| From: | Alvaro Herrera <alvherre(at)commandprompt(dot)com> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | Gregory Stark <stark(at)enterprisedb(dot)com>, Martijn van Oosterhout <kleptog(at)svana(dot)org>, Pg Hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Block-level CRC checks |
| Date: | 2008-11-13 19:47:43 |
| Message-ID: | 20081113194743.GF4062@alvh.no-ip.org |
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| Thread: | |
| Lists: | pgsql-hackers |
Alvaro Herrera wrote:
> Tom Lane wrote:
>
> > Basically, you can't make any critical changes to a shared buffer
> > if you haven't got exclusive lock on it. But that's exactly what
> > this patch is assuming it can do.
>
> It seems to me that the only possible way to close this hole is to
> acquire an exclusive lock before calling FlushBuffers, not shared.
> This lock would be held until the flag has been examined and reset; the
> actual WAL record and write would continue with a shared lock, as now.
We don't seem to have an API for reducing LWLock strength though ...
--
Alvaro Herrera http://www.CommandPrompt.com/
PostgreSQL Replication, Consulting, Custom Development, 24x7 support
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