我想做postgresql的热备份操作。但是运行pg_start_backup后说in progress，然后想停止掉运行pg_stop_backup()却一直挂住不动了。有什么方法可以让他正常终止呢？
postgres=# SELECT pg_start_backup('backup', true);
ERROR: a backup is already in progress
HINT: Run pg_stop_backup() and try again.
postgres=# SELECT pg_stop_backup();
NOTICE: WAL archiving is not enabled; you must ensure that all required WAL segments are copied through other means to complete the backup