Some problem with the NOTIFY/LISTEN

HI

I am using PG 8.1.4, and my server was stop service, and when I checked the log, I found that some process had locked pg_listener in ExclusiveLock, it blocked all of the following processes which use NOTIFY/LISTEN. Can anyone tell me why pg_listener is locked forever?


             max              | granted | locks |  pid  |    query_age    |  current_query 
-------------------------------+---------+-------+-------+-----------------+-----------------
 2011-01-09 08:12:01.941403+08 | t       |     1 | 23864 | 00:00:13.863773 | LISTEN LABC20
 2011-01-09 08:12:01.941403+08 | t       |     1 | 20223 | 05:18:36.472416 | <IDLE>
 2011-01-09 08:12:01.941403+08 | t       |     1 | 23453 | 00:00:43.793547 | LISTEN LABD21
 2011-01-09 08:12:01.941403+08 | t       |     1 | 20051 | 00:01:30.370326 | <IDLE>
 .....
 2011-01-09 08:12:01.941403+08 | t       |     1 | 19805 | 00:01:23.648079 | <IDLE>
 2011-01-09 08:12:01.941403+08 | t       |     1 | 23872 | 00:00:13.79683  | LISTEN LABD21
 2011-01-09 08:12:01.941403+08 | t       |     1 | 23844 | 00:00:15.338939 | LISTEN LABE11
(100 rows)

              now              |   relname   | transaction |  pid  |      mode       | granted
-------------------------------+-------------+-------------+-------+-----------------+---------
 2011-01-09 08:11:01.883414+08 | pg_listener |   835435890 | 19759 | ExclusiveLock   | f
 2011-01-09 08:11:01.883414+08 | pg_listener |   835436051 | 20444 | ExclusiveLock   | f
 2011-01-09 08:11:01.883414+08 | pg_listener |   835435898 | 19695 | ExclusiveLock   | f
 2011-01-09 08:11:01.883414+08 | pg_listener |   835435963 | 20090 | ExclusiveLock   | f
 2011-01-09 08:11:01.883414+08 | pg_listener |   835436024 | 20285 | ExclusiveLock   | f
 ......
 2011-01-09 08:11:01.883414+08 | pg_listener |   835436007 | 20247 | ExclusiveLock   | f
(176 rows)


Before that there are two deadlock detected
Jan  9 08:10:40 SUC01 postgres[19767]: [2-1] ERROR:  deadlock detected
Jan  9 08:10:40 SUC01 postgres[19767]: [2-2] DETAIL: 
Jan  9 08:12:32 SUC01 postgres[19767]: [3-1] ERROR:  deadlock detected
Jan  9 08:12:32 SUC01 postgres[19767]: [3-2] DETAIL: 
Jan  9 08:12:32 SUC01 postgres[19767]: [3-3] STATEMENT:  UNLISTEN LABD11

Thanks a lot
Richard