/// Gets a [`Future`] that will get woken up with any waiters
pub(crate) fn get_future(&self) -> Future {
let mut lock = self.notify_pending.lock().unwrap();
+ let mut self_idx = 0;
if let Some(existing_state) = &lock.1 {
- if existing_state.lock().unwrap().callbacks_made {
+ let mut locked = existing_state.lock().unwrap();
+ if locked.callbacks_made {
// If the existing `FutureState` has completed and actually made callbacks,
// consider the notification flag to have been cleared and reset the future state.
+ mem::drop(locked);
lock.1.take();
lock.0 = false;
+ } else {
+ self_idx = locked.next_idx;
+ locked.next_idx += 1;
}
}
if let Some(existing_state) = &lock.1 {
- Future { state: Arc::clone(&existing_state) }
+ Future { state: Arc::clone(&existing_state), self_idx }
} else {
let state = Arc::new(Mutex::new(FutureState {
callbacks: Vec::new(),
+ std_future_callbacks: Vec::new(),
callbacks_with_state: Vec::new(),
complete: lock.0,
callbacks_made: false,
+ next_idx: 1,
}));
lock.1 = Some(Arc::clone(&state));
- Future { state }
+ Future { state, self_idx: 0 }
}
}
define_callback!();
pub(crate) struct FutureState {
- // When we're tracking whether a callback counts as having woken the user's code, we check the
- // first bool - set to false if we're just calling a Waker, and true if we're calling an actual
- // user-provided function.
- callbacks: Vec<(bool, Box<dyn FutureCallback>)>,
- callbacks_with_state: Vec<(bool, Box<dyn Fn(&Arc<Mutex<FutureState>>) -> () + Send>)>,
+ // `callbacks` count as having woken the users' code (as they go direct to the user), but
+ // `std_future_callbacks` and `callbacks_with_state` do not (as the first just wakes a future,
+ // we only count it after another `poll()` and the second wakes a `Sleeper` which handles
+ // setting `callbacks_made` itself).
+ callbacks: Vec<Box<dyn FutureCallback>>,
+ std_future_callbacks: Vec<(usize, StdWaker)>,
+ callbacks_with_state: Vec<Box<dyn Fn(&Arc<Mutex<FutureState>>) -> () + Send>>,
complete: bool,
callbacks_made: bool,
+ next_idx: usize,
}
fn complete_future(this: &Arc<Mutex<FutureState>>) -> bool {
let mut state_lock = this.lock().unwrap();
let state = &mut *state_lock;
- for (counts_as_call, callback) in state.callbacks.drain(..) {
+ for callback in state.callbacks.drain(..) {
callback.call();
- state.callbacks_made |= counts_as_call;
+ state.callbacks_made = true;
}
- for (counts_as_call, callback) in state.callbacks_with_state.drain(..) {
+ for (_, waker) in state.std_future_callbacks.drain(..) {
+ waker.0.wake_by_ref();
+ }
+ for callback in state.callbacks_with_state.drain(..) {
(callback)(this);
- state.callbacks_made |= counts_as_call;
}
state.complete = true;
state.callbacks_made
}
/// A simple future which can complete once, and calls some callback(s) when it does so.
-///
-/// Clones can be made and all futures cloned from the same source will complete at the same time.
-#[derive(Clone)]
pub struct Future {
state: Arc<Mutex<FutureState>>,
+ self_idx: usize,
}
impl Future {
mem::drop(state);
callback.call();
} else {
- state.callbacks.push((true, callback));
+ state.callbacks.push(callback);
}
}
/// Waits until this [`Future`] completes.
#[cfg(feature = "std")]
- pub fn wait(self) {
- Sleeper::from_single_future(self).wait();
+ pub fn wait(&self) {
+ Sleeper::from_single_future(&self).wait();
}
/// Waits until this [`Future`] completes or the given amount of time has elapsed.
///
/// Returns true if the [`Future`] completed, false if the time elapsed.
#[cfg(feature = "std")]
- pub fn wait_timeout(self, max_wait: Duration) -> bool {
- Sleeper::from_single_future(self).wait_timeout(max_wait)
+ pub fn wait_timeout(&self, max_wait: Duration) -> bool {
+ Sleeper::from_single_future(&self).wait_timeout(max_wait)
}
#[cfg(test)]
}
}
+impl Drop for Future {
+ fn drop(&mut self) {
+ self.state.lock().unwrap().std_future_callbacks.retain(|(idx, _)| *idx != self.self_idx);
+ }
+}
+
use core::task::Waker;
struct StdWaker(pub Waker);
-impl FutureCallback for StdWaker {
- fn call(&self) { self.0.wake_by_ref() }
-}
/// This is not exported to bindings users as Rust Futures aren't usable in language bindings.
impl<'a> StdFuture for Future {
Poll::Ready(())
} else {
let waker = cx.waker().clone();
- state.callbacks.push((false, Box::new(StdWaker(waker))));
+ state.std_future_callbacks.retain(|(idx, _)| *idx != self.self_idx);
+ state.std_future_callbacks.push((self.self_idx, StdWaker(waker)));
Poll::Pending
}
}
#[cfg(feature = "std")]
impl Sleeper {
/// Constructs a new sleeper from one future, allowing blocking on it.
- pub fn from_single_future(future: Future) -> Self {
- Self { notifiers: vec![future.state] }
+ pub fn from_single_future(future: &Future) -> Self {
+ Self { notifiers: vec![Arc::clone(&future.state)] }
}
/// Constructs a new sleeper from two futures, allowing blocking on both at once.
// Note that this is the common case - a ChannelManager and ChainMonitor.
- pub fn from_two_futures(fut_a: Future, fut_b: Future) -> Self {
- Self { notifiers: vec![fut_a.state, fut_b.state] }
+ pub fn from_two_futures(fut_a: &Future, fut_b: &Future) -> Self {
+ Self { notifiers: vec![Arc::clone(&fut_a.state), Arc::clone(&fut_b.state)] }
}
/// Constructs a new sleeper on many futures, allowing blocking on all at once.
pub fn new(futures: Vec<Future>) -> Self {
- Self { notifiers: futures.into_iter().map(|f| f.state).collect() }
+ Self { notifiers: futures.into_iter().map(|f| Arc::clone(&f.state)).collect() }
}
/// Prepares to go into a wait loop body, creating a condition variable which we can block on
/// and an `Arc<Mutex<Option<_>>>` which gets set to the waking `Future`'s state prior to the
*notified_fut_mtx.lock().unwrap() = Some(Arc::clone(¬ifier_mtx));
break;
}
- notifier.callbacks_with_state.push((false, Box::new(move |notifier_ref| {
+ notifier.callbacks_with_state.push(Box::new(move |notifier_ref| {
*notified_fut_ref.lock().unwrap() = Some(Arc::clone(notifier_ref));
cv_ref.notify_all();
- })));
+ }));
}
}
(cv, notified_fut_mtx)
// Wait on the other thread to finish its sleep, note that the leak only happened if we
// actually have to sleep here, not if we immediately return.
- Sleeper::from_two_futures(future_a, future_b).wait();
+ Sleeper::from_two_futures(&future_a, &future_b).wait();
join_handle.join().unwrap();
// then drop the notifiers and make sure the future states are gone.
mem::drop(notifier_a);
mem::drop(notifier_b);
+ mem::drop(future_a);
+ mem::drop(future_b);
assert!(future_state_a.upgrade().is_none() && future_state_b.upgrade().is_none());
}
let future = Future {
state: Arc::new(Mutex::new(FutureState {
callbacks: Vec::new(),
+ std_future_callbacks: Vec::new(),
callbacks_with_state: Vec::new(),
complete: false,
callbacks_made: false,
- }))
+ next_idx: 1,
+ })),
+ self_idx: 0,
};
let callback = Arc::new(AtomicBool::new(false));
let callback_ref = Arc::clone(&callback);
let future = Future {
state: Arc::new(Mutex::new(FutureState {
callbacks: Vec::new(),
+ std_future_callbacks: Vec::new(),
callbacks_with_state: Vec::new(),
complete: false,
callbacks_made: false,
- }))
+ next_idx: 1,
+ })),
+ self_idx: 0,
};
complete_future(&future.state);
let mut future = Future {
state: Arc::new(Mutex::new(FutureState {
callbacks: Vec::new(),
+ std_future_callbacks: Vec::new(),
callbacks_with_state: Vec::new(),
complete: false,
callbacks_made: false,
- }))
+ next_idx: 2,
+ })),
+ self_idx: 0,
};
- let mut second_future = Future { state: Arc::clone(&future.state) };
+ let mut second_future = Future { state: Arc::clone(&future.state), self_idx: 1 };
let (woken, waker) = create_waker();
assert_eq!(Pin::new(&mut future).poll(&mut Context::from_waker(&waker)), Poll::Pending);
// Set both notifiers as woken without sleeping yet.
notifier_a.notify();
notifier_b.notify();
- Sleeper::from_two_futures(notifier_a.get_future(), notifier_b.get_future()).wait();
+ Sleeper::from_two_futures(¬ifier_a.get_future(), ¬ifier_b.get_future()).wait();
// One future has woken us up, but the other should still have a pending notification.
- Sleeper::from_two_futures(notifier_a.get_future(), notifier_b.get_future()).wait();
+ Sleeper::from_two_futures(¬ifier_a.get_future(), ¬ifier_b.get_future()).wait();
// However once we've slept twice, we should no longer have any pending notifications
- assert!(!Sleeper::from_two_futures(notifier_a.get_future(), notifier_b.get_future())
+ assert!(!Sleeper::from_two_futures(¬ifier_a.get_future(), ¬ifier_b.get_future())
.wait_timeout(Duration::from_millis(10)));
// Test ordering somewhat more.
notifier_a.notify();
- Sleeper::from_two_futures(notifier_a.get_future(), notifier_b.get_future()).wait();
+ Sleeper::from_two_futures(¬ifier_a.get_future(), ¬ifier_b.get_future()).wait();
}
#[test]
// After sleeping one future (not guaranteed which one, however) will have its notification
// bit cleared.
- Sleeper::from_two_futures(notifier_a.get_future(), notifier_b.get_future()).wait();
+ Sleeper::from_two_futures(¬ifier_a.get_future(), ¬ifier_b.get_future()).wait();
// By registering a callback on the futures for both notifiers, one will complete
// immediately, but one will remain tied to the notifier, and will complete once the
notifier_b.notify();
assert!(callback_a.load(Ordering::SeqCst) && callback_b.load(Ordering::SeqCst));
- Sleeper::from_two_futures(notifier_a.get_future(), notifier_b.get_future()).wait();
- assert!(!Sleeper::from_two_futures(notifier_a.get_future(), notifier_b.get_future())
+ Sleeper::from_two_futures(¬ifier_a.get_future(), ¬ifier_b.get_future()).wait();
+ assert!(!Sleeper::from_two_futures(¬ifier_a.get_future(), ¬ifier_b.get_future())
.wait_timeout(Duration::from_millis(10)));
}
+
+ #[test]
+ #[cfg(feature = "std")]
+ fn multi_poll_stores_single_waker() {
+ // When a `Future` is `poll()`ed multiple times, only the last `Waker` should be called,
+ // but previously we'd store all `Waker`s until they're all woken at once. This tests a few
+ // cases to ensure `Future`s avoid storing an endless set of `Waker`s.
+ let notifier = Notifier::new();
+ let future_state = Arc::clone(¬ifier.get_future().state);
+ assert_eq!(future_state.lock().unwrap().std_future_callbacks.len(), 0);
+
+ // Test that simply polling a future twice doesn't result in two pending `Waker`s.
+ let mut future_a = notifier.get_future();
+ assert_eq!(Pin::new(&mut future_a).poll(&mut Context::from_waker(&create_waker().1)), Poll::Pending);
+ assert_eq!(future_state.lock().unwrap().std_future_callbacks.len(), 1);
+ assert_eq!(Pin::new(&mut future_a).poll(&mut Context::from_waker(&create_waker().1)), Poll::Pending);
+ assert_eq!(future_state.lock().unwrap().std_future_callbacks.len(), 1);
+
+ // If we poll a second future, however, that will store a second `Waker`.
+ let mut future_b = notifier.get_future();
+ assert_eq!(Pin::new(&mut future_b).poll(&mut Context::from_waker(&create_waker().1)), Poll::Pending);
+ assert_eq!(future_state.lock().unwrap().std_future_callbacks.len(), 2);
+
+ // but when we drop the `Future`s, the pending Wakers will also be dropped.
+ mem::drop(future_a);
+ assert_eq!(future_state.lock().unwrap().std_future_callbacks.len(), 1);
+ mem::drop(future_b);
+ assert_eq!(future_state.lock().unwrap().std_future_callbacks.len(), 0);
+
+ // Further, after polling a future twice, if the notifier is woken all Wakers are dropped.
+ let mut future_a = notifier.get_future();
+ assert_eq!(Pin::new(&mut future_a).poll(&mut Context::from_waker(&create_waker().1)), Poll::Pending);
+ assert_eq!(future_state.lock().unwrap().std_future_callbacks.len(), 1);
+ assert_eq!(Pin::new(&mut future_a).poll(&mut Context::from_waker(&create_waker().1)), Poll::Pending);
+ assert_eq!(future_state.lock().unwrap().std_future_callbacks.len(), 1);
+ notifier.notify();
+ assert_eq!(future_state.lock().unwrap().std_future_callbacks.len(), 0);
+ assert_eq!(Pin::new(&mut future_a).poll(&mut Context::from_waker(&create_waker().1)), Poll::Ready(()));
+ assert_eq!(future_state.lock().unwrap().std_future_callbacks.len(), 0);
+ }
}
projects / rust-lightning / commitdiff