1use crate::{App, PlatformDispatcher, RunnableMeta, RunnableVariant};
2use async_task::Runnable;
3use futures::channel::mpsc;
4use smol::prelude::*;
5use std::{
6 fmt::Debug,
7 marker::PhantomData,
8 mem::{self, ManuallyDrop},
9 num::NonZeroUsize,
10 panic::Location,
11 pin::Pin,
12 rc::Rc,
13 sync::{
14 Arc,
15 atomic::{AtomicUsize, Ordering},
16 },
17 task::{Context, Poll},
18 thread::{self, ThreadId},
19 time::{Duration, Instant},
20};
21use util::TryFutureExt;
22use waker_fn::waker_fn;
23
24#[cfg(any(test, feature = "test-support"))]
25use rand::rngs::StdRng;
26
27/// A pointer to the executor that is currently running,
28/// for spawning background tasks.
29#[derive(Clone)]
30pub struct BackgroundExecutor {
31 #[doc(hidden)]
32 pub dispatcher: Arc<dyn PlatformDispatcher>,
33}
34
35/// A pointer to the executor that is currently running,
36/// for spawning tasks on the main thread.
37///
38/// This is intentionally `!Send` via the `not_send` marker field. This is because
39/// `ForegroundExecutor::spawn` does not require `Send` but checks at runtime that the future is
40/// only polled from the same thread it was spawned from. These checks would fail when spawning
41/// foreground tasks from background threads.
42#[derive(Clone)]
43pub struct ForegroundExecutor {
44 #[doc(hidden)]
45 pub dispatcher: Arc<dyn PlatformDispatcher>,
46 not_send: PhantomData<Rc<()>>,
47}
48
49/// Task is a primitive that allows work to happen in the background.
50///
51/// It implements [`Future`] so you can `.await` on it.
52///
53/// If you drop a task it will be cancelled immediately. Calling [`Task::detach`] allows
54/// the task to continue running, but with no way to return a value.
55#[must_use]
56#[derive(Debug)]
57pub struct Task<T>(TaskState<T>);
58
59#[derive(Debug)]
60enum TaskState<T> {
61 /// A task that is ready to return a value
62 Ready(Option<T>),
63
64 /// A task that is currently running.
65 Spawned(async_task::Task<T, RunnableMeta>),
66}
67
68impl<T> Task<T> {
69 /// Creates a new task that will resolve with the value
70 pub fn ready(val: T) -> Self {
71 Task(TaskState::Ready(Some(val)))
72 }
73
74 /// Detaching a task runs it to completion in the background
75 pub fn detach(self) {
76 match self {
77 Task(TaskState::Ready(_)) => {}
78 Task(TaskState::Spawned(task)) => task.detach(),
79 }
80 }
81}
82
83impl<E, T> Task<Result<T, E>>
84where
85 T: 'static,
86 E: 'static + Debug,
87{
88 /// Run the task to completion in the background and log any
89 /// errors that occur.
90 #[track_caller]
91 pub fn detach_and_log_err(self, cx: &App) {
92 let location = core::panic::Location::caller();
93 cx.foreground_executor()
94 .spawn(self.log_tracked_err(*location))
95 .detach();
96 }
97}
98
99impl<T> Future for Task<T> {
100 type Output = T;
101
102 fn poll(self: Pin<&mut Self>, cx: &mut Context) -> Poll<Self::Output> {
103 match unsafe { self.get_unchecked_mut() } {
104 Task(TaskState::Ready(val)) => Poll::Ready(val.take().unwrap()),
105 Task(TaskState::Spawned(task)) => task.poll(cx),
106 }
107 }
108}
109
110/// A task label is an opaque identifier that you can use to
111/// refer to a task in tests.
112#[derive(Clone, Copy, PartialEq, Eq, Hash, Debug)]
113pub struct TaskLabel(NonZeroUsize);
114
115impl Default for TaskLabel {
116 fn default() -> Self {
117 Self::new()
118 }
119}
120
121impl TaskLabel {
122 /// Construct a new task label.
123 pub fn new() -> Self {
124 static NEXT_TASK_LABEL: AtomicUsize = AtomicUsize::new(1);
125 Self(
126 NEXT_TASK_LABEL
127 .fetch_add(1, Ordering::SeqCst)
128 .try_into()
129 .unwrap(),
130 )
131 }
132}
133
134type AnyLocalFuture<R> = Pin<Box<dyn 'static + Future<Output = R>>>;
135
136type AnyFuture<R> = Pin<Box<dyn 'static + Send + Future<Output = R>>>;
137
138/// BackgroundExecutor lets you run things on background threads.
139/// In production this is a thread pool with no ordering guarantees.
140/// In tests this is simulated by running tasks one by one in a deterministic
141/// (but arbitrary) order controlled by the `SEED` environment variable.
142impl BackgroundExecutor {
143 #[doc(hidden)]
144 pub fn new(dispatcher: Arc<dyn PlatformDispatcher>) -> Self {
145 Self { dispatcher }
146 }
147
148 /// Enqueues the given future to be run to completion on a background thread.
149 #[track_caller]
150 pub fn spawn<R>(&self, future: impl Future<Output = R> + Send + 'static) -> Task<R>
151 where
152 R: Send + 'static,
153 {
154 self.spawn_internal::<R>(Box::pin(future), None)
155 }
156
157 /// Enqueues the given future to be run to completion on a background thread.
158 /// The given label can be used to control the priority of the task in tests.
159 #[track_caller]
160 pub fn spawn_labeled<R>(
161 &self,
162 label: TaskLabel,
163 future: impl Future<Output = R> + Send + 'static,
164 ) -> Task<R>
165 where
166 R: Send + 'static,
167 {
168 self.spawn_internal::<R>(Box::pin(future), Some(label))
169 }
170
171 #[track_caller]
172 fn spawn_internal<R: Send + 'static>(
173 &self,
174 future: AnyFuture<R>,
175 label: Option<TaskLabel>,
176 ) -> Task<R> {
177 let dispatcher = self.dispatcher.clone();
178 let location = core::panic::Location::caller();
179 let (runnable, task) = async_task::Builder::new()
180 .metadata(RunnableMeta { location })
181 .spawn(
182 move |_| future,
183 move |runnable| dispatcher.dispatch(RunnableVariant::Meta(runnable), label),
184 );
185 runnable.schedule();
186 Task(TaskState::Spawned(task))
187 }
188
189 /// Used by the test harness to run an async test in a synchronous fashion.
190 #[cfg(any(test, feature = "test-support"))]
191 #[track_caller]
192 pub fn block_test<R>(&self, future: impl Future<Output = R>) -> R {
193 if let Ok(value) = self.block_internal(false, future, None) {
194 value
195 } else {
196 unreachable!()
197 }
198 }
199
200 /// Block the current thread until the given future resolves.
201 /// Consider using `block_with_timeout` instead.
202 pub fn block<R>(&self, future: impl Future<Output = R>) -> R {
203 if let Ok(value) = self.block_internal(true, future, None) {
204 value
205 } else {
206 unreachable!()
207 }
208 }
209
210 #[cfg(not(any(test, feature = "test-support")))]
211 pub(crate) fn block_internal<Fut: Future>(
212 &self,
213 _background_only: bool,
214 future: Fut,
215 timeout: Option<Duration>,
216 ) -> Result<Fut::Output, impl Future<Output = Fut::Output> + use<Fut>> {
217 use std::time::Instant;
218
219 let mut future = Box::pin(future);
220 if timeout == Some(Duration::ZERO) {
221 return Err(future);
222 }
223 let deadline = timeout.map(|timeout| Instant::now() + timeout);
224
225 let parker = parking::Parker::new();
226 let unparker = parker.unparker();
227 let waker = waker_fn(move || {
228 unparker.unpark();
229 });
230 let mut cx = std::task::Context::from_waker(&waker);
231
232 loop {
233 match future.as_mut().poll(&mut cx) {
234 Poll::Ready(result) => return Ok(result),
235 Poll::Pending => {
236 let timeout =
237 deadline.map(|deadline| deadline.saturating_duration_since(Instant::now()));
238 if let Some(timeout) = timeout {
239 if !parker.park_timeout(timeout)
240 && deadline.is_some_and(|deadline| deadline < Instant::now())
241 {
242 return Err(future);
243 }
244 } else {
245 parker.park();
246 }
247 }
248 }
249 }
250 }
251
252 #[cfg(any(test, feature = "test-support"))]
253 #[track_caller]
254 pub(crate) fn block_internal<Fut: Future>(
255 &self,
256 background_only: bool,
257 future: Fut,
258 timeout: Option<Duration>,
259 ) -> Result<Fut::Output, impl Future<Output = Fut::Output> + use<Fut>> {
260 use std::sync::atomic::AtomicBool;
261
262 use parking::Parker;
263
264 let mut future = Box::pin(future);
265 if timeout == Some(Duration::ZERO) {
266 return Err(future);
267 }
268 let Some(dispatcher) = self.dispatcher.as_test() else {
269 return Err(future);
270 };
271
272 let mut max_ticks = if timeout.is_some() {
273 dispatcher.gen_block_on_ticks()
274 } else {
275 usize::MAX
276 };
277
278 let parker = Parker::new();
279 let unparker = parker.unparker();
280
281 let awoken = Arc::new(AtomicBool::new(false));
282 let waker = waker_fn({
283 let awoken = awoken.clone();
284 let unparker = unparker.clone();
285 move || {
286 awoken.store(true, Ordering::SeqCst);
287 unparker.unpark();
288 }
289 });
290 let mut cx = std::task::Context::from_waker(&waker);
291
292 let duration = Duration::from_secs(
293 option_env!("GPUI_TEST_TIMEOUT")
294 .and_then(|s| s.parse::<u64>().ok())
295 .unwrap_or(180),
296 );
297 let mut test_should_end_by = Instant::now() + duration;
298
299 loop {
300 match future.as_mut().poll(&mut cx) {
301 Poll::Ready(result) => return Ok(result),
302 Poll::Pending => {
303 if max_ticks == 0 {
304 return Err(future);
305 }
306 max_ticks -= 1;
307
308 if !dispatcher.tick(background_only) {
309 if awoken.swap(false, Ordering::SeqCst) {
310 continue;
311 }
312
313 if !dispatcher.parking_allowed() {
314 if dispatcher.advance_clock_to_next_delayed() {
315 continue;
316 }
317 let mut backtrace_message = String::new();
318 let mut waiting_message = String::new();
319 if let Some(backtrace) = dispatcher.waiting_backtrace() {
320 backtrace_message =
321 format!("\nbacktrace of waiting future:\n{:?}", backtrace);
322 }
323 if let Some(waiting_hint) = dispatcher.waiting_hint() {
324 waiting_message = format!("\n waiting on: {}\n", waiting_hint);
325 }
326 panic!(
327 "parked with nothing left to run{waiting_message}{backtrace_message}",
328 )
329 }
330 dispatcher.push_unparker(unparker.clone());
331 parker.park_timeout(Duration::from_millis(1));
332 if Instant::now() > test_should_end_by {
333 panic!("test timed out after {duration:?} with allow_parking")
334 }
335 }
336 }
337 }
338 }
339 }
340
341 /// Block the current thread until the given future resolves
342 /// or `duration` has elapsed.
343 pub fn block_with_timeout<Fut: Future>(
344 &self,
345 duration: Duration,
346 future: Fut,
347 ) -> Result<Fut::Output, impl Future<Output = Fut::Output> + use<Fut>> {
348 self.block_internal(true, future, Some(duration))
349 }
350
351 /// Scoped lets you start a number of tasks and waits
352 /// for all of them to complete before returning.
353 pub async fn scoped<'scope, F>(&self, scheduler: F)
354 where
355 F: FnOnce(&mut Scope<'scope>),
356 {
357 let mut scope = Scope::new(self.clone());
358 (scheduler)(&mut scope);
359 let spawned = mem::take(&mut scope.futures)
360 .into_iter()
361 .map(|f| self.spawn(f))
362 .collect::<Vec<_>>();
363 for task in spawned {
364 task.await;
365 }
366 }
367
368 /// Get the current time.
369 ///
370 /// Calling this instead of `std::time::Instant::now` allows the use
371 /// of fake timers in tests.
372 pub fn now(&self) -> Instant {
373 self.dispatcher.now()
374 }
375
376 /// Returns a task that will complete after the given duration.
377 /// Depending on other concurrent tasks the elapsed duration may be longer
378 /// than requested.
379 pub fn timer(&self, duration: Duration) -> Task<()> {
380 if duration.is_zero() {
381 return Task::ready(());
382 }
383 let location = core::panic::Location::caller();
384 let (runnable, task) = async_task::Builder::new()
385 .metadata(RunnableMeta { location })
386 .spawn(move |_| async move {}, {
387 let dispatcher = self.dispatcher.clone();
388 move |runnable| dispatcher.dispatch_after(duration, RunnableVariant::Meta(runnable))
389 });
390 runnable.schedule();
391 Task(TaskState::Spawned(task))
392 }
393
394 /// in tests, start_waiting lets you indicate which task is waiting (for debugging only)
395 #[cfg(any(test, feature = "test-support"))]
396 pub fn start_waiting(&self) {
397 self.dispatcher.as_test().unwrap().start_waiting();
398 }
399
400 /// in tests, removes the debugging data added by start_waiting
401 #[cfg(any(test, feature = "test-support"))]
402 pub fn finish_waiting(&self) {
403 self.dispatcher.as_test().unwrap().finish_waiting();
404 }
405
406 /// in tests, run an arbitrary number of tasks (determined by the SEED environment variable)
407 #[cfg(any(test, feature = "test-support"))]
408 pub fn simulate_random_delay(&self) -> impl Future<Output = ()> + use<> {
409 self.dispatcher.as_test().unwrap().simulate_random_delay()
410 }
411
412 /// in tests, indicate that a given task from `spawn_labeled` should run after everything else
413 #[cfg(any(test, feature = "test-support"))]
414 pub fn deprioritize(&self, task_label: TaskLabel) {
415 self.dispatcher.as_test().unwrap().deprioritize(task_label)
416 }
417
418 /// in tests, move time forward. This does not run any tasks, but does make `timer`s ready.
419 #[cfg(any(test, feature = "test-support"))]
420 pub fn advance_clock(&self, duration: Duration) {
421 self.dispatcher.as_test().unwrap().advance_clock(duration)
422 }
423
424 /// in tests, run one task.
425 #[cfg(any(test, feature = "test-support"))]
426 pub fn tick(&self) -> bool {
427 self.dispatcher.as_test().unwrap().tick(false)
428 }
429
430 /// in tests, run all tasks that are ready to run. If after doing so
431 /// the test still has outstanding tasks, this will panic. (See also [`Self::allow_parking`])
432 #[cfg(any(test, feature = "test-support"))]
433 pub fn run_until_parked(&self) {
434 self.dispatcher.as_test().unwrap().run_until_parked()
435 }
436
437 /// in tests, prevents `run_until_parked` from panicking if there are outstanding tasks.
438 /// This is useful when you are integrating other (non-GPUI) futures, like disk access, that
439 /// do take real async time to run.
440 #[cfg(any(test, feature = "test-support"))]
441 pub fn allow_parking(&self) {
442 self.dispatcher.as_test().unwrap().allow_parking();
443 }
444
445 /// undoes the effect of [`Self::allow_parking`].
446 #[cfg(any(test, feature = "test-support"))]
447 pub fn forbid_parking(&self) {
448 self.dispatcher.as_test().unwrap().forbid_parking();
449 }
450
451 /// adds detail to the "parked with nothing let to run" message.
452 #[cfg(any(test, feature = "test-support"))]
453 pub fn set_waiting_hint(&self, msg: Option<String>) {
454 self.dispatcher.as_test().unwrap().set_waiting_hint(msg);
455 }
456
457 /// in tests, returns the rng used by the dispatcher and seeded by the `SEED` environment variable
458 #[cfg(any(test, feature = "test-support"))]
459 pub fn rng(&self) -> StdRng {
460 self.dispatcher.as_test().unwrap().rng()
461 }
462
463 /// How many CPUs are available to the dispatcher.
464 pub fn num_cpus(&self) -> usize {
465 #[cfg(any(test, feature = "test-support"))]
466 return 4;
467
468 #[cfg(not(any(test, feature = "test-support")))]
469 return num_cpus::get();
470 }
471
472 /// Whether we're on the main thread.
473 pub fn is_main_thread(&self) -> bool {
474 self.dispatcher.is_main_thread()
475 }
476
477 #[cfg(any(test, feature = "test-support"))]
478 /// in tests, control the number of ticks that `block_with_timeout` will run before timing out.
479 pub fn set_block_on_ticks(&self, range: std::ops::RangeInclusive<usize>) {
480 self.dispatcher.as_test().unwrap().set_block_on_ticks(range);
481 }
482}
483
484/// ForegroundExecutor runs things on the main thread.
485impl ForegroundExecutor {
486 /// Creates a new ForegroundExecutor from the given PlatformDispatcher.
487 pub fn new(dispatcher: Arc<dyn PlatformDispatcher>) -> Self {
488 Self {
489 dispatcher,
490 not_send: PhantomData,
491 }
492 }
493
494 /// Enqueues the given Task to run on the main thread at some point in the future.
495 #[track_caller]
496 pub fn spawn<R>(&self, future: impl Future<Output = R> + 'static) -> Task<R>
497 where
498 R: 'static,
499 {
500 let dispatcher = self.dispatcher.clone();
501 let location = core::panic::Location::caller();
502
503 #[track_caller]
504 fn inner<R: 'static>(
505 dispatcher: Arc<dyn PlatformDispatcher>,
506 future: AnyLocalFuture<R>,
507 location: &'static core::panic::Location<'static>,
508 ) -> Task<R> {
509 let (runnable, task) = spawn_local_with_source_location(
510 future,
511 move |runnable| dispatcher.dispatch_on_main_thread(RunnableVariant::Meta(runnable)),
512 RunnableMeta { location },
513 );
514 runnable.schedule();
515 Task(TaskState::Spawned(task))
516 }
517 inner::<R>(dispatcher, Box::pin(future), location)
518 }
519}
520
521/// Variant of `async_task::spawn_local` that includes the source location of the spawn in panics.
522///
523/// Copy-modified from:
524/// <https://github.com/smol-rs/async-task/blob/ca9dbe1db9c422fd765847fa91306e30a6bb58a9/src/runnable.rs#L405>
525#[track_caller]
526fn spawn_local_with_source_location<Fut, S, M>(
527 future: Fut,
528 schedule: S,
529 metadata: M,
530) -> (Runnable<M>, async_task::Task<Fut::Output, M>)
531where
532 Fut: Future + 'static,
533 Fut::Output: 'static,
534 S: async_task::Schedule<M> + Send + Sync + 'static,
535 M: 'static,
536{
537 #[inline]
538 fn thread_id() -> ThreadId {
539 std::thread_local! {
540 static ID: ThreadId = thread::current().id();
541 }
542 ID.try_with(|id| *id)
543 .unwrap_or_else(|_| thread::current().id())
544 }
545
546 struct Checked<F> {
547 id: ThreadId,
548 inner: ManuallyDrop<F>,
549 location: &'static Location<'static>,
550 }
551
552 impl<F> Drop for Checked<F> {
553 fn drop(&mut self) {
554 assert!(
555 self.id == thread_id(),
556 "local task dropped by a thread that didn't spawn it. Task spawned at {}",
557 self.location
558 );
559 unsafe { ManuallyDrop::drop(&mut self.inner) };
560 }
561 }
562
563 impl<F: Future> Future for Checked<F> {
564 type Output = F::Output;
565
566 fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
567 assert!(
568 self.id == thread_id(),
569 "local task polled by a thread that didn't spawn it. Task spawned at {}",
570 self.location
571 );
572 unsafe { self.map_unchecked_mut(|c| &mut *c.inner).poll(cx) }
573 }
574 }
575
576 // Wrap the future into one that checks which thread it's on.
577 let future = Checked {
578 id: thread_id(),
579 inner: ManuallyDrop::new(future),
580 location: Location::caller(),
581 };
582
583 unsafe {
584 async_task::Builder::new()
585 .metadata(metadata)
586 .spawn_unchecked(move |_| future, schedule)
587 }
588}
589
590/// Scope manages a set of tasks that are enqueued and waited on together. See [`BackgroundExecutor::scoped`].
591pub struct Scope<'a> {
592 executor: BackgroundExecutor,
593 futures: Vec<Pin<Box<dyn Future<Output = ()> + Send + 'static>>>,
594 tx: Option<mpsc::Sender<()>>,
595 rx: mpsc::Receiver<()>,
596 lifetime: PhantomData<&'a ()>,
597}
598
599impl<'a> Scope<'a> {
600 fn new(executor: BackgroundExecutor) -> Self {
601 let (tx, rx) = mpsc::channel(1);
602 Self {
603 executor,
604 tx: Some(tx),
605 rx,
606 futures: Default::default(),
607 lifetime: PhantomData,
608 }
609 }
610
611 /// How many CPUs are available to the dispatcher.
612 pub fn num_cpus(&self) -> usize {
613 self.executor.num_cpus()
614 }
615
616 /// Spawn a future into this scope.
617 #[track_caller]
618 pub fn spawn<F>(&mut self, f: F)
619 where
620 F: Future<Output = ()> + Send + 'a,
621 {
622 let tx = self.tx.clone().unwrap();
623
624 // SAFETY: The 'a lifetime is guaranteed to outlive any of these futures because
625 // dropping this `Scope` blocks until all of the futures have resolved.
626 let f = unsafe {
627 mem::transmute::<
628 Pin<Box<dyn Future<Output = ()> + Send + 'a>>,
629 Pin<Box<dyn Future<Output = ()> + Send + 'static>>,
630 >(Box::pin(async move {
631 f.await;
632 drop(tx);
633 }))
634 };
635 self.futures.push(f);
636 }
637}
638
639impl Drop for Scope<'_> {
640 fn drop(&mut self) {
641 self.tx.take().unwrap();
642
643 // Wait until the channel is closed, which means that all of the spawned
644 // futures have resolved.
645 self.executor.block(self.rx.next());
646 }
647}