Re: GUC patch for Win32

Tom Lane wrote:
>
> Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us> writes:
> > Tom Lane wrote:
> >> Where exactly is the interlock to ensure that the new backend will end up
> >> with the correct settings if someone is changing the values at about
> >> the time of the fork?
>
> > Postmaster creates a new file, then does rename() to move it to the name
> > used by the backends. It can't move it until the file is not in use.
>
> And?
>
> How exactly does that guarantee that the new backend will see an update
> occurring at about the same time? I'm pretty sure that GUC is fired up
> before backends start listening to signals (and that's assuming the
> Windows port has a Unixy idea of signal response, which I seem to recall
> you telling me wasn't the case).

So far the postmaster is not multi-threaded, so it will not create a new
file and start a backend at the same time. Also, the rename() call is
supposed to be atomic. So there is allways a file, and it's either the
old or the new one, never something in between.

Jan

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