[Fwd: Re: [PATCHES] Support for QNX6, POSIX IPC and PTHREAD-style locking]

Igor, we have split out the System V shared memory and IPC stuff into
separate files in the current CVS. Would you be able to make POSIX
files that would work on QNX6? It is on our TODO list to get QNX6
working for 7.3, and you are the most capable person to do this.

(FYI, I have heard reports that people applied your patches to 7.2 and
got PostgreSQL 7.2 working on QNX6.)

I know your work for 7.2 didn't get integrated because there was such
confusion during testing and we didn't have the infrastructure ready for
such a split, but now we do have things set up so your POSIX stuff
should go in very cleanly, and I am sure other platforms would benefit
from this as well.

We start beta September 1. Because things are split out, you should be
able to work during beta independently on the POSIX stuff.

---------------------------------------------------------------------------

Igor Kovalenko wrote:

Alright, here I am for discussion. I feel somewhat out of context
though. There's been good deal of discussion in PATCHES/PORTS already.
Should I introduce the patch again or someone who already looked into it
will explain where do we stand now? Note also, the patch was later split
into parts which deal with QNX6 support and POSIX IPC separately. I
submitted that, but don't know which version was archived.

- igor

-------- Original Message --------
Subject: Re: [PATCHES] Support for QNX6, POSIX IPC and PTHREAD-style
locking
Date: Mon, 25 Feb 2002 16:19:11 -0500 (EST)
From: Bruce Momjian<pgman@candle.pha.pa.us>
To: Igor Kovalenko<Igor.Kovalenko@motorola.com>

Actually, yes. This is a pretty major patch and they want this
discussed on hackers. Could you post to hackers and we can continue the
discussion?

---------------------------------------------------------------------------

Igor Kovalenko wrote:

Thanks. Any problems yet?
- igor

Bruce Momjian wrote:

Your patch has been added to the PostgreSQL unapplied patches list at:

http://candle.pha.pa.us/cgi-bin/pgpatches

I will try to apply it within the next 48 hours.

---------------------------------------------------------------------------

Igor Kovalenko wrote:

Here is the patch which adds following things to 7.2:

1. Support for QNX6 (builds cleanly on stock installation and passes all
regression tests).

2. HAVE_POSIX_IPC feature, which if enabled switches implementation of
IpcSemaphoreXXX() (ipc.[ch]) to POSIX semaphores and mmap(). Enabled on QNX6
but should be useful for lot of platforms. Since IpcSemaphoreCreate() really
assumed SysV semaphores, I had to change its prototype *when* this feature
is enabled. That function is called from proc.c and spin.c, which were
patched accordingly for POSIX case (with #ifdef guards).

3. USE_PTHREAD_MUTEXES feature, which if enabled implements S_LOCK stuff
with PTHREAD mutexes. It is useful (better than spinlocks) on non-SMP
systems when overhead of kernel call is small compared to overhead of
scheduling. Enabled on QNX6.

4. USE_PTHREAD_SPINLOCKS feature which if enabled implements S_LOCK stuff
with PTHREAD spinlocks (may not be available on all platforms). It might be
better on SMP systems when hardware does not support TAS (in which case SysV
semaphores would be used as of now and it is hard to be worse than that).
MIPS systems come to mind (and QNX6 runs on them, so it will be enabled on
QNX6 in such cases).

I haven't put checks for (2), (3) or (4) into configure to not break
supported platforms in unexpected ways. Benefits of (3) and (4) are really
OS and hardware dependent, so if you think they could be useful for your
platform, they have to be enabled in appropriate OS-specific header.

Same for HAVE_POSIX_IPC, but that one in fact can be useful on lot of
platforms. I've seen benchmark suggesting POSIX semaphores are 4 times
faster on Linux than SysV ones. It certainly applies to QNX4 as well and
makes emulation of SysV stuff unnecessary. I believe it could be extended to
support platforms like Darwin and BeOS which currently also rely on SysV
emulation. If there's interest from involved people, we could come up with a
better unified abstraction model and implementations for all supported
platforms...

I've been warned it might be considered too 'major' for 7.2, but please look
at the patch before judging. I tried my best to not break existing stuff,
all changes are only activated when explicitly enabled, QNX6-specific or
obviously compatible (the only 'unguarded' changes are typecasts for things
like SemId = -1, since its type is pointer in case of POSIX and fix for
broken QNX qsort() which I believe is already commited into CVS). I've spent
considerable time doing this and would really appreciate if it went into
7.2. Code builds and runs clean with or without any of above features
enabled.

The patch generated as recursive GNU-diff between original 7.2b2 and patched
(+ make distclean) top level directories, like 'diff -crP pgsql-original
pgsql-patched'.
It is big mostly because it contains whole new files for QNX6 (-P treats
missing files as empty).

regards,
- igor

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