| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Heikki Linnakangas <hlinnakangas(at)vmware(dot)com> |
| Cc: | Andres Freund <andres(at)anarazel(dot)de>, Robert Haas <robertmhaas(at)gmail(dot)com>, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>, Peter Geoghegan <pg(at)heroku(dot)com>, Pg Hackers <pgsql-hackers(at)postgresql(dot)org>, Ants Aasma <ants(at)cybertec(dot)at> |
| Subject: | Re: better atomics - v0.6 |
| Date: | 2014-09-24 18:28:18 |
| Message-ID: | 22793.1411583298@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
Heikki Linnakangas <hlinnakangas(at)vmware(dot)com> writes:
> On 09/24/2014 07:57 PM, Andres Freund wrote:
>> On 2014-09-24 12:44:09 -0400, Tom Lane wrote:
>>> I think the question is more like "what in the world happened to confining
>>> ourselves to a small set of atomics".
>> I fail to see why the existance of a wrapper around compare-exchange
>> (which is one of the primitives we'd agreed upon) runs counter to
>> the agreement that we'll only rely on a limited number of atomics on the
>> hardware level?
> It might be a useful function, but if there's no hardware implementation
> for it, it doesn't belong in atomics.h. We don't want to turn it into a
> general library of useful little functions.
Note that the spinlock code separates s_lock.h (hardware implementations)
from spin.h (a hardware-independent abstraction layer). Perhaps there's
room for a similar separation here. I tend to agree with Heikki that
wrappers around compare-exchange ought not be conflated with
compare-exchange itself, even if there might theoretically be
architectures where the wrapper function could be implemented directly.
regards, tom lane
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