Horton

Re: Unportable implementation of background worker start

Tom Lane <tgl@sss.pgh.pa.us>

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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Andres Freund <andres@anarazel.de>
Cc: cm@enterprisedb.com, remi_zara@mac.com, Alvaro Herrera <alvherre@2ndquadrant.com>, pgsql-hackers@postgresql.org
Date: 2017-04-24T22:14:41Z
Lists: pgsql-hackers 
Andres Freund <andres@anarazel.de> writes:
> On 2017-04-24 17:33:39 -0400, Tom Lane wrote:
>> coypu's problem is unrelated:

> Note I was linking the 9.6 report form coypu, not HEAD. Afaics the 9.6
> failure is the same as gharial's mode of failure.

[ looks closer... ]  Oh: the 9.6 run occurred first, and the failures on
HEAD and 9.5 are presumably follow-on damage because the stuck postmaster
hasn't released semaphores.

A bit of googling establishes that NetBSD 5.1 has a broken pselect
implementation:

http://gnats.netbsd.org/cgi-bin/query-pr-single.pl?number=43625

That says they fixed it in later versions but not 5.1 :-(

I can't find any similar smoking gun on the web for HPUX, but
I'd fully expect their bug database to be behind a paywall.

What I'm inclined to do is to revert the pselect change but not the other,
to see if that fixes these two animals.  If it does, we could look into
blacklisting these particular platforms when choosing pselect.

			regards, tom lane

Commits

  1. Cope with glibc too old to have epoll_create1().

  2. Make latch.c more paranoid about child-process cases.

  3. Allow multiple bgworkers to be launched per postmaster iteration.

  4. Revert "Use pselect(2) not select(2), if available, to wait in postmaster's loop."

  5. Use pselect(2) not select(2), if available, to wait in postmaster's loop.

  6. Run the postmaster's signal handlers without SA_RESTART.

  7. Fix postmaster's handling of fork failure for a bgworker process.

  8. Partially revert commit 536d47bd9d5fce8d91929bee3128fa1d08dbcc57.

  9. Avoid depending on non-POSIX behavior of fcntl(2).

  10. Remove long-obsolete catering for platforms without F_SETFD/FD_CLOEXEC.