BUG #6101: ALTER TABLE hangs with AccessExclusiveLock

The following bug has been logged online:

Bug reference:      6101
Logged by:          Dmitry
Email address:      y4gr5rzn@gmail.com
PostgreSQL version: 9.0.4
Operating system:   Debian i686 2.6.32-5-686-bigmem
Description:        ALTER TABLE hangs with AccessExclusiveLock
Details:

ALTER locks the table AccessExclusiveLock and hangs.
I can break it with Ctrl-C in psql, but it 100% reproduces in any session.

Command: ALTER TABLE Amazon.Books ADD COLUMN textsearchable_index_col
tsvector;

Similar reports:
http://archives.postgresql.org/pgsql-admin/2002-04/msg00284.php
http://www.justskins.com/forums/how-to-release-a-133616.html

pg_locks: AccessExclusiveLock granted=f
ps:
postgres  3535  0.0  0.0  50064   652 ?        Ss   Jul05   0:00 postgres:
al mydb [local] idle in transaction
postgres 22295  0.1  1.0  51804 34028 ?        Ss   Jul03   7:18 postgres:
al mydb [local] ALTER TABLE waiting

Also, i can submit SQL table description, full pg_locks, pg_class,
pg_stat_activity.