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Re: [PATCH] Use CC atomic builtins if available [was: Re: TAS patch for building on armel/armhf thumb]

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>
Cc: Robert Haas <robertmhaas(at)gmail(dot)com>, PostgreSQL Bugs <pgsql-bugs(at)postgresql(dot)org>
Subject: Re: [PATCH] Use CC atomic builtins if available [was: Re: TAS patch for building on armel/armhf thumb]
Date: 2011-12-19 15:25:12
Message-ID: 20126.1324308312@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-bugs
Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com> writes:
> On 19.12.2011 16:31, Robert Haas wrote:
>> On Sun, Dec 18, 2011 at 5:42 PM, Martin Pitt<mpitt(at)debian(dot)org>  wrote:
>>> I agree. How about a patch like this? It uses builtin atomics if
>>> available, and falls back to the custom implementations if not.

>> -1.  Absent some evidence that gcc's implementations are superior to
>> ours, I think we should not change stuff that works now.  That's
>> likely to lead to subtle bugs that are hard to find and perhaps
>> dependent on the exact compiler version used.

> Ok, we're in disagreement on that then. I don't feel very strongly about 
> it, let's see what others think.

I agree with Robert.  There is no evidence whatsoever that this would
be an improvement, and unless somebody cares to provide such evidence,
we shouldn't risk changing code that's so full of portability hazards.

> Actually, I believe our Itanium (and possibly ARM, too) implementation 
> of S_UNLOCK() is wrong as it is.

Hmm.  Anybody got a large itanium box we could play with?  If it is
wrong, I'd expect it would show up pretty quickly under pgbench or
similar.

			regards, tom lane

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Subject: Re: [PATCH] Use CC atomic builtins if available [was: Re: TAS patch for building on armel/armhf thumb]
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Subject: R: R: BUG #6342: libpq blocks forever in "poll" function

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