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: 2017-04-21T00:05:02Z
Lists: pgsql-hackers 
Andres Freund <andres@anarazel.de> writes:
> On 2017-04-20 19:53:02 -0400, Tom Lane wrote:
>> So ... what would you say to replacing epoll_create() with
>> epoll_create1(EPOLL_CLOEXEC) ?  Then a WaitEventSet would not
>> represent inheritable-across-exec resources on any platform,
>> making it a lot easier to deal with the EXEC_BACKEND case.

> I'm generally quite in favor of using CLOEXEC as much as possible in our
> tree.  I'm a bit concerned with epoll_create1's availability tho - the
> glibc support for it was introduced in 2.9, whereas epoll_create is in
> 2.3.2.  On the other hand 2.9 was released 2008-11-13.

Also, if it's not there we'd fall back to using plain poll(), which is
not so awful that we need to work hard to avoid it.  I'd just as soon
keep the number of combinations down.

			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.