fix

Signed-off-by: Peter M <petermm@gmail.com>

Author: petermm

src/libAtomVM/dist_nifs.c

@@ -122,47 +122,28 @@ static void dist_connection_dtor(ErlNifEnv *caller_env, void *obj)
         enif_demonitor_process(caller_env, conn_obj, &conn_obj->connection_process_monitor);
     }
 
-    // Collect monitors to demonitor outside the lock to avoid holding lock
-    // across potentially blocking enif_demonitor_process calls
-    struct ListHead monitors_to_free;
-    list_init(&monitors_to_free);
-
+    // Must hold lock while calling enif_demonitor_process to prevent race
+    // with dist_connection_down callback
     struct ListHead *remote_monitors = synclist_wrlock(&conn_obj->remote_monitors);
     struct ListHead *item;
     struct ListHead *tmp;
     MUTABLE_LIST_FOR_EACH (item, tmp, remote_monitors) {
-        list_remove(item);
-        list_append(&monitors_to_free, item);
-    }
-    synclist_unlock(&conn_obj->remote_monitors);
-    synclist_destroy(&conn_obj->remote_monitors);
-
-    // Now demonitor and free outside the lock
-    MUTABLE_LIST_FOR_EACH (item, tmp, &monitors_to_free) {
         struct RemoteMonitor *remote_monitor = GET_LIST_ENTRY(item, struct RemoteMonitor, head);
         enif_demonitor_process(caller_env, conn_obj, &remote_monitor->process_monitor);
         list_remove(item);
         free(remote_monitor);
     }
-
-    // Collect packets to free outside the lock
-    struct ListHead packets_to_free;
-    list_init(&packets_to_free);
+    synclist_unlock(&conn_obj->remote_monitors);
+    synclist_destroy(&conn_obj->remote_monitors);
 
     struct ListHead *pending_packets = synclist_wrlock(&conn_obj->pending_packets);
     MUTABLE_LIST_FOR_EACH (item, tmp, pending_packets) {
-        list_remove(item);
-        list_append(&packets_to_free, item);
-    }
-    synclist_unlock(&conn_obj->pending_packets);
-    synclist_destroy(&conn_obj->pending_packets);
-
-    // Free packets outside the lock
-    MUTABLE_LIST_FOR_EACH (item, tmp, &packets_to_free) {
         struct DistributionPacket *packet = GET_LIST_ENTRY(item, struct DistributionPacket, head);
         list_remove(item);
         free(packet);
     }
+    synclist_unlock(&conn_obj->pending_packets);
+    synclist_destroy(&conn_obj->pending_packets);
 }
 
 static void dist_enqueue_message(term control_message, term payload, struct DistConnection *connection, GlobalContext *global)