Re: condition variables

On Tue, Sep 13, 2016 at 10:55 PM, Peter Geoghegan <pg(at)heroku(dot)com> wrote:
> On Thu, Aug 11, 2016 at 2:47 PM, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
>> Another approach to the problem is to use a latch wait loop. That
>> almost works. Interrupts can be serviced, and you can recheck shared
>> memory to see whether the condition for proceeding is satisfied after
>> each iteration of the loop. There's only one problem: when you do
>> something that might cause the condition to be satisfied for other
>> waiting backends, you need to set their latch - but you don't have an
>> easy way to know exactly which processes are waiting, so how do you
>> call SetLatch? I originally thought of adding a function like
>> SetAllLatches(ParallelContext *) and maybe that can work, but then I
>> had what I think is a better idea, which is to introduce a notion of
>> condition variables.
>
> I don't see a CF entry for this. Are you planning to work on this
> again soon, Robert?
>
> I have an eye on this patch due to my work on parallel CREATE INDEX.
> It would be nice to have some rough idea of when you intend to commit
> this.

I basically figured I would commit it when and if it became clear that
it'd get good use in some other patch which was on the road to being
committed. I don't think it needs much work, just the assurance that
it will get some use.

--
Robert Haas
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