Re: Shared memory changes in 9.4?

Maciek Sakrejda <m(dot)sakrejda(at)gmail(dot)com> writes:
> I've been trying to take the 9.4 beta for a spin, but seem to have run into
> a shared memory issue on startup:

> FATAL: could not open shared memory segment "/PostgreSQL.1804289383":
> Permission denied

> We're running Postgres inside LXC, which I suspect is causing problems
> here, but 9.0 through 9.3 run just fine in the same configuration. Any idea
> what may have changed? I suspect the solution here is tweaking some LXC
> setting, but I was hoping someone can point me in the right direction.

This message is coming out of the new "dynamic shared memory" code.
I'm not real sure why that's being invoked at startup; perhaps Robert Haas
can elucidate. Anyway the short answer is that this sounds like a
portability hazard in the new code in src/backend/storage/ipc/dsm_impl.c.
Perhaps you can look into that and identify what's up.

regards, tom lane