simultaneous use of JDBC and libpq

Hi,

I am wondering if it is thread-safe to use both JDBC and libpq
simultaneously.

On a Linux, JDBC is used by Tomcat and libpq is used by a client
software written in C language. So JDBC and libpq are used by two
different programs.
If the same row in the same table is updated (update SQL command)
through libpq and
read (select SQL command) by JDBC, then would it cause a thread problem?
I am not using any transaction, and using just select, update, and
sometimes insert.

I am using PostgreSQL 7.3.6 with pg73jdbc3.jar downloaded and libpq that
came with Redhat Enterprise 3.

Thank you very much in advance.

Bob