Re: unchecked out of memory in postmaster.c

Tom Lane wrote:
> Alvaro Herrera <alvherre@commandprompt.com> writes:
> > Some time ago I noticed that in postmaster.c there's a corner case which
> > probably causes postmaster to exit in out-of-memory condition.  See
> > BackendStartup, near the bottom, there's a call to DLNewElem().  The
> > problem is that this function calls palloc() and thus can elog(ERROR) on
> > OOM, but postmaster has no way to defend itself from this and would die.
>
> So?  There are probably hundreds of palloc calls that are reachable from
> the postmaster main loop.  If this were allocating more than a few bytes
> of memory, it might be worth worrying about.

Hundreds?  I think you'd be hard pressed to find as much as a dozen :-)
I mean stuff that's called inside ServerLoop, of course.  There are a
few places calling alloc-type functions, but as far as I see they use
calloc or malloc, and behave "sanely" (i.e. not elog(ERROR)) in OOM.

Note that BackendStartup itself is very careful about allocating a
Backend struct, even when it's just ~10 bytes on 32 bits machines.

I think a patch to solve this is as simple as the attached.

--
Alvaro Herrera                                http://www.CommandPrompt.com/
The PostgreSQL Company - Command Prompt, Inc.