Fix deadlock when moving clients. Thanks to oddsock for producing a testcase and

backtrace, and karl for fixing my brain

svn path=/icecast/trunk/icecast/; revision=10017

src/source.c

@@ -340,7 +340,9 @@ void source_move_clients (source_t *source, source_t *dest)
     {
         client_t *client;
 
-        /* we need to move the client and pending trees */
+        /* we need to move the client and pending trees - we must take the
+         * locks in this order to avoid deadlocks */
+        avl_tree_wlock (source->client_tree);
         avl_tree_wlock (source->pending_tree);
 
         if (source->on_demand == 0 && source->format == NULL)
@@ -381,7 +383,6 @@ void source_move_clients (source_t *source, source_t *dest)
             count++;
         }
 
-        avl_tree_wlock (source->client_tree);
         while (1)
         {
             avl_node *node = avl_get_first (source->client_tree);
@@ -409,10 +410,12 @@ void source_move_clients (source_t *source, source_t *dest)
 
         source->listeners = 0;
         stats_event (source->mount, "listeners", "0");
-        avl_tree_unlock (source->client_tree);
 
     } while (0);
 
+    avl_tree_unlock (source->pending_tree);
+    avl_tree_unlock (source->client_tree);
+
     /* see if we need to wake up an on-demand relay */
     if (dest->running == 0 && dest->on_demand && count)
     {
@@ -420,7 +423,6 @@ void source_move_clients (source_t *source, source_t *dest)
         slave_rebuild_mounts();
     }
 
-    avl_tree_unlock (source->pending_tree);
     avl_tree_unlock (dest->pending_tree);
     thread_mutex_unlock (&move_clients_mutex);
 }