Re: PostmasterContext survives into parallel workers!?

Robert Haas <robertmhaas(at)gmail(dot)com> writes:
> On Mon, Aug 1, 2016 at 4:18 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>> Now, I'm undecided whether to flush that context only in parallel workers,
>> or to try to make it go away for all bgworkers of any stripe. The latter
>> seems a little better from a security standpoint, but I wonder if anyone
>> has a use-case where that'd be a bad idea?

> I think it would be better to get rid of it in all bgworkers.

I looked into this, and immediately found this in the spot in postmaster.c
that would be the obvious place to kill the PostmasterContext:

/* Do NOT release postmaster's working memory context */

MyBgworkerEntry = &rw->rw_worker;
StartBackgroundWorker();

This comment was in Alvaro's original commit adding bgworkers (da07a1e8).
It looks to me like the reason for it is simply not having bothered to
copy the rw->rw_worker data to somewhere that would survive deletion
of the PostmasterContext. I wonder though if anyone remembers a more
fundamental reason? Surely the bgworker is not supposed to touch any
of the rest of the BackgroundWorkerList?

regards, tom lane