Trigger function in a multi-threaded environment behavior

We have a multi-threaded environment in linux where multiple threads are
performing database operations(insert, update, select and at times delete as
well) in transaction mode (which may span across stored

procedures) using unixodbc. Now this as is, works fine.

If we introduce postgres triggers (trigger functions) on some of the tables
to track insert/update/delete operations, (This is done by keeping and
updating a counter field for every insert, update and delete operation
performed on a set of tables inside trigger function) at this point, one or
more threads get stuck in lock while executing the query, to the extent that
sometimes even with the pgadmin, the database tables cannot be updated.

We are using postgres v8.4 and unixodbc v2.2.14.

Here in this case when using postgres triggers in a multithreaded
application, do we have to take care of table/row level locks inside trigger
function.

Thanks,

Hardik