| From: | Noah Misch <noah(at)2ndQuadrant(dot)com> |
|---|---|
| To: | Robert Haas <robertmhaas(at)gmail(dot)com> |
| Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, pgsql-hackers(at)postgresql(dot)org |
| Subject: | Re: sinval synchronization considered harmful |
| Date: | 2011-07-25 22:24:07 |
| Message-ID: | 20110725222405.GA8255@tornado.leadboat.com |
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| Thread: | |
| Lists: | pgsql-hackers |
On Fri, Jul 22, 2011 at 03:54:03PM -0400, Robert Haas wrote:
> On Fri, Jul 22, 2011 at 3:28 PM, Noah Misch <noah(at)2ndquadrant(dot)com> wrote:
> > This is attractive, and I don't see any problems with it. (In theory, you could
> > hit a case where the load of resetState gives an ancient "false" just as the
> > counters wrap to match. Given that the wrap interval is 1000000x as long as the
> > reset interval, I'm not worried about problems on actual silicon.)
>
> It's actually 262,144 times as long - see MSGNUMWRAPAROUND.
Ah, so it is.
> It would be pretty easy to eliminate even the theoretical possibility
> of a race by getting rid of resetState altogether and using nextMsgNum
> = -1 to mean that. Maybe I should go ahead and do that.
Seems like a nice simplification.
--
Noah Misch http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services
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