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: Alvaro Herrera <alvherre@2ndquadrant.com>, pgsql-hackers@postgresql.org
Date: 2017-04-21T20:13:55Z
Lists: pgsql-hackers 
Tom Lane <tgl@sss.pgh.pa.us> writes:
> Andres Freund <andres@anarazel.de> writes:
>> On 2017-04-21 14:08:21 -0400, Tom Lane wrote:
>>> but I see that SUSv2
>>> mandates that fcntl.h provide both F_SETFD and FD_CLOEXEC, so by our own
>>> coding rules it ought to be okay to assume they're there.  I'm tempted to
>>> rip out the quoted bit, as well as the #ifdef F_SETFD, from libpq and see
>>> if anything in the buildfarm complains.

>> +1

> Done, we'll soon see what happens.

Should have seen this coming, I guess: some of the Windows critters are
falling over, apparently because they lack fcntl() altogether.  So the
#ifdef F_SETFD was really acting as a proxy for "#ifdef HAVE_FCNTL".

There's no HAVE_FCNTL test in configure ATM, and I'm thinking it would
be pretty silly to add one, since surely it would succeed on anything
Unix-y enough to run the configure script.

I'm guessing the best thing to do is put back #ifdef F_SETFD;
alternatively we might spell it like "#ifndef WIN32", but I'm unsure
if that'd do what we want on Cygwin or MinGW.

In non-Windows code paths in latch.c, we probably wouldn't need to
bother with #ifdef F_SETFD.

Hopefully we can leave in the removal of "#define FD_CLOEXEC".
Will wait a bit longer for more results.

			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.