Disconnect if socket cannot be put into non-blocking mode

hlinnaka · hlinnaka · commit f8c5317d0015 · 2024-03-12T10:18:32.000+02:00
Commit 387da18 moved the code to put socket into non-blocking mode from socket_set_nonblocking() into the one-time initialization function, pq_init(). In socket_set_nonblocking(), there indeed was a risk of recursion on failure like the comment said, but in pq_init(), ERROR or FATAL is fine. There's even another elog(FATAL) just after this, if setting FD_CLOEXEC fails. Note that COMMERROR merely logged the error, it did not close the connection, so if putting the socket to non-blocking mode failed we would use the connection anyway. You might not immediately notice, because most socket operations in a regular backend wait for the socket to become readable/writable anyway. But e.g. replication will be quite broken. Backpatch to all supported versions. Discussion: https://www.postgresql.org/message-id/d40a5cd0-2722-40c5-8755-12e9e811fa3c@iki.fi
diff --git a/src/backend/libpq/pqcomm.c b/src/backend/libpq/pqcomm.c
@@ -189,14 +189,10 @@ pq_init(void)
 	 * nonblocking mode and use latches to implement blocking semantics if
 	 * needed. That allows us to provide safely interruptible reads and
 	 * writes.
-	 *
-	 * Use COMMERROR on failure, because ERROR would try to send the error to
-	 * the client, which might require changing the mode again, leading to
-	 * infinite recursion.
 	 */
 #ifndef WIN32
 	if (!pg_set_noblock(MyProcPort->sock))
-		ereport(COMMERROR,
+		ereport(FATAL,
 				(errmsg("could not set socket to nonblocking mode: %m")));
 #endif
 
