Ceph » rgw

while ((int)num_spawned() > spawn_window) {
            set_status() << "num_spawned() > spawn_window";
            yield wait_for_child();
            int ret;
            while (collect(&ret, lease_stack)) {
              if (ret < 0) {
                ldout(sync_env->cct, 0) << "ERROR: a sync operation returned error" << dendl;
                /* we have reported this error */
              }
              /* not waiting for child here */
            }
          }

here, wait_for_child maybe wait for lease_cr or error_repo, then it will always wait.