fdf_core/
dispatcher.rs

1// Copyright 2024 The Fuchsia Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style license that can be
3// found in the LICENSE file.
4
5//! Safe bindings for the driver runtime dispatcher stable ABI
6
7use fdf_sys::*;
8
9use core::cell::RefCell;
10use core::ffi;
11use core::marker::PhantomData;
12use core::mem::ManuallyDrop;
13use core::ptr::{NonNull, null_mut};
14use std::sync::atomic::{AtomicPtr, Ordering};
15use std::sync::{Arc, Weak};
16
17use zx::Status;
18
19use crate::shutdown_observer::ShutdownObserver;
20
21pub use fdf_sys::fdf_dispatcher_t;
22pub use libasync::{
23    AfterDeadline, AsyncDispatcher, AsyncDispatcherRef, JoinHandle, OnDispatcher, Task,
24};
25
26/// A marker trait for a function type that can be used as a shutdown observer for [`Dispatcher`].
27pub trait ShutdownObserverFn: FnOnce(DispatcherRef<'_>) + Send + 'static {}
28impl<T> ShutdownObserverFn for T where T: FnOnce(DispatcherRef<'_>) + Send + 'static {}
29
30/// A builder for [`Dispatcher`]s
31#[derive(Default)]
32pub struct DispatcherBuilder {
33    #[doc(hidden)]
34    pub options: u32,
35    #[doc(hidden)]
36    pub name: String,
37    #[doc(hidden)]
38    pub scheduler_role: String,
39    #[doc(hidden)]
40    pub shutdown_observer: Option<Box<dyn ShutdownObserverFn>>,
41}
42
43impl DispatcherBuilder {
44    /// See `FDF_DISPATCHER_OPTION_UNSYNCHRONIZED` in the C API
45    pub(crate) const UNSYNCHRONIZED: u32 = fdf_sys::FDF_DISPATCHER_OPTION_UNSYNCHRONIZED;
46    /// See `FDF_DISPATCHER_OPTION_ALLOW_SYNC_CALLS` in the C API
47    pub(crate) const ALLOW_THREAD_BLOCKING: u32 = fdf_sys::FDF_DISPATCHER_OPTION_ALLOW_SYNC_CALLS;
48
49    /// Creates a new [`DispatcherBuilder`] that can be used to configure a new dispatcher.
50    /// For more information on the threading-related flags for the dispatcher, see
51    /// https://fuchsia.dev/fuchsia-src/concepts/drivers/driver-dispatcher-and-threads
52    pub fn new() -> Self {
53        Self::default()
54    }
55
56    /// Sets whether parallel callbacks in the callbacks set in the dispatcher are allowed. May
57    /// not be set with [`Self::allow_thread_blocking`].
58    ///
59    /// See https://fuchsia.dev/fuchsia-src/concepts/drivers/driver-dispatcher-and-threads
60    /// for more information on the threading model of driver dispatchers.
61    pub fn unsynchronized(mut self) -> Self {
62        assert!(
63            !self.allows_thread_blocking(),
64            "you may not create an unsynchronized dispatcher that allows synchronous calls"
65        );
66        self.options |= Self::UNSYNCHRONIZED;
67        self
68    }
69
70    /// Whether or not this is an unsynchronized dispatcher
71    pub fn is_unsynchronized(&self) -> bool {
72        (self.options & Self::UNSYNCHRONIZED) == Self::UNSYNCHRONIZED
73    }
74
75    /// This dispatcher may not share zircon threads with other drivers. May not be set with
76    /// [`Self::unsynchronized`].
77    ///
78    /// See https://fuchsia.dev/fuchsia-src/concepts/drivers/driver-dispatcher-and-threads
79    /// for more information on the threading model of driver dispatchers.
80    pub fn allow_thread_blocking(mut self) -> Self {
81        assert!(
82            !self.is_unsynchronized(),
83            "you may not create an unsynchronized dispatcher that allows synchronous calls"
84        );
85        self.options |= Self::ALLOW_THREAD_BLOCKING;
86        self
87    }
88
89    /// Whether or not this dispatcher allows synchronous calls
90    pub fn allows_thread_blocking(&self) -> bool {
91        (self.options & Self::ALLOW_THREAD_BLOCKING) == Self::ALLOW_THREAD_BLOCKING
92    }
93
94    /// A descriptive name for this dispatcher that is used in debug output and process
95    /// lists.
96    pub fn name(mut self, name: &str) -> Self {
97        self.name = name.to_string();
98        self
99    }
100
101    /// A hint string for the runtime that may or may not impact the priority the work scheduled
102    /// by this dispatcher is handled at. It may or may not impact the ability for other drivers
103    /// to share zircon threads with the dispatcher.
104    pub fn scheduler_role(mut self, role: &str) -> Self {
105        self.scheduler_role = role.to_string();
106        self
107    }
108
109    /// A callback to be called before after the dispatcher has completed asynchronous shutdown.
110    pub fn shutdown_observer<F: ShutdownObserverFn>(mut self, shutdown_observer: F) -> Self {
111        self.shutdown_observer = Some(Box::new(shutdown_observer));
112        self
113    }
114
115    /// Create the dispatcher as configured by this object. This must be called from a
116    /// thread managed by the driver runtime. The dispatcher returned is owned by the caller,
117    /// and will initiate asynchronous shutdown when the object is dropped unless
118    /// [`Dispatcher::release`] is called on it to convert it into an unowned [`DispatcherRef`].
119    pub fn create(self) -> Result<Dispatcher, Status> {
120        let mut out_dispatcher = null_mut();
121        let options = self.options;
122        let name = self.name.as_ptr() as *mut ffi::c_char;
123        let name_len = self.name.len();
124        let scheduler_role = self.scheduler_role.as_ptr() as *mut ffi::c_char;
125        let scheduler_role_len = self.scheduler_role.len();
126        let observer =
127            ShutdownObserver::new(self.shutdown_observer.unwrap_or_else(|| Box::new(|_| {})))
128                .into_ptr();
129        // SAFETY: all arguments point to memory that will be available for the duration
130        // of the call, except `observer`, which will be available until it is unallocated
131        // by the dispatcher exit handler.
132        Status::ok(unsafe {
133            fdf_dispatcher_create(
134                options,
135                name,
136                name_len,
137                scheduler_role,
138                scheduler_role_len,
139                observer,
140                &mut out_dispatcher,
141            )
142        })?;
143        // SAFETY: `out_dispatcher` is valid by construction if `fdf_dispatcher_create` returns
144        // ZX_OK.
145        Ok(Dispatcher(unsafe { NonNull::new_unchecked(out_dispatcher) }))
146    }
147
148    /// As with [`Self::create`], this creates a new dispatcher as configured by this object, but
149    /// instead of returning an owned reference it immediately releases the reference to be
150    /// managed by the driver runtime.
151    pub fn create_released(self) -> Result<DispatcherRef<'static>, Status> {
152        self.create().map(Dispatcher::release)
153    }
154}
155
156/// An owned handle for a dispatcher managed by the driver runtime.
157#[derive(Debug)]
158pub struct Dispatcher(pub(crate) NonNull<fdf_dispatcher_t>);
159
160// SAFETY: The api of fdf_dispatcher_t is thread safe.
161unsafe impl Send for Dispatcher {}
162unsafe impl Sync for Dispatcher {}
163thread_local! {
164    pub(crate) static OVERRIDE_DISPATCHER: RefCell<Option<NonNull<fdf_dispatcher_t>>> = const { RefCell::new(None) };
165}
166
167impl Dispatcher {
168    /// Creates a dispatcher ref from a raw handle.
169    ///
170    /// # Safety
171    ///
172    /// Caller is responsible for ensuring that the given handle is valid and
173    /// not owned by any other wrapper that will free it at an arbitrary
174    /// time.
175    pub unsafe fn from_raw(handle: NonNull<fdf_dispatcher_t>) -> Self {
176        Self(handle)
177    }
178
179    fn get_raw_flags(&self) -> u32 {
180        // SAFETY: the inner fdf_dispatcher_t is valid by construction
181        unsafe { fdf_dispatcher_get_options(self.0.as_ptr()) }
182    }
183
184    /// Whether this dispatcher's tasks and futures can run on multiple threads at the same time.
185    pub fn is_unsynchronized(&self) -> bool {
186        (self.get_raw_flags() & DispatcherBuilder::UNSYNCHRONIZED) != 0
187    }
188
189    /// Whether this dispatcher is allowed to call blocking functions or not
190    pub fn allows_thread_blocking(&self) -> bool {
191        (self.get_raw_flags() & DispatcherBuilder::ALLOW_THREAD_BLOCKING) != 0
192    }
193
194    /// Whether this is the dispatcher the current thread is running on
195    pub fn is_current_dispatcher(&self) -> bool {
196        // SAFETY: we don't do anything with the dispatcher pointer, and NULL is returned if this
197        // isn't a dispatcher-managed thread.
198        self.0.as_ptr() == unsafe { fdf_dispatcher_get_current_dispatcher() }
199    }
200
201    /// Releases ownership over this dispatcher and returns a [`DispatcherRef`]
202    /// that can be used to access it. The lifetime of this reference is static because it will
203    /// exist so long as this current driver is loaded, but the driver runtime will shut it down
204    /// when the driver is unloaded.
205    pub fn release(self) -> DispatcherRef<'static> {
206        DispatcherRef(ManuallyDrop::new(self), PhantomData)
207    }
208
209    /// Returns a [`DispatcherRef`] that references this dispatcher with a lifetime constrained by
210    /// `self`.
211    pub fn as_dispatcher_ref(&self) -> DispatcherRef<'_> {
212        DispatcherRef(ManuallyDrop::new(Dispatcher(self.0)), PhantomData)
213    }
214}
215
216impl AsyncDispatcher for Dispatcher {
217    fn as_async_dispatcher_ref(&self) -> AsyncDispatcherRef<'_> {
218        let async_dispatcher =
219            NonNull::new(unsafe { fdf_dispatcher_get_async_dispatcher(self.0.as_ptr()) })
220                .expect("No async dispatcher on driver dispatcher");
221        unsafe { AsyncDispatcherRef::from_raw(async_dispatcher) }
222    }
223}
224
225impl Drop for Dispatcher {
226    fn drop(&mut self) {
227        // SAFETY: we only ever provide an owned `Dispatcher` to one owner, so when
228        // that one is dropped we can invoke the shutdown of the dispatcher
229        unsafe { fdf_dispatcher_shutdown_async(self.0.as_mut()) }
230    }
231}
232
233/// An owned reference to a driver runtime dispatcher that auto-releases when dropped. This gives
234/// you the best of both worlds of having an `Arc<Dispatcher>` and a `DispatcherRef<'static>`
235/// created by [`Dispatcher::release`]:
236///
237/// - You can vend [`Weak`]-like pointers to it that will not cause memory access errors if used
238///   after the dispatcher has shut down, like an [`Arc`].
239/// - You can tie its terminal lifetime to that of the driver itself.
240///
241/// This is particularly useful in tests.
242#[derive(Debug)]
243pub struct AutoReleaseDispatcher(Arc<AtomicPtr<fdf_dispatcher>>);
244
245impl AutoReleaseDispatcher {
246    /// Returns a weakened reference to this dispatcher. This weak reference will only be valid so
247    /// long as the [`AutoReleaseDispatcher`] object that spawned it is alive, after which it will
248    /// no longer be usable to spawn tasks on.
249    pub fn downgrade(&self) -> WeakDispatcher {
250        WeakDispatcher::from(self)
251    }
252}
253
254impl From<Dispatcher> for AutoReleaseDispatcher {
255    fn from(dispatcher: Dispatcher) -> Self {
256        let dispatcher_ptr = dispatcher.release().0.0.as_ptr();
257        Self(Arc::new(AtomicPtr::new(dispatcher_ptr)))
258    }
259}
260
261impl Drop for AutoReleaseDispatcher {
262    fn drop(&mut self) {
263        // Store nullptr into the atomic so that any future attempts to obtain a strong reference
264        // through a WeakDispatcher will not successfully upgrade.
265        self.0.store(null_mut(), Ordering::Relaxed);
266        // We want to allow for any outstanding `on_dispatcher` calls to finish before returning
267        // from drop, so we're going to loop until the strong reference count goes down to zero,
268        // after which any future attempts to call `on_dispatcher` on a `WeakDispatcher` will fail.
269        while Arc::strong_count(&self.0) > 1 {
270            // This sleep is kind of gross, but it should happen extremely rarely and
271            // `on_dispatcher` calls should not be performing any blocking work.
272            std::thread::sleep(std::time::Duration::from_nanos(100))
273        }
274    }
275}
276
277/// An unowned but reference counted reference to a dispatcher. This would usually come from
278/// an [`AutoReleaseDispatcher`] reference to a dispatcher.
279///
280/// The advantage to using this instead of using [`Weak`] directly is that it controls the lifetime
281/// of any given strong reference to the dispatcher, since the only way to access that strong
282/// reference is through [`OnDispatcher::on_dispatcher`]. This makes it much easier to be sure
283/// that you aren't leaving any dangling strong references to the dispatcher object around.
284#[derive(Clone, Debug)]
285pub struct WeakDispatcher(Weak<AtomicPtr<fdf_dispatcher>>);
286
287impl From<&AutoReleaseDispatcher> for WeakDispatcher {
288    fn from(value: &AutoReleaseDispatcher) -> Self {
289        Self(Arc::downgrade(&value.0))
290    }
291}
292
293impl OnDispatcher for WeakDispatcher {
294    fn on_dispatcher<R>(&self, f: impl FnOnce(Option<AsyncDispatcherRef<'_>>) -> R) -> R {
295        let Some(dispatcher_ptr) = self.0.upgrade() else {
296            return f(None);
297        };
298        let Some(dispatcher) = NonNull::new(dispatcher_ptr.load(Ordering::Relaxed)) else {
299            return f(None);
300        };
301        // SAFETY: As long as we hold the strong reference in dispatcher_ptr, the
302        // AutoReleaseDispatcher will not allow its drop to finish and the dispatcher should still
303        // be valid.
304        f(Some(unsafe { DispatcherRef::from_raw(dispatcher) }.as_async_dispatcher_ref()))
305    }
306}
307
308/// An unowned reference to a driver runtime dispatcher such as is produced by calling
309/// [`Dispatcher::release`]. When this object goes out of scope it won't shut down the dispatcher,
310/// leaving that up to the driver runtime or another owner.
311#[derive(Debug)]
312pub struct DispatcherRef<'a>(ManuallyDrop<Dispatcher>, PhantomData<&'a Dispatcher>);
313
314impl<'a> DispatcherRef<'a> {
315    /// Creates a dispatcher ref from a raw handle.
316    ///
317    /// # Safety
318    ///
319    /// Caller is responsible for ensuring that the given handle is valid for
320    /// the lifetime `'a`.
321    pub unsafe fn from_raw(handle: NonNull<fdf_dispatcher_t>) -> Self {
322        // SAFETY: Caller promises the handle is valid.
323        Self(ManuallyDrop::new(unsafe { Dispatcher::from_raw(handle) }), PhantomData)
324    }
325
326    /// Creates a dispatcher ref from an [`AsyncDispatcherRef`].
327    ///
328    /// # Panics
329    ///
330    /// Note that this will cause an assert if the [`AsyncDispatcherRef`] was not created from a
331    /// driver dispatcher in the first place.
332    pub fn from_async_dispatcher(dispatcher: AsyncDispatcherRef<'a>) -> Self {
333        let handle = NonNull::new(unsafe {
334            fdf_dispatcher_downcast_async_dispatcher(dispatcher.inner().as_ptr())
335        })
336        .unwrap();
337        unsafe { Self::from_raw(handle) }
338    }
339}
340
341impl<'a> AsyncDispatcher for DispatcherRef<'a> {
342    fn as_async_dispatcher_ref(&self) -> AsyncDispatcherRef<'_> {
343        self.0.as_async_dispatcher_ref()
344    }
345}
346
347impl<'a> Clone for DispatcherRef<'a> {
348    fn clone(&self) -> Self {
349        Self(ManuallyDrop::new(Dispatcher(self.0.0)), PhantomData)
350    }
351}
352
353impl<'a> core::ops::Deref for DispatcherRef<'a> {
354    type Target = Dispatcher;
355    fn deref(&self) -> &Self::Target {
356        &self.0
357    }
358}
359
360impl<'a> core::ops::DerefMut for DispatcherRef<'a> {
361    fn deref_mut(&mut self) -> &mut Self::Target {
362        &mut self.0
363    }
364}
365
366impl<'a> OnDispatcher for DispatcherRef<'a> {
367    fn on_dispatcher<R>(&self, f: impl FnOnce(Option<AsyncDispatcherRef<'_>>) -> R) -> R {
368        f(Some(self.as_async_dispatcher_ref()))
369    }
370}
371
372/// A placeholder for the currently active dispatcher. Use [`OnDispatcher::on_dispatcher`] to
373/// access it when needed.
374#[derive(Clone, Copy, Debug, PartialEq)]
375pub struct CurrentDispatcher;
376
377impl OnDispatcher for CurrentDispatcher {
378    fn on_dispatcher<R>(&self, f: impl FnOnce(Option<AsyncDispatcherRef<'_>>) -> R) -> R {
379        let dispatcher = OVERRIDE_DISPATCHER
380            .with(|global| *global.borrow())
381            .or_else(|| {
382                // SAFETY: NonNull::new will null-check that we have a current dispatcher.
383                NonNull::new(unsafe { fdf_dispatcher_get_current_dispatcher() })
384            })
385            .map(|dispatcher| {
386                // SAFETY: We constrain the lifetime of the `DispatcherRef` we provide to the
387                // function below to the span of the current function. Since we are running on
388                // the dispatcher, or another dispatcher that is bound to the same lifetime (through
389                // override_dispatcher), we can be sure that the dispatcher will not be shut
390                // down before that function completes.
391                let async_dispatcher = NonNull::new(unsafe {
392                    fdf_dispatcher_get_async_dispatcher(dispatcher.as_ptr())
393                })
394                .expect("No async dispatcher on driver dispatcher");
395                unsafe { AsyncDispatcherRef::from_raw(async_dispatcher) }
396            });
397        f(dispatcher)
398    }
399}
400
401#[cfg(test)]
402mod tests {
403    use super::*;
404
405    use std::sync::{Arc, Once, Weak, mpsc};
406
407    use futures::channel::mpsc as async_mpsc;
408    use futures::{SinkExt, StreamExt};
409    use zx::sys::ZX_OK;
410
411    use core::ffi::{c_char, c_void};
412    use core::ptr::null_mut;
413
414    static GLOBAL_DRIVER_ENV: Once = Once::new();
415
416    pub fn ensure_driver_env() {
417        GLOBAL_DRIVER_ENV.call_once(|| {
418            // SAFETY: calling fdf_env_start, which does not have any soundness
419            // concerns for rust code, and this is only used in tests.
420            unsafe {
421                assert_eq!(fdf_env_start(0), ZX_OK);
422            }
423        });
424    }
425    pub fn with_raw_dispatcher<T>(name: &str, p: impl for<'a> FnOnce(Weak<Dispatcher>) -> T) -> T {
426        with_raw_dispatcher_flags(name, DispatcherBuilder::ALLOW_THREAD_BLOCKING, p)
427    }
428
429    pub(crate) fn with_raw_dispatcher_flags<T>(
430        name: &str,
431        flags: u32,
432        p: impl for<'a> FnOnce(Weak<Dispatcher>) -> T,
433    ) -> T {
434        ensure_driver_env();
435
436        let (shutdown_tx, shutdown_rx) = mpsc::channel();
437        let mut dispatcher = null_mut();
438        let mut observer = ShutdownObserver::new(move |dispatcher| {
439            // SAFETY: we verify that the dispatcher has no tasks left queued in it,
440            // just because this is testing code.
441            assert!(!unsafe { fdf_env_dispatcher_has_queued_tasks(dispatcher.0.0.as_ptr()) });
442            shutdown_tx.send(()).unwrap();
443        })
444        .into_ptr();
445        let driver_ptr = &mut observer as *mut _ as *mut c_void;
446        // SAFETY: The pointers we pass to this function are all stable for the
447        // duration of this function, and are not available to copy or clone to
448        // client code (only through a ref to the non-`Clone`` `Dispatcher`
449        // wrapper).
450        let res = unsafe {
451            fdf_env_dispatcher_create_with_owner(
452                driver_ptr,
453                flags,
454                name.as_ptr() as *const c_char,
455                name.len(),
456                "".as_ptr() as *const c_char,
457                0_usize,
458                observer,
459                &mut dispatcher,
460            )
461        };
462        assert_eq!(res, ZX_OK);
463        let dispatcher = Arc::new(Dispatcher(NonNull::new(dispatcher).unwrap()));
464
465        let res = p(Arc::downgrade(&dispatcher));
466
467        // this initiates the dispatcher shutdown on a driver runtime
468        // thread. When all tasks on the dispatcher have completed, the wait
469        // on the shutdown_rx below will end and we can tear it down.
470        let weak_dispatcher = Arc::downgrade(&dispatcher);
471        drop(dispatcher);
472        shutdown_rx.recv().unwrap();
473        assert_eq!(
474            0,
475            weak_dispatcher.strong_count(),
476            "a dispatcher reference escaped the test body"
477        );
478
479        res
480    }
481
482    #[test]
483    fn start_test_dispatcher() {
484        with_raw_dispatcher("testing", |dispatcher| {
485            println!("hello {dispatcher:?}");
486        })
487    }
488
489    #[test]
490    fn post_task_on_dispatcher() {
491        with_raw_dispatcher("testing task", |dispatcher| {
492            let (tx, rx) = mpsc::channel();
493            let dispatcher = Weak::upgrade(&dispatcher).unwrap();
494            dispatcher
495                .post_task_sync(move |status| {
496                    assert_eq!(status, Status::from_raw(ZX_OK));
497                    tx.send(status).unwrap();
498                })
499                .unwrap();
500            assert_eq!(rx.recv().unwrap(), Status::from_raw(ZX_OK));
501        });
502    }
503
504    #[test]
505    fn post_task_on_subdispatcher() {
506        let (shutdown_tx, shutdown_rx) = mpsc::channel();
507        with_raw_dispatcher("testing task top level", move |dispatcher| {
508            let (tx, rx) = mpsc::channel();
509            let (inner_tx, inner_rx) = mpsc::channel();
510            let dispatcher = Weak::upgrade(&dispatcher).unwrap();
511            dispatcher
512                .post_task_sync(move |status| {
513                    assert_eq!(status, Status::from_raw(ZX_OK));
514                    let inner = DispatcherBuilder::new()
515                        .name("testing task second level")
516                        .scheduler_role("")
517                        .allow_thread_blocking()
518                        .shutdown_observer(move |_dispatcher| {
519                            println!("shutdown observer called");
520                            shutdown_tx.send(1).unwrap();
521                        })
522                        .create()
523                        .unwrap();
524                    inner
525                        .post_task_sync(move |status| {
526                            assert_eq!(status, Status::from_raw(ZX_OK));
527                            tx.send(status).unwrap();
528                        })
529                        .unwrap();
530                    // we want to make sure the inner dispatcher lives long
531                    // enough to run the task, so we sent it out to the outer
532                    // closure.
533                    inner_tx.send(inner).unwrap();
534                })
535                .unwrap();
536            assert_eq!(rx.recv().unwrap(), Status::from_raw(ZX_OK));
537            inner_rx.recv().unwrap();
538        });
539        assert_eq!(shutdown_rx.recv().unwrap(), 1);
540    }
541
542    async fn ping(mut tx: async_mpsc::Sender<u8>, mut rx: async_mpsc::Receiver<u8>) {
543        println!("starting ping!");
544        tx.send(0).await.unwrap();
545        while let Some(next) = rx.next().await {
546            println!("ping! {next}");
547            tx.send(next + 1).await.unwrap();
548        }
549    }
550
551    async fn pong(
552        fin_tx: std::sync::mpsc::Sender<()>,
553        mut tx: async_mpsc::Sender<u8>,
554        mut rx: async_mpsc::Receiver<u8>,
555    ) {
556        println!("starting pong!");
557        while let Some(next) = rx.next().await {
558            println!("pong! {next}");
559            if next > 10 {
560                println!("bye!");
561                break;
562            }
563            tx.send(next + 1).await.unwrap();
564        }
565        fin_tx.send(()).unwrap();
566    }
567
568    #[test]
569    fn async_ping_pong() {
570        with_raw_dispatcher("async ping pong", |dispatcher| {
571            let (fin_tx, fin_rx) = mpsc::channel();
572            let (ping_tx, pong_rx) = async_mpsc::channel(10);
573            let (pong_tx, ping_rx) = async_mpsc::channel(10);
574            dispatcher.spawn(ping(ping_tx, ping_rx)).unwrap();
575            dispatcher.spawn(pong(fin_tx, pong_tx, pong_rx)).unwrap();
576
577            fin_rx.recv().expect("to receive final value");
578        });
579    }
580
581    async fn slow_pong(
582        fin_tx: std::sync::mpsc::Sender<()>,
583        mut tx: async_mpsc::Sender<u8>,
584        mut rx: async_mpsc::Receiver<u8>,
585    ) {
586        use zx::MonotonicDuration;
587        println!("starting pong!");
588        while let Some(next) = rx.next().await {
589            println!("pong! {next}");
590            fuchsia_async::Timer::new(fuchsia_async::MonotonicInstant::after(
591                MonotonicDuration::from_seconds(1),
592            ))
593            .await;
594            if next > 10 {
595                println!("bye!");
596                break;
597            }
598            tx.send(next + 1).await.unwrap();
599        }
600        fin_tx.send(()).unwrap();
601    }
602
603    #[test]
604    fn mixed_executor_async_ping_pong() {
605        with_raw_dispatcher("async ping pong", |dispatcher| {
606            let (fin_tx, fin_rx) = mpsc::channel();
607            let (ping_tx, pong_rx) = async_mpsc::channel(10);
608            let (pong_tx, ping_rx) = async_mpsc::channel(10);
609
610            // spawn ping on the driver dispatcher
611            dispatcher.spawn(ping(ping_tx, ping_rx)).unwrap();
612
613            // and run pong on the fuchsia_async executor
614            let mut executor = fuchsia_async::LocalExecutor::default();
615            executor.run_singlethreaded(slow_pong(fin_tx, pong_tx, pong_rx));
616
617            fin_rx.recv().expect("to receive final value");
618        });
619    }
620}
fdf_core/dispatcher.rs

fdf_core/
dispatcher.rs
