Add test and comment for #203

core/src/parking_lot.rs

@@ -1198,6 +1198,11 @@ mod deadlock_impl {
     pub unsafe fn release_resource(key: usize) {
         with_thread_data(|thread_data| {
             let resources = &mut (*thread_data.deadlock_data.resources.get());
+
+            // There is only one situation where we can fail to find the
+            // resource: we are currently running TLS destructors and our
+            // ThreadData has already been freed. There isn't much we can do
+            // about it at this point, so just ignore it.
             if let Some(p) = resources.iter().rposition(|x| *x == key) {
                 resources.swap_remove(p);
             }

src/rwlock.rs

@@ -579,4 +579,28 @@ mod tests {
         assert_eq!(*(mutex.read()), *(deserialized.read()));
         assert_eq!(contents, *(deserialized.read()));
     }
+
+    #[test]
+    fn test_issue_203() {
+        struct Bar(RwLock<()>);
+
+        impl Drop for Bar {
+            fn drop(&mut self) {
+                let _n = self.0.write();
+            }
+        }
+
+        thread_local! {
+            static B: Bar = Bar(RwLock::new(()));
+        }
+
+        thread::spawn(|| {
+            B.with(|_| ());
+
+            let a = RwLock::new(());
+            let _a = a.read();
+        })
+        .join()
+        .unwrap();
+    }
 }