use alloc::sync::Arc;
use core::mem;
-use core::time::Duration;
-use sync::{Condvar, Mutex};
+use crate::sync::{Condvar, Mutex};
+
+use crate::prelude::*;
#[cfg(any(test, feature = "std"))]
-use std::time::Instant;
+use std::time::{Duration, Instant};
use core::future::Future as StdFuture;
use core::task::{Context, Poll};
use core::pin::Pin;
-use prelude::*;
/// Used to signal to one of many waiters that the condition they're waiting on has happened.
pub(crate) struct Notifier {
/// Wake waiters, tracking that wake needs to occur even if there are currently no waiters.
pub(crate) fn notify(&self) {
let mut lock = self.notify_pending.lock().unwrap();
- lock.0 = true;
+ let mut future_probably_generated_calls = false;
if let Some(future_state) = lock.1.take() {
- future_state.lock().unwrap().complete();
+ future_probably_generated_calls |= future_state.lock().unwrap().complete();
+ future_probably_generated_calls |= Arc::strong_count(&future_state) > 1;
+ }
+ if future_probably_generated_calls {
+ // If a future made some callbacks or has not yet been drop'd (i.e. the state has more
+ // than the one reference we hold), assume the user was notified and skip setting the
+ // notification-required flag. This will not cause the `wait` functions above to return
+ // and avoid any future `Future`s starting in a completed state.
+ return;
}
+ lock.0 = true;
mem::drop(lock);
self.condvar.notify_all();
}
Future {
state: Arc::new(Mutex::new(FutureState {
callbacks: Vec::new(),
- complete: false,
+ complete: true,
}))
}
} else if let Some(existing_state) = &lock.1 {
}
impl FutureState {
- fn complete(&mut self) {
+ fn complete(&mut self) -> bool {
+ let mut made_calls = false;
for callback in self.callbacks.drain(..) {
callback.call();
+ made_calls = true;
}
self.complete = true;
+ made_calls
}
}
impl Future {
/// Registers a callback to be called upon completion of this future. If the future has already
/// completed, the callback will be called immediately.
+ ///
+ /// (C-not exported) use the bindings-only `register_callback_fn` instead
pub fn register_callback(&self, callback: Box<dyn FutureCallback>) {
let mut state = self.state.lock().unwrap();
if state.complete {
state.callbacks.push(callback);
}
}
+
+ // C bindings don't (currently) know how to map `Box<dyn Trait>`, and while it could add the
+ // following wrapper, doing it in the bindings is currently much more work than simply doing it
+ // here.
+ /// Registers a callback to be called upon completion of this future. If the future has already
+ /// completed, the callback will be called immediately.
+ #[cfg(c_bindings)]
+ pub fn register_callback_fn<F: 'static + FutureCallback>(&self, callback: F) {
+ self.register_callback(Box::new(callback));
+ }
}
mod std_future {
use core::future::Future as FutureTrait;
use core::task::{Context, Poll, RawWaker, RawWakerVTable, Waker};
+ #[test]
+ fn notifier_pre_notified_future() {
+ // Previously, if we generated a future after a `Notifier` had been notified, the future
+ // would never complete. This tests this behavior, ensuring the future instead completes
+ // immediately.
+ let notifier = Notifier::new();
+ notifier.notify();
+
+ let callback = Arc::new(AtomicBool::new(false));
+ let callback_ref = Arc::clone(&callback);
+ notifier.get_future().register_callback(Box::new(move || assert!(!callback_ref.fetch_or(true, Ordering::SeqCst))));
+ assert!(callback.load(Ordering::SeqCst));
+ }
+
+ #[test]
+ fn notifier_future_completes_wake() {
+ // Previously, if we were only using the `Future` interface to learn when a `Notifier` has
+ // been notified, we'd never mark the notifier as not-awaiting-notify. This caused the
+ // `lightning-background-processor` to persist in a tight loop.
+ let notifier = Notifier::new();
+
+ // First check the simple case, ensuring if we get notified a new future isn't woken until
+ // a second `notify`.
+ let callback = Arc::new(AtomicBool::new(false));
+ let callback_ref = Arc::clone(&callback);
+ notifier.get_future().register_callback(Box::new(move || assert!(!callback_ref.fetch_or(true, Ordering::SeqCst))));
+ assert!(!callback.load(Ordering::SeqCst));
+
+ notifier.notify();
+ assert!(callback.load(Ordering::SeqCst));
+
+ let callback = Arc::new(AtomicBool::new(false));
+ let callback_ref = Arc::clone(&callback);
+ notifier.get_future().register_callback(Box::new(move || assert!(!callback_ref.fetch_or(true, Ordering::SeqCst))));
+ assert!(!callback.load(Ordering::SeqCst));
+
+ notifier.notify();
+ assert!(callback.load(Ordering::SeqCst));
+
+ // Then check the case where the future is fetched before the notification, but a callback
+ // is only registered after the `notify`, ensuring that it is still sufficient to ensure we
+ // don't get an instant-wake when we get a new future.
+ let future = notifier.get_future();
+ notifier.notify();
+
+ let callback = Arc::new(AtomicBool::new(false));
+ let callback_ref = Arc::clone(&callback);
+ future.register_callback(Box::new(move || assert!(!callback_ref.fetch_or(true, Ordering::SeqCst))));
+ assert!(callback.load(Ordering::SeqCst));
+
+ let callback = Arc::new(AtomicBool::new(false));
+ let callback_ref = Arc::clone(&callback);
+ notifier.get_future().register_callback(Box::new(move || assert!(!callback_ref.fetch_or(true, Ordering::SeqCst))));
+ assert!(!callback.load(Ordering::SeqCst));
+ }
+
#[cfg(feature = "std")]
#[test]
fn test_wait_timeout() {
- use sync::Arc;
+ use crate::sync::Arc;
use std::thread;
let persistence_notifier = Arc::new(Notifier::new());
// waker, which we do here with a trivial Arc<AtomicBool> data element to track woke-ness.
const WAKER_V_TABLE: RawWakerVTable = RawWakerVTable::new(waker_clone, wake, wake_by_ref, drop);
unsafe fn wake_by_ref(ptr: *const ()) { let p = ptr as *const Arc<AtomicBool>; assert!(!(*p).fetch_or(true, Ordering::SeqCst)); }
- unsafe fn drop(ptr: *const ()) { let p = ptr as *mut Arc<AtomicBool>; Box::from_raw(p); }
+ unsafe fn drop(ptr: *const ()) { let p = ptr as *mut Arc<AtomicBool>; let _freed = Box::from_raw(p); }
unsafe fn wake(ptr: *const ()) { wake_by_ref(ptr); drop(ptr); }
unsafe fn waker_clone(ptr: *const ()) -> RawWaker {
let p = ptr as *const Arc<AtomicBool>;
projects / rust-lightning / blobdiff