X-Git-Url: http://git.bitcoin.ninja/index.cgi?a=blobdiff_plain;f=lightning%2Fsrc%2Futil%2Fwakers.rs;h=fdbc22f116600b7162bdbdcafa4a6f314af944e1;hb=626c60600ef3a4ec93d5f13df8d766bf3a7cd664;hp=6d8b03cbd7c4c66e9c686bad5afbec601df96ee5;hpb=7527e4b7df674fc2f5442514bb7b1d2294e59ce8;p=rust-lightning

diff --git a/lightning/src/util/wakers.rs b/lightning/src/util/wakers.rs
index 6d8b03cb..fdbc22f1 100644
--- a/lightning/src/util/wakers.rs
+++ b/lightning/src/util/wakers.rs
@@ -33,6 +33,20 @@ pub(crate) struct Notifier {
 	condvar: Condvar,
 }
 
+macro_rules! check_woken {
+	($guard: expr, $retval: expr) => { {
+		if $guard.0 {
+			$guard.0 = false;
+			if $guard.1.as_ref().map(|l| l.lock().unwrap().complete).unwrap_or(false) {
+				// If we're about to return as woken, and the future state is marked complete, wipe
+				// the future state and let the next future wait until we get a new notify.
+				$guard.1.take();
+			}
+			return $retval;
+		}
+	} }
+}
+
 impl Notifier {
 	pub(crate) fn new() -> Self {
 		Self {
@@ -57,16 +71,9 @@ impl Notifier {
 	pub(crate) fn wait(&self) {
 		loop {
 			let mut guard = self.propagate_future_state_to_notify_flag();
-			if guard.0 {
-				guard.0 = false;
-				return;
-			}
+			check_woken!(guard, ());
 			guard = self.condvar.wait(guard).unwrap();
-			let result = guard.0;
-			if result {
-				guard.0 = false;
-				return
-			}
+			check_woken!(guard, ());
 		}
 	}
 
@@ -75,24 +82,20 @@ impl Notifier {
 		let current_time = Instant::now();
 		loop {
 			let mut guard = self.propagate_future_state_to_notify_flag();
-			if guard.0 {
-				guard.0 = false;
-				return true;
-			}
+			check_woken!(guard, true);
 			guard = self.condvar.wait_timeout(guard, max_wait).unwrap().0;
+			check_woken!(guard, true);
 			// Due to spurious wakeups that can happen on `wait_timeout`, here we need to check if the
 			// desired wait time has actually passed, and if not then restart the loop with a reduced wait
 			// time. Note that this logic can be highly simplified through the use of
 			// `Condvar::wait_while` and `Condvar::wait_timeout_while`, if and when our MSRV is raised to
 			// 1.42.0.
 			let elapsed = current_time.elapsed();
-			let result = guard.0;
-			if result || elapsed >= max_wait {
-				guard.0 = false;
-				return result;
+			if elapsed >= max_wait {
+				return false;
 			}
 			match max_wait.checked_sub(elapsed) {
-				None => return result,
+				None => return false,
 				Some(_) => continue
 			}
 		}
@@ -149,16 +152,19 @@ impl<F: Fn() + Send> FutureCallback for F {
 }
 
 pub(crate) struct FutureState {
-	callbacks: Vec<Box<dyn FutureCallback>>,
+	// 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>)>,
 	complete: bool,
 	callbacks_made: bool,
 }
 
 impl FutureState {
 	fn complete(&mut self) {
-		for callback in self.callbacks.drain(..) {
+		for (counts_as_call, callback) in self.callbacks.drain(..) {
 			callback.call();
-			self.callbacks_made = true;
+			self.callbacks_made |= counts_as_call;
 		}
 		self.complete = true;
 	}
@@ -181,7 +187,7 @@ impl Future {
 			mem::drop(state);
 			callback.call();
 		} else {
-			state.callbacks.push(callback);
+			state.callbacks.push((true, callback));
 		}
 	}
 
@@ -209,10 +215,11 @@ impl<'a> StdFuture for Future {
 	fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
 		let mut state = self.state.lock().unwrap();
 		if state.complete {
+			state.callbacks_made = true;
 			Poll::Ready(())
 		} else {
 			let waker = cx.waker().clone();
-			state.callbacks.push(Box::new(StdWaker(waker)));
+			state.callbacks.push((false, Box::new(StdWaker(waker))));
 			Poll::Pending
 		}
 	}
@@ -430,4 +437,36 @@ mod tests {
 		assert_eq!(Pin::new(&mut future).poll(&mut Context::from_waker(&waker)), Poll::Ready(()));
 		assert_eq!(Pin::new(&mut second_future).poll(&mut Context::from_waker(&second_waker)), Poll::Ready(()));
 	}
+
+	#[test]
+	fn test_dropped_future_doesnt_count() {
+		// Tests that if a Future gets drop'd before it is poll()ed `Ready` it doesn't count as
+		// having been woken, leaving the notify-required flag set.
+		let notifier = Notifier::new();
+		notifier.notify();
+
+		// If we get a future and don't touch it we're definitely still notify-required.
+		notifier.get_future();
+		assert!(notifier.wait_timeout(Duration::from_millis(1)));
+		assert!(!notifier.wait_timeout(Duration::from_millis(1)));
+
+		// Even if we poll'd once but didn't observe a `Ready`, we should be notify-required.
+		let mut future = notifier.get_future();
+		let (woken, waker) = create_waker();
+		assert_eq!(Pin::new(&mut future).poll(&mut Context::from_waker(&waker)), Poll::Pending);
+
+		notifier.notify();
+		assert!(woken.load(Ordering::SeqCst));
+		assert!(notifier.wait_timeout(Duration::from_millis(1)));
+
+		// However, once we do poll `Ready` it should wipe the notify-required flag.
+		let mut future = notifier.get_future();
+		let (woken, waker) = create_waker();
+		assert_eq!(Pin::new(&mut future).poll(&mut Context::from_waker(&waker)), Poll::Pending);
+
+		notifier.notify();
+		assert!(woken.load(Ordering::SeqCst));
+		assert_eq!(Pin::new(&mut future).poll(&mut Context::from_waker(&waker)), Poll::Ready(()));
+		assert!(!notifier.wait_timeout(Duration::from_millis(1)));
+	}
 }