Horton

Re: Back-patch use of unnamed POSIX semaphores for Linux?

Andres Freund <andres@anarazel.de>

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From: Andres Freund <andres@anarazel.de>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Robert Haas <robertmhaas@gmail.com>, "pgsql-hackers@postgresql.org" <pgsql-hackers@postgresql.org>
Date: 2016-12-07T22:51:21Z
Lists: pgsql-hackers 
On 2016-12-06 23:54:43 -0500, Tom Lane wrote:
> You're attacking a straw man.  I didn't propose changing our behavior
> anywhere but Linux.  AFAIK, on that platform unnamed POSIX semaphores
> are futexes, which have been a stable feature since 2003 according to
> https://en.wikipedia.org/wiki/Futex#History.  Anybody who did need
> to compile PG for use with a pre-2.6 kernel could override the default,
> anyway.

Back then futexes weren't "robust" though (crash handling and such was
unusable). They only started to be reliable in the ~2007-2008 frame
IIRC.  That still should be ok though.

Regards,

Andres

Commits

  1. Make the different Unix-y semaphore implementations ABI-compatible.

  2. Use unnamed POSIX semaphores, if available, on Linux and FreeBSD.