1use crate::{App, PlatformDispatcher};
2use async_task::Runnable;
3use futures::channel::mpsc;
4use smol::prelude::*;
5use std::mem::ManuallyDrop;
6use std::panic::Location;
7use std::thread::{self, ThreadId};
8use std::{
9 fmt::Debug,
10 marker::PhantomData,
11 mem,
12 num::NonZeroUsize,
13 pin::Pin,
14 rc::Rc,
15 sync::{
16 Arc,
17 atomic::{AtomicUsize, Ordering::SeqCst},
18 },
19 task::{Context, Poll},
20 time::{Duration, Instant},
21};
22use util::TryFutureExt;
23use waker_fn::waker_fn;
24
25#[cfg(any(test, feature = "test-support"))]
26use rand::rngs::StdRng;
27
28/// A pointer to the executor that is currently running,
29/// for spawning background tasks.
30#[derive(Clone)]
31pub struct BackgroundExecutor {
32 #[doc(hidden)]
33 pub dispatcher: Arc<dyn PlatformDispatcher>,
34}
35
36/// A pointer to the executor that is currently running,
37/// for spawning tasks on the main thread.
38///
39/// This is intentionally `!Send` via the `not_send` marker field. This is because
40/// `ForegroundExecutor::spawn` does not require `Send` but checks at runtime that the future is
41/// only polled from the same thread it was spawned from. These checks would fail when spawning
42/// foreground tasks from from background threads.
43#[derive(Clone)]
44pub struct ForegroundExecutor {
45 #[doc(hidden)]
46 pub dispatcher: Arc<dyn PlatformDispatcher>,
47 not_send: PhantomData<Rc<()>>,
48}
49
50/// Task is a primitive that allows work to happen in the background.
51///
52/// It implements [`Future`] so you can `.await` on it.
53///
54/// If you drop a task it will be cancelled immediately. Calling [`Task::detach`] allows
55/// the task to continue running, but with no way to return a value.
56#[must_use]
57#[derive(Debug)]
58pub struct Task<T>(TaskState<T>);
59
60#[derive(Debug)]
61enum TaskState<T> {
62 /// A task that is ready to return a value
63 Ready(Option<T>),
64
65 /// A task that is currently running.
66 Spawned(async_task::Task<T>),
67}
68
69impl<T> Task<T> {
70 /// Creates a new task that will resolve with the value
71 pub const fn ready(val: T) -> Self {
72 Task(TaskState::Ready(Some(val)))
73 }
74
75 /// Detaching a task runs it to completion in the background
76 pub fn detach(self) {
77 match self {
78 Task(TaskState::Ready(_)) => {}
79 Task(TaskState::Spawned(task)) => task.detach(),
80 }
81 }
82}
83
84impl<E, T> Task<Result<T, E>>
85where
86 T: 'static,
87 E: 'static + Debug,
88{
89 /// Run the task to completion in the background and log any
90 /// errors that occur.
91 #[track_caller]
92 pub fn detach_and_log_err(self, cx: &App) {
93 let location = core::panic::Location::caller();
94 cx.foreground_executor()
95 .spawn(self.log_tracked_err(*location))
96 .detach();
97 }
98}
99
100impl<T> Future for Task<T> {
101 type Output = T;
102
103 fn poll(self: Pin<&mut Self>, cx: &mut Context) -> Poll<Self::Output> {
104 match unsafe { self.get_unchecked_mut() } {
105 Task(TaskState::Ready(val)) => Poll::Ready(val.take().unwrap()),
106 Task(TaskState::Spawned(task)) => task.poll(cx),
107 }
108 }
109}
110
111/// A task label is an opaque identifier that you can use to
112/// refer to a task in tests.
113#[derive(Clone, Copy, PartialEq, Eq, Hash, Debug)]
114pub struct TaskLabel(NonZeroUsize);
115
116impl Default for TaskLabel {
117 fn default() -> Self {
118 Self::new()
119 }
120}
121
122impl TaskLabel {
123 /// Construct a new task label.
124 pub fn new() -> Self {
125 static NEXT_TASK_LABEL: AtomicUsize = AtomicUsize::new(1);
126 Self(NEXT_TASK_LABEL.fetch_add(1, SeqCst).try_into().unwrap())
127 }
128}
129
130type AnyLocalFuture<R> = Pin<Box<dyn 'static + Future<Output = R>>>;
131
132type AnyFuture<R> = Pin<Box<dyn 'static + Send + Future<Output = R>>>;
133
134/// BackgroundExecutor lets you run things on background threads.
135/// In production this is a thread pool with no ordering guarantees.
136/// In tests this is simulated by running tasks one by one in a deterministic
137/// (but arbitrary) order controlled by the `SEED` environment variable.
138impl BackgroundExecutor {
139 #[doc(hidden)]
140 pub fn new(dispatcher: Arc<dyn PlatformDispatcher>) -> Self {
141 Self { dispatcher }
142 }
143
144 /// Enqueues the given future to be run to completion on a background thread.
145 pub fn spawn<R>(&self, future: impl Future<Output = R> + Send + 'static) -> Task<R>
146 where
147 R: Send + 'static,
148 {
149 self.spawn_internal::<R>(Box::pin(future), None)
150 }
151
152 /// Enqueues the given future to be run to completion on a background thread.
153 /// The given label can be used to control the priority of the task in tests.
154 pub fn spawn_labeled<R>(
155 &self,
156 label: TaskLabel,
157 future: impl Future<Output = R> + Send + 'static,
158 ) -> Task<R>
159 where
160 R: Send + 'static,
161 {
162 self.spawn_internal::<R>(Box::pin(future), Some(label))
163 }
164
165 fn spawn_internal<R: Send + 'static>(
166 &self,
167 future: AnyFuture<R>,
168 label: Option<TaskLabel>,
169 ) -> Task<R> {
170 let dispatcher = self.dispatcher.clone();
171 let (runnable, task) =
172 async_task::spawn(future, move |runnable| dispatcher.dispatch(runnable, label));
173 runnable.schedule();
174 Task(TaskState::Spawned(task))
175 }
176
177 /// Used by the test harness to run an async test in a synchronous fashion.
178 #[cfg(any(test, feature = "test-support"))]
179 #[track_caller]
180 pub fn block_test<R>(&self, future: impl Future<Output = R>) -> R {
181 if let Ok(value) = self.block_internal(false, future, None) {
182 value
183 } else {
184 unreachable!()
185 }
186 }
187
188 /// Block the current thread until the given future resolves.
189 /// Consider using `block_with_timeout` instead.
190 pub fn block<R>(&self, future: impl Future<Output = R>) -> R {
191 if let Ok(value) = self.block_internal(true, future, None) {
192 value
193 } else {
194 unreachable!()
195 }
196 }
197
198 #[cfg(not(any(test, feature = "test-support")))]
199 pub(crate) fn block_internal<Fut: Future>(
200 &self,
201 _background_only: bool,
202 future: Fut,
203 timeout: Option<Duration>,
204 ) -> Result<Fut::Output, impl Future<Output = Fut::Output> + use<Fut>> {
205 use std::time::Instant;
206
207 let mut future = Box::pin(future);
208 if timeout == Some(Duration::ZERO) {
209 return Err(future);
210 }
211 let deadline = timeout.map(|timeout| Instant::now() + timeout);
212
213 let parker = parking::Parker::new();
214 let unparker = parker.unparker();
215 let waker = waker_fn(move || {
216 unparker.unpark();
217 });
218 let mut cx = std::task::Context::from_waker(&waker);
219
220 loop {
221 match future.as_mut().poll(&mut cx) {
222 Poll::Ready(result) => return Ok(result),
223 Poll::Pending => {
224 let timeout =
225 deadline.map(|deadline| deadline.saturating_duration_since(Instant::now()));
226 if let Some(timeout) = timeout {
227 if !parker.park_timeout(timeout)
228 && deadline.is_some_and(|deadline| deadline < Instant::now())
229 {
230 return Err(future);
231 }
232 } else {
233 parker.park();
234 }
235 }
236 }
237 }
238 }
239
240 #[cfg(any(test, feature = "test-support"))]
241 #[track_caller]
242 pub(crate) fn block_internal<Fut: Future>(
243 &self,
244 background_only: bool,
245 future: Fut,
246 timeout: Option<Duration>,
247 ) -> Result<Fut::Output, impl Future<Output = Fut::Output> + use<Fut>> {
248 use std::sync::atomic::AtomicBool;
249
250 use parking::Parker;
251
252 let mut future = Box::pin(future);
253 if timeout == Some(Duration::ZERO) {
254 return Err(future);
255 }
256 let Some(dispatcher) = self.dispatcher.as_test() else {
257 return Err(future);
258 };
259
260 let mut max_ticks = if timeout.is_some() {
261 dispatcher.gen_block_on_ticks()
262 } else {
263 usize::MAX
264 };
265
266 let parker = Parker::new();
267 let unparker = parker.unparker();
268
269 let awoken = Arc::new(AtomicBool::new(false));
270 let waker = waker_fn({
271 let awoken = awoken.clone();
272 let unparker = unparker.clone();
273 move || {
274 awoken.store(true, SeqCst);
275 unparker.unpark();
276 }
277 });
278 let mut cx = std::task::Context::from_waker(&waker);
279
280 loop {
281 match future.as_mut().poll(&mut cx) {
282 Poll::Ready(result) => return Ok(result),
283 Poll::Pending => {
284 if max_ticks == 0 {
285 return Err(future);
286 }
287 max_ticks -= 1;
288
289 if !dispatcher.tick(background_only) {
290 if awoken.swap(false, SeqCst) {
291 continue;
292 }
293
294 if !dispatcher.parking_allowed() {
295 if dispatcher.advance_clock_to_next_delayed() {
296 continue;
297 }
298 let mut backtrace_message = String::new();
299 let mut waiting_message = String::new();
300 if let Some(backtrace) = dispatcher.waiting_backtrace() {
301 backtrace_message =
302 format!("\nbacktrace of waiting future:\n{:?}", backtrace);
303 }
304 if let Some(waiting_hint) = dispatcher.waiting_hint() {
305 waiting_message = format!("\n waiting on: {}\n", waiting_hint);
306 }
307 panic!(
308 "parked with nothing left to run{waiting_message}{backtrace_message}",
309 )
310 }
311 dispatcher.set_unparker(unparker.clone());
312 parker.park();
313 }
314 }
315 }
316 }
317 }
318
319 /// Block the current thread until the given future resolves
320 /// or `duration` has elapsed.
321 pub fn block_with_timeout<Fut: Future>(
322 &self,
323 duration: Duration,
324 future: Fut,
325 ) -> Result<Fut::Output, impl Future<Output = Fut::Output> + use<Fut>> {
326 self.block_internal(true, future, Some(duration))
327 }
328
329 /// Scoped lets you start a number of tasks and waits
330 /// for all of them to complete before returning.
331 pub async fn scoped<'scope, F>(&self, scheduler: F)
332 where
333 F: FnOnce(&mut Scope<'scope>),
334 {
335 let mut scope = Scope::new(self.clone());
336 (scheduler)(&mut scope);
337 let spawned = mem::take(&mut scope.futures)
338 .into_iter()
339 .map(|f| self.spawn(f))
340 .collect::<Vec<_>>();
341 for task in spawned {
342 task.await;
343 }
344 }
345
346 /// Get the current time.
347 ///
348 /// Calling this instead of `std::time::Instant::now` allows the use
349 /// of fake timers in tests.
350 pub fn now(&self) -> Instant {
351 self.dispatcher.now()
352 }
353
354 /// Returns a task that will complete after the given duration.
355 /// Depending on other concurrent tasks the elapsed duration may be longer
356 /// than requested.
357 pub fn timer(&self, duration: Duration) -> Task<()> {
358 if duration.is_zero() {
359 return Task::ready(());
360 }
361 let (runnable, task) = async_task::spawn(async move {}, {
362 let dispatcher = self.dispatcher.clone();
363 move |runnable| dispatcher.dispatch_after(duration, runnable)
364 });
365 runnable.schedule();
366 Task(TaskState::Spawned(task))
367 }
368
369 /// in tests, start_waiting lets you indicate which task is waiting (for debugging only)
370 #[cfg(any(test, feature = "test-support"))]
371 pub fn start_waiting(&self) {
372 self.dispatcher.as_test().unwrap().start_waiting();
373 }
374
375 /// in tests, removes the debugging data added by start_waiting
376 #[cfg(any(test, feature = "test-support"))]
377 pub fn finish_waiting(&self) {
378 self.dispatcher.as_test().unwrap().finish_waiting();
379 }
380
381 /// in tests, run an arbitrary number of tasks (determined by the SEED environment variable)
382 #[cfg(any(test, feature = "test-support"))]
383 pub fn simulate_random_delay(&self) -> impl Future<Output = ()> + use<> {
384 self.dispatcher.as_test().unwrap().simulate_random_delay()
385 }
386
387 /// in tests, indicate that a given task from `spawn_labeled` should run after everything else
388 #[cfg(any(test, feature = "test-support"))]
389 pub fn deprioritize(&self, task_label: TaskLabel) {
390 self.dispatcher.as_test().unwrap().deprioritize(task_label)
391 }
392
393 /// in tests, move time forward. This does not run any tasks, but does make `timer`s ready.
394 #[cfg(any(test, feature = "test-support"))]
395 pub fn advance_clock(&self, duration: Duration) {
396 self.dispatcher.as_test().unwrap().advance_clock(duration)
397 }
398
399 /// in tests, run one task.
400 #[cfg(any(test, feature = "test-support"))]
401 pub fn tick(&self) -> bool {
402 self.dispatcher.as_test().unwrap().tick(false)
403 }
404
405 /// in tests, run all tasks that are ready to run. If after doing so
406 /// the test still has outstanding tasks, this will panic. (See also [`Self::allow_parking`])
407 #[cfg(any(test, feature = "test-support"))]
408 pub fn run_until_parked(&self) {
409 self.dispatcher.as_test().unwrap().run_until_parked()
410 }
411
412 /// in tests, prevents `run_until_parked` from panicking if there are outstanding tasks.
413 /// This is useful when you are integrating other (non-GPUI) futures, like disk access, that
414 /// do take real async time to run.
415 #[cfg(any(test, feature = "test-support"))]
416 pub fn allow_parking(&self) {
417 self.dispatcher.as_test().unwrap().allow_parking();
418 }
419
420 /// undoes the effect of [`Self::allow_parking`].
421 #[cfg(any(test, feature = "test-support"))]
422 pub fn forbid_parking(&self) {
423 self.dispatcher.as_test().unwrap().forbid_parking();
424 }
425
426 /// adds detail to the "parked with nothing let to run" message.
427 #[cfg(any(test, feature = "test-support"))]
428 pub fn set_waiting_hint(&self, msg: Option<String>) {
429 self.dispatcher.as_test().unwrap().set_waiting_hint(msg);
430 }
431
432 /// in tests, returns the rng used by the dispatcher and seeded by the `SEED` environment variable
433 #[cfg(any(test, feature = "test-support"))]
434 pub fn rng(&self) -> StdRng {
435 self.dispatcher.as_test().unwrap().rng()
436 }
437
438 /// How many CPUs are available to the dispatcher.
439 pub fn num_cpus(&self) -> usize {
440 #[cfg(any(test, feature = "test-support"))]
441 return 4;
442
443 #[cfg(not(any(test, feature = "test-support")))]
444 return num_cpus::get();
445 }
446
447 /// Whether we're on the main thread.
448 pub fn is_main_thread(&self) -> bool {
449 self.dispatcher.is_main_thread()
450 }
451
452 #[cfg(any(test, feature = "test-support"))]
453 /// in tests, control the number of ticks that `block_with_timeout` will run before timing out.
454 pub fn set_block_on_ticks(&self, range: std::ops::RangeInclusive<usize>) {
455 self.dispatcher.as_test().unwrap().set_block_on_ticks(range);
456 }
457}
458
459/// ForegroundExecutor runs things on the main thread.
460impl ForegroundExecutor {
461 /// Creates a new ForegroundExecutor from the given PlatformDispatcher.
462 pub fn new(dispatcher: Arc<dyn PlatformDispatcher>) -> Self {
463 Self {
464 dispatcher,
465 not_send: PhantomData,
466 }
467 }
468
469 /// Enqueues the given Task to run on the main thread at some point in the future.
470 #[track_caller]
471 pub fn spawn<R>(&self, future: impl Future<Output = R> + 'static) -> Task<R>
472 where
473 R: 'static,
474 {
475 let dispatcher = self.dispatcher.clone();
476
477 #[track_caller]
478 fn inner<R: 'static>(
479 dispatcher: Arc<dyn PlatformDispatcher>,
480 future: AnyLocalFuture<R>,
481 ) -> Task<R> {
482 let (runnable, task) = spawn_local_with_source_location(future, move |runnable| {
483 dispatcher.dispatch_on_main_thread(runnable)
484 });
485 runnable.schedule();
486 Task(TaskState::Spawned(task))
487 }
488 inner::<R>(dispatcher, Box::pin(future))
489 }
490}
491
492/// Variant of `async_task::spawn_local` that includes the source location of the spawn in panics.
493///
494/// Copy-modified from:
495/// <https://github.com/smol-rs/async-task/blob/ca9dbe1db9c422fd765847fa91306e30a6bb58a9/src/runnable.rs#L405>
496#[track_caller]
497fn spawn_local_with_source_location<Fut, S>(
498 future: Fut,
499 schedule: S,
500) -> (Runnable<()>, async_task::Task<Fut::Output, ()>)
501where
502 Fut: Future + 'static,
503 Fut::Output: 'static,
504 S: async_task::Schedule<()> + Send + Sync + 'static,
505{
506 #[inline]
507 fn thread_id() -> ThreadId {
508 std::thread_local! {
509 static ID: ThreadId = thread::current().id();
510 }
511 ID.try_with(|id| *id)
512 .unwrap_or_else(|_| thread::current().id())
513 }
514
515 struct Checked<F> {
516 id: ThreadId,
517 inner: ManuallyDrop<F>,
518 location: &'static Location<'static>,
519 }
520
521 impl<F> Drop for Checked<F> {
522 fn drop(&mut self) {
523 assert!(
524 self.id == thread_id(),
525 "local task dropped by a thread that didn't spawn it. Task spawned at {}",
526 self.location
527 );
528 unsafe { ManuallyDrop::drop(&mut self.inner) };
529 }
530 }
531
532 impl<F: Future> Future for Checked<F> {
533 type Output = F::Output;
534
535 fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
536 assert!(
537 self.id == thread_id(),
538 "local task polled by a thread that didn't spawn it. Task spawned at {}",
539 self.location
540 );
541 unsafe { self.map_unchecked_mut(|c| &mut *c.inner).poll(cx) }
542 }
543 }
544
545 // Wrap the future into one that checks which thread it's on.
546 let future = Checked {
547 id: thread_id(),
548 inner: ManuallyDrop::new(future),
549 location: Location::caller(),
550 };
551
552 unsafe { async_task::spawn_unchecked(future, schedule) }
553}
554
555/// Scope manages a set of tasks that are enqueued and waited on together. See [`BackgroundExecutor::scoped`].
556pub struct Scope<'a> {
557 executor: BackgroundExecutor,
558 futures: Vec<Pin<Box<dyn Future<Output = ()> + Send + 'static>>>,
559 tx: Option<mpsc::Sender<()>>,
560 rx: mpsc::Receiver<()>,
561 lifetime: PhantomData<&'a ()>,
562}
563
564impl<'a> Scope<'a> {
565 fn new(executor: BackgroundExecutor) -> Self {
566 let (tx, rx) = mpsc::channel(1);
567 Self {
568 executor,
569 tx: Some(tx),
570 rx,
571 futures: Default::default(),
572 lifetime: PhantomData,
573 }
574 }
575
576 /// How many CPUs are available to the dispatcher.
577 pub fn num_cpus(&self) -> usize {
578 self.executor.num_cpus()
579 }
580
581 /// Spawn a future into this scope.
582 pub fn spawn<F>(&mut self, f: F)
583 where
584 F: Future<Output = ()> + Send + 'a,
585 {
586 let tx = self.tx.clone().unwrap();
587
588 // SAFETY: The 'a lifetime is guaranteed to outlive any of these futures because
589 // dropping this `Scope` blocks until all of the futures have resolved.
590 let f = unsafe {
591 mem::transmute::<
592 Pin<Box<dyn Future<Output = ()> + Send + 'a>>,
593 Pin<Box<dyn Future<Output = ()> + Send + 'static>>,
594 >(Box::pin(async move {
595 f.await;
596 drop(tx);
597 }))
598 };
599 self.futures.push(f);
600 }
601}
602
603impl Drop for Scope<'_> {
604 fn drop(&mut self) {
605 self.tx.take().unwrap();
606
607 // Wait until the channel is closed, which means that all of the spawned
608 // futures have resolved.
609 self.executor.block(self.rx.next());
610 }
611}