1use anyhow::{anyhow, Result};
2use async_task::Runnable;
3use backtrace::{Backtrace, BacktraceFmt, BytesOrWideString};
4use parking_lot::Mutex;
5use postage::{barrier, prelude::Stream as _};
6use rand::prelude::*;
7use smol::{channel, prelude::*, Executor, Timer};
8use std::{
9 any::Any,
10 fmt::{self, Debug},
11 marker::PhantomData,
12 mem,
13 ops::RangeInclusive,
14 pin::Pin,
15 rc::Rc,
16 sync::{
17 atomic::{AtomicBool, Ordering::SeqCst},
18 Arc,
19 },
20 task::{Context, Poll},
21 thread,
22 time::{Duration, Instant},
23};
24use waker_fn::waker_fn;
25
26use crate::{
27 platform::{self, Dispatcher},
28 util,
29};
30
31pub enum Foreground {
32 Platform {
33 dispatcher: Arc<dyn platform::Dispatcher>,
34 _not_send_or_sync: PhantomData<Rc<()>>,
35 },
36 Test(smol::LocalExecutor<'static>),
37 Deterministic(Arc<Deterministic>),
38}
39
40pub enum Background {
41 Deterministic {
42 executor: Arc<Deterministic>,
43 },
44 Production {
45 executor: Arc<smol::Executor<'static>>,
46 _stop: channel::Sender<()>,
47 },
48}
49
50type AnyLocalFuture = Pin<Box<dyn 'static + Future<Output = Box<dyn Any + 'static>>>>;
51type AnyFuture = Pin<Box<dyn 'static + Send + Future<Output = Box<dyn Any + Send + 'static>>>>;
52type AnyTask = async_task::Task<Box<dyn Any + Send + 'static>>;
53type AnyLocalTask = async_task::Task<Box<dyn Any + 'static>>;
54
55#[must_use]
56pub enum Task<T> {
57 Ready(Option<T>),
58 Local {
59 any_task: AnyLocalTask,
60 result_type: PhantomData<T>,
61 },
62 Send {
63 any_task: AnyTask,
64 result_type: PhantomData<T>,
65 },
66}
67
68unsafe impl<T: Send> Send for Task<T> {}
69
70struct DeterministicState {
71 rng: StdRng,
72 seed: u64,
73 scheduled_from_foreground: Vec<(Runnable, Backtrace)>,
74 scheduled_from_background: Vec<(Runnable, Backtrace)>,
75 spawned_from_foreground: Vec<(Runnable, Backtrace)>,
76 forbid_parking: bool,
77 block_on_ticks: RangeInclusive<usize>,
78 now: Instant,
79 pending_timers: Vec<(Instant, barrier::Sender)>,
80}
81
82pub struct Deterministic {
83 state: Arc<Mutex<DeterministicState>>,
84 parker: Mutex<parking::Parker>,
85}
86
87impl Deterministic {
88 fn new(seed: u64) -> Self {
89 Self {
90 state: Arc::new(Mutex::new(DeterministicState {
91 rng: StdRng::seed_from_u64(seed),
92 seed,
93 scheduled_from_foreground: Default::default(),
94 scheduled_from_background: Default::default(),
95 spawned_from_foreground: Default::default(),
96 forbid_parking: false,
97 block_on_ticks: 0..=1000,
98 now: Instant::now(),
99 pending_timers: Default::default(),
100 })),
101 parker: Default::default(),
102 }
103 }
104
105 fn spawn_from_foreground(&self, future: AnyLocalFuture) -> AnyLocalTask {
106 let backtrace = Backtrace::new_unresolved();
107 let scheduled_once = AtomicBool::new(false);
108 let state = self.state.clone();
109 let unparker = self.parker.lock().unparker();
110 let (runnable, task) = async_task::spawn_local(future, move |runnable| {
111 let mut state = state.lock();
112 let backtrace = backtrace.clone();
113 if scheduled_once.fetch_or(true, SeqCst) {
114 state.scheduled_from_foreground.push((runnable, backtrace));
115 } else {
116 state.spawned_from_foreground.push((runnable, backtrace));
117 }
118 unparker.unpark();
119 });
120 runnable.schedule();
121 task
122 }
123
124 fn spawn(&self, future: AnyFuture) -> AnyTask {
125 let backtrace = Backtrace::new_unresolved();
126 let state = self.state.clone();
127 let unparker = self.parker.lock().unparker();
128 let (runnable, task) = async_task::spawn(future, move |runnable| {
129 let mut state = state.lock();
130 state
131 .scheduled_from_background
132 .push((runnable, backtrace.clone()));
133 unparker.unpark();
134 });
135 runnable.schedule();
136 task
137 }
138
139 fn run(&self, mut future: AnyLocalFuture) -> Box<dyn Any> {
140 let woken = Arc::new(AtomicBool::new(false));
141 loop {
142 if let Some(result) = self.run_internal(woken.clone(), &mut future) {
143 return result;
144 }
145
146 if !woken.load(SeqCst) && self.state.lock().forbid_parking {
147 panic!("deterministic executor parked after a call to forbid_parking");
148 }
149
150 woken.store(false, SeqCst);
151 self.parker.lock().park();
152 }
153 }
154
155 fn run_until_parked(&self) {
156 let woken = Arc::new(AtomicBool::new(false));
157 let mut future = any_local_future(std::future::pending::<()>());
158 self.run_internal(woken, &mut future);
159 }
160
161 fn run_internal(
162 &self,
163 woken: Arc<AtomicBool>,
164 future: &mut AnyLocalFuture,
165 ) -> Option<Box<dyn Any>> {
166 let unparker = self.parker.lock().unparker();
167 let waker = waker_fn(move || {
168 woken.store(true, SeqCst);
169 unparker.unpark();
170 });
171
172 let mut cx = Context::from_waker(&waker);
173 let mut trace = Trace::default();
174 loop {
175 let mut state = self.state.lock();
176 let runnable_count = state.scheduled_from_foreground.len()
177 + state.scheduled_from_background.len()
178 + state.spawned_from_foreground.len();
179
180 let ix = state.rng.gen_range(0..=runnable_count);
181 if ix < state.scheduled_from_foreground.len() {
182 let (_, backtrace) = &state.scheduled_from_foreground[ix];
183 trace.record(&state, backtrace.clone());
184 let runnable = state.scheduled_from_foreground.remove(ix).0;
185 drop(state);
186 runnable.run();
187 } else if ix - state.scheduled_from_foreground.len()
188 < state.scheduled_from_background.len()
189 {
190 let ix = ix - state.scheduled_from_foreground.len();
191 let (_, backtrace) = &state.scheduled_from_background[ix];
192 trace.record(&state, backtrace.clone());
193 let runnable = state.scheduled_from_background.remove(ix).0;
194 drop(state);
195 runnable.run();
196 } else if ix < runnable_count {
197 let (_, backtrace) = &state.spawned_from_foreground[0];
198 trace.record(&state, backtrace.clone());
199 let runnable = state.spawned_from_foreground.remove(0).0;
200 drop(state);
201 runnable.run();
202 } else {
203 drop(state);
204 if let Poll::Ready(result) = future.poll(&mut cx) {
205 return Some(result);
206 }
207
208 let state = self.state.lock();
209 if state.would_park() {
210 return None;
211 }
212 }
213 }
214 }
215
216 fn block_on(&self, future: &mut AnyLocalFuture) -> Option<Box<dyn Any>> {
217 let unparker = self.parker.lock().unparker();
218 let waker = waker_fn(move || {
219 unparker.unpark();
220 });
221 let max_ticks = {
222 let mut state = self.state.lock();
223 let range = state.block_on_ticks.clone();
224 state.rng.gen_range(range)
225 };
226
227 let mut cx = Context::from_waker(&waker);
228 let mut trace = Trace::default();
229 for _ in 0..max_ticks {
230 let mut state = self.state.lock();
231 let runnable_count = state.scheduled_from_background.len();
232 let ix = state.rng.gen_range(0..=runnable_count);
233 if ix < state.scheduled_from_background.len() {
234 let (_, backtrace) = &state.scheduled_from_background[ix];
235 trace.record(&state, backtrace.clone());
236 let runnable = state.scheduled_from_background.remove(ix).0;
237 drop(state);
238 runnable.run();
239 } else {
240 drop(state);
241 if let Poll::Ready(result) = future.as_mut().poll(&mut cx) {
242 return Some(result);
243 }
244 let state = self.state.lock();
245 if state.scheduled_from_background.is_empty() {
246 if state.forbid_parking {
247 panic!("deterministic executor parked after a call to forbid_parking");
248 }
249 drop(state);
250 self.parker.lock().park();
251 }
252
253 continue;
254 }
255 }
256
257 None
258 }
259}
260
261impl DeterministicState {
262 fn would_park(&self) -> bool {
263 self.scheduled_from_foreground.is_empty()
264 && self.scheduled_from_background.is_empty()
265 && self.spawned_from_foreground.is_empty()
266 }
267}
268
269#[derive(Default)]
270struct Trace {
271 executed: Vec<Backtrace>,
272 scheduled: Vec<Vec<Backtrace>>,
273 spawned_from_foreground: Vec<Vec<Backtrace>>,
274}
275
276impl Trace {
277 fn record(&mut self, state: &DeterministicState, executed: Backtrace) {
278 self.scheduled.push(
279 state
280 .scheduled_from_foreground
281 .iter()
282 .map(|(_, backtrace)| backtrace.clone())
283 .collect(),
284 );
285 self.spawned_from_foreground.push(
286 state
287 .spawned_from_foreground
288 .iter()
289 .map(|(_, backtrace)| backtrace.clone())
290 .collect(),
291 );
292 self.executed.push(executed);
293 }
294
295 fn resolve(&mut self) {
296 for backtrace in &mut self.executed {
297 backtrace.resolve();
298 }
299
300 for backtraces in &mut self.scheduled {
301 for backtrace in backtraces {
302 backtrace.resolve();
303 }
304 }
305
306 for backtraces in &mut self.spawned_from_foreground {
307 for backtrace in backtraces {
308 backtrace.resolve();
309 }
310 }
311 }
312}
313
314impl Debug for Trace {
315 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
316 struct FirstCwdFrameInBacktrace<'a>(&'a Backtrace);
317
318 impl<'a> Debug for FirstCwdFrameInBacktrace<'a> {
319 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> std::fmt::Result {
320 let cwd = std::env::current_dir().unwrap();
321 let mut print_path = |fmt: &mut fmt::Formatter<'_>, path: BytesOrWideString<'_>| {
322 fmt::Display::fmt(&path, fmt)
323 };
324 let mut fmt = BacktraceFmt::new(f, backtrace::PrintFmt::Full, &mut print_path);
325 for frame in self.0.frames() {
326 let mut formatted_frame = fmt.frame();
327 if frame
328 .symbols()
329 .iter()
330 .any(|s| s.filename().map_or(false, |f| f.starts_with(&cwd)))
331 {
332 formatted_frame.backtrace_frame(frame)?;
333 break;
334 }
335 }
336 fmt.finish()
337 }
338 }
339
340 for ((backtrace, scheduled), spawned_from_foreground) in self
341 .executed
342 .iter()
343 .zip(&self.scheduled)
344 .zip(&self.spawned_from_foreground)
345 {
346 writeln!(f, "Scheduled")?;
347 for backtrace in scheduled {
348 writeln!(f, "- {:?}", FirstCwdFrameInBacktrace(backtrace))?;
349 }
350 if scheduled.is_empty() {
351 writeln!(f, "None")?;
352 }
353 writeln!(f, "==========")?;
354
355 writeln!(f, "Spawned from foreground")?;
356 for backtrace in spawned_from_foreground {
357 writeln!(f, "- {:?}", FirstCwdFrameInBacktrace(backtrace))?;
358 }
359 if spawned_from_foreground.is_empty() {
360 writeln!(f, "None")?;
361 }
362 writeln!(f, "==========")?;
363
364 writeln!(f, "Run: {:?}", FirstCwdFrameInBacktrace(backtrace))?;
365 writeln!(f, "+++++++++++++++++++")?;
366 }
367
368 Ok(())
369 }
370}
371
372impl Drop for Trace {
373 fn drop(&mut self) {
374 let trace_on_panic = if let Ok(trace_on_panic) = std::env::var("EXECUTOR_TRACE_ON_PANIC") {
375 trace_on_panic == "1" || trace_on_panic == "true"
376 } else {
377 false
378 };
379 let trace_always = if let Ok(trace_always) = std::env::var("EXECUTOR_TRACE_ALWAYS") {
380 trace_always == "1" || trace_always == "true"
381 } else {
382 false
383 };
384
385 if trace_always || (trace_on_panic && thread::panicking()) {
386 self.resolve();
387 dbg!(self);
388 }
389 }
390}
391
392impl Foreground {
393 pub fn platform(dispatcher: Arc<dyn platform::Dispatcher>) -> Result<Self> {
394 if dispatcher.is_main_thread() {
395 Ok(Self::Platform {
396 dispatcher,
397 _not_send_or_sync: PhantomData,
398 })
399 } else {
400 Err(anyhow!("must be constructed on main thread"))
401 }
402 }
403
404 pub fn test() -> Self {
405 Self::Test(smol::LocalExecutor::new())
406 }
407
408 pub fn spawn<T: 'static>(&self, future: impl Future<Output = T> + 'static) -> Task<T> {
409 let future = any_local_future(future);
410 let any_task = match self {
411 Self::Deterministic(executor) => executor.spawn_from_foreground(future),
412 Self::Platform { dispatcher, .. } => {
413 fn spawn_inner(
414 future: AnyLocalFuture,
415 dispatcher: &Arc<dyn Dispatcher>,
416 ) -> AnyLocalTask {
417 let dispatcher = dispatcher.clone();
418 let schedule =
419 move |runnable: Runnable| dispatcher.run_on_main_thread(runnable);
420 let (runnable, task) = async_task::spawn_local(future, schedule);
421 runnable.schedule();
422 task
423 }
424 spawn_inner(future, dispatcher)
425 }
426 Self::Test(executor) => executor.spawn(future),
427 };
428 Task::local(any_task)
429 }
430
431 pub fn run<T: 'static>(&self, future: impl 'static + Future<Output = T>) -> T {
432 let future = any_local_future(future);
433 let any_value = match self {
434 Self::Deterministic(executor) => executor.run(future),
435 Self::Platform { .. } => panic!("you can't call run on a platform foreground executor"),
436 Self::Test(executor) => smol::block_on(executor.run(future)),
437 };
438 *any_value.downcast().unwrap()
439 }
440
441 pub fn would_park(&self) -> bool {
442 match self {
443 Self::Deterministic(executor) => executor.state.lock().would_park(),
444 _ => panic!("this method can only be called on a deterministic executor"),
445 }
446 }
447
448 pub fn forbid_parking(&self) {
449 match self {
450 Self::Deterministic(executor) => {
451 let mut state = executor.state.lock();
452 state.forbid_parking = true;
453 state.rng = StdRng::seed_from_u64(state.seed);
454 }
455 _ => panic!("this method can only be called on a deterministic executor"),
456 }
457 }
458
459 pub async fn timer(&self, duration: Duration) {
460 match self {
461 Self::Deterministic(executor) => {
462 let (tx, mut rx) = barrier::channel();
463 {
464 let mut state = executor.state.lock();
465 let wakeup_at = state.now + duration;
466 state.pending_timers.push((wakeup_at, tx));
467 }
468 rx.recv().await;
469 }
470 _ => {
471 Timer::after(duration).await;
472 }
473 }
474 }
475
476 pub fn advance_clock(&self, duration: Duration) {
477 match self {
478 Self::Deterministic(executor) => {
479 executor.run_until_parked();
480
481 let mut state = executor.state.lock();
482 state.now += duration;
483 let now = state.now;
484 let mut pending_timers = mem::take(&mut state.pending_timers);
485 drop(state);
486
487 pending_timers.retain(|(wakeup, _)| *wakeup > now);
488 executor.state.lock().pending_timers.extend(pending_timers);
489 }
490 _ => panic!("this method can only be called on a deterministic executor"),
491 }
492 }
493
494 pub fn set_block_on_ticks(&self, range: RangeInclusive<usize>) {
495 match self {
496 Self::Deterministic(executor) => executor.state.lock().block_on_ticks = range,
497 _ => panic!("this method can only be called on a deterministic executor"),
498 }
499 }
500}
501
502impl Background {
503 pub fn new() -> Self {
504 let executor = Arc::new(Executor::new());
505 let stop = channel::unbounded::<()>();
506
507 for i in 0..2 * num_cpus::get() {
508 let executor = executor.clone();
509 let stop = stop.1.clone();
510 thread::Builder::new()
511 .name(format!("background-executor-{}", i))
512 .spawn(move || smol::block_on(executor.run(stop.recv())))
513 .unwrap();
514 }
515
516 Self::Production {
517 executor,
518 _stop: stop.0,
519 }
520 }
521
522 pub fn num_cpus(&self) -> usize {
523 num_cpus::get()
524 }
525
526 pub fn spawn<T, F>(&self, future: F) -> Task<T>
527 where
528 T: 'static + Send,
529 F: Send + Future<Output = T> + 'static,
530 {
531 let future = any_future(future);
532 let any_task = match self {
533 Self::Production { executor, .. } => executor.spawn(future),
534 Self::Deterministic { executor, .. } => executor.spawn(future),
535 };
536 Task::send(any_task)
537 }
538
539 pub fn block_with_timeout<F, T>(
540 &self,
541 timeout: Duration,
542 future: F,
543 ) -> Result<T, impl Future<Output = T>>
544 where
545 T: 'static,
546 F: 'static + Unpin + Future<Output = T>,
547 {
548 let mut future = any_local_future(future);
549 if !timeout.is_zero() {
550 let output = match self {
551 Self::Production { .. } => smol::block_on(util::timeout(timeout, &mut future)).ok(),
552 Self::Deterministic { executor, .. } => executor.block_on(&mut future),
553 };
554 if let Some(output) = output {
555 return Ok(*output.downcast().unwrap());
556 }
557 }
558 Err(async { *future.await.downcast().unwrap() })
559 }
560
561 pub async fn scoped<'scope, F>(&self, scheduler: F)
562 where
563 F: FnOnce(&mut Scope<'scope>),
564 {
565 let mut scope = Scope {
566 futures: Default::default(),
567 _phantom: PhantomData,
568 };
569 (scheduler)(&mut scope);
570 let spawned = scope
571 .futures
572 .into_iter()
573 .map(|f| self.spawn(f))
574 .collect::<Vec<_>>();
575 for task in spawned {
576 task.await;
577 }
578 }
579}
580
581pub struct Scope<'a> {
582 futures: Vec<Pin<Box<dyn Future<Output = ()> + Send + 'static>>>,
583 _phantom: PhantomData<&'a ()>,
584}
585
586impl<'a> Scope<'a> {
587 pub fn spawn<F>(&mut self, f: F)
588 where
589 F: Future<Output = ()> + Send + 'a,
590 {
591 let f = unsafe {
592 mem::transmute::<
593 Pin<Box<dyn Future<Output = ()> + Send + 'a>>,
594 Pin<Box<dyn Future<Output = ()> + Send + 'static>>,
595 >(Box::pin(f))
596 };
597 self.futures.push(f);
598 }
599}
600
601pub fn deterministic(seed: u64) -> (Rc<Foreground>, Arc<Background>) {
602 let executor = Arc::new(Deterministic::new(seed));
603 (
604 Rc::new(Foreground::Deterministic(executor.clone())),
605 Arc::new(Background::Deterministic { executor }),
606 )
607}
608
609impl<T> Task<T> {
610 pub fn ready(value: T) -> Self {
611 Self::Ready(Some(value))
612 }
613
614 fn local(any_task: AnyLocalTask) -> Self {
615 Self::Local {
616 any_task,
617 result_type: PhantomData,
618 }
619 }
620
621 pub fn detach(self) {
622 match self {
623 Task::Ready(_) => {}
624 Task::Local { any_task, .. } => any_task.detach(),
625 Task::Send { any_task, .. } => any_task.detach(),
626 }
627 }
628}
629
630impl<T: Send> Task<T> {
631 fn send(any_task: AnyTask) -> Self {
632 Self::Send {
633 any_task,
634 result_type: PhantomData,
635 }
636 }
637}
638
639impl<T: fmt::Debug> fmt::Debug for Task<T> {
640 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
641 match self {
642 Task::Ready(value) => value.fmt(f),
643 Task::Local { any_task, .. } => any_task.fmt(f),
644 Task::Send { any_task, .. } => any_task.fmt(f),
645 }
646 }
647}
648
649impl<T: 'static> Future for Task<T> {
650 type Output = T;
651
652 fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
653 match unsafe { self.get_unchecked_mut() } {
654 Task::Ready(value) => Poll::Ready(value.take().unwrap()),
655 Task::Local { any_task, .. } => {
656 any_task.poll(cx).map(|value| *value.downcast().unwrap())
657 }
658 Task::Send { any_task, .. } => {
659 any_task.poll(cx).map(|value| *value.downcast().unwrap())
660 }
661 }
662 }
663}
664
665fn any_future<T, F>(future: F) -> AnyFuture
666where
667 T: 'static + Send,
668 F: Future<Output = T> + Send + 'static,
669{
670 async { Box::new(future.await) as Box<dyn Any + Send> }.boxed()
671}
672
673fn any_local_future<T, F>(future: F) -> AnyLocalFuture
674where
675 T: 'static,
676 F: Future<Output = T> + 'static,
677{
678 async { Box::new(future.await) as Box<dyn Any> }.boxed_local()
679}