scx_arena: Drop cluster Arc references before processing cores

Drop topo.all_clusters before iterating topo.all_cores to release Arc
references. Clusters hold Arc references to cores, preventing
Arc::into_inner() from succeeding during topology setup.

Signed-off-by: Daniel Hodges <[email protected]>

Author: hodgesds

rust/scx_arena/scx_arena/src/arenalib.rs

@@ -173,6 +173,10 @@ impl<'a> ArenaLib<'a> {
             )?;
         }
 
+        // Drop all_clusters to release Arc references to cores before processing cores
+        // Clusters may hold Arc references to cores, so we need to drop them first
+        drop(topo.all_clusters);
+
         for (core_id, core) in topo.all_cores {
             self.setup_topology_node(
                 Arc::<Core>::into_inner(core)

rust/scx_arena/selftests/src/main.rs

@@ -145,6 +145,9 @@ fn setup_topology(skel: &mut BpfSkel<'_>) -> Result<()> {
         )?;
     }
 
+    // Drop all_clusters to release Arc references to cores before processing cores
+    drop(topo.all_clusters);
+
     for (_, core) in topo.all_cores {
         setup_topology_node(
             skel,