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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