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Re: BUG #1632: Several jailed PostgreSQL instances.

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: "Nicolai Petri (lists)" <lists(at)petri(dot)cc>
Cc: "Achilleus Mantzios" <achill(at)matrix(dot)gatewaynet(dot)com>,"Alexander Rusinov" <boot(at)eurocom(dot)od(dot)ua>, pgsql-bugs(at)postgresql(dot)org
Subject: Re: BUG #1632: Several jailed PostgreSQL instances.
Date: 2005-04-30 16:42:32
Message-ID: 2186.1114879352@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-bugs
"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

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