Miri reports a deadlock in async-lock

[notgull]

smol-rs/async-lock#80 (comment)

Given that this only cropped up after the v5.0 update, it's probably this crate's fault.

[notgull]

Verified that this bug was introduced in commit smol-rs/async-lock@ff4c96fe4dc72f423 or commit 86b7780, as the combination of these two commits are the first commits that observe this bug.

Diff applies to async-lock:

diff --git a/Cargo.toml b/Cargo.toml
index 88a24be..8062767 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -15,7 +15,7 @@ categories = ["asynchronous", "concurrency"]
 exclude = ["/.*"]
 
 [dependencies]
-event-listener = { version = "5.0.0", default-features = false }
+event-listener = { version = "4.0.0", default-features = false }
 event-listener-strategy = { version = "0.5.0", default-features = false }
 pin-project-lite = "0.2.11"
 
@@ -31,3 +31,7 @@ waker-fn = "1.1.0"
 
 [target.'cfg(target_family = "wasm")'.dev-dependencies]
 wasm-bindgen-test = "0.3"
+
+[patch.crates-io]
+event-listener = { git = "https://github.com/smol-rs/event-listener", rev = "86b7780" }
+event-listener-strategy = { path = "../event-listener-strategy" }
diff --git a/src/lib.rs b/src/lib.rs
index 6d64aa3..4debf8c 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -73,13 +73,13 @@ macro_rules! pin {
 
 mod barrier;
 mod mutex;
-mod once_cell;
+//mod once_cell;
 mod rwlock;
 mod semaphore;
 
 pub use barrier::{Barrier, BarrierWaitResult};
 pub use mutex::{Mutex, MutexGuard, MutexGuardArc};
-pub use once_cell::OnceCell;
+//pub use once_cell::OnceCell;
 pub use rwlock::{
     RwLock, RwLockReadGuard, RwLockReadGuardArc, RwLockUpgradableReadGuard,
     RwLockUpgradableReadGuardArc, RwLockWriteGuard, RwLockWriteGuardArc,

Diff applied to event-listener-strategy:

diff --git a/Cargo.toml b/Cargo.toml
index fe6bf0d..13e6170 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -13,7 +13,7 @@ categories = ["asynchronous", "concurrency"]
 exclude = ["/.*"]
 
 [dependencies]
-event-listener = { version = "5.0.0", default-features = false }
+event-listener = { version = "4.0.0", default-features = false }
 pin-project-lite = "0.2.12"
 
 [features]
diff --git a/src/lib.rs b/src/lib.rs
index e36210a..4ca69cf 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -74,7 +74,7 @@ use core::marker::PhantomData;
 use core::pin::Pin;
 use core::task::{Context, Poll};
 
-use event_listener::{EventListener, Listener};
+use event_listener::EventListener;
 
 #[doc(hidden)]
 pub use pin_project_lite::pin_project;
@@ -434,11 +434,11 @@ pub trait Strategy<'a> {
     type Future: Future + 'a;
 
     /// Poll the event listener until it is ready.
-    fn poll<T, L: Listener<T> + Unpin>(
+    fn poll(
         &mut self,
-        event_listener: &mut Option<L>,
+        event_listener: &mut Option<EventListener>,
         context: &mut Self::Context,
-    ) -> Poll<T>;
+    ) -> Poll<()>;
 
     /// Wait for the event listener to become ready.
     fn wait(&mut self, evl: EventListener) -> Self::Future;
@@ -466,11 +466,11 @@ impl<'a, 'evl> Strategy<'evl> for NonBlocking<'a> {
     }
 
     #[inline]
-    fn poll<T, L: Listener<T> + Unpin>(
+    fn poll(
         &mut self,
-        event_listener: &mut Option<L>,
+        event_listener: &mut Option<EventListener>,
         context: &mut Self::Context,
-    ) -> Poll<T> {
+    ) -> Poll<()> {
         let poll = Pin::new(
             event_listener
                 .as_mut()
@@ -503,11 +503,11 @@ impl<'evl> Strategy<'evl> for Blocking {
     }
 
     #[inline]
-    fn poll<T, L: Listener<T> + Unpin>(
+    fn poll(
         &mut self,
-        event_listener: &mut Option<L>,
+        event_listener: &mut Option<EventListener>,
         _context: &mut Self::Context,
-    ) -> Poll<T> {
+    ) -> Poll<()> {
         let result = event_listener
             .take()
             .expect("`event_listener` should never be `None`")

[notgull]

...then again, these race conditions have a habit of only popping up when the stars align. At this point I think instrumenting async-lock with loom is the only option.