PG_DUMP and table locking in PG7.4

Hi,

I'm using PG_DUMP for backing up a postgres 7.4 database. As I have
seen, the pg_dump aquires a table lock while dump the table's content.
What will happen, if I have a basic table and several inherited tables.
Will the PG_DUMP tool only aquire locks on the inherited tables or on
the parent-table, too? 

Thanks in advance!

Cheers,
Yann