backend/rs: delay client cleanup

delay client cleanup until the state lock is dropped
to prevent potential deadlocks in drop impls of the
client state.

Author: cmeissl

wayland-backend/CHANGELOG.md

@@ -2,6 +2,10 @@
 
 ## Unreleased
 
+### Bugfixes
+
+- backend/rs: Prevent a potential deadlock during client cleanup
+
 ## 0.3.7 -- 2024-09-04
 
 ### Bugfixes

wayland-backend/src/rs/server_impl/client.rs

@@ -720,15 +720,15 @@ impl<D> ClientStore<D> {
     pub(crate) fn cleanup(
         &mut self,
         pending_destructors: &mut Vec<PendingDestructor<D>>,
-    ) -> SmallVec<[ClientId; 1]> {
+    ) -> SmallVec<[Client<D>; 1]> {
         let mut cleaned = SmallVec::new();
         for place in &mut self.clients {
             if place.as_ref().map(|client| client.killed).unwrap_or(false) {
                 // Remove the client from the store and flush it one last time before dropping it
                 let mut client = place.take().unwrap();
                 client.queue_all_destructors(pending_destructors);
                 let _ = client.flush();
-                cleaned.push(ClientId { id: client.id });
+                cleaned.push(client);
             }
         }
         cleaned

wayland-backend/src/rs/server_impl/handle.rs

@@ -53,6 +53,7 @@ impl<D> State<D> {
                     ObjectId { id: object_id },
                 );
             }
+            std::mem::drop(dead_clients);
         }
     }
 

wayland-backend/src/rs/server_impl/registry.rs

@@ -127,7 +127,7 @@ impl<D> Registry<D> {
         Some((target_global.interface, target_global.id.clone(), target_global.handler.clone()))
     }
 
-    pub(crate) fn cleanup(&mut self, dead_clients: &[ClientId]) {
+    pub(crate) fn cleanup(&mut self, dead_clients: &[Client<D>]) {
         self.known_registries
             .retain(|obj_id| !dead_clients.iter().any(|cid| cid.id == obj_id.client_id))
     }