Re: Resetting PGPROC atomics in ProcessInit()

On October 27, 2018 3:36:45 PM GMT+01:00, Amit Kapila <amit.kapila16@gmail.com> wrote:
>On Sat, Oct 27, 2018 at 4:11 PM Andres Freund <andres@anarazel.de>
>wrote:
>>
>> Hi,
>>
>> I just noticed, while working on a patch adding things to PGPROC,
>that
>> the group clearning patches for the proc array and clog reset atomics
>in
>> InitProcess().
>>
>> I'm not a big fan of that, because it means that it's not safe to
>look
>> at the atomics of backends that aren't currently in use.  Is there
>any
>> reason to not instead initialize them in InitProcGlobal() and just
>> assert in InitProcess() that they're 0?
>>
>
>It seems the code written has followed a natural practice i.e PGPROC
>members are initialized in InitProcess and ProcGlobal members (like
>procArrayGroupFirst) are initialized in InitProcGlobal.  For your use
>case, can't you look at procArrayGroupFirst?  If not, then I think we
>can do what you are saying as I don't see a problem in initializing
>them in InitProcGlobal.

In my opinion that's an argument for resetting the contents with pg_atomic_write, but not reinitializing the atomic (which could reset the spinlock inside while somebody else holds it).

It's not really a problem for me, but I think the code is pretty much wrong like this...

Andres
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