postgresql-server exiting abnormally after an OS upgrade

Hi,

I've been running postgresql-server for some time on an OpenBSD box, and the
latest OS upgrade (which also upgraded from 9.3 to 9.4) seems to have broken it
in some way. I tried downgrading back to 9.3.6, but the issue persists, so it
looks like something else is broken, and not postgresql per se.

Of course, I did the proper upgrade procedure, pg_dumpall, move everything out
of the way, and reinit the db.

I also tried *not* reimporting the db on my last wipeout, and keeping the
completely empty database. It crashed too upon connection attempts (which fail
to authenticate because I haven't even created the users), so I guess the data
is no problem. The database is pretty small, and very few concurrent users (the
*whole* backup is ~400kB).

Here's the error which repeats ad infinitum:

LOG: database system was shut down at 2015-02-12 14:41:29 GMT
LOG: database system is ready to accept connections
LOG: autovacuum launcher started
LOG: server process (PID 21205) was terminated by signal 6: Abort trap
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 abnormally and possibly corrupted shared memory.
HINT: In a moment you should be able to reconnect to the database and repeat your command.
LOG: all server processes terminated; reinitializing
LOG: database system was interrupted; last known up at 2015-02-12 14:42:04 GMT
LOG: database system was not properly shut down; automatic recovery in progress
LOG: record with zero length at 0/1690A90
LOG: redo is not required
LOG: database system is ready to accept connections
LOG: autovacuum launcher started

I've searchd all over, and found little or nothing of help. Nothing seemed to
change the situation.

I believe that these settings *are* relevant, so:

kern.seminfo.semmni=256
kern.seminfo.semmns=512
kern.seminfo.semmnu=256
kern.seminfo.semmap=256

kern.shminfo.shmmax=134217728
kern.shminfo.shmseg=256

I also tried setting shared_buffers = 16MB, which, while small, discards
several potential configuration issues.

Note that before upgrading to the latest OS version, pg worked fine. Also
relevant, other users of the same release have confirmed not having this issue
and pg working fine for them.

Any pointer?

Thanks,

--
Hugo Osvaldo Barrera
A: Because we read from top to bottom, left to right.
Q: Why should I start my reply below the quoted text?