deadlock detected when inserting data

I am running OSDL-dbt1 - an e-commerce workload
(http://www.osdl.org/lab_activities/kernel_testing/osdl_database_test_suite/osdl_dbt-1/)
against PostgreSQL: 7.3.3.  During the test, I saw a lot of messages in
the database log file:

NOTICE:  _sc_id=0, _add_flag=0, _itemcount=0, _i_id=597, _pp_i_id=159,
c_id=32760
ERROR:  deadlock detected
WARNING:  Error occurred while executing PL/pgSQL function shopping_cart
WARNING:  line 311 at SQL statement
WARNING:  ROLLBACK: no transaction in progress

The shopping_cart transaction does update/insert to shopping_cart and
shopping_cart_line tables, and if it is a new shopping_cart, it queries
the SEQUENCE scid to get a new shopping_cart.

I tried to search the mailing list, and got the impression that if there
are foreign key related to the tables, then deadlock happens.  But that
is not my case.  I do not have foreign key either referring to this two
tables, or defined on those tables.

Can anyone give some suggestions how I should analyze this problem?  Or
are there any documentation?  I am not driving the database very hard.
The only comparison I have are the previous runs I did against SAPDB,
which performs better.

Let me know if you need more info.

TIA,

Jenny
--
Jenny Zhang
Open Source Development Lab
12725 SW Millikan Way, Suite 400
Beaverton, OR 97005
(503)626-2455 ext 31