fix(threading): make auto-reset regression deterministic

ci/evidence/provenance-audit.json

@@ -1,6 +1,6 @@
 {
   "schema": 1,
-  "recorded_unix_seconds": 1786610180,
+  "recorded_unix_seconds": 1786611260,
   "upstream_commit": "2aa70bb68513b39795da5d13c88f31b86e85a3ba",
   "material_count": 27,
   "generated_output_count": 8,
@@ -12,7 +12,7 @@
   "dependency_manifest_sha256": "5f80b45ab18a45365673b55b52d68318bc31f602ce2f6559f573027cc446c58e",
   "third_party_notices_sha256": "c4d381944a9b57277963d2a5ee4e23a9a064c2ba93a676a49e023931b53a71d6",
   "native_notices_sha256": "b417ee7bf6b748cc86839e5354753c0f8c1f8309d13c0fea379c77f602e69fc0",
-  "distribution_manifest_sha256": "9dc77128962f410e5ff7ecee947d2726e537cc42d9ef57a18d639c9bdcd2406e",
+  "distribution_manifest_sha256": "95af81f60a3823cac35e6716d1500d052bc7e22127d84f705798414a085f6762",
   "unknown_materials": 0,
   "unknown_bundled_assets": 0,
   "status": "ok"

crates/libremetaverse/src/threading_runtime.rs

@@ -913,34 +913,50 @@ impl WaitHandleAsyncFactory {
 mod tests {
     use super::*;
     use std::sync::atomic::{AtomicBool, Ordering};
+    use std::sync::{Barrier, mpsc};
 
     #[test]
     fn auto_reset_releases_exactly_one_waiter_per_signal() {
+        for _ in 0..32 {
             let event = Arc::new(ManagedAutoResetEvent::new_with_constructor().unwrap());
-        let first = Arc::clone(&event);
-        let second = Arc::clone(&event);
-        let first_done = Arc::new(AtomicBool::new(false));
-        let second_done = Arc::new(AtomicBool::new(false));
-        let first_flag = Arc::clone(&first_done);
-        let second_flag = Arc::clone(&second_done);
-        let a = std::thread::spawn(move || {
-            first.wait_one_with_method().unwrap();
-            first_flag.store(true, Ordering::SeqCst);
-        });
-        let b = std::thread::spawn(move || {
-            second.wait_one_with_method().unwrap();
-            second_flag.store(true, Ordering::SeqCst);
-        });
-        std::thread::sleep(Duration::from_millis(20));
+            let ready = Arc::new(Barrier::new(3));
+            let (completed, completions) = mpsc::channel();
+            let mut waiters = Vec::new();
+            for id in 0..2 {
+                let event = Arc::clone(&event);
+                let ready = Arc::clone(&ready);
+                let completed = completed.clone();
+                waiters.push(std::thread::spawn(move || {
+                    ready.wait();
+                    event.wait_one_with_method().unwrap();
+                    completed.send(id).unwrap();
+                }));
+            }
+            drop(completed);
+
+            // Release both contenders together. The signal is deliberately
+            // allowed to race their actual wait calls: an auto-reset event
+            // must retain one signal even when no waiter has blocked yet.
+            ready.wait();
             event.set().unwrap();
-        std::thread::sleep(Duration::from_millis(20));
-        assert_ne!(
-            first_done.load(Ordering::SeqCst),
-            second_done.load(Ordering::SeqCst)
+            let first = completions
+                .recv_timeout(Duration::from_secs(2))
+                .expect("one waiter must consume the first signal");
+            assert_eq!(
+                completions.recv_timeout(Duration::from_millis(10)),
+                Err(mpsc::RecvTimeoutError::Timeout),
+                "one auto-reset signal released both waiters"
             );
+
             event.set().unwrap();
-        a.join().unwrap();
-        b.join().unwrap();
+            let second = completions
+                .recv_timeout(Duration::from_secs(2))
+                .expect("the second waiter must consume the second signal");
+            assert_ne!(first, second);
+            for waiter in waiters {
+                waiter.join().unwrap();
+            }
+        }
     }
 
     #[test]

release/DISTRIBUTION-MANIFEST.json

@@ -1547,8 +1547,8 @@
     },
     {
       "path": "crates/libremetaverse/src/threading_runtime.rs",
-      "bytes": 30843,
-      "sha256": "2ab324af0ba240770e7fd0a6d12d3fc4e6972722d099d9e7914e11cac18bef0e"
+      "bytes": 31537,
+      "sha256": "f08e8055e56655e922b4806f13f003ea0cd3574ad9fb8bdac5d11e1697fc51ab"
     },
     {
       "path": "crates/libremetaverse/src/transfers.rs",