stuck spinlock detected at dynahash.c

today I found in logs:

WARNING:  pgstat wait timeout
WARNING:  pgstat wait timeout
PANIC:  stuck spinlock (0x7fd877761af8) detected at dynahash.c:981
PANIC:  stuck spinlock (0x7fd877761af8) detected at dynahash.c:981
...
LOG:  server process (PID 8078) was terminated by signal 6: Aborted
LOG:  terminating any other active server processes
WARNING:  terminating connection because of crash of another server process
DETAIL:  The postmaster has commanded this server process to roll back
the current transaction and exit, because another server process
exited a
....
LOG:  archiver process (PID 6277) exited with exit code 1
FATAL:  the database system is in recovery mode
....
LOG:  all server processes terminated; reinitializing
.....
LOG:  database system was interrupted; last known up at 2010-10-06 15:03:32 MSD
LOG:  database system was not properly shut down; automatic recovery in progress
LOG:  redo starts at B7/3FF16C28
LOG:  record with zero length at B7/4B810F58
LOG:  redo done at B7/4B810F28
LOG:  last completed transaction was at log time 2010-10-06 15:06:44.254586+04
LOG:  autovacuum launcher started
LOG:  database system is ready to accept connections

what was that?
I google only http://archives.postgresql.org/pgsql-general/2009-11/msg00871.php

postgresql-8.4.4-1.fc13.x86_64

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