O Tom Lane Ýãñáøå óôéò Apr 30, 2005 :
> "Nicolai Petri (lists)" <lists@petri.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
Its obvious that FreeBSD says: DONT USE IPC in jails, so its far from a
bug.
> you need to be complaining to FreeBSD kernel hackers, not us.
Now with XEN, i suspect jailifying IPC in FreeBSD seems even
less attractive of a task, than it might have been back in
4.x days.
Thats about now. But back then, if FreeBSD people had enuf demand
for jailified IPC and finally implemented it, that would give postgresql
a big boost in the hosting field (where FreeBSD is a very popular) vs
mysql.
>
> regards, tom lane
>
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--
-Achilleus