diff --git i/contrib/postgres_fdw/connection.c w/contrib/postgres_fdw/connection.c
index f0c45b00db8..f9da564a539 100644
--- i/contrib/postgres_fdw/connection.c
+++ w/contrib/postgres_fdw/connection.c
@@ -347,6 +347,67 @@ make_new_connection(ConnCacheEntry *entry, UserMapping *user)
 		 entry->conn, server->servername, user->umid, user->userid);
 }
 
+/*
+ * PQconnectStartParams() wrapper that processes interrupts. Backend code
+ * should *never* enter blocking libpq code as that would prevent
+ * cancellations, global barriers etc from being processed.
+ */
+static PGconn *
+libpq_connect_interruptible(const char *const *keywords,
+							const char *const *values,
+							int expand_dbname,
+							uint32 wait_event_info)
+{
+	PGconn *conn;
+	PostgresPollingStatusType status;
+
+	conn = PQconnectStartParams(keywords, values, false);
+
+	if (!conn)
+		return NULL;
+
+	/*
+	 * Poll connection until we have OK or FAILED status.
+	 *
+	 * Per spec for PQconnectPoll, first wait till socket is write-ready.
+	 */
+	status = PGRES_POLLING_WRITING;
+	while (status != PGRES_POLLING_OK && status != PGRES_POLLING_FAILED)
+	{
+		int			io_flag;
+		int			rc;
+
+		if (status == PGRES_POLLING_READING)
+			io_flag = WL_SOCKET_READABLE;
+#ifdef WIN32
+		/* Windows needs a different test while waiting for connection-made */
+		else if (PQstatus(conn->streamConn) == CONNECTION_STARTED)
+			io_flag = WL_SOCKET_CONNECTED;
+#endif
+		else
+			io_flag = WL_SOCKET_WRITEABLE;
+
+		rc = WaitLatchOrSocket(MyLatch,
+							   WL_EXIT_ON_PM_DEATH | WL_LATCH_SET | io_flag,
+							   PQsocket(conn),
+							   0,
+							   wait_event_info);
+
+		/* Interrupted? */
+		if (rc & WL_LATCH_SET)
+		{
+			ResetLatch(MyLatch);
+			CHECK_FOR_INTERRUPTS();
+		}
+
+		/* If socket is ready, advance the libpq state machine */
+		if (rc & io_flag)
+			status = PQconnectPoll(conn);
+	}
+
+	return conn;
+}
+
 /*
  * Connect to remote server using specified server and user mapping properties.
  */
@@ -471,7 +532,8 @@ connect_pg_server(ForeignServer *server, UserMapping *user)
 		}
 
 		/* OK to make connection */
-		conn = PQconnectdbParams(keywords, values, false);
+		conn = libpq_connect_interruptible(keywords, values,
+										   false, PG_WAIT_EXTENSION);
 
 		if (!conn)
 			ReleaseExternalFD();	/* because the PG_CATCH block won't */