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Split lists of Waker and directly-registered Future callbacks

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In the next commit we'll fix a memory leak due to keeping too many
`std::task::Waker` callbacks in `FutureState` from redundant `poll`
calls, but first we need to split handling of `StdWaker`-based
future wake callbacks from normal ones, which we do here.
This commit is contained in:
Matt Corallo 2024-02-13 21:58:46 +00:00
parent 73da722d18
commit 2c987209f9
1 changed files with 20 additions and 16 deletions
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36
lightning/src/util/wakers.rs
View file

@ -69,6 +69,7 @@ impl Notifier {
} 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,
@ -109,11 +110,13 @@ define_callback!(Send);
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<StdWaker>,
callbacks_with_state: Vec<Box<dyn Fn(&Arc<Mutex<FutureState>>) -> () + Send>>,
complete: bool,
callbacks_made: bool,
}
@ -121,13 +124,15 @@ pub(crate) struct FutureState {
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
@ -153,7 +158,7 @@ impl Future {
mem::drop(state);
callback.call();
} else {
state.callbacks.push((true, callback));
state.callbacks.push(callback);
}
}
@ -193,9 +198,6 @@ impl Future {
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 {
@ -208,7 +210,7 @@ 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.push(StdWaker(waker));
Poll::Pending
}
}
@ -251,10 +253,10 @@ impl Sleeper {
*notified_fut_mtx.lock().unwrap() = Some(Arc::clone(&notifier_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)
@ -455,6 +457,7 @@ mod tests {
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,
@ -514,6 +517,7 @@ mod tests {
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,