719
1720 // SAFETY: See the documentation for `make_call` to review the
1721 // contract we must uphold for `call` here.
1722 //
1723 // Per the contract described in the `queue_call`
1724 // documentation, the `callee` pointer which `call` closes
1725 // over must be valid.
1726 let storage = call(store, instance)?;
1727
1728 instance
1729 .concurrent_state_mut(store)
1730 .exit_instance(callee_instance)?;
1731
1732 instance.maybe_pop_call_context(store.store_opaque_mut(), guest_task)?;
1733
1734 let state = instance.concurrent_state_mut(store);
1735 state.guest_task = old_task;
1736 log::trace!("stackless call: restored {old_task:?} as current task");
1737
1738 // SAFETY: `wasmparser` will have validated that the callback
1739 // function returns a `i32` result.
1740 let code = unsafe { storage[0].assume_init() }.get_i32() as u32;
1741
1742 instance.id().get_mut(store).handle_callback_code(
1743 guest_task,
1744 callee_instance,
1745 code,
1746 true,
1747 )?;
1748
1749 Ok(())
1750 })
1751 as Box<dyn FnOnce(&mut dyn VMStore, Instance) -> Result<()> + Send + Sync>
1752 } else {
1753 let token = StoreToken::new(store.as_context_mut());
1754 Box::new(move |store: &mut dyn VMStore, instance: Instance| {
1755 let old_task = instance
1756 .concurrent_state_mut(store)
1757 .guest_task
1758 .replace(guest_task);
1759 log::trace!(
1760 "stackful call: replaced {old_task:?} with {guest_task:?} as current task",
1761 );
1762
1763 let mut flags = instance.id().get(store).instance_flags(callee_instance);
1764
1765 instance.maybe_push_call_context(store.store_opaque_mut(), guest_task)?;
1766
1767 // Unless this is a callback-less (i.e. stackful)
1768 // async-lifted export, we need to record that the instance
1769 // cannot be entered until the call returns.
1770 if !async_ {
1771 instance
1772 .concurrent_state_mut(store)
1773 .enter_instance(callee_instance);
1774 }
1775
1776 // SAFETY: See the documentation for `make_call` to review the
1777 // contract we must uphold for `call` here.
1778 //
1779 // Per the contract described in the `queue_call`
1780 // documentation, the `callee` pointer which `call` closes
1781 // over must be valid.
1782 let storage = call(store, instance)?;
1783
1784 if async_ {
1785 // This is a callback-less (i.e. stackful) async-lifted
1786 // export, so there is no post-return function, and
1787 // either `task.return` or `task.cancel` should have
1788 // been called.
1789 if instance
1790 .concurrent_state_mut(store)
1791 .get(guest_task)?
1792 .lift_result
1793 .is_some()
1794 {
1795 return Err(anyhow!(crate::Trap::NoAsyncResult));
1796 }
1797 } else {
1798 // This is a sync-lifted export, so now is when we lift the
1799 // result, optionally call the post-return function, if any,
1800 // and finally notify any current or future waiters that the
1801 // subtask has returned.
1802
1803 let lift = {
1804 let state = instance.concurrent_state_mut(store);
1805 state.exit_instance(callee_instance)?;
1806
1807 assert!(state.get(guest_task)?.result.is_none());
1808
1809 state.get_mut(guest_task)?.lift_result.take().unwrap()
1810 };
1811
1812 // SAFETY: `result_count` represents the number of core Wasm
1813 // results returned, per `wasmparser`.
1814 let result = (lift.lift)(store, instance, unsafe {
1815 mem::transmute::<&[MaybeUninit<ValRaw>], &[ValRaw]>(
1816 &storage[..result_count],
1817 )
1818 })?;
1819
1820 let post_return_arg = match result_count {
1821 0 => ValRaw::i32(0),
1822 // SAFETY: `result_count` represents the number of
1823 // core Wasm results returned, per `wasmparser`.
1824 1 => unsafe { storage[0].assume_init() },
1825 _ => unreachable!(),
1826 };
1827
1828 if instance
1829 .concurrent_state_mut(store)
1830 .get(guest_task)?
1831 .call_post_return_automatically()
1832 {
1833 unsafe { flags.set_needs_post_return(false) }
1834
1835 if let Some(func) = post_return {
1836 let mut store = token.as_context_mut(store);
1837
1838 // SAFETY: `func` is a valid `*mut VMFuncRef` from
1839 // either `wasmtime-cranelift`-generated fused adapter
1840 // code or `component::Options`. Per `wasmparser`
1841 // post-return signature validation, we know it takes a
1842 // single parameter.
1843 unsafe {
1844 crate::Func::call_unchecked_raw(
1845 &mut store,
1846 func.as_non_null(),
1847 slice::from_ref(&post_return_arg).into(),
1848 )?;
1849 }
1850 }
1851
1852 unsafe { flags.set_may_enter(true) }
1853 }
1854
1855 instance.task_complete(
1856 store,
1857 guest_task,
1858 result,
1859 Status::Returned,
1860 post_return_arg,
1861 )?;
1862 }
1863
1864 instance.maybe_pop_call_context(store.store_opaque_mut(), guest_task)?;
1865
1866 let task = instance.concurrent_state_mut(store).get_mut(guest_task)?;
1867
1868 match &task.caller {
1869 Caller::Host {
1870 remove_task_automatically,
1871 ..
1872 } => {
1873 if *remove_task_automatically {
1874 Waitable::Guest(guest_task)
1875 .delete_from(instance.concurrent_state_mut(store))?;
1876 }
1877 }
1878 Caller::Guest { .. } => {
1879 task.exited = true;
1880 }
1881 }
1882
1883 Ok(())
1884 })
1885 };
1886
1887 self.concurrent_state_mut(store.0)
1888 .push_high_priority(WorkItem::GuestCall(GuestCall {
1889 task: guest_task,
1890 kind: GuestCallKind::Start(fun),
1891 }));
1892
1893 Ok(())
1894 }
1895
1896 /// Prepare (but do not start) a guest->guest call.
1897 ///
1898 /// This is called from fused adapter code generated in
1899 /// `wasmtime_environ::fact::trampoline::Compiler`. `start` and `return_`
1900 /// are synthesized Wasm functions which move the parameters from the caller
1901 /// to the callee and the result from the callee to the caller,
1902 /// respectively. The adapter will call `Self::start_call` immediately
1903 /// after calling this function.
1904 ///
1905 /// SAFETY: All the pointer arguments must be valid pointers to guest
1906 /// entities (and with the expected signatures for the function references
1907 /// -- see `wasmtime_environ::fact::trampoline::Compiler` for details).
1908 unsafe fn prepare_call<T: 'static>(
1909 self,
1910 mut store: StoreContextMut<T>,
1911 start: *mut VMFuncRef,
1912 return_: *mut VMFuncRef,
1913 caller_instance: RuntimeComponentInstanceIndex,
1914 callee_instance: RuntimeComponentInstanceIndex,
1915 task_return_type: TypeTupleIndex,
1916 memory: *mut VMMemoryDefinition,
1917 string_encoding: u8,
1918 caller_info: CallerInfo,
1919 ) -> Result<()> {
1920 enum ResultInfo {
1921 Heap { results: u32 },
1922 Stack { result_count: u32 },
1923 }
1924
1925 let result_info = match &caller_info {
1926 CallerInfo::Async {
1927 has_result: true,
1928 params,
1929 } => ResultInfo::Heap {
1930 results: params.last().unwrap().get_u32(),
1931 },
1932 CallerInfo::Async {
1933 has_result: false, ..
1934 } => ResultInfo::Stack { result_count: 0 },
1935 CallerInfo::Sync {
1936 result_count,
1937 params,
1938 } if *result_count > u32::try_from(MAX_FLAT_RESULTS).unwrap() => ResultInfo::Heap {
1939 results: params.last().unwrap().get_u32(),
1940 },
1941 CallerInfo::Sync { result_count, .. } => ResultInfo::Stack {
1942 result_count: *result_count,
1943 },
1944 };
1945
1946 let sync_caller = matches!(caller_info, CallerInfo::Sync { .. });
1947
1948 // Create a new guest task for the call, closing over the `start` and
1949 // `return_` functions to lift the parameters and lower the result,
1950 // respectively.
1951 let start = SendSyncPtr::new(NonNull::new(start).unwrap());
1952 let return_ = SendSyncPtr::new(NonNull::new(return_).unwrap());
1953 let token = StoreToken::new(store.as_context_mut());
1954 let state = self.concurrent_state_mut(store.0);
1955 let old_task = state.guest_task.take();
1956 let new_task = GuestTask::new(
1957 state,
1958 Box::new(move |store, instance, dst| {
1959 let mut store = token.as_context_mut(store);
1960 assert!(dst.len() <= MAX_FLAT_PARAMS);
1961 let mut src = [MaybeUninit::uninit(); MAX_FLAT_PARAMS];
1962 let count = match caller_info {
1963 // Async callers, if they have a result, use the last
1964 // parameter as a return pointer so chop that off if
1965 // relevant here.
1966 CallerInfo::Async { params, has_result } => {
1967 let params = ¶ms[..params.len() - usize::from(has_result)];
1968 for (param, src) in params.iter().zip(&mut src) {
1969 src.write(*param);
1970 }
1971 params.len()
1972 }
1973
1974 // Sync callers forward everything directly.
1975 CallerInfo::Sync { params, .. } => {
1976 for (param, src) in params.iter().zip(&mut src) {
1977 src.write(*param);
1978 }
1979 params.len()
1980 }
1981 };
1982 // SAFETY: `start` is a valid `*mut VMFuncRef` from
1983 // `wasmtime-cranelift`-generated fused adapter code. Based on
1984 // how it was constructed (see
1985 // `wasmtime_environ::fact::trampoline::Compiler::compile_async_start_adapter`
1986 // for details) we know it takes count parameters and returns
1987 // `dst.len()` results.
1988 unsafe {
1989 crate::Func::call_unchecked_raw(
1990 &mut store,
1991 start.as_non_null(),
1992 NonNull::new(
1993 &mut src[..count.max(dst.len())] as *mut [MaybeUninit<ValRaw>] as _,
1994 )
1995 .unwrap(),
1996 )?;
1997 }
1998 dst.copy_from_slice(&src[..dst.len()]);
1999 let state = instance.concurrent_state_mut(store.0);
2000 let task = state.guest_task.unwrap();
2001 Waitable::Guest(task).set_event(
2002 state,
2003 Some(Event::Subtask {
2004 status: Status::Started,
2005 }),
2006 )?;
2007 Ok(())
2008 }),
2009 LiftResult {
2010 lift: Box::new(move |store, instance, src| {
2011 // SAFETY: See comment in closure passed as `lower_params`
2012 // parameter above.
2013 let mut store = token.as_context_mut(store);
2014 let mut my_src = src.to_owned(); // TODO: use stack to avoid allocation?
2015 if let ResultInfo::Heap { results } = &result_info {
2016 my_src.push(ValRaw::u32(*results));
2017 }
2018 // SAFETY: `return_` is a valid `*mut VMFuncRef` from
2019 // `wasmtime-cranelift`-generated fused adapter code. Based
2020 // on how it was constructed (see
2021 // `wasmtime_environ::fact::trampoline::Compiler::compile_async_return_adapter`
2022 // for details) we know it takes `src.len()` parameters and
2023 // returns up to 1 result.
2024 unsafe {
2025 crate::Func::call_unchecked_raw(
2026 &mut store,
2027 return_.as_non_null(),
2028 my_src.as_mut_slice().into(),
2029 )?;
2030 }
2031 let state = instance.concurrent_state_mut(store.0);
2032 let task = state.guest_task.unwrap();
2033 if sync_caller {
2034 state.get_mut(task)?.sync_result =
2035 Some(if let ResultInfo::Stack { result_count } = &result_info {
2036 match result_count {
2037 0 => None,
2038 1 => Some(my_src[0]),
2039 _ => unreachable!(),
2040 }
2041 } else {
2042 None
2043 });
2044 }
2045 Ok(Box::new(DummyResult) as Box<dyn Any + Send + Sync>)
2046 }),
2047 ty: task_return_type,
2048 memory: NonNull::new(memory).map(SendSyncPtr::new),
2049 string_encoding: StringEncoding::from_u8(string_encoding).unwrap(),
2050 },
2051 Caller::Guest {
2052 task: old_task.unwrap(),
2053 instance: caller_instance,
2054 },
2055 None,
2056 callee_instance,
2057 )?;
2058
2059 let guest_task = state.push(new_task)?;
2060
2061 if let Some(old_task) = old_task {
2062 if !state.may_enter(guest_task) {
2063 bail!(crate::Trap::CannotEnterComponent);
2064 }
2065
2066 state.get_mut(old_task)?.subtasks.insert(guest_task);
2067 };
2068
2069 // Make the new task the current one so that `Self::start_call` knows
2070 // which one to start.
2071 state.guest_task = Some(guest_task);
2072 log::trace!("pushed {guest_task:?} as current task; old task was {old_task:?}");
2073
2074 Ok(())
2075 }
2076
2077 /// Call the specified callback function for an async-lifted export.
2078 ///
2079 /// SAFETY: `function` must be a valid reference to a guest function of the
2080 /// correct signature for a callback.
2081 unsafe fn call_callback<T>(
2082 self,
2083 mut store: StoreContextMut<T>,
2084 callee_instance: RuntimeComponentInstanceIndex,
2085 function: SendSyncPtr<VMFuncRef>,
2086 event: Event,
2087 handle: u32,
2088 may_enter_after_call: bool,
2089 ) -> Result<u32> {
2090 let mut flags = self.id().get(store.0).instance_flags(callee_instance);
2091
2092 let (ordinal, result) = event.parts();
2093 let params = &mut [
2094 ValRaw::u32(ordinal),
2095 ValRaw::u32(handle),
2096 ValRaw::u32(result),
2097 ];
2098 // SAFETY: `func` is a valid `*mut VMFuncRef` from either
2099 // `wasmtime-cranelift`-generated fused adapter code or
2100 // `component::Options`. Per `wasmparser` callback signature
2101 // validation, we know it takes three parameters and returns one.
2102 unsafe {
2103 flags.set_may_enter(false);
2104 crate::Func::call_unchecked_raw(
2105 &mut store,
2106 function.as_non_null(),
2107 params.as_mut_slice().into(),
2108 )?;
2109 flags.set_may_enter(may_enter_after_call);
2110 }
2111 Ok(params[0].get_u32())
2112 }
2113
2114 /// Start a guest->guest call previously prepared using
2115 /// `Self::prepare_call`.
2116 ///
2117 /// This is called from fused adapter code generated in
2118 /// `wasmtime_environ::fact::trampoline::Compiler`. The adapter will call
2119 /// this function immediately after calling `Self::prepare_call`.
2120 ///
2121 /// SAFETY: The `*mut VMFuncRef` arguments must be valid pointers to guest
2122 /// functions with the appropriate signatures for the current guest task.
2123 /// If this is a call to an async-lowered import, the actual call may be
2124 /// deferred and run after this function returns, in which case the pointer
2125 /// arguments must also be valid when the call happens.
2126 unsafe fn start_call<T: 'static>(
2127 self,
2128 mut store: StoreContextMut<T>,
2129 callback: *mut VMFuncRef,
2130 post_return: *mut VMFuncRef,
2131 callee: *mut VMFuncRef,
2132 param_count: u32,
2133 result_count: u32,
2134 flags: u32,
2135 storage: Option<&mut [MaybeUninit<ValRaw>]>,
2136 ) -> Result<u32> {
2137 let token = StoreToken::new(store.as_context_mut());
2138 let async_caller = storage.is_none();
2139 let state = self.concurrent_state_mut(store.0);
2140 let guest_task = state.guest_task.unwrap();
2141 let may_enter_after_call = state.get(guest_task)?.call_post_return_automatically();
2142 let callee = SendSyncPtr::new(NonNull::new(callee).unwrap());
2143 let param_count = usize::try_from(param_count).unwrap();
2144 assert!(param_count <= MAX_FLAT_PARAMS);
2145 let result_count = usize::try_from(result_count).unwrap();
2146 assert!(result_count <= MAX_FLAT_RESULTS);
2147
2148 let task = state.get_mut(guest_task)?;
2149 if !callback.is_null() {
2150 // We're calling an async-lifted export with a callback, so store
2151 // the callback and related context as part of the task so we can
2152 // call it later when needed.
2153 let callback = SendSyncPtr::new(NonNull::new(callback).unwrap());
2154 task.callback = Some(Box::new(
2155 move |store, instance, runtime_instance, event, handle| {
2156 let store = token.as_context_mut(store);
2157 unsafe {
2158 instance.call_callback::<T>(
2159 store,
2160 runtime_instance,
2161 callback,
2162 event,
2163 handle,
2164 may_enter_after_call,
2165 )
2166 }
2167 },
2168 ));
2169 }
2170
2171 let Caller::Guest {
2172 task: caller,
2173 instance: runtime_instance,
2174 } = &task.caller
2175 else {
2176 // As of this writing, `start_call` is only used for guest->guest
2177 // calls.
2178 unreachable!()
2179 };
2180 let caller = *caller;
2181 let caller_instance = *runtime_instance;
2182
2183 let callee_instance = task.instance;
2184
2185 let instance_flags = if callback.is_null() {
2186 None
2187 } else {
2188 Some(self.id().get(store.0).instance_flags(callee_instance))
2189 };
2190
2191 // Queue the call as a "high priority" work item.
2192 unsafe {
2193 self.queue_call(
2194 store.as_context_mut(),
2195 guest_task,
2196 callee,
2197 param_count,
2198 result_count,
2199 instance_flags,
2200 (flags & START_FLAG_ASYNC_CALLEE) != 0,
2201 NonNull::new(callback).map(SendSyncPtr::new),
2202 NonNull::new(post_return).map(SendSyncPtr::new),
2203 )?;
2204 }
2205
2206 let state = self.concurrent_state_mut(store.0);
2207
2208 // Use the caller's `GuestTask::sync_call_set` to register interest in
2209 // the subtask...
2210 let guest_waitable = Waitable::Guest(guest_task);
2211 let old_set = guest_waitable.common(state)?.set;
2212 let set = state.get_mut(caller)?.sync_call_set;
2213 guest_waitable.join(state, Some(set))?;
2214
2215 // ... and suspend this fiber temporarily while we wait for it to start.
2216 //
2217 // Note that we _could_ call the callee directly using the current fiber
2218 // rather than suspend this one, but that would make reasoning about the
2219 // event loop more complicated and is probably only worth doing if
2220 // there's a measurable performance benefit. In addition, it would mean
2221 // blocking the caller if the callee calls a blocking sync-lowered
2222 // import, and as of this writing the spec says we must not do that.
2223 //
2224 // Alternatively, the fused adapter code could be modified to call the
2225 // callee directly without calling a host-provided intrinsic at all (in
2226 // which case it would need to do its own, inline backpressure checks,
2227 // etc.). Again, we'd want to see a measurable performance benefit
2228 // before committing to such an optimization. And again, we'd need to
2229 // update the spec to allow that.
2230 let (status, waitable) = loop {
2231 self.suspend(store.0, SuspendReason::Waiting { set, task: caller })?;
2232
2233 let state = self.concurrent_state_mut(store.0);
2234
2235 let event = guest_waitable.take_event(state)?;
2236 let Some(Event::Subtask { status }) = event else {
2237 unreachable!();
2238 };
2239
2240 log::trace!("status {status:?} for {guest_task:?}");
2241
2242 if status == Status::Returned {
2243 // It returned, so we can stop waiting.
2244 break (status, None);
2245 } else if async_caller {
2246 // It hasn't returned yet, but the caller is calling via an
2247 // async-lowered import, so we generate a handle for the task
2248 // waitable and return the status.
2249 let handle = self.id().get_mut(store.0).guest_tables().0[caller_instance]
2250 .subtask_insert_guest(guest_task.rep())?;
2251 self.concurrent_state_mut(store.0)
2252 .get_mut(guest_task)?
2253 .common
2254 .handle = Some(handle);
2255 break (status, Some(handle));
2256 } else {
2257 // The callee hasn't returned yet, and the caller is calling via
2258 // a sync-lowered import, so we loop and keep waiting until the
2259 // callee returns.
2260 }
2261 };
2262
2263 let state = self.concurrent_state_mut(store.0);
2264
2265 guest_waitable.join(state, old_set)?;
2266
2267 if let Some(storage) = storage {
2268 // The caller used a sync-lowered import to call an async-lifted
2269 // export, in which case the result, if any, has been stashed in
2270 // `GuestTask::sync_result`.
2271 if let Some(result) = state.get_mut(guest_task)?.sync_result.take() {
2272 if let Some(result) = result {
2273 storage[0] = MaybeUninit::new(result);
2274 }
2275
2276 Waitable::Guest(guest_task).delete_from(state)?;
2277 } else {
2278 // This means the callee failed to call either `task.return` or
2279 // `task.cancel` before exiting.
2280 return Err(anyhow!(crate::Trap::NoAsyncResult));
2281 }
2282 }
2283
2284 // Reset the current task to point to the caller as it resumes control.
2285 state.guest_task = Some(caller);
2286 log::trace!("popped current task {guest_task:?}; new task is {caller:?}");
2287
2288 Ok(status.pack(waitable))
2289 }
2290
2291 /// Wrap the specified host function in a future which will call it, passing
2292 /// it an `&Accessor<T>`.
2293 ///
2294 /// See the `Accessor` documentation for details.
2295 pub(crate) fn wrap_call<T, F, R>(
2296 self,
2297 store: StoreContextMut<T>,
2298 closure: F,
2299 ) -> impl Future<Output = Result<R>> + 'static
2300 where
2301 T: 'static,
2302 F: FnOnce(&Accessor<T>) -> Pin<Box<dyn Future<Output = Result<R>> + Send + '_>>
2303 + Send
2304 + Sync
2305 + 'static,
2306 R: Send + Sync + 'static,
2307 {
2308 let token = StoreToken::new(store);
2309 async move {
2310 let mut accessor = Accessor::new(token, Some(self));
2311 closure(&mut accessor).await
2312 }
2313 }
2314
2315 /// Poll the specified future once on behalf of a guest->host call using an
2316 /// async-lowered import.
2317 ///
2318 /// If it returns `Ready`, return `Ok(None)`. Otherwise, if it returns
2319 /// `Pending`, add it to the set of futures to be polled as part of this
2320 /// instance's event loop until it completes, and then return
2321 /// `Ok(Some(handle))` where `handle` is the waitable handle to return.
2322 ///
2323 /// Whether the future returns `Ready` immediately or later, the `lower`
2324 /// function will be used to lower the result, if any, into the guest caller's
2325 /// stack and linear memory unless the task has been cancelled.
2326 pub(crate) fn first_poll<T: 'static, R: Send + 'static>(
2327 self,
2328 mut store: StoreContextMut<T>,
2329 future: impl Future<Output = Result<R>> + Send + 'static,
2330 caller_instance: RuntimeComponentInstanceIndex,
2331 lower: impl FnOnce(StoreContextMut<T>, Instance, R) -> Result<()> + Send + 'static,
2332 ) -> Result<Option<u32>> {
2333 let token = StoreToken::new(store.as_context_mut());
2334 let state = self.concurrent_state_mut(store.0);
2335 let caller = state.guest_task.unwrap();
2336
2337 // Create an abortable future which hooks calls to poll and manages call
2338 // context state for the future.
2339 let (join_handle, future) = JoinHandle::run(async move {
2340 let mut future = pin!(future);
2341 let mut call_context = None;
2342 future::poll_fn(move |cx| {
2343 // Push the call context for managing any resource borrows
2344 // for the task.
2345 tls::get(|store| {
2346 if let Some(call_context) = call_context.take() {
2347 token
2348 .as_context_mut(store)
2349 .0
2350 .component_resource_state()
2351 .0
2352 .push(call_context);
2353 }
2354 });
2355
2356 let result = future.as_mut().poll(cx);
2357
2358 if result.is_pending() {
2359 // Pop the call context for managing any resource
2360 // borrows for the task.
2361 tls::get(|store| {
2362 call_context = Some(
2363 token
2364 .as_context_mut(store)
2365 .0
2366 .component_resource_state()
2367 .0
2368 .pop()
2369 .unwrap(),
2370 );
2371 });
2372 }
2373 result
2374 })
2375 .await
2376 });
2377
2378 // We create a new host task even though it might complete immediately
2379 // (in which case we won't need to pass a waitable back to the guest).
2380 // If it does complete immediately, we'll remove it before we return.
2381 let task = state.push(HostTask::new(caller_instance, Some(join_handle)))?;
2382
2383 log::trace!("new host task child of {caller:?}: {task:?}");
2384 let token = StoreToken::new(store.as_context_mut());
2385
2386 // Map the output of the future to a `HostTaskOutput` responsible for
2387 // lowering the result into the guest's stack and memory, as well as
2388 // notifying any waiters that the task returned.
2389 let mut future = Box::pin(async move {
2390 let result = match future.await {
2391 Some(result) => result,
2392 // Task was cancelled; nothing left to do.
2393 None => return HostTaskOutput::Result(Ok(())),
2394 };
2395 HostTaskOutput::Function(Box::new(move |store, instance| {
2396 let mut store = token.as_context_mut(store);
2397 lower(store.as_context_mut(), instance, result?)?;
2398 let state = instance.concurrent_state_mut(store.0);
2399 state.get_mut(task)?.join_handle.take();
2400 Waitable::Host(task).set_event(
2401 state,
2402 Some(Event::Subtask {
2403 status: Status::Returned,
2404 }),
2405 )?;
2406
2407 Ok(())
2408 }))
2409 });
2410
2411 // Finally, poll the future. We can use a dummy `Waker` here because
2412 // we'll add the future to `ConcurrentState::futures` and poll it
2413 // automatically from the event loop if it doesn't complete immediately
2414 // here.
2415 let poll = self.set_tls(store.0, || {
2416 future
2417 .as_mut()
2418 .poll(&mut Context::from_waker(&Waker::noop()))
2419 });
2420
2421 Ok(match poll {
2422 Poll::Ready(output) => {
2423 // It finished immediately; lower the result and delete the
2424 // task.
2425 output.consume(store.0, self)?;
2426 log::trace!("delete host task {task:?} (already ready)");
2427 self.concurrent_state_mut(store.0).delete(task)?;
2428 None
2429 }
2430 Poll::Pending => {
2431 // It hasn't finished yet; add the future to
2432 // `ConcurrentState::futures` so it will be polled by the event
2433 // loop and allocate a waitable handle to return to the guest.
2434 self.concurrent_state_mut(store.0).push_future(future);
2435 let handle = self.id().get_mut(store.0).guest_tables().0[caller_instance]
2436 .subtask_insert_host(task.rep())?;
2437 self.concurrent_state_mut(store.0)
2438 .get_mut(task)?
2439 .common
2440 .handle = Some(handle);
2441 log::trace!(
2442 "assign {task:?} handle {handle} for {caller:?} instance {caller_instance:?}"
2443 );
2444 Some(handle)
2445 }
2446 })
2447 }
2448
2449 /// Poll the specified future until it completes on behalf of a guest->host
2450 /// call using a sync-lowered import.
2451 ///
2452 /// This is similar to `Self::first_poll` except it's for sync-lowered
2453 /// imports, meaning we don't need to handle cancellation and we can block
2454 /// the caller until the task completes, at which point the caller can
2455 /// handle lowering the result to the guest's stack and linear memory.
2456 pub(crate) fn poll_and_block<R: Send + Sync + 'static>(
2457 self,
2458 store: &mut dyn VMStore,
2459 future: impl Future<Output = Result<R>> + Send + 'static,
2460 caller_instance: RuntimeComponentInstanceIndex,
2461 ) -> Result<R> {
2462 let state = self.concurrent_state_mut(store);
2463
2464 // If there is no current guest task set, that means the host function
2465 // was registered using e.g. `LinkerInstance::func_wrap`, in which case
2466 // it should complete immediately.
2467 let Some(caller) = state.guest_task else {
2468 return match pin!(future).poll(&mut Context::from_waker(&Waker::noop())) {
2469 Poll::Ready(result) => result,
2470 Poll::Pending => {
2471 unreachable!()
2472 }
2473 };
2474 };
2475
2476 // Save any existing result stashed in `GuestTask::result` so we can
2477 // replace it with the new result.
2478 let old_result = state
2479 .get_mut(caller)
2480 .with_context(|| format!("bad handle: {caller:?}"))?
2481 .result
2482 .take();
2483
2484 // Add a temporary host task into the table so we can track its
2485 // progress. Note that we'll never allocate a waitable handle for the
2486 // guest since we're being called synchronously.
2487 let task = state.push(HostTask::new(caller_instance, None))?;
2488
2489 log::trace!("new host task child of {caller:?}: {task:?}");
2490
2491 // Map the output of the future to a `HostTaskOutput` which will take
2492 // care of stashing the result in `GuestTask::result` and resuming this
2493 // fiber when the host task completes.
2494 let mut future = Box::pin(future.map(move |result| {
2495 HostTaskOutput::Function(Box::new(move |store, instance| {
2496 let state = instance.concurrent_state_mut(store);
2497 state.get_mut(caller)?.result = Some(Box::new(result?) as _);
2498
2499 Waitable::Host(task).set_event(
2500 state,
2501 Some(Event::Subtask {
2502 status: Status::Returned,
2503 }),
2504 )?;
2505
2506 Ok(())
2507 }))
2508 })) as HostTaskFuture;
2509
2510 // Finally, poll the future. We can use a dummy `Waker` here because
2511 // we'll add the future to `ConcurrentState::futures` and poll it
2512 // automatically from the event loop if it doesn't complete immediately
2513 // here.
2514 let poll = self.set_tls(store, || {
2515 future
2516 .as_mut()
2517 .poll(&mut Context::from_waker(&Waker::noop()))
2518 });
2519
2520 match poll {
2521 Poll::Ready(output) => {
2522 // It completed immediately; run the `HostTaskOutput` function
2523 // to stash the result and delete the task.
2524 output.consume(store, self)?;
2525 log::trace!("delete host task {task:?} (already ready)");
2526 self.concurrent_state_mut(store).delete(task)?;
2527 }
2528 Poll::Pending => {
2529 // It did not complete immediately; add it to
2530 // `ConcurrentState::futures` so it will be polled via the event
2531 // loop, then use `GuestTask::sync_call_set` to wait for the
2532 // task to complete, suspending the current fiber until it does
2533 // so.
2534 let state = self.concurrent_state_mut(store);
2535 state.push_future(future);
2536
2537 let set = state.get_mut(caller)?.sync_call_set;
2538 Waitable::Host(task).join(state, Some(set))?;
2539
2540 self.suspend(store, SuspendReason::Waiting { set, task: caller })?;
2541 }
2542 }
2543
2544 // Retrieve and return the result.
2545 Ok(*mem::replace(
2546 &mut self.concurrent_state_mut(store).get_mut(caller)?.result,
2547 old_result,
2548 )
2549 .unwrap()
2550 .downcast()
2551 .unwrap())
2552 }
2553
2554 /// Implements the `task.return` intrinsic, lifting the result for the
2555 /// current guest task.
2556 pub(crate) fn task_return(
2557 self,
2558 store: &mut dyn VMStore,
2559 ty: TypeTupleIndex,
2560 options: OptionsIndex,
2561 storage: &[ValRaw],
2562 ) -> Result<()> {
2563 let state = self.concurrent_state_mut(store);
2564 let CanonicalOptions {
2565 string_encoding,
2566 data_model,
2567 ..
2568 } = *state.options(options);
2569 let guest_task = state.guest_task.unwrap();
2570 let lift = state
2571 .get_mut(guest_task)?
2572 .lift_result
2573 .take()
2574 .ok_or_else(|| {
2575 anyhow!("`task.return` or `task.cancel` called more than once for current task")
2576 })?;
2577 assert!(state.get(guest_task)?.result.is_none());
2578
2579 let invalid = ty != lift.ty
2580 || string_encoding != lift.string_encoding
2581 || match data_model {
2582 CanonicalOptionsDataModel::LinearMemory(opts) => match opts.memory {
2583 Some(memory) => {
2584 let expected = lift.memory.map(|v| v.as_ptr()).unwrap_or(ptr::null_mut());
2585 let actual = self.id().get(store).runtime_memory(memory);
2586 expected != actual
2587 }
2588 // Memory not specified, meaning it didn't need to be
2589 // specified per validation, so not invalid.
2590 None => false,
2591 },
2592 // Always invalid as this isn't supported.
2593 CanonicalOptionsDataModel::Gc { .. } => true,
2594 };
2595
2596 if invalid {
2597 bail!("invalid `task.return` signature and/or options for current task");
2598 }
2599
2600 log::trace!("task.return for {guest_task:?}");
2601
2602 let result = (lift.lift)(store, self, storage)?;
2603
2604 self.task_complete(store, guest_task, result, Status::Returned, ValRaw::i32(0))
2605 }
2606
2607 /// Implements the `task.cancel` intrinsic.
2608 pub(crate) fn task_cancel(
2609 self,
2610 store: &mut dyn VMStore,
2611 _caller_instance: RuntimeComponentInstanceIndex,
2612 ) -> Result<()> {
2613 let state = self.concurrent_state_mut(store);
2614 let guest_task = state.guest_task.unwrap();
2615 let task = state.get_mut(guest_task)?;
2616 if !task.cancel_sent {
2617 bail!("`task.cancel` called by task which has not been cancelled")
2618 }
2619 _ = task.lift_result.take().ok_or_else(|| {
2620 anyhow!("`task.return` or `task.cancel` called more than once for current task")
2621 })?;
2622
2623 assert!(task.result.is_none());
2624
2625 log::trace!("task.cancel for {guest_task:?}");
2626
2627 self.task_complete(
2628 store,
2629 guest_task,
2630 Box::new(DummyResult),
2631 Status::ReturnCancelled,
2632 ValRaw::i32(0),
2633 )
2634 }
2635
2636 /// Complete the specified guest task (i.e. indicate that it has either
2637 /// returned a (possibly empty) result or cancelled itself).
2638 ///
2639 /// This will return any resource borrows and notify any current or future
2640 /// waiters that the task has completed.
2641 fn task_complete(
2642 self,
2643 store: &mut dyn VMStore,
2644 guest_task: TableId<GuestTask>,
2645 result: Box<dyn Any + Send + Sync>,
2646 status: Status,
2647 post_return_arg: ValRaw,
2648 ) -> Result<()> {
2649 if self
2650 .concurrent_state_mut(store)
2651 .get(guest_task)?
2652 .call_post_return_automatically()
2653 {
2654 let (calls, host_table, _, instance) = store
2655 .store_opaque_mut()
2656 .component_resource_state_with_instance(self);
2657 ResourceTables {
2658 calls,
2659 host_table: Some(host_table),
2660 guest: Some(instance.guest_tables()),
2661 }
2662 .exit_call()?;
2663 } else {
2664 // As of this writing, the only scenario where `call_post_return_automatically`
2665 // would be false for a `GuestTask` is for host-to-guest calls using
2666 // `[Typed]Func::call_async`, in which case the `function_index`
2667 // should be a non-`None` value.
2668 let function_index = self
2669 .concurrent_state_mut(store)
2670 .get(guest_task)?
2671 .function_index
2672 .unwrap();
2673
2674 self.id()
2675 .get_mut(store)
2676 .post_return_arg_set(function_index, post_return_arg);
2677 }
2678
2679 let state = self.concurrent_state_mut(store);
2680 let task = state.get_mut(guest_task)?;
2681
2682 if let Caller::Host { tx, .. } = &mut task.caller {
2683 if let Some(tx) = tx.take() {
2684 _ = tx.send(result);
2685 }
2686 } else {
2687 task.result = Some(result);
2688 Waitable::Guest(guest_task).set_event(state, Some(Event::Subtask { status }))?;
2689 }
2690
2691 Ok(())
2692 }
2693
2694 /// Implements the `waitable-set.wait` intrinsic.
2695 pub(crate) fn waitable_set_wait(
2696 self,
2697 store: &mut dyn VMStore,
2698 options: OptionsIndex,
2699 set: u32,
2700 payload: u32,
2701 ) -> Result<u32> {
2702 let opts = self.concurrent_state_mut(store).options(options);
2703 let async_ = opts.async_;
2704 let caller_instance = opts.instance;
2705 let rep =
2706 self.id().get_mut(store).guest_tables().0[caller_instance].waitable_set_rep(set)?;
2707
2708 self.waitable_check(
2709 store,
2710 async_,
2711 WaitableCheck::Wait(WaitableCheckParams {
2712 set: TableId::new(rep),
2713 options,
2714 payload,
2715 }),
2716 )
2717 }
2718
2719 /// Implements the `waitable-set.poll` intrinsic.
2720 pub(crate) fn waitable_set_poll(
2721 self,
2722 store: &mut dyn VMStore,
2723 options: OptionsIndex,
2724 set: u32,
2725 payload: u32,
2726 ) -> Result<u32> {
2727 let opts = self.concurrent_state_mut(store).options(options);
2728 let async_ = opts.async_;
2729 let caller_instance = opts.instance;
2730 let rep =
2731 self.id().get_mut(store).guest_tables().0[caller_instance].waitable_set_rep(set)?;
2732
2733 self.waitable_check(
2734 store,
2735 async_,
2736 WaitableCheck::Poll(WaitableCheckParams {
2737 set: TableId::new(rep),
2738 options,
2739 payload,
2740 }),
2741 )
2742 }
2743
2744 /// Implements the `yield` intrinsic.
2745 pub(crate) fn yield_(self, store: &mut dyn VMStore, async_: bool) -> Result<bool> {
2746 self.waitable_check(store, async_, WaitableCheck::Yield)
2747 .map(|_code| {
2748 // TODO: plumb cancellation to here:
2749 // https://github.com/bytecodealliance/wasmtime/issues/11191
2750 false
2751 })
2752 }
2753
2754 /// Helper function for the `waitable-set.wait`, `waitable-set.poll`, and
2755 /// `yield` intrinsics.
2756 fn waitable_check(
2757 self,
2758 store: &mut dyn VMStore,
2759 async_: bool,
2760 check: WaitableCheck,
2761 ) -> Result<u32> {
2762 if async_ {
2763 bail!(
2764 "todo: async `waitable-set.wait`, `waitable-set.poll`, and `yield` not yet implemented"
2765 );
2766 }
2767
2768 let guest_task = self.concurrent_state_mut(store).guest_task.unwrap();
2769
2770 let (wait, set) = match &check {
2771 WaitableCheck::Wait(params) => (true, Some(params.set)),
2772 WaitableCheck::Poll(params) => (false, Some(params.set)),
2773 WaitableCheck::Yield => (false, None),
2774 };
2775
2776 // First, suspend this fiber, allowing any other tasks to run.
2777 self.suspend(store, SuspendReason::Yielding { task: guest_task })?;
2778
2779 log::trace!("waitable check for {guest_task:?}; set {set:?}");
2780
2781 let state = self.concurrent_state_mut(store);
2782 let task = state.get(guest_task)?;
2783
2784 if wait && task.callback.is_some() {
2785 bail!("cannot call `task.wait` from async-lifted export with callback");
2786 }
2787
2788 // If we're waiting, and there are no events immediately available,
2789 // suspend the fiber until that changes.
2790 if wait {
2791 let set = set.unwrap();
2792
2793 if task.event.is_none() && state.get(set)?.ready.is_empty() {
2794 let old = state.get_mut(guest_task)?.wake_on_cancel.replace(set);
2795 assert!(old.is_none());
2796
2797 self.suspend(
2798 store,
2799 SuspendReason::Waiting {
2800 set,
2801 task: guest_task,
2802 },
2803 )?;
2804 }
2805 }
2806
2807 log::trace!("waitable check for {guest_task:?}; set {set:?}, part two");
2808
2809 let result = match check {
2810 // Deliver any pending events to the guest and return.
2811 WaitableCheck::Wait(params) | WaitableCheck::Poll(params) => {
2812 let event = self
2813 .id()
2814 .get_mut(store)
2815 .get_event(guest_task, Some(params.set))?;
2816
2817 let (ordinal, handle, result) = if wait {
2818 let (event, waitable) = event.unwrap();
2819 let handle = waitable.map(|(_, v)| v).unwrap_or(0);
2820 let (ordinal, result) = event.parts();
2821 (ordinal, handle, result)
2822 } else {
2823 if let Some((event, waitable)) = event {
2824 let handle = waitable.map(|(_, v)| v).unwrap_or(0);
2825 let (ordinal, result) = event.parts();
2826 (ordinal, handle, result)
2827 } else {
2828 log::trace!(
2829 "no events ready to deliver via waitable-set.poll to {guest_task:?}; set {:?}",
2830 params.set
2831 );
2832 let (ordinal, result) = Event::None.parts();
2833 (ordinal, 0, result)
2834 }
2835 };
2836 let store = store.store_opaque_mut();
2837 let options = Options::new_index(store, self, params.options);
2838 let ptr = func::validate_inbounds::<(u32, u32)>(
2839 options.memory_mut(store),
2840 &ValRaw::u32(params.payload),
2841 )?;
2842 options.memory_mut(store)[ptr + 0..][..4].copy_from_slice(&handle.to_le_bytes());
2843 options.memory_mut(store)[ptr + 4..][..4].copy_from_slice(&result.to_le_bytes());
2844 Ok(ordinal)
2845 }
2846 // TODO: Check `GuestTask::event` in case it contains
2847 // `Event::Cancelled`, in which case we'll need to return that to
2848 // the guest:
2849 // https://github.com/bytecodealliance/wasmtime/issues/11191
2850 WaitableCheck::Yield => Ok(0),
2851 };
2852
2853 result
2854 }
2855
2856 /// Implements the `subtask.cancel` intrinsic.
2857 pub(crate) fn subtask_cancel(
2858 self,
2859 store: &mut dyn VMStore,
2860 caller_instance: RuntimeComponentInstanceIndex,
2861 async_: bool,
2862 task_id: u32,
2863 ) -> Result<u32> {
2864 let (rep, is_host) =
2865 self.id().get_mut(store).guest_tables().0[caller_instance].subtask_rep(task_id)?;
2866 let (waitable, expected_caller_instance) = if is_host {
2867 let id = TableId::<HostTask>::new(rep);
2868 (
2869 Waitable::Host(id),
2870 self.concurrent_state_mut(store).get(id)?.caller_instance,
2871 )
2872 } else {
2873 let id = TableId::<GuestTask>::new(rep);
2874 if let Caller::Guest { instance, .. } =
2875 &self.concurrent_state_mut(store).get(id)?.caller
2876 {
2877 (Waitable::Guest(id), *instance)
2878 } else {
2879 unreachable!()
2880 }
2881 };
2882 // Since waitables can neither be passed between instances nor forged,
2883 // this should never fail unless there's a bug in Wasmtime, but we check
2884 // here to be sure:
2885 assert_eq!(expected_caller_instance, caller_instance);
2886
2887 log::trace!("subtask_cancel {waitable:?} (handle {task_id})");
2888
2889 let concurrent_state = self.concurrent_state_mut(store);
2890 if let Waitable::Host(host_task) = waitable {
2891 if let Some(handle) = concurrent_state.get_mut(host_task)?.join_handle.take() {
2892 handle.abort();
2893 return Ok(Status::ReturnCancelled as u32);
2894 }
2895 } else {
2896 let caller = concurrent_state.guest_task.unwrap();
2897 let guest_task = TableId::<GuestTask>::new(rep);
2898 let task = concurrent_state.get_mut(guest_task)?;
2899 if task.lower_params.is_some() {
2900 task.lower_params = None;
2901 task.lift_result = None;
2902
2903 // Not yet started; cancel and remove from pending
2904 let callee_instance = task.instance;
2905
2906 let kind = concurrent_state
2907 .instance_state(callee_instance)
2908 .pending
2909 .remove(&guest_task);
2910
2911 if kind.is_none() {
2912 bail!("`subtask.cancel` called after terminal status delivered");
2913 }
2914
2915 return Ok(Status::StartCancelled as u32);
2916 } else if task.lift_result.is_some() {
2917 // Started, but not yet returned or cancelled; send the
2918 // `CANCELLED` event
2919 task.cancel_sent = true;
2920 // Note that this might overwrite an event that was set earlier
2921 // (e.g. `Event::None` if the task is yielding, or
2922 // `Event::Cancelled` if it was already cancelled), but that's
2923 // okay -- this should supersede the previous state.
2924 task.event = Some(Event::Cancelled);
2925 if let Some(set) = task.wake_on_cancel.take() {
2926 let item = match concurrent_state
2927 .get_mut(set)?
2928 .waiting
2929 .remove(&guest_task)
2930 .unwrap()
2931 {
2932 WaitMode::Fiber(fiber) => WorkItem::ResumeFiber(fiber),
2933 WaitMode::Callback => WorkItem::GuestCall(GuestCall {
2934 task: guest_task,
2935 kind: GuestCallKind::DeliverEvent { set: None },
2936 }),
2937 };
2938 concurrent_state.push_high_priority(item);
2939
2940 self.suspend(store, SuspendReason::Yielding { task: caller })?;
2941 }
2942
2943 let concurrent_state = self.concurrent_state_mut(store);
2944 let task = concurrent_state.get_mut(guest_task)?;
2945 if task.lift_result.is_some() {
2946 // Still not yet returned or cancelled; if `async_`, return
2947 // `BLOCKED`; otherwise wait
2948 if async_ {
2949 return Ok(BLOCKED);
2950 } else {
2951 let waitable = Waitable::Guest(guest_task);
2952 let old_set = waitable.common(concurrent_state)?.set;
2953 let set = concurrent_state.get_mut(caller)?.sync_call_set;
2954 waitable.join(concurrent_state, Some(set))?;
2955
2956 self.suspend(store, SuspendReason::Waiting { set, task: caller })?;
2957
2958 waitable.join(self.concurrent_state_mut(store), old_set)?;
2959 }
2960 }
2961 }
2962 }
2963
2964 let event = waitable.take_event(self.concurrent_state_mut(store))?;
2965 if let Some(Event::Subtask {
2966 status: status @ (Status::Returned | Status::ReturnCancelled),
2967 }) = event
2968 {
2969 Ok(status as u32)
2970 } else {
2971 bail!("`subtask.cancel` called after terminal status delivered");
2972 }
2973 }
2974
2975 /// Configures TLS state so `store` will be available via `tls::get` within
2976 /// the closure `f` provided.
2977 ///
2978 /// This is used to ensure that `Future::poll`, which doesn't take a `store`
2979 /// parameter, is able to get access to the `store` during future poll
2980 /// methods.
2981 fn set_tls<R>(self, store: &mut dyn VMStore, f: impl FnOnce() -> R) -> R {
2982 struct Reset<'a>(&'a mut dyn VMStore, Option<ComponentInstanceId>);
2983
2984 impl Drop for Reset<'_> {
2985 fn drop(&mut self) {
2986 self.0.concurrent_async_state_mut().current_instance = self.1;
2987 }
2988 }
2989 let prev = mem::replace(
2990 &mut store.concurrent_async_state_mut().current_instance,
2991 Some(self.id().instance()),
2992 );
2993 let reset = Reset(store, prev);
2994
2995 tls::set(reset.0, f)
2996 }
2997
2998 /// Convenience function to reduce boilerplate.
2999 pub(crate) fn concurrent_state_mut<'a>(
3000 &self,
3001 store: &'a mut StoreOpaque,
3002 ) -> &'a mut ConcurrentState {
3003 self.id().get_mut(store).concurrent_state_mut()
3004 }
3005}
3006
3007/// Trait representing component model ABI async intrinsics and fused adapter
3008/// helper functions.
3009///
3010/// SAFETY (callers): Most of the methods in this trait accept raw pointers,
3011/// which must be valid for at least the duration of the call (and possibly for
3012/// as long as the relevant guest task exists, in the case of `*mut VMFuncRef`
3013/// pointers used for async calls).
3014pub trait VMComponentAsyncStore {
3015 /// A helper function for fused adapter modules involving calls where the
3016 /// one of the caller or callee is async.
3017 ///
3018 /// This helper is not used when the caller and callee both use the sync
3019 /// ABI, only when at least one is async is this used.
3020 unsafe fn prepare_call(
3021 &mut self,
3022 instance: Instance,
3023 memory: *mut VMMemoryDefinition,
3024 start: *mut VMFuncRef,
3025 return_: *mut VMFuncRef,
3026 caller_instance: RuntimeComponentInstanceIndex,
3027 callee_instance: RuntimeComponentInstanceIndex,
3028 task_return_type: TypeTupleIndex,
3029 string_encoding: u8,
3030 result_count: u32,
3031 storage: *mut ValRaw,
3032 storage_len: usize,
3033 ) -> Result<()>;
3034
3035 /// A helper function for fused adapter modules involving calls where the
3036 /// caller is sync-lowered but the callee is async-lifted.
3037 unsafe fn sync_start(
3038 &mut self,
3039 instance: Instance,
3040 callback: *mut VMFuncRef,
3041 callee: *mut VMFuncRef,
3042 param_count: u32,
3043 storage: *mut MaybeUninit<ValRaw>,
3044 storage_len: usize,
3045 ) -> Result<()>;
3046
3047 /// A helper function for fused adapter modules involving calls where the
3048 /// caller is async-lowered.
3049 unsafe fn async_start(
3050 &mut self,
3051 instance: Instance,
3052 callback: *mut VMFuncRef,
3053 post_return: *mut VMFuncRef,
3054 callee: *mut VMFuncRef,
3055 param_count: u32,
3056 result_count: u32,
3057 flags: u32,
3058 ) -> Result<u32>;
3059
3060 /// The `future.write` intrinsic.
3061 fn future_write(
3062 &mut self,
3063 instance: Instance,
3064 ty: TypeFutureTableIndex,
3065 options: OptionsIndex,
3066 future: u32,
3067 address: u32,
3068 ) -> Result<u32>;
3069
3070 /// The `future.read` intrinsic.
3071 fn future_read(
3072 &mut self,
3073 instance: Instance,
3074 ty: TypeFutureTableIndex,
3075 options: OptionsIndex,
3076 future: u32,
3077 address: u32,
3078 ) -> Result<u32>;
3079
3080 /// The `future.drop-writable` intrinsic.
3081 fn future_drop_writable(
3082 &mut self,
3083 instance: Instance,
3084 ty: TypeFutureTableIndex,
3085 writer: u32,
3086 ) -> Result<()>;
3087
3088 /// The `stream.write` intrinsic.
3089 fn stream_write(
3090 &mut self,
3091 instance: Instance,
3092 ty: TypeStreamTableIndex,
3093 options: OptionsIndex,
3094 stream: u32,
3095 address: u32,
3096 count: u32,
3097 ) -> Result<u32>;
3098
3099 /// The `stream.read` intrinsic.
3100 fn stream_read(
3101 &mut self,
3102 instance: Instance,
3103 ty: TypeStreamTableIndex,
3104 options: OptionsIndex,
3105 stream: u32,
3106 address: u32,
3107 count: u32,
3108 ) -> Result<u32>;
3109
3110 /// The "fast-path" implementation of the `stream.write` intrinsic for
3111 /// "flat" (i.e. memcpy-able) payloads.
3112 fn flat_stream_write(
3113 &mut self,
3114 instance: Instance,
3115 ty: TypeStreamTableIndex,
3116 options: OptionsIndex,
3117 payload_size: u32,
3118 payload_align: u32,
3119 stream: u32,
3120 address: u32,
3121 count: u32,
3122 ) -> Result<u32>;
3123
3124 /// The "fast-path" implementation of the `stream.read` intrinsic for "flat"
3125 /// (i.e. memcpy-able) payloads.
3126 fn flat_stream_read(
3127 &mut self,
3128 instance: Instance,
3129 ty: TypeStreamTableIndex,
3130 options: OptionsIndex,
3131 payload_size: u32,
3132 payload_align: u32,
3133 stream: u32,
3134 address: u32,
3135 count: u32,
3136 ) -> Result<u32>;
3137
3138 /// The `stream.drop-writable` intrinsic.
3139 fn stream_drop_writable(
3140 &mut self,
3141 instance: Instance,
3142 ty: TypeStreamTableIndex,
3143 writer: u32,
3144 ) -> Result<()>;
3145
3146 /// The `error-context.debug-message` intrinsic.
3147 fn error_context_debug_message(
3148 &mut self,
3149 instance: Instance,
3150 ty: TypeComponentLocalErrorContextTableIndex,
3151 options: OptionsIndex,
3152 err_ctx_handle: u32,
3153 debug_msg_address: u32,
3154 ) -> Result<()>;
3155}
3156
3157/// SAFETY: See trait docs.
3158impl<T: 'static> VMComponentAsyncStore for StoreInner<T> {
3159 unsafe fn prepare_call(
3160 &mut self,
3161 instance: Instance,
3162 memory: *mut VMMemoryDefinition,
3163 start: *mut VMFuncRef,
3164 return_: *mut VMFuncRef,
3165 caller_instance: RuntimeComponentInstanceIndex,
3166 callee_instance: RuntimeComponentInstanceIndex,
3167 task_return_type: TypeTupleIndex,
3168 string_encoding: u8,
3169 result_count_or_max_if_async: u32,
3170 storage: *mut ValRaw,
3171 storage_len: usize,
3172 ) -> Result<()> {
3173 // SAFETY: The `wasmtime_cranelift`-generated code that calls
3174 // this method will have ensured that `storage` is a valid
3175 // pointer containing at least `storage_len` items.
3176 let params = unsafe { std::slice::from_raw_parts(storage, storage_len) }.to_vec();
3177
3178 unsafe {
3179 instance.prepare_call(
3180 StoreContextMut(self),
3181 start,
3182 return_,
3183 caller_instance,
3184 callee_instance,
3185 task_return_type,
3186 memory,
3187 string_encoding,
3188 match result_count_or_max_if_async {
3189 PREPARE_ASYNC_NO_RESULT => CallerInfo::Async {
3190 params,
3191 has_result: false,
3192 },
3193 PREPARE_ASYNC_WITH_RESULT => CallerInfo::Async {
3194 params,
3195 has_result: true,
3196 },
3197 result_count => CallerInfo::Sync {
3198 params,
3199 result_count,
3200 },
3201 },
3202 )
3203 }
3204 }
3205
3206 unsafe fn sync_start(
3207 &mut self,
3208 instance: Instance,
3209 callback: *mut VMFuncRef,
3210 callee: *mut VMFuncRef,
3211 param_count: u32,
3212 storage: *mut MaybeUninit<ValRaw>,
3213 storage_len: usize,
3214 ) -> Result<()> {
3215 unsafe {
3216 instance
3217 .start_call(
3218 StoreContextMut(self),
3219 callback,
3220 ptr::null_mut(),
3221 callee,
3222 param_count,
3223 1,
3224 START_FLAG_ASYNC_CALLEE,
3225 // SAFETY: The `wasmtime_cranelift`-generated code that calls
3226 // this method will have ensured that `storage` is a valid
3227 // pointer containing at least `storage_len` items.
3228 Some(std::slice::from_raw_parts_mut(storage, storage_len)),
3229 )
3230 .map(drop)
3231 }
3232 }
3233
3234 unsafe fn async_start(
3235 &mut self,
3236 instance: Instance,
3237 callback: *mut VMFuncRef,
3238 post_return: *mut VMFuncRef,
3239 callee: *mut VMFuncRef,
3240 param_count: u32,
3241 result_count: u32,
3242 flags: u32,
3243 ) -> Result<u32> {
3244 unsafe {
3245 instance.start_call(
3246 StoreContextMut(self),
3247 callback,
3248 post_return,
3249 callee,
3250 param_count,
3251 result_count,
3252 flags,
3253 None,
3254 )
3255 }
3256 }
3257
3258 fn future_write(
3259 &mut self,
3260 instance: Instance,
3261 ty: TypeFutureTableIndex,
3262 options: OptionsIndex,
3263 future: u32,
3264 address: u32,
3265 ) -> Result<u32> {
3266 instance
3267 .guest_write(
3268 StoreContextMut(self),
3269 TransmitIndex::Future(ty),
3270 options,
3271 None,
3272 future,
3273 address,
3274 1,
3275 )
3276 .map(|result| result.encode())
3277 }
3278
3279 fn future_read(
3280 &mut self,
3281 instance: Instance,
3282 ty: TypeFutureTableIndex,
3283 options: OptionsIndex,
3284 future: u32,
3285 address: u32,
3286 ) -> Result<u32> {
3287 instance
3288 .guest_read(
3289 StoreContextMut(self),
3290 TransmitIndex::Future(ty),
3291 options,
3292 None,
3293 future,
3294 address,
3295 1,
3296 )
3297 .map(|result| result.encode())
3298 }
3299
3300 fn stream_write(
3301 &mut self,
3302 instance: Instance,
3303 ty: TypeStreamTableIndex,
3304 options: OptionsIndex,
3305 stream: u32,
3306 address: u32,
3307 count: u32,
3308 ) -> Result<u32> {
3309 instance
3310 .guest_write(
3311 StoreContextMut(self),
3312 TransmitIndex::Stream(ty),
3313 options,
3314 None,
3315 stream,
3316 address,
3317 count,
3318 )
3319 .map(|result| result.encode())
3320 }
3321
3322 fn stream_read(
3323 &mut self,
3324 instance: Instance,
3325 ty: TypeStreamTableIndex,
3326 options: OptionsIndex,
3327 stream: u32,
3328 address: u32,
3329 count: u32,
3330 ) -> Result<u32> {
3331 instance
3332 .guest_read(
3333 StoreContextMut(self),
3334 TransmitIndex::Stream(ty),
3335 options,
3336 None,
3337 stream,
3338 address,
3339 count,
3340 )
3341 .map(|result| result.encode())
3342 }
3343
3344 fn future_drop_writable(
3345 &mut self,
3346 instance: Instance,
3347 ty: TypeFutureTableIndex,
3348 writer: u32,
3349 ) -> Result<()> {
3350 instance.guest_drop_writable(StoreContextMut(self), TransmitIndex::Future(ty), writer)
3351 }
3352
3353 fn flat_stream_write(
3354 &mut self,
3355 instance: Instance,
3356 ty: TypeStreamTableIndex,
3357 options: OptionsIndex,
3358 payload_size: u32,
3359 payload_align: u32,
3360 stream: u32,
3361 address: u32,
3362 count: u32,
3363 ) -> Result<u32> {
3364 instance
3365 .guest_write(
3366 StoreContextMut(self),
3367 TransmitIndex::Stream(ty),
3368 options,
3369 Some(FlatAbi {
3370 size: payload_size,
3371 align: payload_align,
3372 }),
3373 stream,
3374 address,
3375 count,
3376 )
3377 .map(|result| result.encode())
3378 }
3379
3380 fn flat_stream_read(
3381 &mut self,
3382 instance: Instance,
3383 ty: TypeStreamTableIndex,
3384 options: OptionsIndex,
3385 payload_size: u32,
3386 payload_align: u32,
3387 stream: u32,
3388 address: u32,
3389 count: u32,
3390 ) -> Result<u32> {
3391 instance
3392 .guest_read(
3393 StoreContextMut(self),
3394 TransmitIndex::Stream(ty),
3395 options,
3396 Some(FlatAbi {
3397 size: payload_size,
3398 align: payload_align,
3399 }),
3400 stream,
3401 address,
3402 count,
3403 )
3404 .map(|result| result.encode())
3405 }
3406
3407 fn stream_drop_writable(
3408 &mut self,
3409 instance: Instance,
3410 ty: TypeStreamTableIndex,
3411 writer: u32,
3412 ) -> Result<()> {
3413 instance.guest_drop_writable(StoreContextMut(self), TransmitIndex::Stream(ty), writer)
3414 }
3415
3416 fn error_context_debug_message(
3417 &mut self,
3418 instance: Instance,
3419 ty: TypeComponentLocalErrorContextTableIndex,
3420 options: OptionsIndex,
3421 err_ctx_handle: u32,
3422 debug_msg_address: u32,
3423 ) -> Result<()> {
3424 instance.error_context_debug_message(
3425 StoreContextMut(self),
3426 ty,
3427 options,
3428 err_ctx_handle,
3429 debug_msg_address,
3430 )
3431 }
3432}
3433
3434/// Represents the output of a host task or background task.
3435pub(crate) enum HostTaskOutput {
3436 /// A plain result
3437 Result(Result<()>),
3438 /// A function to be run after the future completes (e.g. post-processing
3439 /// which requires access to the store and instance).
3440 Function(Box<dyn FnOnce(&mut dyn VMStore, Instance) -> Result<()> + Send>),
3441}
3442
3443impl HostTaskOutput {
3444 /// Retrieve the result of the host or background task, running the
3445 /// post-processing function if present.
3446 fn consume(self, store: &mut dyn VMStore, instance: Instance) -> Result<()> {
3447 match self {
3448 Self::Function(fun) => fun(store, instance),
3449 Self::Result(result) => result,
3450 }
3451 }
3452}
3453
3454type HostTaskFuture = Pin<Box<dyn Future<Output = HostTaskOutput> + Send + 'static>>;
3455
3456/// Represents the state of a pending host task.
3457struct HostTask {
3458 common: WaitableCommon,
3459 caller_instance: RuntimeComponentInstanceIndex,
3460 join_handle: Option<JoinHandle>,
3461}
3462
3463impl HostTask {
3464 fn new(
3465 caller_instance: RuntimeComponentInstanceIndex,
3466 join_handle: Option<JoinHandle>,
3467 ) -> Self {
3468 Self {
3469 common: WaitableCommon::default(),
3470 caller_instance,
3471 join_handle,
3472 }
3473 }
3474}
3475
3476impl TableDebug for HostTask {
3477 fn type_name() -> &'static str {
3478 "HostTask"
3479 }
3480}
3481
3482type CallbackFn = Box<
3483 dyn Fn(&mut dyn VMStore, Instance, RuntimeComponentInstanceIndex, Event, u32) -> Result<u32>
3484 + Send
3485 + Sync
3486 + 'static,
3487>;
3488
3489/// Represents the caller of a given guest task.
3490enum Caller {
3491 /// The host called the guest task.
3492 Host {
3493 /// If present, may be used to deliver the result.
3494 tx: Option<oneshot::Sender<LiftedResult>>,
3495 /// If true, remove the task from the concurrent state that owns it
3496 /// automatically after it completes.
3497 remove_task_automatically: bool,
3498 /// If true, call `post-return` function (if any) automatically.
3499 call_post_return_automatically: bool,
3500 },
3501 /// Another guest task called the guest task
3502 Guest {
3503 /// The id of the caller
3504 task: TableId<GuestTask>,
3505 /// The instance to use to enforce reentrance rules.
3506 ///
3507 /// Note that this might not be the same as the instance the caller task
3508 /// started executing in given that one or more synchronous guest->guest
3509 /// calls may have occurred involving multiple instances.
3510 instance: RuntimeComponentInstanceIndex,
3511 },
3512}
3513
3514/// Represents a closure and related canonical ABI parameters required to
3515/// validate a `task.return` call at runtime and lift the result.
3516struct LiftResult {
3517 lift: RawLift,
3518 ty: TypeTupleIndex,
3519 memory: Option<SendSyncPtr<VMMemoryDefinition>>,
3520 string_encoding: StringEncoding,
3521}
3522
3523/// Represents a pending guest task.
3524struct GuestTask {
3525 /// See `WaitableCommon`
3526 common: WaitableCommon,
3527 /// Closure to lower the parameters passed to this task.
3528 lower_params: Option<RawLower>,
3529 /// See `LiftResult`
3530 lift_result: Option<LiftResult>,
3531 /// A place to stash the type-erased lifted result if it can't be delivered
3532 /// immediately.
3533 result: Option<LiftedResult>,
3534 /// Closure to call the callback function for an async-lifted export, if
3535 /// provided.
3536 callback: Option<CallbackFn>,
3537 /// See `Caller`
3538 caller: Caller,
3539 /// A place to stash the call context for managing resource borrows while
3540 /// switching between guest tasks.
3541 call_context: Option<CallContext>,
3542 /// A place to stash the lowered result for a sync-to-async call until it
3543 /// can be returned to the caller.
3544 sync_result: Option<Option<ValRaw>>,
3545 /// Whether or not the task has been cancelled (i.e. whether the task is
3546 /// permitted to call `task.cancel`).
3547 cancel_sent: bool,
3548 /// Whether or not we've sent a `Status::Starting` event to any current or
3549 /// future waiters for this waitable.
3550 starting_sent: bool,
3551 /// Context-local state used to implement the `context.{get,set}`
3552 /// intrinsics.
3553 context: [u32; 2],
3554 /// Pending guest subtasks created by this task (directly or indirectly).
3555 ///
3556 /// This is used to re-parent subtasks which are still running when their
3557 /// parent task is disposed.
3558 subtasks: HashSet<TableId<GuestTask>>,
3559 /// Scratch waitable set used to watch subtasks during synchronous calls.
3560 sync_call_set: TableId<WaitableSet>,
3561 /// The instance to which the exported function for this guest task belongs.
3562 ///
3563 /// Note that the task may do a sync->sync call via a fused adapter which
3564 /// results in that task executing code in a different instance, and it may
3565 /// call host functions and intrinsics from that other instance.
3566 instance: RuntimeComponentInstanceIndex,
3567 /// If present, a pending `Event::None` or `Event::Cancelled` to be
3568 /// delivered to this task.
3569 event: Option<Event>,
3570 /// If present, indicates that the task is currently waiting on the
3571 /// specified set but may be cancelled and woken immediately.
3572 wake_on_cancel: Option<TableId<WaitableSet>>,
3573 /// The `ExportIndex` of the guest function being called, if known.
3574 function_index: Option<ExportIndex>,
3575 /// Whether or not the task has exited.
3576 exited: bool,
3577}
3578
3579impl GuestTask {
3580 fn new(
3581 state: &mut ConcurrentState,
3582 lower_params: RawLower,
3583 lift_result: LiftResult,
3584 caller: Caller,
3585 callback: Option<CallbackFn>,
3586 component_instance: RuntimeComponentInstanceIndex,
3587 ) -> Result<Self> {
3588 let sync_call_set = state.push(WaitableSet::default())?;
3589
3590 Ok(Self {
3591 common: WaitableCommon::default(),
3592 lower_params: Some(lower_params),
3593 lift_result: Some(lift_result),
3594 result: None,
3595 callback,
3596 caller,
3597 call_context: Some(CallContext::default()),
3598 sync_result: None,
3599 cancel_sent: false,
3600 starting_sent: false,
3601 context: [0u32; 2],
3602 subtasks: HashSet::new(),
3603 sync_call_set,
3604 instance: component_instance,
3605 event: None,
3606 wake_on_cancel: None,
3607 function_index: None,
3608 exited: false,
3609 })
3610 }
3611
3612 /// Dispose of this guest task, reparenting any pending subtasks to the
3613 /// caller.
3614 fn dispose(self, state: &mut ConcurrentState, me: TableId<GuestTask>) -> Result<()> {
3615 // If there are not-yet-delivered completion events for subtasks in
3616 // `self.sync_call_set`, recursively dispose of those subtasks as well.
3617 for waitable in mem::take(&mut state.get_mut(self.sync_call_set)?.ready) {
3618 if let Some(Event::Subtask {
3619 status: Status::Returned | Status::ReturnCancelled,
3620 }) = waitable.common(state)?.event
3621 {
3622 waitable.delete_from(state)?;
3623 }
3624 }
3625
3626 state.delete(self.sync_call_set)?;
3627
3628 // Reparent any pending subtasks to the caller.
3629 if let Caller::Guest {
3630 task,
3631 instance: runtime_instance,
3632 } = &self.caller
3633 {
3634 let task_mut = state.get_mut(*task)?;
3635 let present = task_mut.subtasks.remove(&me);
3636 assert!(present);
3637
3638 for subtask in &self.subtasks {
3639 task_mut.subtasks.insert(*subtask);
3640 }
3641
3642 for subtask in &self.subtasks {
3643 state.get_mut(*subtask)?.caller = Caller::Guest {
3644 task: *task,
3645 instance: *runtime_instance,
3646 };
3647 }
3648 } else {
3649 for subtask in &self.subtasks {
3650 state.get_mut(*subtask)?.caller = Caller::Host {
3651 tx: None,
3652 remove_task_automatically: true,
3653 call_post_return_automatically: true,
3654 };
3655 }
3656 }
3657
3658 Ok(())
3659 }
3660
3661 fn call_post_return_automatically(&self) -> bool {
3662 matches!(
3663 self.caller,
3664 Caller::Guest { .. }
3665 | Caller::Host {
3666 call_post_return_automatically: true,
3667 ..
3668 }
3669 )
3670 }
3671}
3672
3673impl TableDebug for GuestTask {
3674 fn type_name() -> &'static str {
3675 "GuestTask"
3676 }
3677}
3678
3679/// Represents state common to all kinds of waitables.
3680#[derive(Default)]
3681struct WaitableCommon {
3682 /// The currently pending event for this waitable, if any.
3683 event: Option<Event>,
3684 /// The set to which this waitable belongs, if any.
3685 set: Option<TableId<WaitableSet>>,
3686 /// The handle with which the guest refers to this waitable, if any.
3687 handle: Option<u32>,
3688}
3689
3690/// Represents a Component Model Async `waitable`.
3691#[derive(Copy, Clone, Ord, PartialOrd, Eq, PartialEq)]
3692enum Waitable {
3693 /// A host task
3694 Host(TableId<HostTask>),
3695 /// A guest task
3696 Guest(TableId<GuestTask>),
3697 /// The read or write end of a stream or future
3698 Transmit(TableId<TransmitHandle>),
3699}
3700
3701impl Waitable {
3702 /// Retrieve the `Waitable` corresponding to the specified guest-visible
3703 /// handle.
3704 fn from_instance(
3705 state: Pin<&mut ComponentInstance>,
3706 caller_instance: RuntimeComponentInstanceIndex,
3707 waitable: u32,
3708 ) -> Result<Self> {
3709 use crate::runtime::vm::component::Waitable;
3710
3711 let (waitable, kind) = state.guest_tables().0[caller_instance].waitable_rep(waitable)?;
3712
3713 Ok(match kind {
3714 Waitable::Subtask { is_host: true } => Self::Host(TableId::new(waitable)),
3715 Waitable::Subtask { is_host: false } => Self::Guest(TableId::new(waitable)),
3716 Waitable::Stream | Waitable::Future => Self::Transmit(TableId::new(waitable)),
3717 })
3718 }
3719
3720 /// Retrieve the host-visible identifier for this `Waitable`.
3721 fn rep(&self) -> u32 {
3722 match self {
3723 Self::Host(id) => id.rep(),
3724 Self::Guest(id) => id.rep(),
3725 Self::Transmit(id) => id.rep(),
3726 }
3727 }
3728
3729 /// Move this `Waitable` to the specified set (when `set` is `Some(_)`) or
3730 /// remove it from any set it may currently belong to (when `set` is
3731 /// `None`).
3732 fn join(&self, state: &mut ConcurrentState, set: Option<TableId<WaitableSet>>) -> Result<()> {
3733 log::trace!("waitable {self:?} join set {set:?}",);
3734
3735 let old = mem::replace(&mut self.common(state)?.set, set);
3736
3737 if let Some(old) = old {
3738 match *self {
3739 Waitable::Host(id) => state.remove_child(id, old),
3740 Waitable::Guest(id) => state.remove_child(id, old),
3741 Waitable::Transmit(id) => state.remove_child(id, old),
3742 }?;
3743
3744 state.get_mut(old)?.ready.remove(self);
3745 }
3746
3747 if let Some(set) = set {
3748 match *self {
3749 Waitable::Host(id) => state.add_child(id, set),
3750 Waitable::Guest(id) => state.add_child(id, set),
3751 Waitable::Transmit(id) => state.add_child(id, set),
3752 }?;
3753
3754 if self.common(state)?.event.is_some() {
3755 self.mark_ready(state)?;
3756 }
3757 }
3758
3759 Ok(())
3760 }
3761
3762 /// Retrieve mutable access to the `WaitableCommon` for this `Waitable`.
3763 fn common<'a>(&self, state: &'a mut ConcurrentState) -> Result<&'a mut WaitableCommon> {
3764 Ok(match self {
3765 Self::Host(id) => &mut state.get_mut(*id)?.common,
3766 Self::Guest(id) => &mut state.get_mut(*id)?.common,
3767 Self::Transmit(id) => &mut state.get_mut(*id)?.common,
3768 })
3769 }
3770
3771 /// Set or clear the pending event for this waitable and either deliver it
3772 /// to the first waiter, if any, or mark it as ready to be delivered to the
3773 /// next waiter that arrives.
3774 fn set_event(&self, state: &mut ConcurrentState, event: Option<Event>) -> Result<()> {
3775 log::trace!("set event for {self:?}: {event:?}");
3776 self.common(state)?.event = event;
3777 self.mark_ready(state)
3778 }
3779
3780 /// Take the pending event from this waitable, leaving `None` in its place.
3781 fn take_event(&self, state: &mut ConcurrentState) -> Result<Option<Event>> {
3782 let common = self.common(state)?;
3783 let event = common.event.take();
3784 if let Some(set) = self.common(state)?.set {
3785 state.get_mut(set)?.ready.remove(self);
3786 }
3787 Ok(event)
3788 }
3789
3790 /// Deliver the current event for this waitable to the first waiter, if any,
3791 /// or else mark it as ready to be delivered to the next waiter that
3792 /// arrives.
3793 fn mark_ready(&self, state: &mut ConcurrentState) -> Result<()> {
3794 if let Some(set) = self.common(state)?.set {
3795 state.get_mut(set)?.ready.insert(*self);
3796 if let Some((task, mode)) = state.get_mut(set)?.waiting.pop_first() {
3797 let wake_on_cancel = state.get_mut(task)?.wake_on_cancel.take();
3798 assert!(wake_on_cancel.is_none() || wake_on_cancel == Some(set));
3799
3800 let item = match mode {
3801 WaitMode::Fiber(fiber) => WorkItem::ResumeFiber(fiber),
3802 WaitMode::Callback => WorkItem::GuestCall(GuestCall {
3803 task,
3804 kind: GuestCallKind::DeliverEvent { set: Some(set) },
3805 }),
3806 };
3807 state.push_high_priority(item);
3808 }
3809 }
3810 Ok(())
3811 }
3812
3813 /// Handle the imminent delivery of the specified event, e.g. by updating
3814 /// the state of the stream or future.
3815 fn on_delivery(&self, instance: Pin<&mut ComponentInstance>, event: Event) {
3816 match event {
3817 Event::FutureRead {
3818 pending: Some((ty, handle)),
3819 ..
3820 }
3821 | Event::FutureWrite {
3822 pending: Some((ty, handle)),
3823 ..
3824 } => {
3825 let runtime_instance = instance.component().types()[ty].instance;
3826 let (rep, state) = instance.guest_tables().0[runtime_instance]
3827 .future_rep(ty, handle)
3828 .unwrap();
3829 assert_eq!(rep, self.rep());
3830 assert_eq!(*state, TransmitLocalState::Busy);
3831 *state = match event {
3832 Event::FutureRead { .. } => TransmitLocalState::Read { done: false },
3833 Event::FutureWrite { .. } => TransmitLocalState::Write { done: false },
3834 _ => unreachable!(),
3835 };
3836 }
3837 Event::StreamRead {
3838 pending: Some((ty, handle)),
3839 code,
3840 }
3841 | Event::StreamWrite {
3842 pending: Some((ty, handle)),
3843 code,
3844 } => {
3845 let runtime_instance = instance.component().types()[ty].instance;
3846 let (rep, state) = instance.guest_tables().0[runtime_instance]
3847 .stream_rep(ty, handle)
3848 .unwrap();
3849 assert_eq!(rep, self.rep());
3850 assert_eq!(*state, TransmitLocalState::Busy);
3851 let done = matches!(code, ReturnCode::Dropped(_));
3852 *state = match event {
3853 Event::StreamRead { .. } => TransmitLocalState::Read { done },
3854 Event::StreamWrite { .. } => TransmitLocalState::Write { done },
3855 _ => unreachable!(),
3856 };
3857 }
3858 _ => {}
3859 }
3860 }
3861
3862 /// Remove this waitable from the instance's rep table.
3863 fn delete_from(&self, state: &mut ConcurrentState) -> Result<()> {
3864 match self {
3865 Self::Host(task) => {
3866 log::trace!("delete host task {task:?}");
3867 state.delete(*task)?;
3868 }
3869 Self::Guest(task) => {
3870 log::trace!("delete guest task {task:?}");
3871 state.delete(*task)?.dispose(state, *task)?;
3872 }
3873 Self::Transmit(task) => {
3874 state.delete(*task)?;
3875 }
3876 }
3877
3878 Ok(())
3879 }
3880}
3881
3882impl fmt::Debug for Waitable {
3883 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
3884 match self {
3885 Self::Host(id) => write!(f, "{id:?}"),
3886 Self::Guest(id) => write!(f, "{id:?}"),
3887 Self::Transmit(id) => write!(f, "{id:?}"),
3888 }
3889 }
3890}
3891
3892/// Represents a Component Model Async `waitable-set`.
3893#[derive(Default)]
3894struct WaitableSet {
3895 /// Which waitables in this set have pending events, if any.
3896 ready: BTreeSet<Waitable>,
3897 /// Which guest tasks are currently waiting on this set, if any.
3898 waiting: BTreeMap<TableId<GuestTask>, WaitMode>,
3899}
3900
3901impl TableDebug for WaitableSet {
3902 fn type_name() -> &'static str {
3903 "WaitableSet"
3904 }
3905}
3906
3907/// Type-erased closure to lower the parameters for a guest task.
3908type RawLower = Box<
3909 dyn FnOnce(&mut dyn VMStore, Instance, &mut [MaybeUninit<ValRaw>]) -> Result<()> + Send + Sync,
3910>;
3911
3912/// Type-erased closure to lift the result for a guest task.
3913type RawLift = Box<
3914 dyn FnOnce(&mut dyn VMStore, Instance, &[ValRaw]) -> Result<Box<dyn Any + Send + Sync>>
3915 + Send
3916 + Sync,
3917>;
3918
3919/// Type erased result of a guest task which may be downcast to the expected
3920/// type by a host caller (or simply ignored in the case of a guest caller; see
3921/// `DummyResult`).
3922type LiftedResult = Box<dyn Any + Send + Sync>;
3923
3924/// Used to return a result from a `LiftFn` when the actual result has already
3925/// been lowered to a guest task's stack and linear memory.
3926struct DummyResult;
3927
3928/// Represents the state of a currently executing fiber which has been resumed
3929/// via `self::poll_fn`.
3930pub(crate) struct AsyncState {
3931 /// The current instance being polled, if any, which is used to perform
3932 /// checks to ensure that futures are always polled within the correct
3933 /// instance.
3934 current_instance: Option<ComponentInstanceId>,
3935}
3936
3937impl Default for AsyncState {
3938 fn default() -> Self {
3939 Self {
3940 current_instance: None,
3941 }
3942 }
3943}
3944
3945/// Represents the Component Model Async state of a (sub-)component instance.
3946#[derive(Default)]
3947struct InstanceState {
3948 /// Whether backpressure is set for this instance
3949 backpressure: bool,
3950 /// Whether this instance can be entered
3951 do_not_enter: bool,
3952 /// Pending calls for this instance which require `Self::backpressure` to be
3953 /// `true` and/or `Self::do_not_enter` to be false before they can proceed.
3954 pending: BTreeMap<TableId<GuestTask>, GuestCallKind>,
3955}
3956
3957/// Represents the Component Model Async state of a top-level component instance
3958/// (i.e. a `super::ComponentInstance`).
3959pub struct ConcurrentState {
3960 /// The currently running guest task, if any.
3961 guest_task: Option<TableId<GuestTask>>,
3962 /// The set of pending host and background tasks, if any.
3963 ///
3964 /// We must wrap this in a `Mutex` to ensure that `ComponentInstance` and
3965 /// `Store` satisfy a `Sync` bound, but it can't actually be accessed from
3966 /// more than one thread at a time.
3967 ///
3968 /// See `ComponentInstance::poll_until` for where we temporarily take this
3969 /// out, poll it, then put it back to avoid any mutable aliasing hazards.
3970 futures: Mutex<Option<FuturesUnordered<HostTaskFuture>>>,
3971 /// The table of waitables, waitable sets, etc.
3972 table: Table,
3973 /// Per (sub-)component instance states.
3974 ///
3975 /// See `InstanceState` for details and note that this map is lazily
3976 /// populated as needed.
3977 // TODO: this can and should be a `PrimaryMap`
3978 instance_states: HashMap<RuntimeComponentInstanceIndex, InstanceState>,
3979 /// The "high priority" work queue for this instance's event loop.
3980 high_priority: Vec<WorkItem>,
3981 /// The "high priority" work queue for this instance's event loop.
3982 low_priority: Vec<WorkItem>,
3983 /// A place to stash the reason a fiber is suspending so that the code which
3984 /// resumed it will know under what conditions the fiber should be resumed
3985 /// again.
3986 suspend_reason: Option<SuspendReason>,
3987 /// A cached fiber which is waiting for work to do.
3988 ///
3989 /// This helps us avoid creating a new fiber for each `GuestCall` work item.
3990 worker: Option<StoreFiber<'static>>,
3991 /// A place to stash the work item for which we're resuming a worker fiber.
3992 worker_item: Option<WorkerItem>,
3993
3994 /// Reference counts for all component error contexts
3995 ///
3996 /// NOTE: it is possible the global ref count to be *greater* than the sum of
3997 /// (sub)component ref counts as tracked by `error_context_tables`, for
3998 /// example when the host holds one or more references to error contexts.
3999 ///
4000 /// The key of this primary map is often referred to as the "rep" (i.e. host-side
4001 /// component-wide representation) of the index into concurrent state for a given
4002 /// stored `ErrorContext`.
4003 ///
4004 /// Stated another way, `TypeComponentGlobalErrorContextTableIndex` is essentially the same
4005 /// as a `TableId<ErrorContextState>`.
4006 global_error_context_ref_counts:
4007 BTreeMap<TypeComponentGlobalErrorContextTableIndex, GlobalErrorContextRefCount>,
4008
4009 /// Mirror of type information in `ComponentInstance`, placed here for
4010 /// convenience at the cost of an extra `Arc` clone.
4011 component: Component,
4012}
4013
4014impl ConcurrentState {
4015 pub(crate) fn new(component: &Component) -> Self {
4016 Self {
4017 guest_task: None,
4018 table: Table::new(),
4019 futures: Mutex::new(Some(FuturesUnordered::new())),
4020 instance_states: HashMap::new(),
4021 high_priority: Vec::new(),
4022 low_priority: Vec::new(),
4023 suspend_reason: None,
4024 worker: None,
4025 worker_item: None,
4026 global_error_context_ref_counts: BTreeMap::new(),
4027 component: component.clone(),
4028 }
4029 }
4030
4031 /// Take ownership of any fibers and futures owned by this object.
4032 ///
4033 /// This should be used when disposing of the `Store` containing this object
4034 /// in order to gracefully resolve any and all fibers using
4035 /// `StoreFiber::dispose`. This is necessary to avoid possible
4036 /// use-after-free bugs due to fibers which may still have access to the
4037 /// `Store`.
4038 ///
4039 /// Additionally, the futures collected with this function should be dropped
4040 /// within a `tls::set` call, which will ensure than any futures closing
4041 /// over an `&Accessor` will have access to the store when dropped, allowing
4042 /// e.g. `WithAccessor[AndValue]` instances to be disposed of without
4043 /// panicking.
4044 ///
4045 /// Note that this will leave the object in an inconsistent and unusable
4046 /// state, so it should only be used just prior to dropping it.
4047 pub(crate) fn take_fibers_and_futures(
4048 &mut self,
4049 fibers: &mut Vec<StoreFiber<'static>>,
4050 futures: &mut Vec<FuturesUnordered<HostTaskFuture>>,
4051 ) {
4052 for entry in self.table.iter_mut() {
4053 if let Some(set) = entry.downcast_mut::<WaitableSet>() {
4054 for mode in mem::take(&mut set.waiting).into_values() {
4055 if let WaitMode::Fiber(fiber) = mode {
4056 fibers.push(fiber);
4057 }
4058 }
4059 }
4060 }
4061
4062 if let Some(fiber) = self.worker.take() {
4063 fibers.push(fiber);
4064 }
4065
4066 let mut take_items = |list| {
4067 for item in mem::take(list) {
4068 match item {
4069 WorkItem::ResumeFiber(fiber) => {
4070 fibers.push(fiber);
4071 }
4072 WorkItem::PushFuture(future) => {
4073 self.futures
4074 .get_mut()
4075 .unwrap()
4076 .as_mut()
4077 .unwrap()
4078 .push(future.into_inner().unwrap());
4079 }
4080 _ => {}
4081 }
4082 }
4083 };
4084
4085 take_items(&mut self.high_priority);
4086 take_items(&mut self.low_priority);
4087
4088 if let Some(them) = self.futures.get_mut().unwrap().take() {
4089 futures.push(them);
4090 }
4091 }
4092
4093 fn instance_state(&mut self, instance: RuntimeComponentInstanceIndex) -> &mut InstanceState {
4094 self.instance_states.entry(instance).or_default()
4095 }
4096
4097 fn push<V: Send + Sync + 'static>(&mut self, value: V) -> Result<TableId<V>, TableError> {
4098 self.table.push(value)
4099 }
4100
4101 fn get<V: 'static>(&self, id: TableId<V>) -> Result<&V, TableError> {
4102 self.table.get(id)
4103 }
4104
4105 fn get_mut<V: 'static>(&mut self, id: TableId<V>) -> Result<&mut V, TableError> {
4106 self.table.get_mut(id)
4107 }
4108
4109 pub fn add_child<T, U>(
4110 &mut self,
4111 child: TableId<T>,
4112 parent: TableId<U>,
4113 ) -> Result<(), TableError> {
4114 self.table.add_child(child, parent)
4115 }
4116
4117 pub fn remove_child<T, U>(
4118 &mut self,
4119 child: TableId<T>,
4120 parent: TableId<U>,
4121 ) -> Result<(), TableError> {
4122 self.table.remove_child(child, parent)
4123 }
4124
4125 fn delete<V: 'static>(&mut self, id: TableId<V>) -> Result<V, TableError> {
4126 self.table.delete(id)
4127 }
4128
4129 fn push_future(&mut self, future: HostTaskFuture) {
4130 // Note that we can't directly push to `ConcurrentState::futures` here
4131 // since this may be called from a future that's being polled inside
4132 // `Self::poll_until`, which temporarily removes the `FuturesUnordered`
4133 // so it has exclusive access while polling it. Therefore, we push a
4134 // work item to the "high priority" queue, which will actually push to
4135 // `ConcurrentState::futures` later.
4136 self.push_high_priority(WorkItem::PushFuture(Mutex::new(future)));
4137 }
4138
4139 fn push_high_priority(&mut self, item: WorkItem) {
4140 log::trace!("push high priority: {item:?}");
4141 self.high_priority.push(item);
4142 }
4143
4144 fn push_low_priority(&mut self, item: WorkItem) {
4145 log::trace!("push low priority: {item:?}");
4146 self.low_priority.push(item);
4147 }
4148
4149 /// Determine whether the instance associated with the specified guest task
4150 /// may be entered (i.e. is not already on the async call stack).
4151 ///
4152 /// This is an additional check on top of the "may_enter" instance flag;
4153 /// it's needed because async-lifted exports with callback functions must
4154 /// not call their own instances directly or indirectly, and due to the
4155 /// "stackless" nature of callback-enabled guest tasks this may happen even
4156 /// if there are no activation records on the stack (i.e. the "may_enter"
4157 /// field is `true`) for that instance.
4158 fn may_enter(&mut self, mut guest_task: TableId<GuestTask>) -> bool {
4159 let guest_instance = self.get(guest_task).unwrap().instance;
4160
4161 // Walk the task tree back to the root, looking for potential
4162 // reentrance.
4163 //
4164 // TODO: This could be optimized by maintaining a per-`GuestTask` bitset
4165 // such that each bit represents and instance which has been entered by
4166 // that task or an ancestor of that task, in which case this would be a
4167 // constant time check.
4168 loop {
4169 match &self.get_mut(guest_task).unwrap().caller {
4170 Caller::Host { .. } => break true,
4171 Caller::Guest { task, instance } => {
4172 if *instance == guest_instance {
4173 break false;
4174 } else {
4175 guest_task = *task;
4176 }
4177 }
4178 }
4179 }
4180 }
4181
4182 /// Record that we're about to enter a (sub-)component instance which does
4183 /// not support more than one concurrent, stackful activation, meaning it
4184 /// cannot be entered again until the next call returns.
4185 fn enter_instance(&mut self, instance: RuntimeComponentInstanceIndex) {
4186 self.instance_state(instance).do_not_enter = true;
4187 }
4188
4189 /// Record that we've exited a (sub-)component instance previously entered
4190 /// with `Self::enter_instance` and then calls `Self::partition_pending`.
4191 /// See the documentation for the latter for details.
4192 fn exit_instance(&mut self, instance: RuntimeComponentInstanceIndex) -> Result<()> {
4193 self.instance_state(instance).do_not_enter = false;
4194 self.partition_pending(instance)
4195 }
4196
4197 /// Iterate over `InstanceState::pending`, moving any ready items into the
4198 /// "high priority" work item queue.
4199 ///
4200 /// See `GuestCall::is_ready` for details.
4201 fn partition_pending(&mut self, instance: RuntimeComponentInstanceIndex) -> Result<()> {
4202 for (task, kind) in mem::take(&mut self.instance_state(instance).pending).into_iter() {
4203 let call = GuestCall { task, kind };
4204 if call.is_ready(self)? {
4205 self.push_high_priority(WorkItem::GuestCall(call));
4206 } else {
4207 self.instance_state(instance)
4208 .pending
4209 .insert(call.task, call.kind);
4210 }
4211 }
4212
4213 Ok(())
4214 }
4215
4216 /// Implements the `backpressure.set` intrinsic.
4217 pub(crate) fn backpressure_set(
4218 &mut self,
4219 caller_instance: RuntimeComponentInstanceIndex,
4220 enabled: u32,
4221 ) -> Result<()> {
4222 let state = self.instance_state(caller_instance);
4223 let old = state.backpressure;
4224 let new = enabled != 0;
4225 state.backpressure = new;
4226
4227 if old && !new {
4228 // Backpressure was previously enabled and is now disabled; move any
4229 // newly-eligible guest calls to the "high priority" queue.
4230 self.partition_pending(caller_instance)?;
4231 }
4232
4233 Ok(())
4234 }
4235
4236 /// Implements the `context.get` intrinsic.
4237 pub(crate) fn context_get(&mut self, slot: u32) -> Result<u32> {
4238 let task = self.guest_task.unwrap();
4239 let val = self.get(task)?.context[usize::try_from(slot).unwrap()];
4240 log::trace!("context_get {task:?} slot {slot} val {val:#x}");
4241 Ok(val)
4242 }
4243
4244 /// Implements the `context.set` intrinsic.
4245 pub(crate) fn context_set(&mut self, slot: u32, val: u32) -> Result<()> {
4246 let task = self.guest_task.unwrap();
4247 log::trace!("context_set {task:?} slot {slot} val {val:#x}");
4248 self.get_mut(task)?.context[usize::try_from(slot).unwrap()] = val;
4249 Ok(())
4250 }
4251
4252 fn options(&self, options: OptionsIndex) -> &CanonicalOptions {
4253 &self.component.env_component().options[options]
4254 }
4255}
4256
4257/// Provide a type hint to compiler about the shape of a parameter lower
4258/// closure.
4259fn for_any_lower<
4260 F: FnOnce(&mut dyn VMStore, Instance, &mut [MaybeUninit<ValRaw>]) -> Result<()> + Send + Sync,
4261>(
4262 fun: F,
4263) -> F {
4264 fun
4265}
4266
4267/// Provide a type hint to compiler about the shape of a result lift closure.
4268fn for_any_lift<
4269 F: FnOnce(&mut dyn VMStore, Instance, &[ValRaw]) -> Result<Box<dyn Any + Send + Sync>>
4270 + Send
4271 + Sync,
4272>(
4273 fun: F,
4274) -> F {
4275 fun
4276}
4277
4278/// Wrap the specified future in a `poll_fn` which asserts that the future is
4279/// only polled from the event loop of the specified `Instance`.
4280///
4281/// See `Instance::run_concurrent` for details.
4282fn checked<F: Future + Send + 'static>(
4283 instance: Instance,
4284 fut: F,
4285) -> impl Future<Output = F::Output> + Send + 'static {
4286 async move {
4287 let mut fut = pin!(fut);
4288 future::poll_fn(move |cx| {
4289 let message = "\
4290 `Future`s which depend on asynchronous component tasks, streams, or \
4291 futures to complete may only be polled from the event loop of the \
4292 instance from which they originated. Please use \
4293 `Instance::{run_concurrent,spawn}` to poll or await them.\
4294 ";
4295 tls::try_get(|store| {
4296 let matched = match store {
4297 tls::TryGet::Some(store) => {
4298 let a = store.concurrent_async_state_mut().current_instance;
4299 a == Some(instance.id().instance())
4300 }
4301 tls::TryGet::Taken | tls::TryGet::None => false,
4302 };
4303
4304 if !matched {
4305 panic!("{message}")
4306 }
4307 });
4308 fut.as_mut().poll(cx)
4309 })
4310 .await
4311 }
4312}
4313
4314/// Assert that `Instance::run_concurrent` has not been called from within an
4315/// instance's event loop.
4316fn check_recursive_run() {
4317 tls::try_get(|store| {
4318 if !matches!(store, tls::TryGet::None) {
4319 panic!("Recursive `Instance::run_concurrent` calls not supported")
4320 }
4321 });
4322}
4323
4324fn unpack_callback_code(code: u32) -> (u32, u32) {
4325 (code & 0xF, code >> 4)
4326}
4327
4328/// Helper struct for packaging parameters to be passed to
4329/// `ComponentInstance::waitable_check` for calls to `waitable-set.wait` or
4330/// `waitable-set.poll`.
4331struct WaitableCheckParams {
4332 set: TableId<WaitableSet>,
4333 options: OptionsIndex,
4334 payload: u32,
4335}
4336
4337/// Helper enum for passing parameters to `ComponentInstance::waitable_check`.
4338enum WaitableCheck {
4339 Wait(WaitableCheckParams),
4340 Poll(WaitableCheckParams),
4341 Yield,
4342}
4343
4344/// Represents a guest task called from the host, prepared using `prepare_call`.
4345pub(crate) struct PreparedCall<R> {
4346 /// The guest export to be called
4347 handle: Func,
4348 /// The guest task created by `prepare_call`
4349 task: TableId<GuestTask>,
4350 /// The number of lowered core Wasm parameters to pass to the call.
4351 param_count: usize,
4352 /// The `oneshot::Receiver` to which the result of the call will be
4353 /// delivered when it is available.
4354 rx: oneshot::Receiver<LiftedResult>,
4355 _phantom: PhantomData<R>,
4356}
4357
4358impl<R> PreparedCall<R> {
4359 /// Get a copy of the `TaskId` for this `PreparedCall`.
4360 pub(crate) fn task_id(&self) -> TaskId {
4361 TaskId {
4362 handle: self.handle,
4363 task: self.task,
4364 }
4365 }
4366}
4367
4368/// Represents a task created by `prepare_call`.
4369pub(crate) struct TaskId {
4370 handle: Func,
4371 task: TableId<GuestTask>,
4372}
4373
4374impl TaskId {
4375 /// Remove the specified task from the concurrent state to which it belongs.
4376 ///
4377 /// This must be used with care to avoid use-after-delete or double-delete
4378 /// bugs. Specifically, it should only be called on tasks created with the
4379 /// `remove_task_automatically` parameter to `prepare_call` set to `false`,
4380 /// which tells the runtime that the caller is responsible for removing the
4381 /// task from the state; otherwise, it will be removed automatically. Also,
4382 /// it should only be called once for a given task, and only after either
4383 /// the task has completed or the instance has trapped.
4384 pub(crate) fn remove<T>(&self, store: StoreContextMut<T>) -> Result<()> {
4385 Waitable::Guest(self.task).delete_from(self.handle.instance().concurrent_state_mut(store.0))
4386 }
4387}
4388
4389/// Prepare a call to the specified exported Wasm function, providing functions
4390/// for lowering the parameters and lifting the result.
4391///
4392/// To enqueue the returned `PreparedCall` in the `ComponentInstance`'s event
4393/// loop, use `queue_call`.
4394pub(crate) fn prepare_call<T, R>(
4395 mut store: StoreContextMut<T>,
4396 handle: Func,
4397 param_count: usize,
4398 remove_task_automatically: bool,
4399 call_post_return_automatically: bool,
4400 lower_params: impl FnOnce(Func, StoreContextMut<T>, &mut [MaybeUninit<ValRaw>]) -> Result<()>
4401 + Send
4402 + Sync
4403 + 'static,
4404 lift_result: impl FnOnce(Func, &mut StoreOpaque, &[ValRaw]) -> Result<Box<dyn Any + Send + Sync>>
4405 + Send
4406 + Sync
4407 + 'static,
4408) -> Result<PreparedCall<R>> {
4409 let (options, _flags, ty, raw_options) = handle.abi_info(store.0);
4410
4411 let instance = handle.instance().id().get(store.0);
4412 let task_return_type = instance.component().types()[ty].results;
4413 let component_instance = raw_options.instance;
4414 let callback = options.callback();
4415 let memory = options.memory_raw().map(SendSyncPtr::new);
4416 let string_encoding = options.string_encoding();
4417 let token = StoreToken::new(store.as_context_mut());
4418 let state = handle.instance().concurrent_state_mut(store.0);
4419
4420 assert!(state.guest_task.is_none());
4421
4422 let (tx, rx) = oneshot::channel();
4423
4424 let mut task = GuestTask::new(
4425 state,
4426 Box::new(for_any_lower(move |store, instance, params| {
4427 debug_assert!(instance.id() == handle.instance().id());
4428 lower_params(handle, token.as_context_mut(store), params)
4429 })),
4430 LiftResult {
4431 lift: Box::new(for_any_lift(move |store, instance, result| {
4432 debug_assert!(instance.id() == handle.instance().id());
4433 lift_result(handle, store, result)
4434 })),
4435 ty: task_return_type,
4436 memory,
4437 string_encoding,
4438 },
4439 Caller::Host {
4440 tx: Some(tx),
4441 remove_task_automatically,
4442 call_post_return_automatically,
4443 },
4444 callback.map(|callback| {
4445 let callback = SendSyncPtr::new(callback);
4446 Box::new(
4447 move |store: &mut dyn VMStore,
4448 instance: Instance,
4449 runtime_instance,
4450 event,
4451 handle| {
4452 let store = token.as_context_mut(store);
4453 // SAFETY: Per the contract of `prepare_call`, the callback
4454 // will remain valid at least as long is this task exists.
4455 unsafe {
4456 instance.call_callback(
4457 store,
4458 runtime_instance,
4459 callback,
4460 event,
4461 handle,
4462 call_post_return_automatically,
4463 )
4464 }
4465 },
4466 ) as CallbackFn
4467 }),
4468 component_instance,
4469 )?;
4470 task.function_index = Some(handle.index());
4471
4472 let task = state.push(task)?;
4473
4474 Ok(PreparedCall {
4475 handle,
4476 task,
4477 param_count,
4478 rx,
4479 _phantom: PhantomData,
4480 })
4481}
4482
4483/// Queue a call previously prepared using `prepare_call` to be run as part of
4484/// the associated `ComponentInstance`'s event loop.
4485///
4486/// The returned future will resolve to the result once it is available, but
4487/// must only be polled via the instance's event loop. See
4488/// `Instance::run_concurrent` for details.
4489pub(crate) fn queue_call<T: 'static, R: Send + 'static>(
4490 mut store: StoreContextMut<T>,
4491 prepared: PreparedCall<R>,
4492) -> Result<impl Future<Output = Result<R>> + Send + 'static + use<T, R>> {
4493 let PreparedCall {
4494 handle,
4495 task,
4496 param_count,
4497 rx,
4498 ..
4499 } = prepared;
4500
4501 queue_call0(store.as_context_mut(), handle, task, param_count)?;
4502
4503 Ok(checked(
4504 handle.instance(),
4505 rx.map(|result| {
4506 result
4507 .map(|v| *v.downcast().unwrap())
4508 .map_err(anyhow::Error::from)
4509 }),
4510 ))
4511}
4512
4513/// Queue a call previously prepared using `prepare_call` to be run as part of
4514/// the associated `ComponentInstance`'s event loop.
4515fn queue_call0<T: 'static>(
4516 store: StoreContextMut<T>,
4517 handle: Func,
4518 guest_task: TableId<GuestTask>,
4519 param_count: usize,
4520) -> Result<()> {
4521 let (options, flags, _ty, raw_options) = handle.abi_info(store.0);
4522 let is_concurrent = raw_options.async_;
4523 let instance = handle.instance();
4524 let callee = handle.lifted_core_func(store.0);
4525 let callback = options.callback();
4526 let post_return = handle.post_return_core_func(store.0);
4527
4528 log::trace!("queueing call {guest_task:?}");
4529
4530 let instance_flags = if callback.is_none() {
4531 None
4532 } else {
4533 Some(flags)
4534 };
4535
4536 // SAFETY: `callee`, `callback`, and `post_return` are valid pointers
4537 // (with signatures appropriate for this call) and will remain valid as
4538 // long as this instance is valid.
4539 unsafe {
4540 instance.queue_call(
4541 store,
4542 guest_task,
4543 SendSyncPtr::new(callee),
4544 param_count,
4545 1,
4546 instance_flags,
4547 is_concurrent,
4548 callback.map(SendSyncPtr::new),
4549 post_return.map(SendSyncPtr::new),
4550 )
4551 }
4552}