Horton

Re: REL_11_STABLE: dsm.c - cannot unpin a segment that is not pinned

Thomas Munro <thomas.munro@enterprisedb.com>

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From: Thomas Munro <thomas.munro@enterprisedb.com>
To: Justin Pryzby <pryzby@telsasoft.com>
Cc: Pg Hackers <pgsql-hackers@postgresql.org>
Date: 2019-02-17T20:26:53Z
Lists: pgsql-hackers 
On Mon, Feb 18, 2019 at 9:07 AM Justin Pryzby <pryzby@telsasoft.com> wrote:
> On Sun, Feb 17, 2019 at 01:41:45PM -0600, Justin Pryzby wrote:
> > On Sat, Feb 16, 2019 at 09:16:01PM +1300, Thomas Munro wrote:
> > > On Sat, Feb 16, 2019 at 5:31 PM Justin Pryzby <pryzby@telsasoft.com> wrote:
> > > > Thanks, will leave it spinning overnight.
> >
> > No errors in ~36 hours (126 CPU-hrs), so that seems to work.  Thanks.

Great news.  I will commit that.

> Actually...
>
> On killing the postmaster having completed this stress test, one of the
> backends was left running and didn't die on its own.  It did die gracefully
> when I killed the backend or the client.
>
> I was able to repeat the result, on first try, but took numerous attempts to
> repeat the 2nd and 3rd time to save pg_stat_activity.
>
> Is there some issue regarding dsm_postmaster_shutdown ?

Huh.  What exactly do you mean by "killing the postmaster"?  If you
mean SIGKILL or something, one problem with 11 is that
gather_readnext() doesn't respond to postmaster death.  I fixed that
(and every similar place) in master with commit cfdf4dc4fc9, like so:

-                       WaitLatch(MyLatch, WL_LATCH_SET, 0,
WAIT_EVENT_EXECUTE_GATHER);
+                       (void) WaitLatch(MyLatch, WL_LATCH_SET |
WL_EXIT_ON_PM_DEATH, 0,
+
WAIT_EVENT_EXECUTE_GATHER);

-- 
Thomas Munro
http://www.enterprisedb.com

Commits

  1. Fix inconsistent out-of-memory error reporting in dsa.c.

  2. Fix race in dsm_unpin_segment() when handles are reused.

  3. Fix race in dsm_attach() when handles are reused.

  4. Fix rare dsa_allocate() failures due to freepage.c corruption.

  5. Add WL_EXIT_ON_PM_DEATH pseudo-event.