Notice Deadlock detected and Backend cache invalidation initialization failed

Hello,

We're using postgresql 6.4.2 on red hat linux 6.0, kernel 2.2.10 with dbi
1.09 and DBD-Pg 0.91 for web database connectivity. We are occasionally
experiencing deadlocks that are logged to the apache logs as follows:

NOTICE: Deadlock detected -- See the lock(l) manual page for a possible
cause.
NOTICE: Deadlock detected -- See the lock(l) manual page for a possible
cause.
DBD::Pg::st execute failed: ERROR: WaitOnLock: error on wakeup - Aborting
this transaction
Database handle destroyed without explicit disconnect.
Database handle destroyed without explicit disconnect.

However, on Friday, we experienced a much more sivere problem where
shortly after the Deadlock errors, the following occured:

NOTICE: SIAssignBackendId: discarding tag 2147474428
DBI->connect failed: FATAL 1: Backend cache invalidation initialization
failed
at /home/sitesell/cgi-bin/Database_Interaction//database_func.pl line 727

After this, none of the scripts would execute and generated 500 server
errors. When I tried to restart postgresql, I got the following error:

Starting postgresql service: IpcMemoryCreate: shmget failed (Identifier
removed) key=5432010, size=24588, permission=700
IpcMemoryIdGet: shmget failed (Identifier removed) key=5432010,
size=24588, permission=0
IpcMemoryAttach: shmat failed (Invalid argument) id=-2
FATAL 1: AttachSLockMemory: could not attach segment
postmaster []

I do have IPC support compiled into the kernel...

CONFIG_SYSVIPC=y
CONFIG_BSD_PROCESS_ACCT=y
CONFIG_SYSCTL=y

I don't know if these 2 problems are related or not. If anyone knows the
cause for either or both, I'd appreciate any help you could provide.

Thanks,

Trevor Astrope
astrope(at)e-corp(dot)net