Re: BUG #1632: Several jailed PostgreSQL instances.

"Nicolai Petri (lists)" <lists(at)petri(dot)cc> writes:
> It might still be a good idea for postgresql to be able to detect this
> collision without crashing each others backend or doing other weird stuff.

It tries --- see IpcSemaphoreCreate in src/backend/port/sysv_sema.c.
If the "jail" mechanism hides processes from each other but not
semaphore sets, then the attempted detection will fail. I don't think
that's a Postgres bug. The SysV IPC mechanism is defined to expose
process PIDs of processes accessing a shmem segment or sema set;
therefore you can't have a jail mechanism that separates PIDs but not
shmem/semas without fundamentally breaking the API.

Or this might just be a garden-variety kernel bug. In any case I think
you need to be complaining to FreeBSD kernel hackers, not us.

regards, tom lane