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: 2017-04-26T21:05:39Z
Lists: pgsql-hackers

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Andres Freund <andres@anarazel.de> writes:
> I'd still like to get something like your CLOEXEC patch applied
> independently however.

Here's an updated version of that, which makes use of our previous
conclusion that F_SETFD/FD_CLOEXEC are available everywhere except
Windows, and fixes some sloppy thinking about the EXEC_BACKEND case.

I went ahead and changed the call to epoll_create into epoll_create1.
I'm not too concerned about loss of portability there --- it seems
unlikely that many people are still using ten-year-old glibc, and
even less likely that any of them would be interested in running
current Postgres on their stable-unto-death platform.  We could add
a configure test for epoll_create1 if you feel one's needed, but
I think it'd just be a waste of cycles.

I propose to push this into HEAD and 9.6 too.

			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.