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: 2017-04-27T21:06:24Z
Lists: pgsql-hackers 
Andres Freund <andres@anarazel.de> writes:
> On 2017-04-27 16:35:29 -0400, Tom Lane wrote:
>> It looks like it might be sufficient to do "#ifdef EPOLL_CLOEXEC"
>> in latch.c, rather than bothering with a full-blown configure check.

> Yea, that sounds worth trying.  Wonder if we need to care about kernels
> not supporting it, but glibc having support?  I'd be ok skimping on that
> for now.

On my RHEL6 box, <sys/epoll.h> is provided by glibc not the kernel:

$ rpm -qf /usr/include/sys/epoll.h
glibc-headers-2.12-1.209.el6_9.1.x86_64

So I think it's probably safe to assume that the header is in sync
with what glibc can do.

As for kernel (much) older than glibc, I'd rather expect glibc to paper
over that, though I've not looked at the source code to be sure.

			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.