Re: [HACKERS] Weaker shmem interlock w/o postmaster.pid

On Thu, Nov 29, 2018 at 01:10:57PM +0100, Dmitry Dolgov wrote:
> On Sun, Aug 12, 2018 at 8:48 AM Noah Misch <noah(at)leadboat(dot)com> wrote:
> > With 9.3 having a few months left, that's less interesting, but ...

> I'm a bit out of context, but taking into account that 9.3 is already beyond
> EOL, is it still interesting?

Yes.

> As a side note, with this patch recovery tests are failing now on 016_shm.pl
>
> # Failed test 'detected live backend via shared memory'
> # at t/016_shm.pl line 87.
> # '2018-11-28 13:08:08.504 UTC [21924] LOG:
> listening on Unix socket "/tmp/yV2oDNcG8e/gnat/.s.PGSQL.512"
> # 2018-11-28 13:08:08.512 UTC [21925] LOG: database system was
> interrupted; last known up at 2018-11-28 13:08:08 UTC
> # 2018-11-28 13:08:08.512 UTC [21925] LOG: database system was not
> properly shut down; automatic recovery in progress
> # 2018-11-28 13:08:08.512 UTC [21925] LOG: invalid record length at
> 0/165FEF8: wanted 24, got 0
> # 2018-11-28 13:08:08.512 UTC [21925] LOG: redo is not required
> # 2018-11-28 13:08:08.516 UTC [21924] LOG: database system is ready
> to accept connections
> # '
> # doesn't match '(?^:pre-existing shared memory block)'

Thanks for the report. Since commit cfdf4dc made pg_sleep() react to
postmaster death, the test will need a different way to stall a backend. This
doesn't affect non-test code, and the test still passes against cfdf4dc^ and
against REL_11_STABLE. I've queued a task to update the test code, but review
can proceed in parallel.