Server :: FreeRadius - PQexec Blocks Forever Due To Connection Timeout

I've configured the RADIUS to use a PostgreSQL DB for accounting. Everything works fine if the connection from the RAD to the SQL is OK. If the PostgreSQL service dead, the RAD will skip the failed connection and continue to work. That's OK, too. But if I shutdown the network interface of the SQL (simulating a connection lost - timeout problem), the RAD thread which processes accounting request will be hung up, remains as active and unresponsive forever. So the RAD will not return anything to accounting client (my NAS).

As more accounting requests come, spare threads for processing the requests will reduce and be used up eventually. I've debugged for a while and found it's the problem of PQexec() function. The function blocks the thread eternally till if the connection lost. I know the RAD version is a little outdated, but I cannot replace it right now. I wonder if there's a way to make the RAD reply to the NAS even when the connection between the RAD and the SQL lost.