From: | Robert Haas <robertmhaas(at)gmail(dot)com> |
---|---|
To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | Andres Freund <andres(at)2ndquadrant(dot)com>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: dynamic shared memory and locks |
Date: | 2014-01-06 20:48:18 |
Message-ID: | CA+TgmobhQ6pj=dYxyufOtn7Zt__4gSFT0Gs-dCBURd8T7+-iqg@mail.gmail.com |
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Lists: | pgsql-hackers |
On Mon, Jan 6, 2014 at 3:40 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> Robert Haas <robertmhaas(at)gmail(dot)com> writes:
>> On Mon, Jan 6, 2014 at 1:55 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>>> OTOH, the LWLock mechanism has been stable for long enough now that
>>> we can probably suppose this struct is no more subject to churn than
>>> any other widely-known one, so maybe that consideration is no longer
>>> significant.
>
>> On the whole, I'd say it's been more stable than most. But even if we
>> do decide to change it, I'm not sure that really matters very much.
>
> Actually, the real value of a module-local struct definition is that you
> can be pretty darn sure that nothing except the code in that file is
> manipulating the struct contents. I would've preferred that we expose
> only an abstract struct definition, but don't quite see how to do that
> if we're going to embed the things in buffer headers.
Agreed. I think it's good to keep struct definitions private as much
as possible, and I do. But I don't think this is going to cause a big
problem either; lwlocks have been around for a long time and the
conventions for using them are pretty well understood, I think.
--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company
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