qd: replace RefCell with async mutex

Avoid potential run-time borrowing errors across async points.

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>

qemu-display/Cargo.toml

@@ -22,3 +22,4 @@ futures = "0.3.13"
 usbredirhost = "0.0.1"
 async-broadcast = "0.3.3"
 async-trait = "0.1.48"
+async-lock = "2.3.0"

qemu-display/src/usbredir.rs

@@ -1,7 +1,7 @@
 use async_broadcast::{broadcast, Receiver, Sender};
+use async_lock::RwLock;
 use futures::Stream;
 use std::{
-    cell::RefCell,
     collections::HashMap,
     default::Default,
     io::{Read, Write},
@@ -210,7 +210,7 @@ impl Inner {
 
 #[derive(Clone, Debug)]
 pub struct UsbRedir {
-    inner: Arc<RefCell<Inner>>,
+    inner: Arc<RwLock<Inner>>,
 }
 
 impl UsbRedir {
@@ -218,7 +218,7 @@ impl UsbRedir {
         let mut channel = broadcast(1);
         channel.0.set_overflow(true);
         Self {
-            inner: Arc::new(RefCell::new(Inner {
+            inner: Arc::new(RwLock::new(Inner {
                 chardevs,
                 channel,
                 handlers: Default::default(),
@@ -231,7 +231,7 @@ impl UsbRedir {
         device: &rusb::Device<rusb::Context>,
         state: bool,
     ) -> Result<bool> {
-        let mut inner = self.inner.borrow_mut();
+        let mut inner = self.inner.write().await;
         let key = Key::from_device(device);
         let handled = inner.handlers.contains_key(&key);
         // We should do better and watch for owner properties changes, but this would require tasks
@@ -262,19 +262,23 @@ impl UsbRedir {
         Ok(state)
     }
 
-    pub fn is_device_connected(&self, device: &rusb::Device<rusb::Context>) -> bool {
+    pub async fn is_device_connected(&self, device: &rusb::Device<rusb::Context>) -> bool {
-        let inner = self.inner.borrow();
+        let inner = self.inner.read().await;
 
         inner.handlers.contains_key(&Key::from_device(device))
     }
 
     pub async fn n_free_channels(&self) -> i32 {
-        self.inner.borrow().n_available_chardev().await as _
+        let inner = self.inner.read().await;
+
+        inner.n_available_chardev().await as _
     }
 
-    pub fn receive_n_free_channels(&self) -> Pin<Box<dyn Stream<Item = i32>>> {
+    pub async fn receive_n_free_channels(&self) -> Pin<Box<dyn Stream<Item = i32>>> {
+        let inner = self.inner.read().await;
+
         Box::pin(NFreeChannelsStream {
-            receiver: self.inner.borrow().channel.1.clone(),
+            receiver: inner.channel.1.clone(),
         })
     }
 }

qemu-rdw/src/usbredir.rs

@@ -20,12 +20,15 @@ impl Handler {
         widget
             .model()
             .connect_items_changed(clone!(@weak widget => move |model, pos, _rm, add| {
-                for pos in pos..pos + add {
+                let usbredir = usbredir.clone();
-                    let item = model.item(pos).unwrap();
+                MainContext::default().spawn_local(clone!(@weak model => async move {
-                    if let Some(dev) = item.downcast_ref::<rdw::UsbDevice>().unwrap().device() {
+                    for pos in pos..pos + add {
-                        item.set_property("active", usbredir.is_device_connected(&dev)).unwrap();
+                        let item = model.item(pos).unwrap();
+                        if let Some(dev) = item.downcast_ref::<rdw::UsbDevice>().unwrap().device() {
+                            item.set_property("active", usbredir.is_device_connected(&dev).await).unwrap();
+                        }
                     }
-                }
+                }));
             }));
 
         let usbredir = self.usbredir.clone();
@@ -55,7 +58,7 @@ impl Handler {
             widget
                 .set_property("free-channels", usbredir.n_free_channels().await)
                 .unwrap();
-            let mut n = usbredir.receive_n_free_channels();
+            let mut n = usbredir.receive_n_free_channels().await;
             while let Some(n) = n.next().await {
                 widget.set_property("free-channels", n).unwrap();
             }